Expandable stent and method for promoting natural intracranial vasculogenesis process, and use of expandable stent in method for promoting natural intracranial vasculogenesis process

Abstract

To provide an expandable stent which can enhance supply of blood to a downstream tissue of an affected intracranial artery which has narrowing.SOLUTION: An expandable stent (1) comprises a first end (3) and a second end (4) coupled by a center part (5). The center part (5) is configured such that (10) the same is placed in a hole (103) of a narrowing (102) in an expanded state of the stent (1). The first end (3) and the second end (4) contact non-affected parts (104, 106) of an artery (100) adjacent to a proximal end (105) and a distal end (107) of the narrowing (102) and fix the stent (1) into the artery (100). The center part (5) where the stent (1) is in the expanded state, is configured such that a diameter of the hole (103) of the narrowing (102) is maintained to a current diameter, and (15) the diameter of the hole of the narrowing is increased to almost 50% of the non-affected parts (104, 106) of the artery (100) by application of an outward pressure in a radial direction to the narrowing (102).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to an expandable stent, particularly, but not exclusively, for use in treating intracranial atherosclerosis (ICAD). The stent provides a method for restoring sufficient blood flow to mitigate the risk of hypoxia, ischemia, and infarction while being mechanically controlled to prevent lesion snow-ploughing. Additionally, the stent of the present invention is configured to perfuse downstream tissues in an oligemic state to promote natural intracranial angiogenesis.

[0002] The present invention also relates to a method for promoting the natural intracranial angiogenesis process, and further, the present invention relates to the use of an expandable stent in a method for promoting the natural intracranial angiogenesis process.The present invention also relates to a method for treating intracranial atherosclerosis (ICAD).The present invention also relates to the use of an expandable stent in the treatment of intracranial atherosclerosis. [Background technology]

[0003] Intracranial atherosclerotic stenosis (ICAS) is the narrowing (stenosis) of arteries, veins, lumens, or other blood vessels, hereafter referred to as blood vessels, in the brain caused by the buildup of plaque (atheroma) on the inner walls of arteries, thereby reducing blood flow to the brain. This can lead to thromboembolic or hemodynamic ischemic stroke, which is a leading cause of disability worldwide.

[0004] Intracranial atherosclerotic stenosis has a high prevalence among certain ethnicities, and the disease is particularly prevalent among Asians (Lancet Neurol. 2013 November, 12(11):1106-1114). Within the Chinese patient population, the proportion of ischemic strokes due to ICAS can be as high as 50%.

[0005] In the early stages of atherosclerosis, a fatty material collects along the walls of blood vessels, which then thickens and hardens with calcium deposits, resulting first in narrowing and ultimately in blockage of the blood vessel, thereby impeding blood flow therethrough.

[0006] FIG. 1 illustrates an initial narrowing of an affected intracranial artery 100. The artery 100 comprises a wall 101. A stenosis 102 is formed by plaque on the wall 101. The stenosis 102 in FIG. 1 does not completely occlude the artery 100, but rather has a hole 103 passing through it. In FIG. 1, the stenosis 102 is about 90%, i.e., about 90% of the healthy caliber of the artery is occluded. This represents a reduction in the open cross-sectional area of ​​the artery by nearly 100 times. However, symptoms occur at lower levels of stenosis. The plaque may eventually occlude or completely occlude the vessel or artery, or develop a rough surface or thrombus that may repeatedly cause distal embolization. Other plaque characteristics such as intraplaque hemorrhage / hematoma, lipid-rich core, thin fibrous cap, etc. may also result in plaques that are prone to rupture and produce clots to occlude the vessel or repeatedly cause distal embolization.

[0007] The currently recommended approach for the management of ICAS is the use of pharmacological therapy, such as blood-thinning drugs, cholesterol-lowering drugs, and / or blood pressure regulators. However, the rate of ischemic stroke for pharmacologically treated ICAS patients can be as high as 20% at 2 years (Chimowitz Ml, Lynn MJ, Howlett-Smith H, et al. Comparison of warfarin and aspirin for symptomatic intracranial arterial stenosis. N Engl J Med 2005;31:1305-16) (Nahab F, Cotsonis G, Lynnet M, et al. Prevalence and prognosis of coexistent asymptomatic intracranial stenosis. Stroke 2008;39:1039-41). If an ICAS patient develops a second stroke despite being treated with optimal pharmacological therapy, guidelines allow for further intervention. Currently, the recommended interventions are to stent the stenosis as a salvage therapy, to perform balloon angioplasty to open the stenosis, or, more commonly, a combination of both. Stenting serves to widen the stenosis, thereby increasing blood flow through the vessel. Stents can also provide a scaffold for the formation of a smoother plaque surface, preventing the recurrence of distal emboli. However, some studies have shown that the use of metallic stents poses a risk of pushing plaque into adjacent vessels that were not previously affected, through a process known as "snow shoveling." The arterial structure in the brain is highly branched, and a recognized problem with existing stents is the shoveling of material from the stenosis into arterial side branches, or so-called "perforator" arteries, thereby blocking them and causing strokes in the areas formed by these side branches. For these reasons, the use of stents and / or balloon angioplasty is currently reserved exclusively for follow-up or salvage treatments after medical therapy has failed.

[0008] There is therefore a need to provide alternative approaches for the management of ICAS. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Lancet Neurol. November 2013, 12(11):1106~1114 [Non-Patent Document 2] Chimowitz Ml, Lynn MJ, Howlett-Smith H, et al. "Comparison of warfarin and aspirin for symptomatic intracranial arterial stenosis." N Engl J Med 2005, 31:1305-16 [Non-Patent Document 3] Nahab F, Cotsonis G, Lynnet M, et al. “Prevalence and prognosis of coexistent asymptomatic intracranial stenosis.” Stroke 2008, 39:1039-41 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention is directed to providing an expandable stent, the present invention is also directed to a method for promoting the natural intracranial angiogenesis process, and further the present invention is directed to the use of the expandable stent in a method for promoting the natural intracranial angiogenesis process. The present invention is also directed to an intracranial vessel containing the expandable stent. The present invention is also directed to a method for treating intracranial atherosclerosis and the use of the expandable stent in treating intracranial atherosclerosis. Furthermore, the present invention is directed to an expandable stent for use in treating intracranial atherosclerosis and the use of the stent in a method for restoring sufficient blood flow to mitigate the risk of developing hypoxia, ischemia, and infarction while being mechanically controlled to prevent lesion shoveling. The present invention is also directed to a stent, a method and use of the stent to perfuse downstream tissues in ischemic conditions and promote natural intracranial angiogenesis. [Means for solving the problem]

[0011] In accordance with the present invention, there is provided an expandable stent for stenting a stenosis in an intracranial blood vessel, the stent in an expanded state configured to have a first end having a first hole therethrough, a second end spaced from the first end and having a second hole therethrough, and a core extending between the first and second ends and having a central hole therethrough, connecting the first and second holes of the first and second ends to one another, the core having an outer cross-section smaller than the outer cross-sections of the first and second ends, the first and second ends configured to engage an arterial wall of the blood vessel on respective opposite ends of the stenosis in the expanded state of the stent to anchor the stent within the blood vessel, and the core configured to penetrate the holes through the stenosis in the expanded state of the stent and compress material forming the stenosis with an outward radial pressure to at least prevent further narrowing of the holes through the stenosis.

[0012] The present invention also provides an intracranial blood vessel including a stenosis and an expandable stent according to the present invention, wherein the expandable stent in an expanded state is positioned within the blood vessel, a central portion of the stent is positioned within a hole passing through the stenosis and compresses material forming the stenosis, and a first end and a second end of the stent engage the wall of the blood vessel on respective opposite ends of the stenosis.

[0013] Preferably, the first and second ends of the stent in the expanded state engage the wall of the blood vessel adjacent respective opposite ends of the stenosis.

[0014] Additionally, the present invention provides a method for promoting the natural intracranial angiogenesis process that supplies blood to an intracranial site that is supplied through a blood vessel having a stenosis therein, the method comprising: providing an expandable stent having a first end having a first hole therethrough, a second end spaced from the first end and having a second hole therethrough, and a core extending between the first and second ends and having a central hole therethrough communicating the first and second holes of the first and second ends with one another, the core having an outer cross-section smaller than the outer cross-sections of the first and second ends; placing an expandable stent in an unexpanded state within the stenosis, a central portion of the stent passing through a hole through the stenosis and a first end and a second end on opposite ends of the stenosis; and expanding the stent, wherein a first end and a second end of the expanded stent engage the wall of the blood vessel on each opposing end of the stenosis to anchor the stent within the blood vessel and a central portion of the expanded stent compresses the material forming the stenosis with an outward radial pressure to prevent further narrowing of at least the hole through the stenosis and promote the natural intracranial angiogenesis process.

[0015] The invention further provides for the use of an expandable stent in a method for promoting a natural intracranial angiogenesis process to supply blood to a site being fed through a blood vessel having a stenosis therein, the expandable stent comprising a first end having a first hole therethrough, a second end spaced from the first end and having a second hole therethrough, and a core extending between the first and second ends and having a central hole therethrough and communicating the first and second ends with each other, the core having an outer cross-section smaller than the outer cross-sections of the first and second ends. an expandable stent in an unexpanded state is placed within the stenosis, with a central portion of the stent penetrating a hole through the stenosis and with first and second ends on opposite ends of the stenosis, and the stent is expanded to an expanded state, with the first and second ends of the expanded stent engaging the wall of the blood vessel on each of the opposite ends of the stenosis to secure the stent within the blood vessel, and with the central portion of the expanded stent compressing material forming the stenosis with an outward radial pressure to prevent further narrowing of at least the hole through the stenosis and promote the natural intracranial angiogenesis process.

[0016] In one aspect of the invention, the central portion is configured such that in the expanded state of the stent, it compresses only the material of the stenosis and not the wall of the blood vessel.

[0017] In another embodiment of the invention, the first and second ends are configured to engage a wall of the blood vessel adjacent respective opposing ends of the stenosis in the expanded state of the stent.

[0018] In another embodiment of the invention, the first and second ends of the stent in the expanded state have a substantially circular cross-section.

[0019] In a further embodiment of the invention, the first and second ends of the stent in the expanded state are substantially cylindrical in shape.

[0020] In another embodiment of the invention, the first end and the second end are configured to conform to the shape of an adjacent portion of a blood vessel in the expanded state of the stent.

[0021] In another aspect of the invention, the expanded central portion of the stent has a substantially circular cross-section.

[0022] In a further aspect of the invention, the expanded core of the stent is substantially cylindrical in shape.

[0023] In another aspect of the invention, the expanded central portion of the stent is substantially hourglass shaped.

[0024] Preferably, the central portion is configured to conform to the shape of at least a portion of the stenosis in the expanded state of the stent.

[0025] In one aspect of the invention, the core is configured to expand to a predefined maximum cross-sectional area in the expanded state of the stent.

[0026] Preferably, the predefined maximum cross-sectional area of ​​the central portion is smaller than the cross-sectional area of ​​the unaffected portion of the blood vessel adjacent the stenosis to avoid contact between the central portion and the wall of the blood vessel.

[0027] In one embodiment of the invention, the outer diameter of the first and second ends of the stent in its expanded state is 5 mm or less.

[0028] Preferably, the outer diameter of the first and second ends of the stent in its expanded state is in the range of 2 mm to 5 mm.

[0029] Advantageously, the outer diameter of the first and second ends of the stent in its expanded state is in the range of 2.5 mm to 4.5 mm.

[0030] In one embodiment of the invention, the first and second ends of the stent in its expanded state are configured to expand to a diameter within the range of 100% to 125% of the inner diameter of the unaffected portion of the blood vessel adjacent the stenosis.

[0031] Preferably, the first and second ends of the stent in its expanded state are configured to expand to a diameter within the range of 100% to 110% of the inner diameter of the unaffected portion of the blood vessel adjacent the stenosis.

[0032] In another embodiment of the invention, the maximum outer diameter of the stent in an unexpanded state is no greater than 0.6 mm, preferably no greater than 0.5 mm, advantageously no greater than 0.4 mm.

[0033] Preferably, the maximum outer diameter of the stent in an unexpanded state is no greater than 0.3 mm.

[0034] In one embodiment of the invention, the outer diameter of the expanded core of the stent is within the range of 25% to 70% of the outer diameter of the first and second ends.

[0035] Preferably, the outer diameter of the expanded core of the stent is within the range of 40% to 75% of the outer diameter of the first and second ends.

[0036] Advantageously, the outer diameter of the expanded core of the stent is within about 50% of the outer diameter of the first and second ends.

[0037] In one embodiment of the invention, the outer diameters of the first and second ends of the stent in the expanded state are substantially equal to one another.

[0038] In another embodiment of the invention, the inner diameter of the expanded central portion of the stent is within the range of 25% to 70% of the inner diameter of the first and second ends.

[0039] Preferably, the inner diameter of the expanded central portion of the stent is within the range of 40% to 75% of the inner diameter of the first and second ends.

[0040] Advantageously, the inner diameter of the expanded central portion of the stent is within about 50% of the inner diameter of the first and second ends.

[0041] In one embodiment of the invention, the inner diameters of the first and second ends of the stent in the expanded state are substantially equal to one another.

[0042] In another embodiment of the invention, the wall thickness of the stent is in the range of 0.02 mm to 0.15 mm.

[0043] Preferably, the wall thickness of the stent is in the range of 0.05 mm to 0.1 mm.

[0044] In one aspect of the invention, the expanded central portion of the stent is configured to apply a radially outward pressure to the material forming the stenosis that is greater than the radially outward pressure applied to the wall of the blood vessel by the first and second ends.

[0045] In another aspect of the invention, the radially outward pressure applied by the expanded central portion of the stent is such that it minimizes crushing of the stenosis-forming material, thereby minimizing the force of the stenosis-forming material longitudinally along the wall of the blood vessel.

[0046] In a further aspect of the invention, the first and second ends of the stent in the expanded state are configured to compress the wall of the blood vessel with sufficient pressure to prevent stenosis-forming material from being forced between the corresponding one of the first and second ends and the wall of the blood vessel.

[0047] In another aspect of the invention, the expanded central portion of the stent is configured to compress the material forming the stenosis with radially outward pressure, increasing the diameter of the hole through the stenosis to at least 25% of the diameter of the unaffected portion of the blood vessel adjacent the stenosis.

[0048] Preferably, the expanded central portion of the stent is configured to compress the material forming the stenosis with radially outward pressure, increasing the diameter of the hole through the stenosis to at least 30% of the diameter of the unaffected portion of the blood vessel adjacent to the stenosis.

[0049] Advantageously, the expanded central portion of the stent is configured to compress the material forming the stenosis with radially outward pressure, increasing the diameter of the hole through the stenosis to at least 40% of the diameter of the unaffected portion of the blood vessel adjacent the stenosis.

[0050] Preferably, the expanded central portion of the stent is configured to compress the material forming the stenosis with radially outward pressure, increasing the diameter of the hole through the stenosis to at least 50% of the diameter of the unaffected portion of the blood vessel adjacent the stenosis, and may increase the diameter of the hole through the stenosis to at least 70% and even 80% of the diameter of the unaffected portion of the blood vessel adjacent the stenosis.

[0051] Advantageously, the expanded central portion of the stent is configured to exert a radially outward pressure on the material forming the stenosis, increasing the diameter of the hole through the stenosis to an order of 60% of the diameter of the unaffected portion of the blood vessel adjacent to the stenosis.

[0052] In one embodiment of the invention, the core terminates at opposite ends in respective transition sections, and the core is connected and in communication with the first end and the second end through the transition sections.

[0053] In another embodiment of the invention, at least one of the expanded state transitions of the stent extends substantially perpendicular to the center and a corresponding one of the first and second ends.

[0054] In another embodiment of the invention, the two transition sections of the expanded state of the stent extend substantially perpendicular to the center and a corresponding one of the first end and the second end.

[0055] In a further embodiment of the invention, at least one of the transitions in the expanded state of the stent is frustoconical in shape.

[0056] Preferably, the two transition sections of the expanded state of the stent are frusto-conical in shape.

[0057] In one aspect of the invention, the frustoconical portions of each transition portion of the expanded state of the stent define a cone angle in the range of 30° to 160°.

[0058] Preferably, the frustoconical portions of each transition section in the expanded state of the stent define a cone angle within the range of 30° to 110°.

[0059] Advantageously, the frustoconical portions of each transition portion of the expanded state of the stent define a cone angle within the range of 60° to 110°.

[0060] In one aspect of the invention, the transition portions of the stent in its expanded state are configured to engage the material forming the stenosis adjacent each opposing end.

[0061] Preferably, the first and second ends and the central portion are one of a cage-like structure defining interstices therein, a braided structure, and a perforated structure.

[0062] In another embodiment of the invention, the gaps in the center of the stent in its expanded state are smaller in area than the gaps in the first and second ends.

[0063] Preferably, the gaps in the central portion of the expanded state of the stent have an area small enough to minimize and / or prevent the passage of stenosis-forming material therethrough. Advantageously, the gaps in the transition portion of the expanded state of the stent have an area smaller than the area of ​​the gaps in the first and second ends.

[0064] In another aspect of the invention, the gaps in the transition portion of the expanded state of the stent have an area small enough to either minimize or prevent the passage therethrough of stenosis-forming material.

[0065] In one embodiment of the invention, the central portion of the stent defines a major central longitudinal axis, the first end portion defines a first central longitudinal axis, and the second end portion defines a second central longitudinal axis.

[0066] In another embodiment of the present invention, the major central axis, the first central axis, and the second central axis are coincident with one another.

[0067] In another embodiment of the invention, the major central axis is offset from the first and second central axes.

[0068] In a further embodiment of the invention, the first and second central axes are coincident with one another.

[0069] In another embodiment of the invention, the major central axis extends parallel to the first and second central axes.

[0070] In a further embodiment of the invention, the major central axis extends at an angle greater than 0° relative to the first and second central axes.

[0071] In one aspect of the invention, the stent is configured to expand at the blood temperature of a human or animal subject.

[0072] In another aspect of the invention, a biocompatible film is provided on the surface of the stent.

[0073] In a further embodiment of the invention, the biocompatible film is embedded with a pharmaceutical agent to prevent further growth of atherosclerotic plaque.

[0074] In another embodiment of the invention, the stent is embedded or coated at a molecular level with pharmaceutical agents that reduce the thrombogenic potential of the stent and substances that promote angiogenesis.

[0075] In one aspect of the invention, the stent is coated with a therapeutically active substance. Preferably, the therapeutically active substance comprises an angiogenesis promoting substance.

[0076] Advantageously, the angiogenesis promoter comprises methacrylic acid-ecoisodecyl acrylate (MAA-co-IDA, 40% MAA).

[0077] In another aspect of the invention, the stent is configured to minimize endothelial shear stress resulting from the stent.

[0078] Preferably, the stent is configured such that the resulting endothelial shear stress of the stent is 250 Pa or less.

[0079] In one aspect of the invention, the stent comprises a biocompatible material.

[0080] In another aspect of the invention, the stent comprises a biocompatible biodegradable material.

[0081] In a further aspect of the invention, the stent comprises a polymeric material.

[0082] In another aspect of the invention, the stent comprises a self-expanding material.

[0083] In a further aspect of the invention, the stent comprises a shape memory material.

[0084] In another embodiment of the invention, the stent comprises an alloy selected from one or more of nickel, titanium, cobalt, and stainless steel.

[0085] In a further aspect of the invention, the stent comprises a non-self-expanding material.

[0086] In one embodiment of the invention, the first and second ends of the stent in the expanded state engage the wall of the blood vessel adjacent respective opposite ends of the stenosis.

[0087] In another embodiment of the invention, the first and second ends of the stent in the expanded state have a substantially circular cross-section.

[0088] In a further embodiment of the invention, the first and second ends of the stent in the expanded state are substantially cylindrical in shape.

[0089] In another embodiment of the invention, the first and second ends of the stent in an expanded state conform to the shape of an adjacent portion of a blood vessel.

[0090] In one embodiment of the invention, the stent is expanded to an extent that the central portion increases the diameter of the hole that penetrates the stenosis such that the rate of blood flow through the stenosis is within 25% to 80% of the normal blood flow through the vessel in the absence of the stenosis.

[0091] In another embodiment of the invention, the stent is expanded to an extent that the central portion increases the diameter of the hole that penetrates the stenosis such that the rate of blood flow through the stenosis is within 30% to 70% of the normal blood flow through the vessel in the absence of the stenosis.

[0092] In a further embodiment of the invention, the stent is expanded to an extent that the central portion increases the diameter of the hole that penetrates the stenosis such that the rate of blood flow through the stenosis is within 40% to 60% of the normal blood flow through the vessel in the absence of the stenosis.

[0093] Preferably, the stent is expanded to an extent that the central portion increases the diameter of the hole that penetrates the stenosis so that the rate of blood flow through the stenosis is within about 50% of the normal blood flow through the vessel in the absence of the stenosis.

[0094] The present invention further provides a method of treating intracranial atherosclerosis in a subject, the method comprising forming a scaffold in the lesion to control migration of atherosclerotic material and expanding the cavity in the lesion so that downstream tissue is maintained in an ischemic state, and preferably the method comprises administering a medication to the patient to promote the development of collateral vessels to support said ischemic tissue.

[0095] The present invention further provides a method for treating a patient with an intracranial stenosis, the method comprising the steps of measuring the length of the stenosis, measuring the diameter of the hole through the stenosis, measuring the diameter of the blood vessel adjacent the distal and proximal ends of the stenosis, selecting a stent with a central portion having a diameter that is at least 50% of the diameter of the blood vessel adjacent one of the proximal and distal ends of the stenosis, placing the stent in the blood vessel, the central portion of the stent passing through the hole of the stenosis, and configuring the stent to remodel the stenosis and increase the diameter of the hole through the stenosis, preferably to at least 50% of the diameter of the blood vessel adjacent the proximal end of the stenosis. Preferably, the stent is configured to remodel the stenosis within 30 days of placing the stent in the blood vessel.

[0096] The present invention also provides a method for preventing secondary infarction when treating a stenosis in a blood vessel of a subject in which a branch vessel is adjacent to the stenosis, the method comprising providing a stent configured to underperfuse downstream tissue, positioning the stent relative to the stenosis, expanding the stent into an hourglass shape to conform to the stenosis, and verifying preservation of the branch vessel prior to implanting the stent.

[0097] The invention further provides a method for treating a human or animal subject to restore sufficient blood flow through a vessel of the intracranial vasculature to mitigate the risk of one or more of hypoxia, ischemia, and infarction, comprising, when an expandable stent according to the invention is provided, loading an expandable stent in a collapsed state into a proximal end of a lumen through a delivery microcatheter, the distal end of the delivery microcatheter being positioned across the stenosis, advancing the stent in the collapsed state through the lumen of the delivery microcatheter and positioning the stent in the collapsed state within the lumen of the delivery microcatheter adjacent its distal end, such that a central portion of the stent in the collapsed state is disposed within the hole of the stenosis. Preferably, the method further comprises withdrawing the delivery microcatheter while holding the stent with the central portion disposed within the hole of the stenosis to expose a second end of the stent. Preferably, the axial position of the delivery microcatheter is adjusted along with the axial position of the stent such that one of the first and second ends of the stent is positioned within the blood vessel adjacent the distal end of the stenosis.

[0098] Preferably, the method further comprises further withdrawing the delivery microcatheter to expose the entire stent.

[0099] Preferably, the method further comprises expanding the stent to scaffold the stenosis.

[0100] In one embodiment of the invention, the method includes verifying the position of the stent by fluoroscopy.

[0101] Preferably, the method includes separating the stent from the delivery microcatheter or other element of the delivery system.

[0102] In another embodiment of the invention, the method includes capturing an angiographic image of the stent within the stenosis to verify the position of the stent.

[0103] In another aspect of the invention, the method further comprises removing the delivery catheter from the subject.

[0104] In another aspect of the invention, the method includes providing an hourglass shaped center portion on an expandable stent.

[0105] In a further aspect of the invention, the expandable stent comprises a radiopaque marker, preferably disposed at one or both of the first and second ends of the stent.

[0106] In another aspect of the invention, the radiopaque marker is positioned adjacent to the central portion of the hourglass shape with the smallest diameter.

[0107] In another embodiment of the invention, the method includes visualizing the stenosis using fluoroscopy and sizing key features of the stenosis prior to treatment.

[0108] Preferably, the method includes calculating the optimal shape dimensions of a central portion of an hourglass shaped stent for the stenosis.

[0109] In another embodiment of the invention, the method includes positioning the stent in a collapsed state under fluoroscopic guidance so that a central portion of the hourglass shaped stent is disposed within the stenosis.

[0110] Preferably, the stent is expanded with the center of its hourglass shape positioned within the stenosis to expand a hole through the stenosis and perfuse distal tissue to create an ischemic state.

[0111] Preferably, the transition section is configured within the contoured tubular body section.

[0112] Advantageously, the first and second ends, the transition section and the central section are configured in a monolithic structure.

[0113] In one embodiment of the present invention, the cross-sectional area of ​​the opening through the stenosis increases by 30-80%, while the vessel adjacent to the stenosis expands by less than 18%.

[0114] In another embodiment of the invention, the cross-sectional area of ​​the opening through the stenosis increases by 2000%, while the vessel adjacent to the stenosis expands by less than 14%.

[0115] In another embodiment of the invention, the cross-sectional area of ​​the opening through the stenosis increases by 1000%, while the vessel adjacent to the stenosis expands by less than 16%.

[0116] In another embodiment of the invention, the cross-sectional area of ​​the opening through the stenosis is increased by 3000%, while the vessel adjacent to the stenosis is dilated by less than 12%.

[0117] Preferably, the cross-sectional area of ​​the opening through the stenosis increases in the range of 1000% to 3000%, while dilation of the blood vessel adjacent to the stenosis is in the range of 10% to 18%.

[0118] The advantages of the present invention are numerous. Essentially, the expandable stent according to the present invention when placed in a stenosis in a vessel in the intracranial vascular branch system is not intended to completely restore a partially occluded vessel to a completely normal state or to return it to its original internal diameter, but rather to maintain the blood flow through the vessel at a partially restricted level or to increase the flow rate of blood flow through the vessel to anywhere within the range of 25% to 80% of the normal flow rate through that vessel before the formation of the stenosis, and preferably to increase the flow rate of blood flow to about 50% of the normal flow rate through the vessel before the formation of the stenosis. This allows sufficient time for natural intracranial angiogenesis in the intracranial vasculature to proceed, thereby allowing collateral vessels to grow and allow one or more sites supplied with blood through the diseased vessel to supply the site supplied by the diseased vessel or to be supplied through one or more alternative vessels that cannot yet supply the site supplied by the diseased vessel. Thus, after completion of the natural intracranial angiogenesis process, the site supplied by the diseased vessel is fully supplied with blood from the newly grown collateral vessels as a result of the natural intracranial angiogenesis process.

[0119] The stent according to the invention is also adapted to treat cerebral arterial lesions that pose significant risks to patients. These lesions have a high level of restriction (stenosis), and the shear forces of the high velocity blood flowing through these lesions exposes the patient to a high risk of stroke. At the same time, the intracranial vessels of human subjects are small compared to other parts of the body and therefore more fragile than similarly sized vessels in the heart or kidneys or other organs. Forceful stent placement in these vessels has been shown to be inferior to medical therapy. In one embodiment, the invention provides an entirely new strategy for treating these patients. The method of partially dilating these intracranial stenoses with the device of the invention has the effect of restoring sufficient blood flow ensuring that downstream tissues are not hypoxic and at the same time preserving hypoxic conditions in the vascular bed. Hypoxic conditions in the intracranial vascular bed promote the development of collateral vessels (new blood vessels) in the brain in an angiogenesis process, and this treatment strategy allows the brain to develop its own blood circulation redundancy over time. This has the effect of reducing the risk that the stenosis poses to the patient. Even acute occlusion at the site of the original lesion may not significantly harm the patient in the setting of developed collateral vessels.

[0120] Another aspect of the expandable stent of the present invention is the way in which it manages the atherosclerotic material that constitutes the body of the restriction (stenosis). In conventional stent placement, this material is forcibly displaced, which causes the native artery to expand and accommodate. The expandable stent of the present invention avoids such forcible procedures and displaces the atherosclerotic material at a very small level.

[0121] Thus, the expandable stent according to the invention is generally used to increase blood flow through the diseased vessel, and not to restore normal blood flow through the diseased vessel, because restoring normal blood flow through the diseased vessel by increasing the diameter of the hole penetrating the stenosis generally results in the stenosis-forming material being crushed and spreading longitudinally along the vessel wall. Due to the large number of branch vessels in the intracranial vasculature and the close proximity of the branch vessels extending from the main vessel or artery, this results in the stenosis-forming material spreading past one or more branch vessels adjacent to the stenosis, thereby blocking the branch vessel. The crushing and spreading of the stenosis-forming material beyond the stent is generally referred to as "snow shoveling." The expandable stent according to the invention and its use allows snow shoveling while at the same time maintaining sufficient blood flow through the diseased vessel or artery to promote and support the natural intracranial angiogenesis process until it is completed and new or collateral vessels grow to provide an alternative blood supply to one or more sites supplied by the diseased vessel, thus avoiding the risk of blocking the branch vessel or artery adjacent to the stenosis.

[0122] A further advantage of the present invention is that by only partially opening the hole through the stenosis, the risk of intracranial hyperperfusion injury is reduced, and generally avoided. Intracranial hyperperfusion injury can result from the rapid restoration of normal perfusion pressure, potentially resulting in intracranial hemorrhage. In the setting of increased intracranial blood flow, intracranial hyperperfusion can also be accompanied by dysregulation of the intracranial vasculature and hypertension.

[0123] Thus, the advantages of the present invention are numerous. First, the expandable stent avoids shoveling the stenosis-forming material that would otherwise occlude adjacent or adjacent vascular branches to the stenosis. In the neurovascular circulation, some of these vascular branches are called perforator vessels because they emerge from vessels that are contained within the cerebral folds (from the middle intracranial artery) and perforate and penetrate the intracranial tissues of the brain. This is because some of these perforator vessels are associated with very high-level functions such as speech, and therefore occlusion of even one of these small vessels may have devastating consequences for the patient. The expandable stent of the present invention is configured to protect these perforator vessels from being occluded by shoveling while restoring blood flow to ischemic levels. The expandable stent maintains the diameter of the hole penetrating the stenosis or increases it to the extent that blood flow through the affected vessel is maintained at a value of more than 30% of normal, preferably about 50% of normal, while at the same time avoiding shoveling the stenosis-forming material, thereby allowing the natural intracranial angiogenesis process to proceed. The expandable stent according to the present invention maintains sufficient blood flow at least until the natural intracranial angiogenesis process is completed and new or collateral vessels grow to supply the area originally supplied by the diseased vessel or artery. Due to the fact that blood flow is maintained at 50% of normal blood flow, intracranial hyperperfusion is avoided and the risk of stroke is also reduced. In some cases, the expandable stent can be configured to increase blood flow up to 70% of normal, and in some limited cases up to 80% of normal.

[0124] The invention and its many advantages will be more clearly understood from the following description of some preferred embodiments, given by way of example only with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0125] [Figure 1] FIG. 1 is a cross-sectional side view of an affected intracranial artery. [Diagram 2]2 is a side view of an expandable stent according to the present invention for use in maintaining blood flow through a stenosis in the diseased artery of FIG. 1. [Diagram 3] FIG. 3 is an end view of the stent of FIG. 2. [Figure 4] FIG. 3 is a cross-sectional side view of the stent of FIG. 2. [Diagram 5] FIG. 3 is a cross-sectional side view of the stent of FIG. 2 in an unexpanded state. [Figure 6] 3 is a cross-sectional side view of the stent of FIG. 2 in use in the artery of FIG. 1. [Figure 7] 3 is a cross-sectional side view of a delivery system for delivering the stent of FIG. 2 into a stenosis of a diseased artery. [Figure 8] 8 is a cross-sectional side view of the portion of the artery of FIG. 7 illustrating the stent of FIG. 2 positioned within a stenosis of the diseased artery. [Figure 9] 9 is a view similar to FIG. 8 further illustrating the placement of the stent of FIG. 2 within the diseased artery. [Figure 10] FIG. 2 is a side view of an expandable stent according to another embodiment of the present invention. [Figure 11] 2 is a cross-sectional side view of a stent according to another embodiment of the present invention. [Figure 12] 1 is a cross-sectional side view of a stent according to a further embodiment of the present invention illustrated in a stenosis in a diseased artery. [Figure 13] 1 is a cross-sectional side view of a stent according to a further embodiment of the present invention illustrated being placed within a stenosis in an artery. [Figure 14a] FIG. 2 is a side view of a stent according to another embodiment of the present invention. [Figure 14b] 2 is a cross-sectional side view of a stent according to another embodiment of the present invention. [Figure 14c] FIG. 2 is an end view of a stent according to another embodiment of the present invention. [Figure 15a] FIG. 2 is a side view of a stent according to another embodiment of the present invention. [Figure 15b] 2 is a cross-sectional side view of a stent according to another embodiment of the present invention. [Figure 15c]FIG. 2 is an end view of a stent according to another embodiment of the present invention. [Figure 16a] FIG. 2 is a side view of a stent according to another embodiment of the present invention. [Figure 16b] 2 is a cross-sectional side view of a stent according to another embodiment of the present invention. [Figure 16c] FIG. 2 is an end view of a stent according to another embodiment of the present invention. [Figure 17a] FIG. 2 is a side view of a stent according to another embodiment of the present invention. [Figure 17b] 2 is a cross-sectional side view of a stent according to another embodiment of the present invention. [Figure 17c] FIG. 2 is an end view of a stent according to another embodiment of the present invention. [Figure 18] FIG. 2 is a perspective view of a stent according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0126] Referring now to the drawings, and initially to Figures 2 through 6, an expandable stent according to the present invention, generally designated by reference numeral 1, is illustrated. Stent 1 is expandable from an unexpanded state, illustrated in Figure 5, to an expanded state, illustrated in Figures 2, 3, 4, and 6. Stent 1 is of dimensions in an unexpanded state suitable for urging the stent through an intracranial vasculature (not shown) in a delivery microcatheter, as described below, to a stenosis, e.g., a stenosis 102 in an intracranial artery, e.g., in a diseased intracranial artery 100 of the intracranial vasculature (not shown). In the expanded state, stent 1 is of dimensions such that stent 1 expands within stenosis 102, maintains open a hole 103 through stenosis 102, and / or increases the cross-sectional area of ​​hole 103 through stenosis 102, maintaining and / or increasing the amount of blood flow through stenosis 102. Maintaining or increasing the amount of blood flow through the stenosis 102 protects downstream tissues, i.e., tissues supplied with blood through the artery 100, from hypoxia, ischemia, and / or infarction while maintaining the downstream tissues in an ischemic state, thus promoting and allowing the natural intracranial angiogenesis process to complete, thereby allowing neo-collateral vessels to grow and supply the downstream tissues supplied through the diseased artery 100. The dimensions of the stent 1 in its expanded and unexpanded states are described in more detail below.

[0127] The stent 1 in the expanded state comprises a first end 3 and a second end 4, both of which have a circular cross-section and have the same outer and inner diameters. A central portion, also of circular cross-section, extends between the first end 3 and the second end 4, terminating at opposite ends in respective transition sections 7 which connect the central portion 5 to the corresponding one of the first end 3 and the second end 4. In this embodiment of the invention, the transition sections 7 extend substantially perpendicularly from the central portion 5 and perpendicularly from the corresponding one of the first end 3 and the second end 4 when the stent 1 is in the expanded state. However, as described below with reference to Figures 11 to 13, the transition sections 7 may be, for example, truncated cones which gradually increase in cross-sectional area from the central portion 5 to the first end 3 and the second end 4, and indeed in other embodiments of the invention, stents such as those described with reference to Figures 11 to 13 may be preferred over the stent 1.

[0128] The first and second ends 3, 4 are formed by expandable first and second walls 10, 11 having first and second holes 12, 13 therethrough, respectively. The central portion 5 comprises an expandable central wall 15 having a hole 16 therethrough and having first and second holes 12, 13 therethrough communicating the first and second ends 3, 4, respectively. In this embodiment of the invention, in the expanded state of the stent 1, the first and second walls 10, 11 and central wall 15 are each cylindrical. In this embodiment of the invention, the transition section 7 is formed by respective transition walls 17 which are expandable and which in the expanded state of the stent 1 expand outwardly such that the transition walls 17 extend perpendicularly from the central wall 15 and from the first and second walls 10, 11. The central wall 15 of the core 5 defines a longitudinally extending main central axis 18, and the first and second walls 10, 11 of the first and second ends 3, 4 define respective longitudinally extending first and second central axes 21, 22. In this embodiment of the invention, the first and second ends 3, 4 are axially aligned with one another, and the core 5 is axially aligned with the first and second ends 3, 4. Thus, in this embodiment of the invention, the first and second central axes 21, 22 and the main central axis 18 coincide with one another.

[0129] It is contemplated, and indeed will be understood by those skilled in the art, that the first and second walls 10, 11 and the central wall 15 need not necessarily be cylindrical. For example, in the expanded state of the stent 1, the central wall 15 may diverge outwardly from a central point midway between the transition walls 17 toward the transition walls 17, in other words, the central wall 15 may be "hourglass" shaped, whereby the diameter of the central wall 15 adjacent the transition walls 17 is greater than the diameter of the central wall 15 at the central point midway between the transition walls 17, in which case the diameter of the diverging portion of the cylindrical wall 15 gradually increases from the central point of the central wall 15 toward the transition walls 17. In fact, it is contemplated that depending on the shape of the holes 103 penetrating the stenosis 102 when the stent 1 is expanded in situ, the central wall 15 may assume a shape corresponding to the outline of the holes 103 penetrating the stenosis 102.

[0130] It is also contemplated that the first and second walls 10, 11 of the first and second ends 3, 4 may be shaped other than cylindrical, and in some embodiments of the present invention, the first and second walls 10, 11 of the stent 1 in an expanded state may be shaped such that the first and second walls 10, 11 merge longitudinally from the transition wall 17, or merge from a midpoint halfway between the corresponding transition wall 17 and the corresponding free end 19 of the end walls 10, 11 toward the corresponding transition wall 17 and the corresponding free end 19. Indeed, it is contemplated that when in situ, the first and second walls 10, 11 of the first and second ends 3, 4, respectively, may be shaped to correspond to the longitudinal contours of the proximal and distal undiseased portions 104, 106, respectively, of the artery adjacent the proximal and distal ends 105, 107, respectively, of the stenosis 102.

[0131] It goes without saying that the central wall 15 of the central portion 5 and the first and second walls 10, 11 of the first and second ends 3, 4 may assume any suitable shape in the expanded state of the stent 1, and when the stent 1 is placed in situ within the artery 100, for example, the outer surfaces of the first and second end walls 10, 11 and the central wall 15 may be concave or convex.

[0132] It will also be understood that in some embodiments of the present invention, the first and second ends may not be axially aligned with each other, and further, the central portion 5 may not be axially aligned with the first and second ends 3 and 4. In this case, only the central axes 18, 21, and 22 of the central portion 5 and those portions of the first and second ends 3 and 4 coincide. For example, if the first and second ends 3 and 4 are axially aligned, the first and second central axes 21 and 22 coincide with each other, and if the central portion 5 is not axially aligned with the first and second ends 3 and 4, the major central axis 18 of the central portion 5 is offset from the first and second central axes 21 and 22 of the first and second ends 3 and 4. Generally, in such cases, the major central axis 18 will extend parallel to the first and second central axes 21 and 22 of the first and second ends 3 and 4. However, it is contemplated that in some cases, the major central axis 18 of the core 5 may extend at an angle relative to the first and second central axes 21, 22 of the first and second ends 3, 4. Indeed, in use, depending on the shape and angle of the hole 103 through the constriction 102, the core 5 may assume an orientation that extends at an angle relative to the first and second ends 3, 4. In this case, it is contemplated that the first and second central axes of the first and second ends 3, 4 may not be axially aligned, but are offset from one another, and the major central axis 18 of the core 5 may extend at an angle relative to the first and second central axes 21, 22 of the first and second ends 3, 4. Additionally, if the stenosis 102 is located in a curved or angled artery, the first and second central axes 21, 22 of the first and second ends 3, 4 may extend at an angle to each other and at different angles to the main central axis 18 of the core 5.

[0133] The size of the expanded stent 1 is generally selected based on the diameter of the stenosis 102 and the length of the stenosis 102, and also based on the diameter of the non-diseased portion of the artery 200 adjacent to the stenosis 102. Generally, the stent 1 comprises a first end 3, a second end 4, and a central portion 5, as well as a transition portion 7 having holes through it of different diameters and lengths to accommodate arteries or vessels of different diameters and stenoses of different lengths. The selection of a stent for a particular stenosis in a particular artery or vessel is generally a two-step process. First, a surgeon, interventionist, or other surgical or medical personnel measures the length of the stenosis and the diameter of the holes through the stenosis, as well as the diameter of the non-diseased portions 104 and 106 of the artery adjacent to each opposite end of the stenosis. A suitable size of the stent 1 according to the present invention is then selected. If a suitable size of the stent 1 does not exist, a suitable size of the stent 1 according to the present invention will be manufactured.

[0134] In this embodiment of the invention, stenosis 102 is formed by plaque on the arterial wall 101 of artery 100. The diameter of hole 103 through stenosis 102 is about 0.6 mm. The length L of stenosis 102 is about 5 mm. The diameter D of proximal and distal unaffected portions 104, 106, respectively, of artery 100 adjacent respective proximal and distal ends 105, 107, respectively, of stenosis 102 is about 3 mm.

[0135] Thus, in this embodiment of the invention, the stent 1 is configured such that when placed in situ within the stenosis 102, it is expanded such that the central portion 5 has an outer diameter d1 of about 1.5 mm and the first and second ends 3, 4 have equal outer diameters D1 of about 3.5 mm. The axial length L1 of the central portion 5 of the stent 1 in its expanded state is about 5 mm, while the axial lengths L2 of the first and second ends 3, 4 of the stent 1 in its expanded state in this embodiment of the invention are equal, in this embodiment of the invention about 2 mm. It will be appreciated that the axial lengths of the first and second ends 3, 4 of the stent 1 may be the same or different.

[0136] As mentioned above, the dimensions of the stent 1 in the expanded state are highly dependent on the dimensions of the artery and its stenosis, and are selected to suit the particular stenosis. Typically, however, in the expanded state, the outer diameter d1 of the central portion 5 of the stent 1 will be in the range of 1 mm to 3 mm, more typically in the range of 1.2 mm to 2.5 mm. The outer diameters D1 of the first and second ends 3 and 4 of the stent 1 in the expanded state are generally in the range of 2 mm to 5 mm, more typically in the range of 2.5 mm to 4.5 mm. In addition, the length L1 of the central portion 5 of the stent 1 in the expanded state of the stent is typically in the range of 5 mm to 20 mm, more typically in the range of 5 mm to 15 mm. The axial length L2 of each of the first and second ends 3 and 4 of the stent 1 in the expanded state is generally in the range of 2 mm to 4 mm, more typically in the range of 2 mm to 3 mm, which may be the same axial length or different axial lengths.

[0137] In order for the unexpanded stent 1 to be able to be navigated through the intracranial vasculature and delivered to the stenosis 102 in the artery 100, generally in an unexpanded state, the stent 1 has a substantially constant outer diameter d3 along its entire axial length L3 of 0.6 mm or less, and the axial length L3 of the unexpanded stent 1 will generally be 30 mm or less. See FIG. 5. However, depending on the location of the artery or blood vessel and its stenosis within the intracranial vasculature, the maximum outer diameter d3 of the unexpanded stent 1 will be 0.5 mm or less. Ideally, the unexpanded stent 1 has a maximum outer diameter d3 of 0.4 mm or less and a length L3 of 25 mm or less.

[0138] The relationship between the outer diameter d1 of the central portion 5 and the outer diameter D1 of the first and second ends 3 and 4 of the stent 1 in its expanded state is selected such that the radially outward pressure exerted by the central portion 5 on the stenosis 102 is sufficient to maintain the diameter of the hole 103 penetrating the stenosis 102 at at least 25% of the diameter of the proximal and distal undiseased portions 104 and 106 of the artery 100 adjacent the proximal and distal ends 105 and 107 of the stenosis 102, and such that the radially outward pressure exerted by the first and second ends 3 and 4 on the proximal and distal undiseased portions 104 and 106 of the wall 101 of the artery 100 adjacent the respective proximal and distal ends 105 and 107 of the stenosis 102 is sufficient to fix the stent 1 within the artery 100 against its arterial wall 101. The pressure applied by the first end 3 and the second end 4 to the arterial wall 101 may also be sufficient in many cases to prevent material forming the stenosis from being crushed longitudinally from the stenosis 102 along the wall 101 of the artery 100 between the first end 3 and the second end 4 and the wall 101 of the artery 100.

[0139] The outer diameter d1 of the central portion 5 of the stent 1 in the expanded state is selected to apply a radially outward pressure to the stenosis to increase the diameter of the hole 103 passing through the stenosis 102 to within the range of 25% to 60%, and in some cases up to 75% or even 80% of the diameter of the proximal and distal undiseased portions 104 and 106 of the artery 100 adjacent the proximal and distal ends 105 and 107 of the stenosis 102, respectively. However, ideally, the outer diameter of the central portion 5 in the expanded state is such that sufficient radially outward pressure is applied to the stenosis 102 to increase the diameter of the hole 103 passing through to about 50% of the diameter of the proximal and distal undiseased portions 104 and 106 of the artery 100 adjacent the proximal and distal ends 105 and 107 of the stenosis 102, respectively.

[0140] Additionally, and generally, the outer diameter d1 of the expanded core 5 of the stent 1 is selected such that the radially outward pressure applied by the core 5 of the stent 1 in the expanded state is sufficient to increase the diameter of the holes 103 through the stenosis 102, thereby increasing the blood flow rate through the artery 100 to greater than 50% of the normal blood flow rate through the artery prior to the formation of the stenosis. Since the resistance to flow is inversely proportional to the fourth power of the inner diameter of the conduit, the outer diameter of the expanded core 5 of the stent 1 is selected based on this relationship to restore the blood flow rate through the holes 103 of the stenosis 102 to greater than 50% of the normal blood flow rate. This is sufficient to maintain blood flow to downstream tissues supplied by the diseased artery 100 while maintaining the downstream tissues in an ischemic state, protecting the downstream tissues from hypoxia, ischemia, and / or infarction, as has been found, and also to promote the natural intracranial angiogenesis process until it is completed and new collateral vessels grow to supply the sites supplied by the diseased artery. However, in some embodiments of the present invention, it is contemplated that the outer diameter of the expanded central portion 5 of the stent 1 may be such that, depending on the current flow rate, at the current flow rate or slightly higher than the current flow rate, the outer diameter may be sufficient to protect downstream tissue from hypoxia, ischemia, and / or infarction while maintaining the downstream tissue in an ischemic state, such that it gently compresses the stenosis 102 to maintain blood flow through the artery.

[0141] In general, the radially outward pressure applied by the central portion 5 to the stenosis 102 is greater than the radially outward pressure applied by the first end 3 and the second end 4 to the wall 101 adjacent the proximal undiseased portion 104 and the distal undiseased portion 106 of the artery 100 in the expanded state of the stent 1. However, the central portion 5 is selected such that the maximum cross-sectional area over which the central wall 15 can expand is limited to a predefined maximum cross-sectional area that is smaller than the cross-sectional areas of the proximal undiseased portion 104 and the distal undiseased portion 106 of the artery 100 adjacent the stenosis 102. This is to ensure that the central wall 15 of the central portion 5 in the expanded state of the stent 1 is spaced away from the arterial wall 101 of the artery 100 and does not contact the arterial wall 101 of the undiseased portion of the artery 100 adjacent the stenosis 102.

[0142] The stent 1 in this embodiment of the invention is formed from a perforated material that is perforated to form appropriately connected struts 23 with gaps 20 therebetween that extend through the material. In this embodiment of the invention, the material of the stent 1 comprises a shape memory metal, such that the stent 1 is self-expanding, and preferably expands at normal blood temperatures within the human or animal body. While many metals and other materials can be used to provide such a self-expanding stent, in this embodiment of the invention, the material of the stent is a nickel titanium alloy known as Nitinol. In the unexpanded state of the stent 1, the stent 1 is radially compressed such that the struts 23 are adjacent to one another, and depending on the pattern of perforations that form the stent 1, the struts 23 in the compressed unexpanded state of the stent 1 may extend axially.

[0143] The gap 20a through the central wall 15 of the core portion 5 in the expanded state of the stent 1 has an area smaller than the area of ​​the gap 20b through the first wall 10 and the second wall 11 of the first end 3 and the second end 4. The gap 20c through the transition wall 17 of the transition portion 7 has an area substantially similar to the area of ​​the gap 20a through the central wall 15 of the core portion 5. In this embodiment of the invention, the gaps 20a and 20c through the central wall 15 of the core portion 5 and the transition wall 17 of the transition portion 7 of the stent 1 in the expanded state have areas small enough to at least minimize, and preferably prevent, material forming a stenosis 102 through the gaps 20a and 20c in the core portion 5 and the transition portion 7. Additionally, by making the gaps 20a and 20c in the core portion 5 and the transition portion 7 have a smaller area than the gaps 20b in the first end portion 3 and the second end portion 4, the result is that the radially outward pressure applied by the core portion 5 to the stenosis 102 is greater than the radially outward pressure applied by the first end portion 3 and the second end portion 4 to the proximal portion 104 and the distal portion 106 of the artery 100.

[0144] The wall thickness of the first and second walls 10 and 11 of the first and second ends 3 and 4 is similar to the wall thickness of the central wall 15 of the central portion 5. Thus, the relationship between the inner diameter d2 of the central wall 15 of the central portion 5 and the inner diameter D2 of the first and second walls 10 and 11 of the first and second ends 3 and 4 is substantially similar to the relationship between the outer diameter d1 of the central wall 15 of the central portion 5 and the outer diameter D1 of the first and second walls 10 and 11 of the first and second ends 3 and 4. In this embodiment of the invention, the wall thickness of the first and second end walls 10 and 11, the central wall 15, and the transition wall 17 is about 0.1 mm. However, it is contemplated that the thickness of the first and second end walls, the central wall, and the transition wall may be in the range between 0.02 mm and 0.15 mm, but preferably the thickness of the first and second end walls, the central wall, and the transition wall is ideally within the range of 0.05 mm to 0.1 mm. The thickness of the first and second end walls, the central wall, and the transition wall are selected to optimize between stent strength and function on the one hand, and minimize endothelial shear stress resulting from use of the stent on the other hand. Typically, the wall thickness of the stent is selected to provide an endothelial shear stress of 250 Pa or less.

[0145] In this embodiment of the invention, the stent is configured such that, in the expanded state of the stent, the outer diameter of the first end 3 and the second end 4 of the stent is approximately 110% of the diameter of the proximal and distal undiseased portions 104, 106 of the artery adjacent the proximal and distal ends 105, 107, respectively, of the stenosis 102. However, it is contemplated that the outer diameter of the first end 3 and the second end 4 of the stent 1 may be configured to expand to a diameter, in the expanded state of the stent, that is within the range of 100% to 125% of the diameter of the proximal and distal undiseased portions 104, 106 of the artery adjacent the proximal and distal ends 105, 107, respectively, of the stenosis 102, preferably within the range of 100% to 110% of the diameter of the artery at the proximal and distal undiseased portions 104, 106 of the artery.

[0146] The stent 1 is coated with a therapeutically active substance, and in this embodiment of the invention, is coated with two therapeutically active substances, one of which includes a pro-angiogenic substance and the other of which prevents further growth of plaque. Typically, the pro-angiogenic substance includes methacrylic acid-eco-isodecyl acrylate (MAA-co-IDA, 40% MAA). The therapeutically active substance for preventing further growth of plaque may include one or more of sirolimus and paclitaxel.

[0147] 7-9, a delivery system 30 for delivering a stent 1 to a stenosis 102 in an artery 100 is illustrated. The delivery system 30 comprises a delivery microcatheter 31 extending between a proximal end 32 and a distal end 33. A slot 34 passes through the delivery microcatheter 31 from the proximal end 32 to the distal end 33 to accommodate delivery of the stent 1 therethrough to the stenosis 102 when the distal end 33 of the delivery microcatheter 31 is positioned within the stenosis 102 and protrudes distally from the stenosis. See FIG. 7. The slot 34 has a diameter such that the unexpanded stent 1 is freely slidable through the slot 34, which varies depending on the diameter of the unexpanded stent, typically in the range of 0.68 mm to 0.84 mm. The outer diameter of the delivery microcatheter 31 is such that the delivery microcatheter 31 can be forced through the intracranial vasculature to a suitable entry point, which may typically be the femoral, radial, brachial, or carotid artery, and from such suitable entry point through the hole 103 in the stenosis 102. In addition, the delivery microcatheter 31 has sufficient flexibility to facilitate manipulation of the delivery microcatheter 31 through the intracranial vasculature to the stenosis 102 in the artery 100.

[0148] An elongated positioning member 40, having a diameter smaller than the diameter of the hole 34 of the delivery microcatheter 31, is provided for delivering the stent 1 through the delivery hole 34 of the delivery microcatheter 31 within the artery 100 to the stenosis 102. The positioning member 40 extends between a proximal end 41 and a distal end 42 and terminates at the distal end 42 in a releasable coupling mechanism 44 for releasably coupling the positioning member 40 to the stent 1 adjacent the free end 19 of the first wall 10 of the first end 3. The first end 3 of the stent 1 is configured for placement within a proximal unaffected portion 104 of the artery 100 adjacent the proximal end 105 of the stenosis 102, and the second end 4 is configured for placement within a distal unaffected portion 106 of the artery 100 adjacent the distal end 107 of the stenosis 102. In this embodiment of the invention, the coupling mechanism 44 for coupling the free end 19 of the first wall 10 of the first end 3 to the positioning member 40 is a conventional coupling mechanism known to those skilled in the art and is operable from the proximal end 41 of the positioning member 40 to release the stent 1 from the positioning member 40 when the stent 1 is properly positioned within the stenosis 102. Alternatively, the coupling mechanism may be releasably coupled to the free end 19 of the second end wall 11 of the second end 4.

[0149] In use, the procedure for delivering the stent 1 to the stenosis 102 in the artery 100 typically begins with placing a guidewire (not shown) into the intracranial vasculature, typically through the femoral, radial, brachial, or carotid artery. The guidewire is forced into the intracranial vasculature from the entry point and through the intracranial vasculature to the stenosis 102 in the artery 100. The guidewire is forced through hole 103 into the stenosis 102 such that the distal end of the guidewire penetrates into the artery 100 distal to the distal end 107 of the stenosis 102. The delivery microcatheter 31 is then forced over the guidewire through the intracranial vasculature until the distal end 33 of the delivery microcatheter 31 penetrates hole 103 through the stenosis 102 and into the distal unaffected portion 106 of the artery 100 adjacent the distal end 107 of the stenosis 102. The guidewire is then withdrawn through the lumen 34 of the delivery microcatheter 31 .

[0150] The stent 1 in an unexpanded state is coupled to the positioning member 40 adjacent the distal end 42 by a coupling mechanism 44. When the stent 1 in an unexpanded state is coupled to the distal end 42 of the positioning member 40, the positioning member 40 urges the stent 1 with the second end 4 leading the stent 1 into the hole 34 of the delivery microcatheter 31 adjacent the proximal end 32. The stent 1 is then urged by the positioning member 40 through the hole 34 of the delivery microcatheter 31 to the distal end 33. When the stent 1 is in the hole 34 of the delivery microcatheter 31 adjacent the distal end 33, the tip of the stent 1, i.e., the second end wall 10 of the second end 4, is exposed by slightly withdrawing the delivery microcatheter 31 proximally. The second end wall 11 of the second end 4 of the stent 1 is exposed and begins to expand into the distal unaffected portion 106 of the artery adjacent the distal end 107 of the stenosis 102 after contact with blood at the subject's normal body temperature. See Figure 8.

[0151] The position of the stent 1 is adjusted by simultaneously appropriately maneuvering the delivery microcatheter 31 and the positioning member 40 to properly position the second wall 11 of the second end 4 at the correct location within the distal undiseased portion 106 of the artery 100 adjacent the distal end 107 of the stenosis 102. After the second wall 11 of the second end 4 is properly positioned within the distal undiseased portion 106 of the artery 100 adjacent the distal end 107 of the stenosis 102, the delivery microcatheter 31 is withdrawn further proximally to fully expose the stent 1.

[0152] The remaining portion of the stent 1 expands after contacting blood in the artery 100 at body temperature, such that the central wall 15 of the central portion 5, located within the hole 103 of the stenosis 102, compresses the stenosis 102, and the first wall 10 of the first end 3 compresses the proximal unaffected portion 104 of the artery 100 adjacent the proximal end 105 of the stenosis 102. The material forming the stenosis 102 is entirely contained within the annulus 108 defined by the central wall 15 of the central portion 5, the distal wall 17 of the transition portion 7, and the portion of the wall 101 of the artery 100 adjacent the stenosis 102.

[0153] The positioning member 40 is separated from the stent 1 by separating the coupling mechanism 44 from the stent 1. The positioning member 40 and delivery microcatheter 31 are withdrawn through the intracranial vasculature and then, optionally, through the femoral, radial, brachial, or carotid arteries.

[0154] When the stent 1 is in an expanded state within the stenosis 102, the material forming the stenosis 102 is held within the annulus 108 by the central wall 15 of the central portion 5 and the transition walls 17 of the transition portion 7, and by the action of the first and second walls 10 and 11 of the first and second ends 3 and 4 compressing the proximal and distal undiseased portions 104 and 106 of the artery 100 adjacent the proximal and distal ends 105 and 107 of the stenosis 102. The action of the first and second walls 10 and 11 of the first and second ends 3 and 4 against the proximal and distal undiseased portions 104 and 106 keeps the stent 1 secured within the artery 100 and prevents the material forming the stenosis 102 from being forced between the wall 101 of the artery 100 and the first and second walls 10 and 11 of the first and second ends 3 and 4. The central wall 15 of the central portion 5 compresses the stenosis 102 to either maintain the diameter of the hole 103 through the stenosis 102 at the diameter it had prior to placing the stent 1 within the stenosis 102, or to increase the diameter of the hole 103 through the stenosis 102 to a diameter sufficient to maintain the flow of blood through the artery 100 at 50% or more of the normal flow of blood through the artery 100 prior to the formation of the stenosis 102. By maintaining the flow of blood through the artery 100 at 50% or more of the normal flow, downstream tissues are protected from hypoxia, ischemia, and infarction while maintaining the downstream tissues in an ischemic state. Thus, the natural intracranial angiogenesis process is promoted, whereby new and collateral vessels grow to provide blood supply to downstream tissues supplied by the diseased artery 100.

[0155] Providing a therapeutically active intracranial angiogenic substance coated on the stent further enhances the natural intracranial angiogenic process and the therapeutically active substance coated on the stent to prevent further growth of plaque prevents or at least minimizes further growth of plaque.

[0156] Referring now to FIG. 10, a stent according to another embodiment of the present invention is illustrated, generally designated by reference number 50. Stent 50 is substantially similar to stent 1, and similar components are identified by the same reference numbers. Stent 50 in this embodiment of the present invention is also particularly suitable for stenting an intracranial artery, such as artery 100 having a stenosis 102 therein, to maintain or increase the flow rate of blood flow through the stenosis 102, protecting the downstream tissue from hypoxia, ischemia, and / or infarction while maintaining the downstream tissue in an ischemic state, and then promoting native intracranial angiogenesis. The dimensions of stent 50 are within the dimensional range described with reference to stent 1. The main difference between stent 50 and stent 1 is in transition section 7. In this embodiment of the invention, instead of transition portion 7 being formed by transition walls 17 extending perpendicularly from central wall 15 of central portion 5 and perpendicularly from first wall 10 and second wall 11 of first end 3 and second end 4, transition portion 7 of stent 50 is formed by frusto-conical wall portion 52 which in turn are formed by transition walls 53 diverging outwardly from central wall 15 of central portion 5 to first wall 10 and second wall 11 of first end 3 and second end 4, respectively.

[0157] The wall thickness of the transition wall 53 is substantially similar to the wall thickness of the first wall 10 and the second wall 11 and the central wall 15 of the first end 3 and the second end 4 and the central portion 5, respectively. The outer diameter of the transition wall 53 adjacent the central wall 15 of the central portion 5 is similar to the outer diameter d1 of the central wall 15. The inner diameter of the transition wall 53 adjacent the central wall 15 of the central portion 5 is similar to the inner diameter d2 of the central wall 15 of the central portion 5. The outer diameter of the transition wall 53 adjacent the first wall 10 and the second wall 11 of the first end 3 and the second end 4 is similar to the outer diameter D1 of the first wall 10 and the second wall 11 of the first end 3 and the second end 4, and the inner diameter of the transition wall 53 adjacent the first wall 10 and the second wall 11 of the first end 3 and the second end 4 is similar to the inner diameter D2 of the first wall 10 and the second wall 11 of the first end 3 and the second end 4.

[0158] In this embodiment of the invention, the cone angle defined by the frusto-conical transition walls 53 is approximately 60°. This therefore results in the outer diameter of each transition wall 53 increasing from the central wall 15 to a corresponding one of the first wall 10 and second wall 11 at a rate of approximately 1.72 mm per mm of length from the central wall 15.

[0159] In this embodiment of the invention, stent 50 comprises a shape memory alloy known as Nitinol and is formed with a perforated structure having gaps 20. The gaps 20a and 20c through the central wall 15 and the transition wall 53 have an area that is less than the area of ​​the gaps 20b through the first wall 10 and the second wall 11 of stent 50. In this embodiment of the invention, the area of ​​the gaps 20a and 20c through the central wall 15 and the transition wall 53 is such that it minimizes, and generally prevents, the material that forms the stenosis 102 from penetrating through the central wall 15 and the transition wall 53.

[0160] In this embodiment of the invention, stent 50 is also coated with a therapeutically active intracranial angiogenesis promoting substance, and a therapeutically active substance to prevent plaque growth.

[0161] The use of the stent 50 and the delivery of the stent 50 to the stenosis 102 of the artery 100 are similar to those already described with reference to the use and delivery of the stent 1 to the stenosis 102 of the artery 100. However, in this embodiment of the invention, when the stent 50 is urged through the hole 34 of the delivery microcatheter 31 by the positioning member 40, the delivery microcatheter 31 is urged proximally to expose both the second end wall 11 and the adjacent transition wall 53, thereby allowing the second wall 11 and the adjacent transition wall 53 to expand after contacting blood in the subject's artery 100, allowing the second wall 11 of the stent 50 to engage and compress the distal unaffected portion 106 of the artery 100 distal to the stenosis 102. However, thereafter, the manipulation of the delivery microcatheter 31 and the positioning member 40 to precisely position the stent 50 within the stenosis 102 is similar to the operations described with reference to the delivery and positioning of the stent 1.

[0162] Referring now to FIG. 11, a stent according to another embodiment of the present invention is illustrated, generally designated by reference number 60. Stent 60 is substantially similar to stent 1, and similar components are identified by the same reference numbers. Stent 60 in this embodiment of the present invention is also particularly suitable for stenting an intracranial artery, such as intracranial artery 100 having a stenosis 102 therein, to maintain or increase the flow rate of blood flow through the stenosis 102 to protect downstream tissues from hypoxia, ischemia, and / or infarction while maintaining the downstream tissue in an ischemic state, and then promote native intracranial angiogenesis. The dimensions of stent 60 are within the dimensional range described with reference to stent 1. The only difference between stent 60 and stent 1 is that in stent 60, central portion 5 is an "hourglass" shape with a minimum outer diameter d1. The transition portion 7 extending from central portion 3 is a truncated cone shape, similar to transition portion 7 of stent 50. In this embodiment of the invention, the area of ​​the gaps 20a and 20c in the central portion 5 and the transition portion 7 has an area that is less than the area of ​​the gaps 20b in the first end 3 and the second end 4. Additionally, in this embodiment of the invention, the area of ​​the gaps 20a and 20c in the central portion 5 and the transition portion 7 is such that it at least minimizes, and preferably prevents, the material forming the constriction 102 from penetrating through the gaps 20a and 20c in the central portion 5 and the transition portion 7.

[0163] Stent 60 and its uses are otherwise substantially similar to those described with reference to stent 1, and have dimensions within the ranges described in connection with stent 1.

[0164] 12, a stent according to a further embodiment of the present invention is illustrated, generally designated by reference number 70. Stent 70 is substantially similar to stent 1, and similar components are identified by the same reference numbers. Stent 70 in this embodiment of the present invention is also particularly suitable for stenting a diseased artery, for example, artery 100 having a stenosis 102 therein, to maintain or increase the flow rate of blood flow through the stenosis 102 to protect downstream tissues from hypoxia, ischemia, and / or infarction while maintaining the downstream tissue in an ischemic state, and then promote native angiogenesis. The diameter dimension of stent 70 is within the diameter dimension range described with reference to stent 1. However, in this case, a perforator artery 109 branches off from artery 100 at a location adjacent to stenosis 102. In this embodiment of the invention, the length L1 of the stent 70 between the first end 3 and the second end 4, including the central portion 5 and the transition portion 7, is of sufficient length to engage the proximal unaffected portion 104 and the distal unaffected portion 106 of the artery such that the first end 3 and the second end 4 are both contained within the annulus 108 defined between the central portion 5, the transition portion 7, and the wall 101 of the artery 100 adjacent the stenosis 102.

[0165] In this embodiment of the invention, the radially outward pressure exerted by the central portion 5 on the stenosis 102 is such that the flow rate of blood through the artery 100 is maintained at approximately 50% of the normal flow rate of blood through the artery 100 prior to the formation of the stenosis 102. However, the radially outward pressure exerted by the central portion 5 on the stenosis 102 is such that it prevents the material forming the stenosis 102 from being overly crushed between the central portion 5 and the arterial wall 101, which would otherwise cause the material of the stenosis to extend longitudinally along the arterial wall 101 and ultimately occlude the perforator artery 109. In this embodiment of the invention, the areas of the gaps 20a in the central portion 5 and the gaps 20c in the transition portion 7 are such that they prevent the material forming the stenosis 102 from penetrating therethrough, but the areas of the gaps 20a and 20c penetrating the central portion 5 and the transition portion 7 are such that they allow blood flow through the central portion 5 and the transition portion 7 into the perforator artery 109.

[0166] 13, a stent according to another embodiment of the present invention, generally designated by reference numeral 80, is illustrated that is suitable for maintaining or increasing the diameter of a hole 103 through the stenosis 102, maintaining or increasing the amount of blood flow through the stenosis 102 to protect downstream tissues from hypoxia, ischemia, and / or infarction while maintaining the downstream tissue in an ischemic state, and then urging the stent 102 in an intracranial artery 100 through the intracranial vasculature to promote and support the native intracranial angiogenesis process. In this embodiment of the present invention, the stent 80 is not a self-expanding material and is therefore configured to be delivered to the stenosis 102 by a balloon microcatheter 82. The balloon microcatheter 82 comprises an elongated microcatheter 83 that terminates at a distal end 84 within a balloon 85. The balloon 85 has a suitable shape such that when inflated, it expands to assume the approximate shape of the stenosis 102 and the proximal unaffected portion 104 and the distal unaffected portion 106 of the artery 100. The stent 80 is configured to assume a shape substantially similar to that of the stent 50 when expanded by the balloon 85 within the stenosis 102, such that the stent 80 includes a first end 3, a second end 4, a central portion 5 having a diameter smaller than the diameters of the first end 3 and the second end 4, and respective frustoconical transition portions 7 extending from the central portion 5 to the first end 3 and the second end 4 when expanded by the balloon 85. The material of the stent 80 is such that after expansion by the balloon 85 within the stenosis 102, the stent 80 retains its expanded shape, thereby maintaining the holes 103 through the stenosis 102 at a diameter that provides a blood flow rate through the stenosis 102 that is approximately 50% of the normal flow rate through the artery 100 prior to the formation of the stenosis 102. The material of the stent is of a perforated structure having gaps 20 that extend through the first end 3, the second end 4, the central portion 5, and the transition portions 7. The gaps 20a and 20c through the central portion 5 and the transition portion 7 are smaller than the gaps through the first end 3 and the second end 4, as already explained with reference to the stent 1.

[0167] Delivery of the stent 80 to the stenosis 102 is substantially similar to the delivery of the stent 1 to the stenosis 102 as previously described with reference to Figures 7 to 9, except that instead of delivering the stent 80 through the delivery microcatheter 31 by the positioning member 40, the stent 1 in an unexpanded state is delivered through the delivery microcatheter 31 on a balloon microcatheter 82. The stent 80 in an unexpanded state is placed on a balloon 85 in a deflated state and delivered through the delivery microcatheter 31 to the stenosis 102. After the balloon 85 with the stent 80 in an unexpanded state is placed within the stenosis 102, the balloon 85 is inflated, which then expands the stent 80 within the stenosis 102, such that the central portion 5 of the stent 80 compresses the stenosis 102 and the first end 3 and second end 4 of the stent 80 compress and engage the proximal unaffected portion 104 and the distal unaffected portion 106 of the artery 100. After positioning of the stent 80 within the stenosis 102 is complete, the balloon 85 is deflated and withdrawn along with the delivery microcatheter, as previously described with reference to Figures 7-9.

[0168] 14a, 14b, and 14c through 17a, 17b, and 17c, there are illustrated four expandable stents according to further embodiments of the present invention, generally designated by reference numerals 90 to 93, which are respectively used in a human or animal subject to open or at least keep open a stenosis in a diseased artery in the intracranial vasculature, maintain or increase the amount of blood flow through the stenosis 102 to protect downstream tissue from hypoxia, ischemia, and / or infarction while maintaining the downstream tissue in an ischemic state, and then promote the natural angiogenesis process. Expandable stents 90 to 93 are substantially similar to expandable stent 1 described with reference to Figures 2 to 6, and similar components are identified by the same reference numerals. The main difference between stents 90 to 93 and stent 1 is that in the expanded state of each of stents 90 to 93, the central portion 5 of each of stents 90 to 93 is eccentrically disposed with respect to the first end 3 and the second end 4. In other words, the main central axis 95 defined by the central portion 5 of each stent 90 to 93 is offset from the first central axis 96 and the second central axis 97 defined by the first end 3 and the second end 4 of a corresponding one of the stents 90 to 93. In this embodiment of the invention, the first end 3 and the second end 4 of the stents 90 to 93 are axially aligned with one another, and therefore the first central axis 96 and the second central axis 97 coincide with one another. However, the major central axis 95 of the core 5 of each stent 90 to 93 extends parallel to the first and second central axes 96 and 97 of the first and second ends 3 and 4 of a corresponding one of the stents 90 to 93 and is laterally offset from the first and second central axes 96 and 97 of the first and second ends 3 and 4. However, it is contemplated that in some cases the major central axis 95 of the core 5 may extend at an angle relative to the first and second central axes 96 and 97 of the first and second ends 3 and 4 of the corresponding stent 90 to 93. The stents 90 to 93 are particularly suited for use in diseased intracranial arteries where the stenosis is asymmetrically located within the diseased artery.

[0169] In stents 90 and 91, the transition section 7 extends perpendicularly from the central section 5 and also from the first and second ends 3 and 4. In stents 92 and 93, the transition section 7 is formed by a transition wall 17 that is asymmetrically frustoconical. Additionally, in stents 90 and 92 of Figures 14a, 14b, and 14c, and 16a, 16b, and 16c, the central wall 15 of the central section 5 and the first and second end walls 10 and 11 of each of stents 90 and 92 extend tangentially to one another along one side of the stent.

[0170] The dimensions of stents 90 to 93 are within ranges similar to those described with reference to stent 1, which is described with reference to Figures 2 to 6. In addition, stents 90 to 93 may or may not be coated with a therapeutically active substance as described with reference to stent 1.

[0171] The use of stents 90-93 within the intracranial vasculature and delivery to a stenosis is similar to that already described with reference to stent 1 and with reference to Figures 2-9. Otherwise, stents 90-93, their use and delivery are similar to stent 1.

[0172] 18, a stent according to another embodiment of the present invention is illustrated, generally designated by reference number 200, which is also suitable for advancing through a delivery microcatheter placed in the intracranial vasculature to a stenosis similar to stenosis 102 in an intracranial artery similar to intracranial artery 100 to achieve a threshold level of expansion to a hole 103 through the stenosis 102 to maintain blood flow through the stenosis 102 to prevent hypoxia, ischemia of the infarct, and to promote and support the natural intracranial angiogenesis process. Stent 200 is substantially similar to stent 1, except that transition section 7 is formed by a frustoconical portion, and for convenience, components similar to those of stent 1 are identified by the same reference numbers. In FIG. 18, stent 200 is illustrated with a support element passing through stent 200. The support element does not form part of stent 200.

[0173] In this embodiment of the invention, stent 200 is a self-expanding stent made from a Nitinol material including struts 23 connected at crown portions 201 defining gaps 20 therebetween, stent 200 having a highly polished surface finish. With reference to FIG. 18, it is noted that the stent includes a first portion 3, a second portion 4, and a central portion 5, similar to the embodiments described with reference to stents 1, 50, 60, 70, and 80. In this embodiment, stent 200 includes a transition portion that is frustoconical defining a cone angle of approximately 110°. Crown portions 201 include V- or U-shaped elements in the stent pattern, with struts 23 interconnecting crown portions 201.

[0174] The stent 200 further comprises a plurality of ring structures, seven in this embodiment of the invention. Each ring structure comprises a plurality of interconnected struts 23 and a crown 201 that are arranged to form a tubular ring about a main central axis 18, a first central axis 21, and a second central axis 22, which coincide in this embodiment of the invention. Adjacent rings are connected together with connectors. In one embodiment, the connectors are configured to space adjacent rings apart from one another. In another embodiment, the crown 201 of a first ring interpenetrates with the crown 201 of an adjacent ring.

[0175] The stent 200 has an expanded state and a collapsed state. In the fully expanded state, the stent 200 is unstressed. The stent 200 is compressed, and therefore stressed, to assume the collapsed state for delivery. In the expanded state, the V angle θ of the crown portion 201 is large, and in the collapsed state, the V angle θ of the crown portion 201 is small. In fact, the V angle θ of the crown portion 201 is less than 5° in the collapsed state. In contrast, the V angle θ of the crown portion 201 is relatively large in the expanded state. Preferably, the V angle θ is greater than 40° in the expanded state. More preferably, the V angle θ is greater than 60°, and even more preferably, the V angle θ is greater than 80°.

[0176] The stent 200 of this embodiment is conformable and designed to protect flow to perforators and branch vessels, such as the perforator artery 109 of FIG. 12. The larger V angle in the expanded configuration is configured to be sized to provide a flow orifice formed by the gaps 20 between the struts 23. The struts 23 are configured to be short and narrow. Short, narrow struts are difficult to steer, but increase the conformability of the stent 200, and the narrow struts 23 maintain flow through the flow orifices formed by the gaps 20. In one embodiment, the struts 23 are configured such that at least one ring in the stent is less than 2 mm in length. In another embodiment, the struts 23 are configured such that at least one ring in the stent is less than 1.5 mm in length. In yet another embodiment, the struts 23 are configured such that at least one ring in the stent is less than 1.0 mm in length. In one embodiment, the struts 23 are configured such that they are less than 80 micrometers wide. In another embodiment, the struts 23 are configured such that they are less than 60 micrometers wide. In yet another embodiment, the struts 23 are configured to be less than 40 micrometers wide.

[0177] In one embodiment, at least one ring of the stent structure comprises six struts 23 with three pairs of opposing crowns 201. In another embodiment, at least one ring of the stent structure comprises eight struts 23 with four pairs of opposing crowns 201. In another embodiment, at least one ring of the stent structure comprises ten struts 23 with five pairs of opposing crowns 201. In another embodiment, at least one ring of the stent structure comprises twelve struts 23 with six pairs of opposing crowns 201. In another embodiment, at least one ring of the stent structure comprises fourteen struts 23 with seven pairs of opposing crowns 201. In another embodiment, at least one ring of the stent structure comprises sixteen struts 23 with eight pairs of opposing crowns 201. In the embodiment of the stent 200 illustrated in FIG. 18, at least one ring of the stent structure comprises eighteen struts 23 with nine pairs of opposing crowns 201. In one embodiment, the number of struts in a first ring is greater than the number of struts in an adjacent ring. In one embodiment, the number of struts in a first ring is equal to the number of struts in an adjacent ring. In one embodiment, the length of the first ring is greater than the length of the second adjacent ring.

[0178] The stent 200 of FIG. 18 is shaped to form an undulating tubular structure having a waist-waisted section, i.e., a central portion 5. In one embodiment, the stent is cut from a Nitinol tube using a laser process, deburred, and grit blasted. Shaping the stent 200 involves heating the stent to a temperature in excess of 400° C. for several minutes until the desired shape is programmed into the stent 200. The stent is cooled, and the stent is electropolished to form a surface with a highly polished finish.

[0179] In one embodiment, the stent comprises a fully connected structure. In such an embodiment, all crowns of the stent are directly or indirectly connected to adjacent crowns. The exceptions to this interconnection are the crowns that define the very distal and very proximal ends of the stent. These crowns are not connected to adjacent crowns.

[0180] In another embodiment, the stent 200 is configured to allow visualization under fluoroscopy. In this embodiment, a highly radiopaque metal is incorporated into the structure. The incorporation of the radiopaque metal allows the interventionist to visualize the distal end of the stent, which may be the first end 3 or the second end 4, the proximal end of the stent, which is the other of the first end 3 and the second end 4, the central portion 5, and the transitions 7 between the central portion 5 and the first end 3 and the second end 4.

[0181] In one embodiment, the radiopaque element comprises gold, platinum, tantalum, or tungsten. In another embodiment, the incorporation of the radiopaque element comprises an alloy of Nitinol and a radiopaque element. In another embodiment, the incorporation of the radiopaque element comprises placing a radiopaque marker into the structure of the stent. In one embodiment, the radiopaque marker comprises a cylindrical slug of radiopaque metal pressed into a plurality of laser drilled holes in the structure of the stent. Suitable radiopaque metals for use in the cylindrical slug include gold, platinum, tantalum, tungsten, or an alloy containing a substantial portion of one or more of these elements.

[0182] In one embodiment, the central portion 5 of the stent 200 is configured to significantly expand the hole 103 of the stenosis 102 without inducing a corresponding expansion in the vessel wall 100 in the region of the stenosis 102. This advantage of the present invention is demonstrated in the following examples of embodiments of a stent similar to stent 200, but deployed in stenoses 102 of various sizes. EXAMPLES

[0183] input Inner diameter of blood vessel 100 D 3mm The outer diameter d of the central portion 5 of the stent 200 is 11.4 mm. External cross-sectional area of ​​blood vessel 100 adjacent to stenosis 102: 7.07 mm 2 External cross-sectional area of ​​the central portion 5 of the stent 200: 1.54 mm 2 Diameter d of hole 103 penetrating stenosis 102: 0.25 mm Cross-sectional area of ​​hole 103 penetrating stenosis 102: 0.046 mm 2 % of stenotic blockages: 92% calculation Increase in cross-sectional area of ​​hole 103 through stenosis 102 3036% Cross-sectional area of ​​the constricted annulus formed by the displacement material of the constriction: 1.490 mm 2 Diameter of the dilated vessel adjacent to the stenosis: 3.30 mm Increase in vessel diameter adjacent to stenosis 10% conclusion At a 92% stenosis, the stent 200 of this embodiment can increase the cross-sectional area of ​​the stenotic hole by over 3000%, yet only expand the vessel diameter by 10%. EXAMPLES

[0184] input Inner diameter of blood vessel 100 D 2.5mm The outer diameter d of the central portion 5 of the stent 200 is 11.2 mm. External cross-sectional area of ​​blood vessel 100 adjacent to stenosis 102: 4.91 mm 2 External cross-sectional area of ​​the central portion 5 of the stent 200: 1.13 mm 2 Diameter d of hole 103 penetrating stenosis 102: 0.3 mm Cross-sectional area of ​​hole 103 penetrating stenosis 102: 0.071 mm 2 % of obstructions due to stenosis 102 88% calculation Increase in cross-sectional area of ​​hole 103 through stenosis 102: 1500% Cross-sectional area of ​​the constricted annulus formed by the displacement material of the constriction: 1.060 mm 2 Diameter of the dilated vessel adjacent to the stenosis: 2.76 mm Increase in vessel diameter adjacent to stenosis 10.3% conclusion At an 88% stenosis, the stent 200 of this embodiment can increase the cross-sectional area of ​​the stenotic hole by over 1500%, but only expand the vessel diameter by 10.3%. EXAMPLES

[0185] input Inner diameter of blood vessel 100 D 2mm The outer diameter d of the central portion 5 of the stent 200 is 11.1 mm. External cross-sectional area of ​​blood vessel 100 adjacent stenosis 102: 3.14 mm 2 External cross-sectional area of ​​the central portion 5 of the stent 200: 0.95 mm 2 Diameter d of hole 103 penetrating stenosis 102: 0.5 mm Cross-sectional area of ​​hole 102 through stenosis 102: 0.196 mm 2 % of stenotic blockages: 75% calculation Increase in cross-sectional area of ​​hole 103 through stenosis 102: 384% Cross-sectional area of ​​the constricted annulus formed by the displaced material of the constriction: 0.754 mm 2 Diameter of the dilated vessel adjacent to the stenosis: 2.23 mm Increase in vessel diameter adjacent to stenosis 11.4% conclusion At a 75% stenosis, the stent 200 of this example can increase the cross-sectional area of ​​the stenotic hole by over 384%, yet the vessel diameter only expands by 11.4%.

[0186] Thus, from the above three examples, it can be seen that different sizes of the stent 200 according to the invention when used in stenoses of different hole diameters can cause a significant increase in the cross-sectional area of ​​the hole of the stenosis for a relatively small increase in the diameter of the vessel resulting from the radially outward action of the central portion 5 of the stent 200 on the material forming the stenosis. Typically, the increase in the cross-sectional area of ​​the hole penetrating the stenosis can be in the range of 300% to over 3000% for an increase in the diameter of the vessel adjacent to the stenosis in the range of 10% to 12%.

[0187] In embodiments of the invention where the stent is not described as being coated with a therapeutically active substance, stents according to the invention are typically, but not necessarily, preferably coated with a therapeutically active substance. Preferred therapeutically active substances for coating stents according to these embodiments of the invention are angiogenesis promoting substances. Stents according to the invention may be coated with any suitable angiogenesis promoting substance, for example methacrylic acid-ecoisodecyl acrylate (MAA-co-IDA, 40% MAA).

[0188] Although the stent according to the present invention is described as comprising Nitinol, it is contemplated that the stent may comprise any suitable biocompatible material, such as stainless steel or cobalt alloy. By providing the stent with a perforated structure, the amount of metal in the stent is minimized, which has the advantage of reducing the thrombogenic potential of the stent, and allows blood to flow from the stented artery to the perforator artery through the central, transition, first and second walls of the stent's central, transition, first and second ends, respectively, as described in connection with stent 80 of FIG. 13. The less material used in the stent, the less likely it is to promote the formation of thrombus after implantation in the artery.

[0189] Although stents according to the present invention have been described as including shape memory metals, the stents may be non-shape memory metals and may also be non-self-expanding materials. For example, it is contemplated that the stent may be made from a material that is a non-self-expanding material, such as in the case of stent 80. Moreover, one of ordinary skill in the art will readily recognize that stent 80 may be made from a self-expanding shape memory material.

[0190] Although the stent according to the invention has been described for stenting a stenosis in an intracranial artery, the stent according to the invention may be used for stenting a stenosis in any intracranial vessel, such as a vein, lumen, or other such intracranial vessel.

[0191] In other embodiments of the stent, a biocompatible film or membrane may be provided on at least one surface of the stent. The film or membrane may be perforated or non-perforated.

[0192] The film or membrane may be a non-woven fabric made from plastic fibers, which is adhered to or forms a bond with the walls of the stent. The film or membrane may also be made into thin strands that can be woven into a lattice that is layered on the stent. The membrane and / or lattice may be disposed on the stent in a manner that is aligned with the struts of the stent, or alternatively not aligned. In some embodiments of the invention, the membrane may have a porous structure that can accommodate pharmaceutical materials and release these materials into the surrounding vessel and plaque under physiological conditions.

[0193] The membrane may optionally be embedded or coated with one or more pharmaceutical or other compositions that have a desired effect on the properties of the stent. This addresses the challenge of coating the surface of a stent with a pharmaceutical material. These compositions can release drugs over time into the surrounding tissue, the vessel surface, or into the plaque. Growth inhibitors such as paclitaxel and rapamycin may be advantageous. Other examples are materials that prevent thrombosis or prevent liquid embolic agents or adhesives from adhering to the membrane and / or stent.

[0194] The film or membrane may be suitably made of a polymeric material, such as polyurethane, polytetrafluoroethylene, polyester, polyamide, or polyolefin. These polymeric membranes do not easily adhere to the stent. Conventionally, the stent membrane is mechanically applied to the vessel wall or plaque by the radial force of the expanded stent. However, in the present invention, the center of the stent does not contact the arterial wall. The stent according to the present invention, having a membrane made of a polymeric material that does not easily adhere to the wall of the stent, uses a suitable connection of the membrane to the stent, typically a mechanical connection. This type of connection is also useful when the stent needs to be re-inserted into a microcatheter for adjustment or repositioning of the stent to another area.

[0195] The membrane of the stent may be conveniently made by spraying onto the stent wall, provided that the stent wall has an affinity with the polymer for forming a suitable bond, or by electrospinning a nonwoven fabric around the struts of the stent, where the fibers of the membrane are separated from the polymer solution by applying an electric current and deposited on the substrate. The technique of electrospinning is well known in the art and will not be described in further detail here. The deposition causes the fibers to coalesce into a nonwoven fabric, which can be formed into a braid that can be woven, if so selected. The fibers generally have a diameter of 100 to 1000 nm. The membranes made by electrospinning are very thin, uniform in thickness, and can easily form bonds with the stent wall. Such membranes have sufficient strength to withstand the mechanical stresses of compression of the stent into a deliverable state and of maneuvering the stent along and into tortuous vessels. Such membranes can be easily mechanically punctured as needed without forming openings that cause ruptures or cracks. The thickness and length of the fibers can be controlled by the electrospinning process. Examples of such membranes include poly(lactide-co-caprolactone) (PLCL), which may have a degradation time of 6-18 months, poly(caprolactone) (PCL), which may have a degradation time of 2-3 years, or more rigid materials such as polylactide (PLA), poly(lactide-co-glycoside) (PLGA), polyacrylonitrile (PAN), or polyurethane (PU).

[0196] The membrane may be composed of a single layer or multiple layers. The multiple layers may be made by different methods, for example, the first layer may be made by electrospinning, the second layer by spray coating, and the third layer by electrospinning. An active pharmaceutical or other agent may be embedded in one or more of these layers. The agent may be released by diffusion or by degradation or corrosion of the layers of the membrane. Radiopaque materials may also be embedded in the membrane to make them more easily visible to the techniques used during stent implantation. In particular, to further promote and support angiogenesis, the stent may be coated with methacrylic acid-eco-isodecyl acrylate (MAA-co-IDA, 40% MAA) or similar materials known to promote angiogenesis.

[0197] The membrane may be interwoven with graphene to improve its strength and flexibility. Additionally or alternatively, the membrane may include a thin film of Nitinol.

[0198] Stents can be made from biodegradable materials that have a limited life span. Polymer-based stents are traditionally based on poly(L-lactide) (PLLA), chosen because of its ability to maintain a radially strong scaffold that degrades over time into lactic acid, a naturally secreted molecule that the body can use for metabolism. Other polymers in development include tyrosine polycarbonate and salicylic acid.

[0199] Although a particular delivery system has been described for delivering the stent 1 to a stenosis in an intracranial artery, other suitable delivery means may be used, for example, via a balloon catheter. The stent according to the invention is made to be inserted without the need for pre-dilatation of the blood vessel. However, in some conditions, pre-dilatation of the ICAS may be indicated to navigate the delivery microcatheter or balloon microcatheter past the stenosis focal point. Similarly, the stent may be made so that post-dilatation (expansion of the stent by a balloon after insertion) is not required. However, in some cases, such as when there is a severely calcified atherosclerotic plaque, post-dilatation may be advantageous. Thus, the stent does not require pre- or post-dilatation per se, but is compatible with pre- and post-dilatation. If the stent is not self-expanding, a further aspect of the invention is to provide a shaped expansion balloon, which expands the outer end of the stent more than the inner section, resulting in an expanded stent shape with dimensions as already described for self-expanding stents, as described with reference to Figures 2 to 12 and Figures 14 to 18.

[0200] The stents according to the invention are described as having perforated expandable walls, which may be folded in a non-expanded state to form a low profile that can be delivered into the arterial system. In the low profile configuration, they can be delivered into smaller intracranial vessels and arteries through smaller microcatheters. The configuration of the stent can be an open, closed, or woven stent design. The structure of the stent is exemplified as a closed cell type. The cell structure of the stent makes the stent self-expandable after insertion into the artery. The stent according to the invention assumes a dumbbell shape after expansion.

[0201] The stent may be configured with a reattachment system so that it can be repositioned even when fully delivered, and the operator may readjust the deployment until completely satisfied with the positioning of the stent with respect to the stenosis. Conventional electrolytic cutting of an intravascular stent implant involves the use of a galvanic eroding structure at the end of the delivery wire at the connection point between the delivery wire and the intravascular stent implant. Such a device may use a voltage applied to the intravascular implant that acts as an anode for electrothrombosis. Alternatively, a mechanical reattachment system may be used.

[0202] Accurate deployment of the stent may be achieved through appropriately positioned radiopaque markers visible under fluoroscopy, as known in the art. Optionally, markers may be provided at the proximal and distal ends of the central portion of the stent. Alternatively or in addition, the central portion of the stent may be made more radiopaque by providing a gold coating on the struts of the stent. Similarly, the entire stent may be substantially coated with a radiopaque marker, such as gold. Of course, any other radiopaque marker may be provided on the stent.

[0203] If the stent is made from a biodegradable material and has a limited life span, the stent will remain in place until it dissolves. Antiplatelet therapy is often recommended for patients who receive a stent. If the stent is biodegradable, the antiplatelet medication may be discontinued after the stent dissolves.

[0204] If the stents are not biodegradable, they are left in place to provide a scaffold for the endothelial cells to grow onto over time.

[0205] The stent is deployed over the stenotic area (as described above). A narrower central portion is placed into the hole of the stenosis, either maintaining the diameter of the hole or increasing it enough to restore blood flow distally. The diameter of the central portion is sufficient to open the stenosis and restore blood flow, but does not completely open the stenosis, rather achieving approximately 50% of the diameter of a healthy artery.

[0206] The relatively small diameter of the central portion of the stent according to the present invention serves to minimize the amount of material from the stenosis that is forced into the adjacent unoccupied area of ​​the artery. Furthermore, the suboptimal angioplasty achieved by the stent minimizes the likelihood of disrupting the plaque of the stenosis, thus minimizing the likelihood of distal vessel stenosis.

[0207] Conventional self-expanding stents are fixed in place by the outward force of the stent on the vessel wall along the entire length of the stent. This outward force presses a significant amount of atheromatous debris against the vessel wall. The atheromatous debris that presses against the vessel wall can be pushed into adjacent side branches or small vessels (snow shoveling). The arterial structure in the brain is highly branched, and the presence of numerous side branches can easily cause snow shoveling when a significant amount of atheromatous debris is pressed against the arterial wall.

[0208] During use of the stent according to the invention, the two larger diameter first and second ends press against the arterial wall of the artery, stabilizing and supporting the narrower central portion, whose function is to open the stenosis. This structure minimizes the amount of plaque pushed along the arterial wall by the stent, since only the first and second ends contact the arterial wall.

[0209] The central portion of the stent is made to exert a greater radially outward force than the force exerted by the first and second ends.

[0210] As explained above, having the central and transitional portions of the stent of the present invention formed with relatively small gaps minimizes, and generally prevents, material from the stenosis from passing through the gaps in the central and transitional portions of the stent of the present invention. If material from the stenosis is forced through the gaps in the stent, small particles of plaque may be released from the stent and return to the vessel, a so-called "cheese-grating" effect. These small plaque particles may become suspended and enter the peripheral circulation and travel deeper into the cerebral vasculature, potentially causing distal embolization. By minimizing the area of ​​the gaps in the central and transitional portions of the stent of the present invention, the "cheese-grating" effect is minimized.

[0211] Similarly, a dual layer structure for a stent according to the present invention can be used to further reduce the "cheese grater" effect of atherosclerotic plaque.

[0212] A biocompatible film or membrane may be provided on the surface of the stent to further reduce the occurrence of the "cheese shavings" effect, thereby minimizing the release of distal emboli into the intracranial circulation.

[0213] The stent of the present invention provides an early stage non-medical treatment for ICAS and reduces complications associated with conventional stent treatment of ICAS by, for example, minimizing plaque being pushed into the stent interstices ("cheese shavings"), reducing plaque being pushed by the stent into the side branch arteries (snow shoveling), reducing the risk of intracranial hyperperfusion injury, providing low shear stress to reduce the occurrence of restenosis, minimizing plaque occluding the stent, and ultimately reducing morbidity and mortality.

[0214] It is also contemplated that a stent according to the present invention may comprise a composite structure, for example, Drawn Filled Tube Nitinol (DFT).

[0215] It is also contemplated that a stent according to the present invention may be coated with graphene.

[0216] Although the stent according to the invention has been described and illustrated with the axial lengths of the first and second walls at the first and second ends being equal, it is contemplated that in some embodiments of the invention, the axial lengths of the first and second walls at the first and second ends of the stent may be different. For example, it is contemplated that the first wall at the first end, which would be located at the proximal end of the stenosis, may have an axial length that is shorter than the axial length of the second wall at the second end. Alternatively, the axial length of the second wall at the second end of the stent may be shorter than the axial length of the first wall at the first end of the stent. In general, when a perforator vessel is located relatively close to either the proximal or distal end of a stenosis, the axial length of the first or second wall at the first or second end may be shorter than the axial length of the other of the first and second walls at the first and second ends of the stent, depending on the stent, to engage the unaffected portion of the artery adjacent the stenosis between the stenosis and the perforator vessel without occluding or covering the perforator vessel. For example, when a perforator vessel is relatively close to a stenosis on the distal end of the stenosis, the second wall at the second end of the stent has an axial length shorter than the axial length of the first wall at the first end of the stent, and the axial length of the second wall at the second end is such that the second end of the stent is adjacent the stenosis and engages the unaffected portion of the artery between the stenosis and the adjacent perforator vessel.

[0217] Thus, it is contemplated that the axial lengths of the first and second walls at the first and second ends of a stent according to the present invention may be the same or different.

[0218] In addition, it will be appreciated that the outer and inner diameters of the first and second ends may be different, for example, if the diameter of the blood vessel at each opposite end of the stenosis is different, the diameters of the first and second ends will be selected accordingly.

[0219] It is also contemplated that when the stent 70 described with reference to Figure 12 is positioned at a stenosis, instead of the second end 4 of the stent being disposed distal to the perforator 109, the stent may be biased proximally to dispose the second end 4 of the stent between the stenosis and the perforator 109. It is further contemplated that when a perforator 109 branches off from an artery or vessel adjacent to the stenosis, either proximal or distal to the stenosis, and there is no space between the stenosis and the branched perforator vessel, adjacent ones of the first and second ends of the stent may be positioned to extend beyond the perforator vessel 19, with the blood supply being accommodated within the perforator vessel 103 through gaps 20b through corresponding ones of the first and second walls of the associated ones of the first and second ends 3 and 4 of the stent. [Explanation of symbols]

[0220] 1 Stent 3 First end 4 Second end 5 Center 7 Transition section 10 The First Wall 11 The Second Wall 12 First Hole 13 Second Hole 15 Center wall 16 holes 17 Transition Wall 18 Main center axis 19 Free end, perforator vessel 20 Gap 20a, 20b, 20c Gap 21 First central axis 22 Second central axis 23 Strut 30 Delivery System 31 Delivery Microcatheter 32 Proximal end 33 Distal end 34 Slotted hole 40 Elongated positioning member 41 Proximal end 42 Distal end 44 Releasable coupling mechanism 50 Stents 52 Cone-shaped wall section 53 Transition Wall 60 Stents 70 Stents 80 Stents 82 Balloon Microcatheter 83 Long and thin microcatheter 84 Distal end 85 Balloon 90 to 93 Stents 95 Main center axis 96 First central axis 97 Second central axis 100 Affected intracranial arteries 101 Wall 102 Stenosis 103 holes 104 Proximal unaffected portion 105 Proximal end 106 Distal unaffected part 107 Distal end 108 Ring 109 Perforator Arteries 200 Arteries, stents 201 Crown section

Claims

1. 1. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the intracranial stent configured to have a first end (3) when the intracranial stent is in an expanded state, a second end (4) spaced from the first end (3) when the intracranial stent is in an expanded state, and a central portion (5) located between the first end (3) and the second end (4) when the intracranial stent is in an expanded state, the central portion (5) having an outer diameter smaller than an outer diameter of the first end (3) and an outer diameter larger than an outer diameter of the second end (4). an expandable intracranial stent having an outer diameter smaller than the diameter of the central portion of the stent, the central portion terminating at each opposite end with a respective transition portion 7, each of the transition portions 7 being generally frustoconical in shape and connecting adjacent ends of the central portion to a corresponding one of the first end 3 and the second end 4, the first end 3 and the second end 4 and the central portion 5 forming a pattern of interstices 20, the intracranial stent having an unexpanded state with a maximum outer diameter not exceeding 0.6 mm and being self-expanding to an expanded state.

2. The expandable intracranial stent of claim 1, wherein the central portion (5) of the stent in its expanded state is substantially hourglass shaped.

3. The stent has a central portion (5) defining a longitudinally extending main central axis (95), a first end portion (3) defining a longitudinally extending first central axis (96), and a second end portion (4) defining a longitudinally extending second central axis (96); 2. The expandable intracranial stent of claim 1, wherein the central portion (5), the first end portion (3), and the second end portion (4) are configured such that, in an expanded state of the stent, the main central axis (95) is offset from the first central axis (96) and the second central axis (96) or extends at an angle greater than 0° relative to the first central axis (96) and the second central axis (96).

4. An expandable intracranial stent as described in claim 1, wherein the outer diameter of the core (5) of the stent in its expanded state is within the range of 25% to 70% of the outer diameter of one of the first end (3) and the second end (4), and preferably the outer diameter of the core (5) of the stent in its expanded state is within the range of approximately 50% of the outer diameter of the first end (3) and the second end (4).

5. An expandable intracranial stent as described in claim 1, wherein the outer diameters of the first end (3) and the second end (4) of the stent in its expanded state are the same or different, and the axial lengths of the first end (3) and the second end (4) of the stent in its expanded state are the same or different.

6. An expandable intracranial stent as described in claim 1, wherein the outer surfaces of the first end walls (10) and second end walls (11) of the first end (3) and second end (4) of the stent, as well as the outer surface of the central wall (15) of the central portion (5) of the stent, may be non-cylindrical, e.g., concave or convex, along their axial length, in the expanded state.

7. 2. The expandable intracranial stent of claim 1, wherein the first and second ends and the core are one of a cage-like structure, a braided structure, and a perforated structure that defines gaps (20) between the core and the first and second ends and gaps (20) between the transition sections in an expanded state of the stent, and an area of ​​the gaps (20) in the core is smaller than an area of ​​the gaps (20) between the first and second ends and an area of ​​the gaps (20) between the transition sections in an expanded state of the stent, the area of ​​the gaps (20) in the core is smaller than an area of ​​the gaps (20) between the first and second ends and the area of ​​the gaps (20) between the transition sections.

8. The expandable intracranial stent of claim 1, wherein the gaps (20) are formed by a plurality of struts (23) having a width of less than 80 micrometers.

9. 9. The expandable intracranial stent of claim 8, wherein the struts (23) forming the gaps (20) form rings extending around a corresponding one of a main central axis (18) defined by the central portion (5) of the stent, a first central axis (21) defined by the first end portion (3) of the stent, or a second central axis (22) defined by the second end portion (4) of the stent, each of the rings defining a plurality of crowns (201), adjacent rings being connected by adjacent crowns (201) to form a corresponding one of the central portion (5), the first end (3) or the second end (4), each of the crowns (201) being defined by an adjacent pair of struts (23), a length of each strut (23) of at least one ring in an expanded state of the stent is less than 2 mm, preferably less than 1 mm, and preferably a width of the struts (23) forming the rings is less than 80 micrometers.

10. 10. The expandable intracranial stent of claim 9, wherein each pair of struts (23) defining a crown portion (201) of each ring defines a V angle of a corresponding crown portion (201), the V angle of each crown portion (201) being less than 5° in the unexpanded state of the stent and the V angle being greater than 40° in the expanded state of the stent.

11. An expandable intracranial stent as described in claim 1, wherein the axial length of the central portion (5) of the stent in the expanded state is in the range of 5 mm to 20 mm, preferably the axial length of the first end (3) of the stent in the expanded state is in the range of 2 mm to 4 mm, and advantageously the axial length of the second end (4) of the stent in the expanded state is in the range of 2 mm to 4 mm.

12. The expandable intracranial stent of claim 1, wherein the outer diameter of the stent in an unexpanded state is substantially constant along the entire length of the stent.

13. 10. The expandable intracranial stent of claim 1, wherein the stent is coated with a therapeutically active agent, the therapeutically active agent being coated on the stent and including one or both of an angiogenesis promoting agent or a plaque inhibiting agent.

14. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the intracranial stent having a first end (3) when the intracranial stent is in an expanded state, a second end (4) spaced from the first end (3) when the intracranial stent is in an expanded state, and a central portion (5) located between the first end (3) and the second end (4) when the intracranial stent is in an expanded state, the outer diameter of the central portion (5) being between 25% and 7% of the outer diameter of the first end (3). 0% or in the range of 25% to 70% of the outer diameter of the second end (4), a pattern of gaps (20) is formed in the first and second ends (3) and the central portion (5), and when the intracranial stent is in an expanded state, an area of ​​the gaps (20) in the central portion (5) is less than the area of ​​each of the gaps (20) in the first and second ends (3) and (4), and the intracranial stent has a maximum outer diameter of no more than 0.6 mm in an unexpanded state.

15. The expandable intracranial stent of claim 4, wherein the gaps (20) are formed by a plurality of struts (23) having a width of less than 80 micrometers.

16. 1. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the stent in an expanded state comprising a first end (3) having a first hole (12) therethrough, a second end (4) spaced from the first end (3) and having a second hole (13) therethrough, and a core (5) extending between the first end (3) and the second end (4) and having a central hole (16) therethrough and connecting the first hole (12) and the second hole (13) of the first end (3) and the second end (4) to each other, the core (5) having an outer cross-section smaller than the outer cross-sections of the first end (3) and the second end (4), and said first and second ends (3) (4) are configured in an expanded state of the stent to engage an arterial wall of the blood vessel on respective opposite ends of the stenosis to anchor the stent within the blood vessel, and said central portion (5) is configured in an expanded state of the stent to penetrate a hole through the stenosis and compress material forming the stenosis with an outward radial pressure to at least prevent further narrowing of the hole through the stenosis, and said central portion (5) in the expanded state of the stent is configured to apply a radially outward pressure to material forming the stenosis that is greater than the radially outward pressure applied to the wall of the blood vessel by said first end (3) and said second end (4).

17. 1. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the intracranial stent configured to have a first end (3) when the intracranial stent is in an expanded state, a second end (4) spaced from the first end (3) when the intracranial stent is in an expanded state, and a central portion (5) located between the first end (3) and the second end (4) when the intracranial stent is in an expanded state, the central portion (5) having a wall thickness in the range of 0.02 mm to 0.15 mm and an outer diameter smaller than the outer diameters of the first end (3) and the second end (4). an expandable intracranial stent having a first end (3) and a second end (4) and a central portion (5) formed with a pattern of gaps (20), and respective transition portions extending from the first end (3) and the second end (4) to corresponding ends of the central portion (5) connect the first end (3) and the second end (4) to respective opposite ends of the central portion (5), and when the intracranial stent is in an expanded state, an axial length of the first end (3) is the same as or different from an axial length of the second end (4), and the intracranial stent self-expands to an expanded state.

18. The expandable intracranial stent of claim 17, wherein the maximum outer diameter of the stent in an unexpanded state is 0.6 mm or less.

19. 1. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the stent in an expanded state comprising a first end (3) having a first hole (12) therethrough, a second end (4) spaced from the first end (3) and having a second hole (13) therethrough, and a core (5) extending between the first end (3) and the second end (4) and having a central hole (16) therethrough and connecting the first hole (12) and the second hole (13) of the first end (3) and the second end (4) to each other, the core (5) having an outer cross-section smaller than the outer cross-sections of the first end (3) and the second end (4), the core (5) terminating at opposite ends in respective transition sections (7). an expandable intracranial stent including a central portion (5) connected to and in communication with the first end (3) and the second end (4) through the transition portion (7), the transition portion (7) in the expanded state of the stent configured to engage with the material forming the stenosis adjacent to their respective opposite ends, the first end (3) and the second end (4) configured to engage with an arterial wall of the blood vessel on their respective opposite ends of the stenosis in the expanded state of the stent to anchor the stent within the blood vessel, and the central portion (5) configured to penetrate a hole through the stenosis in the expanded state of the stent and compress the material forming the stenosis with a radially outward pressure to at least prevent further narrowing of the hole through the stenosis.

20. An expandable intracranial stent as claimed in claim 19, wherein the two transitional sections (7) in the expanded state of the stent are frustoconical in shape.

21. The expandable intracranial stent of claim 20, wherein the transition portion (7) in the expanded state of the stent is asymmetric in shape.

22. An expandable intracranial stent as described in any one of claims 19 to 21, wherein the stent is configured such that when placed in an artery, the central portion (5) and the transition portion (7) together with the arterial wall adjacent the stenosis define an annulus containing material forming the stenosis.

23. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the stent in an expanded state being configured to have a first end (3) having a first hole (12) therethrough, a second end (4) spaced from the first end (3) and having a second hole (13) therethrough, and a core (5) extending between the first end (3) and the second end (4) and having a central hole (16) therethrough and connecting the first hole (12) and the second hole (13) of the first end (3) and the second end (4) to each other, the core (5) being configured to extend between the first end (3) and the second end (4).

1. An expandable intracranial stent having an outer cross-section smaller than the outer cross-sections of said first end (3) and said second end (4), said first end (3) and said second end (4) being configured in an expanded state of the stent to engage an arterial wall of the blood vessel on respective opposite ends of the stenosis to anchor the stent within the blood vessel, and said central portion (5) being configured in the expanded state of the stent to penetrate a hole through the stenosis and compress material forming the stenosis with a radially outward pressure to increase the diameter of the hole through the stenosis to within 25% to 80% of an unaffected portion of the blood vessel adjacent the stenosis.

24. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the stent in an expanded state being configured to have a first end (3) having a first hole (12) therethrough, a second end (4) spaced from the first end (3) and having a second hole (13) therethrough, and a core (5) extending between the first end (3) and the second end (4) and having a central hole (16) therethrough and connecting the first hole (12) and the second hole (13) of the first end (3) and the second end (4) to each other, the core (5) being configured to extend between the first end (3) and the second end (4) and having a central hole (16) therethrough and connecting the first hole (12) and the second hole (13) of the first end (3) and the second end (4) to each other, the core (5) being configured to extend between the first end (3) and the second end (4).

1. An expandable intracranial stent having an outer cross-section smaller than an outer cross-section of an end portion (4), wherein the first end portion (3) and the second end portion (4) are configured to engage an arterial wall of the blood vessel on respective opposite ends of the stenosis in an expanded state of the stent to anchor the stent within the blood vessel, and wherein the central portion (5) is configured to penetrate a hole through the stenosis in an expanded state of the stent and compress material forming the stenosis with a force that expands the diameter of the hole through the stenosis to increase the blood flow velocity through the stenosis to a range of 25% to 80% of the normal blood flow velocity through the blood vessel without the stenosis.

25. 1. An expandable intracranial stent configured for stenting a stenosis in an intracranial blood vessel, the stent in an expanded state being configured to have a first end (3) having a first hole (12) therethrough, a second end (4) spaced from the first end (3) and having a second hole (13) therethrough, and a core (5) extending between the first end (3) and the second end (4) and having a central hole (16) therethrough, the central hole (5) communicating the first hole (12) and the second hole (13) of the first end (3) and the second end (4) with each other, a central portion (5) having an outer cross-section smaller than the outer cross-sections of said first end (3) and said second end (4), said first end (3) and said second end (4) being configured in an expanded state of the stent to engage an arterial wall of said blood vessel on respective opposite ends of said stenosis to anchor said stent within said blood vessel, and said central portion (5) being configured in an expanded state of the stent to penetrate a hole through said stenosis and compress material forming said stenosis with sufficient force to dilate said stenosis without the need for pre-dilatation of said stenosis.

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