Improved electrode and percutaneous lead wire and method of use

Abstract

To provide an improved implantable pulse generator (IPG) for using optical reflectometry in spinal cord stimulation (SCS).SOLUTION: A percutaneous lead wire 1400 is provided which includes a generally tubular, multi-duct, flexible lead wire body. The lead wire body supports a distal set of electrodes and a proximal set of contacts which are connected by conductors in the ducts. The lead wire body further houses an optical fiber with a side firing section. The side firing section is held adjacent an optical transmission window, integrally formed with the flexible lead wire body. A cylindrical ferrule is provided to position the fiber in a header of an IPG.SELECTED DRAWING: Figure 13A

Description

[Technical field]

[0001] The present invention relates to an improved Implantable Pulse Generator (IPG) and header combination for the use of optical reflectometry in Spinal Cord Stimulation (SCS). [Background technology]

[0002] Chronic pain can result from a variety of conditions, particularly from nerve injury, as in the case of neuropathic pain, or from chronic stimulation of mechanical nociceptors, such as spinal pain. Functional ability can be severely affected by pain that is often refractory to pharmacological and surgical treatments. In such cases, spinal cord electrical stimulation ("SCS") is an effective treatment for pain by modulating the physiological transmission of pain signals from the periphery to the brain. This can be achieved by applying electrical stimulation to the spinal cord via an electrode array implanted adjacent to the spinal canal.

[0003] Electrode leads for spinal cord stimulator (SCS) systems can be classified as either "percutaneous leads" or "surgical leads." Percutaneous lead arrays contain multiple cylindrical electrode contacts arranged collinearly along a thin cylindrical cable that is introduced into the body via an injection needle. In contrast, surgical leads are generally comprised of an array of electrode contacts protruding to one side from a thin lead body that is composed of a flexible panel that is placed directly into the dorsal epidural space via a surgical laminotomy.

[0004] In FIG. 1, the spinal column 1 includes a number of vertebrae, grouped into four sections or types: lumbar 2, thoracic 3, cervical 4, and sacral 5. The cervical vertebrae 4 include the first cervical vertebra (C1) through the seventh cervical vertebra (C7). Just below the seventh cervical vertebra is the first of twelve thoracic vertebrae 3, including the first thoracic vertebra (T1) through the twelfth thoracic vertebra (T12). Just below the twelfth lumbar vertebra 3 are the five lumbar vertebrae 2, including the first lumbar vertebra (L1) through the fifth lumbar vertebra (L5), the fifth lumbar vertebra attached to the sacral vertebrae 5 (S1 through S5), and the sacral vertebrae 5, which naturally fuse together in adults.

[0005] In FIG. 2, a representative vertebra 10, the thoracic vertebra, is shown to have several notable features commonly shared with the lumbar vertebra 2 and cervical vertebra 4. The thick oval-shaped portion of bone forming the anterior surface of the vertebra 10 is the vertebral body 12. The vertebral body 12 is attached to a bony vertebral arch 13 through which the spinal nerves 11 pass. The vertebral arch 13 forming the posterior portion of the vertebra 10 is composed of two pedicles 14, which are short stout processes extending from the sides of the vertebral body 12 and the bilateral laminae 15. Broad plates projecting from the pedicles 14 join in a triangular shape to form a hollow archway, the spinal canal 16. Spinous processes 17 project from the junctions of the bilateral laminae 15. Transverse processes 18 project from the junctions of the pedicles 14 and the bilateral laminae 15. The structure of the vertebral arches protects the spinal cord 20 and spinal nerves 11 which pass through the spinal canal.

[0006] Surrounding the spinal cord 20 is the dura mater 21, which contains cerebrospinal fluid (CSF) 22. The epidural space 24 is the space within the spinal canal outside the dura mater.

[0007] 1, 2 and 3, an electrode array placement for spinal cord stimulation according to the prior art is shown. An electrode array 30 is placed in the epidural space 24 between the dura 21 and the wall of the spinal canal 16 toward the dorsal aspect of the spinal canal nearest the bilateral lamina 15 and spinous processes 17.

[0008] 4 shows a prior art surgical electrode array 30 including electrode contacts 35 sealed in a elastomeric housing 36. The electrode array 30 has an electrode lead 31 connected to an electrical pulse generator 32 and a controller 33. Each electrode contact has a separate conductor within the electrode lead 31 so that the current to each contact can be controlled independently.

[0009] Spinal cord stimulators often include an implantable pulse generator (IPG) 32 that monitors and delivers the electrical stimulation to the spine via the electrode array 31. The IPG is typically implanted subcutaneously near the upper buttocks or flank and is contained in a titanium can that draws power from a battery. The electrode array is connected to the IPG using subcutaneous leads.

[0010] The subcutaneous leads connect to electrode contacts on the header of an IPG and are typically secured to the IPG with anchor screws.

[0011] The IPG delivers pulses of electrical current to the electrode array, which passes through the electrodes to target neurons in the ascending tracts of the spinal cord. The resulting electric field disrupts pain perception. Controlling the amplitude of the stimulating electric field is paramount to the success of spinal cord stimulation. Delivering insufficient current will fail to depolarize the target neurons, rendering the treatment ineffective. Conversely, delivering too much current will depolarize the targeted neurons but stimulate additional cell populations, resulting in the perception of noxious stimulation.

[0012] Establishing a consistent therapeutic and harmless level of stimulation is premised on establishing an ideal current density in the target neurons of the spinal cord. In principle, this should be a simple matter of establishing an optimal electrode current, taking into account the local bulk conductivity of the surrounding tissue. In reality, however, because the spinal cord is suspended in cerebrospinal fluid within the spinal canal, movement of the spinal cord changes the optimal electrode current as a function of the patient's position and activity. It has been shown that significant changes occur in the distance between the epidural electrode array and the target spinal neurons. Therefore, optimal stimulation requires dynamic adjustment of the electrode stimulation current as a function of the distance between the electrode array and the spinal cord.

[0013] Thus, dynamic modulation of electrode currents of a spinal cord stimulator as a function of the distance between the electrode array and the spinal cord has several advantages: excessive stimulation currents can be avoided, thereby reducing the possibility of harmful stimulation and potentially reducing device power consumption, and insufficient stimulation currents can be avoided, thereby eliminating periods of reduced therapeutic efficacy.

[0014] Dynamic modulation of electrode current can be controlled through the use of optical reflectometry to determine the thickness of the dorsal cerebrospinal fluid (dCSF) column between the spinal cord and the electrode array. Optical signals are sent to the surrounding tissue and collected by a sensor, and the approximate distance between the electrode and the spinal cord is calculated. The magnitude of stimulation is modified accordingly to provide the optimal current for pain relief. An example of this technique is shown in U.S. Patent No. 10,035,019 to Wolf II, which is incorporated herein by reference.

[0015] One challenge for subcutaneous IPG implants is the long-term survival of the IPG in the harsh in vivo environment. Intrusion of body fluids can result in functional and mechanical degradation. Proteins commonly found in blood and interstitial fluids are known to bind metal ions and cause corrosion. Some materials can trigger immune responses and alter the local pH balance at the implantation site. Specialized polymers and epoxies can circumvent some of these issues, but often exhibit unacceptably high levels of cytotoxicity. As a result, it is essential that the IPG internal components are maintained in a sealed environment and that the external IPG components are biocompatible.

[0016] Similarly, another challenge with subcutaneous IPG implants is that the surrounding tissue tends to deteriorate around the IPG due to the increased pressure that the edges of the IPG place on the tissue. Erosion of the device through the skin can occur, usually at the corners of the device where pressure is concentrated, necessitating revision surgery to replace the device.

[0017] Another challenge to the implementation of optical reflectometry for adaptive spinal cord stimulation is that leads that are imprecisely coupled to the IPG header are susceptible to movement that disturbs the stability of the optical signal. An unstable optical signal results in an undesirable signal-to-noise ratio that results in errors in the delivered current and inaccurate stimulation.

[0018] Yet another challenge with subcutaneous IPG implants is extended recharge times. IPGs that contain rechargeable batteries must be periodically recharged. Electromagnetic induction has evolved as the most widely used technology to recharge IPG batteries. However, during recharge, eddy currents are generated in the casing of the IPG that cause a temperature rise. To maintain acceptable temperatures, the charge duty cycle is typically shorter than ideal, thereby lengthening the time required to recharge.

[0019] The prior art has attempted to address these challenges in a number of ways.

[0020] For example, U.S. Patent No. 6,011,993 to Tziviskos et al. describes a method for producing a strong ceramic case capable of housing electronic devices with a good hermetic seal for implantation in the body, but Tziviskos does not describe how to effectively connect or secure leads or optical fibers.

[0021] As another example, U.S. Patent No. 6,324,428 to Weinberg et al. describes a medical implant that includes internal electronics in a preferred configuration that minimizes the implant's volume and facilitates implantation, but Weinberg does not describe design features that reduce erosion of the device, nor does he describe methods for coupling electrical leads or optical fibers to the implant.

[0022] Similarly, U.S. Patent No. 7,742,817 to Malinowski et al. describes an IPG with connectors for electrical leads and an epoxy coating for biocompatibility, although Malinowski does not disclose the use of optics in the design to achieve the appropriate pulse strength.

[0023] Deficiencies exist in the prior art related to the accuracy of lead connections when using optical reflectometry for spinal cord stimulation. Thus, there is a need in the art for improved IPG cases, connectors, leads, and electrodes that provide a stable optical signal while optimizing the longevity of the IPG. [Brief description of the drawings]

[0024] In the detailed description of the preferred embodiments presented below, reference is made to the accompanying drawings. [Figure 1] FIG. 1 is a lateral view of the human spine showing the approximate location of an electrode array for spinal cord stimulation. [Diagram 2] Figure 2 shows an axial view of the thoracic spine showing the location of the spinal cord and electrode arrays for spinal cord stimulation. [Diagram 3] FIG. 3 shows a sagittal section of the human spine showing the approximate location of an electrode array for spinal cord stimulation. [Figure 4] FIG. 4 shows a prior art surgical electrode array and lead connector for spinal cord stimulation. [Diagram 5] FIG. 5 shows a schematic diagram of a preferred embodiment IPG charging and communication system. [Figure 6A] FIG. 6A is an isometric view of a recommended IPG device. [Figure 6B] FIG. 6B is a cross-sectional top view of a preferred IPG shape showing a hyperelliptic curve. [Figure 6C] FIG. 6C is a cross-sectional front view of a preferred IPG shape showing a hyperelliptical curve. [Figure 6D] FIG. 6D is a cross-sectional side view of a preferred IPG shape showing a hyperelliptical curve. [Figure 6E]FIG. 6E is an isometric view of a preferred IPG shape showing a hyperelliptic curve. [Figure 6F] FIG. 6F is an isometric view of a recommended IPG device. [Figure 7A] FIG. 7A is a side view of the header of a preferred IPG device. [Figure 7B] FIG. 7B is a cross-sectional top view of the header of a preferred IPG device. [Figure 7C] FIG. 7C is a detailed diagram of a recommended header for an improved IPG device. [Figure 7D] FIG. 7D is a top view of the priority header bay of the improved IPG device. [Figure 7E] FIG. 7E is a rear view of the header of the improved IPG device. [Figure 8] FIG. 8 is a cross-sectional view of a preferred IPG body. [Figure 9A] FIG. 9A is a plan view of the optical window of the improved IPG device. [Figure 9B] FIG. 9B is a cross-sectional side view of an optical window for an improved IPG device. [Figure 10A] FIG. 10A is a plan view of the optical window of the improved IPG device. [Figure 10B] FIG. 10B is a cross-sectional side view of an optical window for an improved IPG device. [Figure 11A] FIG. 11A is a plan view of the optical window of the improved IPG device. [Figure 11B] FIG. 11B is a cross-sectional side view of an optical window for an improved IPG device. [Figure 11C] FIG. 11C is an isometric view of the optical window of the improved IPG device. [Figure 11D] FIG. 11D is an isometric view of the optical window of the improved IPG device. [Figure 12A] FIG. 12A is a front view of a daughter board suitable for the improved IPG device. [Figure 12B] FIG. 12B is a rear view of a daughter board suitable for the improved IPG device. [Figure 12C]FIG. 12C is an isometric view of a daughter board suitable for the improved IPG device. [Figure 12D] FIG. 12D is a schematic diagram of the optical signals of the improved IPG device. [Figure 12E] FIG. 12E is a graphical representation of the advantages of the lead configuration. [Figure 12F] FIG. 12F is a method diagram for calculating the stimulus. [Figure 12G] FIG. 12G is a front view of the daughter board of the improved IPG device. [Figure 12H] FIG. 12H is a rear view of the daughter board of the improved IPG device. [Figure 12I] FIG. 12I is an isometric view of the daughter board of the improved IPG device. [Figure 12J] FIG. 12J is a schematic diagram of the optical signals of the improved IPG device. [Figure 13A] FIG. 13A is a side view of a preferred embodiment of a subcutaneous lead. [Figure 13B] FIG. 13B is a cross-sectional view of a preferred embodiment of a subcutaneous lead. [Figure 13C] FIG. 13C is a cross-sectional view of an alternative embodiment of a subcutaneous lead. [Figure 13D] FIG. 13D is an exploded side view of the optical fiber and ferrule configuration. [Figure 13E] FIG. 13E is a side view of a preferred embodiment of the optical fiber and ferrule assembly. [Figure 13F] FIG. 13F is an exploded side view of the optical fiber and collet components. [Figure 13G] FIG. 13G is a side view of a preferred embodiment of the optical fiber and collet components. [Figure 13H] FIG. 13H is an exploded side view of the lead assembly. [Figure 13I] FIG. 13I is a top view of the fiber optic threading assembly. [Figure 13J] FIG. 13J is a top view of the fiber optic threading component. [Figure 13K] FIG. 13K is an exploded perspective view of the fiber optic threading assembly. [Figure 14A] FIG. 14A is a plan view of a preferred surgical lead. [Figure 14B] FIG. 14B is a cross-sectional view of a preferred surgical lead. [Figure 14C] FIG. 14C is a cross-sectional view of a preferred surgical lead. [Figure 15A] FIG. 15A is a plan view of a preferred surgical lead. [Figure 15B] FIG. 15B is a cross-sectional view of a preferred surgical lead. [Figure 16A] FIG. 16A is a plan view of a surgical lead. [Figure 16B] FIG. 16B is a cross-sectional view of a surgical lead. [Figure 16C] FIG. 16C is an isometric view of a parabolic reflector for a surgical lead. [Figure 17A] FIG. 17A is a plan view of a surgical lead. [Figure 17B] FIG. 17B is a cross-sectional view of a surgical lead. [Figure 18] FIG. 18 is a flow chart of the steps of a preferred method for surgical lead placement. [Figure 19] FIG. 19 is a flow chart of the steps of a preferred method for placement of a percutaneous lead. [Figure 20] FIG. 20 is a method flow chart of the steps of a preferred method for securing an optical fiber in the stylet pathway of a lead. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In the following description, like parts are designated throughout the specification and figures are each designated by the same numerals. The figures are not necessarily drawn to scale and may be shown in exaggerated or generalized form for clarity and conciseness.

[0026] Referring now to FIG. 5, an IPG charging and communication system 500 includes an IPG device 510 that is subcutaneously implanted below a skin surface 530 .

[0027] The IPG device 510 has an external non-metallic case 507 that facilitates charging and transmission of communication signals along with an external system manager 516, as will be further described.

[0028] The IPG device 510 further includes a main processor 505 operably connected to the signal processor 509. The main processor 505 is further operably connected to a secondary coil 511 and an RF antenna 532, as described.

[0029] The signal processor 509 is operatively connected to the optoelectronic device 503 as will be further described.

[0030] Optoelectronic devices 503 are positioned to transmit and receive light to and from leads 512 of surgical leads 514, respectively, as will be further described.

[0031] The main processor 505 is further operatively connected to a battery 533, a secondary coil 511, and an RF antenna 532. During use, the main processor 505 relieves charge on the battery 533 from current induced in the secondary coil 511 by the primary coil 518, as will be further described. The main processor 505 further receives signals from the RF antenna 532 for use in communicating data regarding the operation of the IPG device, as will be further described.

[0032] The system further includes an external system manager 516. The external system manager 516 includes an external processor 520 operatively connected to a primary coil 518 and an RF antenna 534.

[0033] In use, the external processor 520 contains a set of instructions that control the charging signal sent to the primary coil 518. In use, the primary coil 518 is physically placed near the secondary coil 511 and activated. Activation of the primary coil induces a current in the secondary coil that is sent by the main processor to the battery to charge the battery. Because no eddy currents occur in the non-metallic case, activation of the primary coil and inductive charging of the battery can continue. The continuous charging duty cycle of the IPG is significantly improved over prior art reducing IPG charging times.

[0034] RF antenna 534 is used to send and receive signals to RF antenna 532 to receive information and control the operation of the IPG device 510, as will be further described.

[0035] 6A, an IPG device 501 includes an IPG body 506 and a header 502. Leads 504 are removably secured to the header, as will be further described.

[0036] A preferred shape of the IPG device 501 will now be described with reference to Figures 6B, 6C, 6D and 6E. In general, the preferred shape of the IPG case is defined by the equations of two unique super ellipses, one for each side and top perspective. The case is symmetric about each major axis. The geometry of the IPG case is important because a near Gaussian distribution of curvature across the surface significantly reduces the risk of the case eroding through the skin after implantation of the IPG device, thereby improving the survival of surgical implants. The equation of the preferred super ellipses that defines the shape of the case is preferably the Lamé curve equation.

[0037] The three-dimensional shape of the device is a volume of revolution with principal axes x, y, and z. The volume of revolution is symmetric about each of the principal axes. With reference to FIG. 6C, from the front, in the xy plane, the volume of revolution is preferably a circle defined by the following equation:

[0038]

number

[0039] Where: a = width along the x-axis b = height along the y-axis r=radius Typical values ​​for a and b are around 50 mm. Typical value for r is around 25 mm.

[0040] Referring to FIG. 6D, when viewed from the side, in the yz plane, the solid of revolution is preferably superimposed as defined by the following equation:

[0041]

number

[0042] Where: b = height along the y-axis c = depth along the z axis n is between about 1.5 and about 5, and is preferably about 2. A typical value for b is about 50 mm. A typical value for c is about 12 mm.

[0043] In one preferred embodiment, the superellipse in the yz plane is rotated about the z axis to obtain the volume of the solid of revolution.

[0044] Referring to FIG. 6B, from above, in the xz plane, the volume of the solid of revolution is preferably a super-ellipse defined by the following equation:

[0045]

number

[0046] Where: a = width along the x-axis c = depth along the z axis A typical value for a is about 50 mm. A typical value for c is about 12 mm.

[0047] Referring now to FIG. 6F, an exploded view of the improved IPG device 600 is illustrated.

[0048] The IPG device 600 is comprised of a header 602 and an IPG body 606. The IPG body 606 is further comprised of an IPG casing 622, an optical window 618, and an electrical feed-through plate 616. The IPG casing 622 is formed by two opposing shell halves, 622a and 622b, sealed at a joint 620. In a preferred embodiment, the IPG casing 802 is a ceramic material such as alumina, sapphire, or zirconia. In another embodiment, the IPG casing can be formed of a molded amorphous glass such as Pyrex. In an alternative embodiment, the IPG casing is comprised of titanium or an alloy. In a preferred embodiment, a ceramic braze with induction welding is applied to the joint of the casing halves. Other processes can be used to join the halves.

[0049] The header is secured to the header bay 619 by a suitable medical grade permanent adhesive, as will be further described.

[0050] Optical window 618 is preferably a crystalline insert in the wall of the header bay sealed within the IPG casing, as will be further described. Alternatively, in embodiments in which the IPG casing is formed of an optically transparent material, optical window 618 can take the form of a pair of polished surfaces integrally formed in the header bay wall of the IPG casing adjacent the header body.

[0051] Leads 604 are removably coupled to header 602 and secured in place using anchor screws 614 or 615 as will be further described.

[0052] 7A, the header 700 is comprised of a header body 701. The header body is preferably formed of a cast rigid non-metallic material of sufficient strength to support the radial force from the anchor screws, such as methyl PMMA or polyester reinforced with glass or graphite fibers. The header body includes a plurality of generally latitudinal and parallel lead channels, such as lead channel 702. In a preferred embodiment, the header body includes four lead channels. Alternatively, there may be two lead channels. Each lead channel, such as lead channel 702, is generally cylindrical and includes a lead channel axis, such as axis 719, which forms the optical axis of the lead, as will be further described.

[0053] Each lead channel includes eight annular connector bays, such as connector bay 703, formed in series within each lead channel. Connector bays 703 are equally spaced along the channel axis of each lead channel. Each connector bay houses a canted coil connector spring, such as canted coil spring 704. Each canted coil connector spring is a helical metal coil that forms an annulus and is spring loaded to exert an inwardly directed radial bias on a metal lead connector, as described further below. Preferably, the canted coil springs are platinum alloy to ensure fail-safe electrical and mechanical contact with the lead contacts. In a preferred embodiment, the canted coil springs are Bal Conn® for neuromodulation therapy, available from Bal Seal Engineering, Foothill Ranch, Calif. Each canted coil spring is connected to one connector pin, such as connector pin 706, at the base of the header.

[0054] Header body 701 is adjacent to the IPG casing and includes a set of horizontal threaded holes that extend from the exterior of the header body to the lead channels and are perpendicular to the lead channels, such as threaded hole 732. An anchor screw, such as anchor screw 708, is disposed in each threaded hole.

[0055] In a preferred embodiment, the threaded holes are drilled or cast directly into the header body, or are threaded into the IPG case. The IPG casing is molded into the lead wire casing. This configuration is important because it eliminates the need for separate anchor blocks in the header, saving space by incorporating these components into the IPG casing. Additionally, locating the anchor screws nearest the proximal end of the lead wire channel provides a secure mechanical connection of the lead nearest the optical component, promoting a stable optical signal.

[0056] Optionally, the header body can further include an integrally formed anchor block 799. In this embodiment, the threaded hole and anchor screw are in the anchor block adjacent the optical window. The anchor block is preferably a medically inert metal, such as titanium, that is molded into the header body.

[0057] 7B, threaded hole 732 receives anchor screw 708. Directly opposite threaded hole 732 is threaded hole 707. Threaded hole 707 receives anchor screw 705.

[0058] 7C, frusto-conical centering surface 724 is adjacent to and coaxial with lead channel 702. The frusto-conical centering surface 724 centers the lead on the optical axis of the lead channel when the lead is inserted therein. The frusto-conical centering surface is adjacent anchoring chamber 728. The anchoring chamber is bounded by cylindrical alignment surface 726 and is coaxial with the frusto-conical centering surface. The anchoring chamber is also bounded by stop surface 730. Stop surface 730 is an annular ring at the proximal end of the anchoring chamber. The stop surface is coaxial with the anchoring chamber. In use, stop surface 730 abuts the proximal end of the lead body and prevents insertion beyond a desired point in lead channel 702 during assembly. Each of these surfaces is important for precise alignment of the leads and the optical fibers to facilitate efficient and accurate transfer of optical signals.

[0059] Anchor screws 708 engage the lead wire anchor ring in the anchor ring chamber when the IPG is assembled. If the header body has threaded holes, install the anchor screws with a torque-limiting driver to avoid straining the header. If the header body includes the anchor block, the anchor block allows the anchor screws to apply sufficient axial force to the anchor ring to hold the anchor ring securely in place without destroying the header body.

[0060] The lead channel further comprises a ferrule chamber 727 bounded by an alignment cylinder 712. The ferrule chamber is coaxial with the lead channel.

[0061] A ferrule centering surface 716 is adjacent to and coaxial with the alignment cylinder 712 and is designed to optically align the ferrule and the optical fiber with the optical axis of the lead channel. The alignment cylinder 712 forms a chamfer angle 8 with the ferrule centering surface 716. In a preferred embodiment, the chamfer angle 8 ranges from about 135° to about 150°, ±5°. The ferrule centering surface 716 centers and aligns the lead and the proximal end of the optical ferrule with the buffer gap 734, the optical window 718, and the composite optoelectronic device 740.

[0062] Cylindrical buffer surface 714 is adjacent and coaxial with ferrule centering surface 716. Cylindrical buffer surface 714 forms a buffer gap 734 between the proximal end of the optical ferrule and an optical window 718. The buffer gap prevents pressure on the optical window from fluid or tissue accumulation at the ferrule tip or from irregularities in the polished surface of the optical fiber at the ferrule tip.

[0063] 7D, the electrically piercing plate 616 comprises a flat insulating body, preferably a ceramic material, and is secured to the plate by a suitable adhesive or ceramic. The header body is secured to the bottom of the header bay 619 by a tamper-evident solder joint. Electrical feed-through plate 616 is comprised of multiple receivers, such as receiver 746, which are connected to a main circuit board as will be described further. Connector pins 706 at the base of the header body interface with the receivers.

[0064] 7E, in a preferred embodiment, the header is comprised of four lead channels 702, 709, 713, and 717. Each lead channel includes a vertically oriented threaded hole 732, 707, 733, and 739, and an anchor screw 708, 705, 711, and 715, respectively.

[0065] In the prior art, there is typically an anchor ring that is engaged by a set screw to secure the lead contacts in the header. The anchor ring is typically located distal to the contacts, and a separate anchor block is required to engage the lead and set screw. One advantage of this embodiment is that the anchor ring can be located proximal to the lead contacts, closest to the ends of the leads. This location eliminates the need for a separate anchor block and reduces the size of the IPG casing if threaded holes 732, 707, 733, and 739 are integrated into the header body, as can be achieved by ceramic or glass injection molding. Additionally, the location of the anchor ring closest to the proximal tip of the lead provides mechanical fixation of the lead closest to the optical components, promoting a stable optical signal.

[0066] Referring now to FIG. 8, the IPG body 800 is further comprised of an IPG casing 802 , an optical window 806 , an electrical feed-through plate 804 , a composite optoelectronic device 816 , a connector card 812 , a main circuit board 818 , a battery 808 , and a capacitor 810 .

[0067] The electrical components are secured within the casing with suitable insulating plastic standoffs such as standoffs 820 and 821 .

[0068] An electrical feed-through plate 804 is enclosed in the IPG casing 802 adjacent to the header bay. The electrical feed-through plate is mechanically secured to a connector card 812 and connected to the main circuit board 818 by a flexible ribbon cable 805.

[0069] An optical window 806 is sealed to the IPG casing at a position perpendicular to both the electrical feed-through plate and the lead channels. In a preferred embodiment, optical window 806 is constructed from synthetic sapphire, which provides optimal optical properties for transmitting visible red or infrared light between a composite optoelectronic device 816 and an optical transmission fiber, as will be further described.

[0070] A composite optoelectronic device 816 is positioned adjacent to the optical window and held in a parallel position with the optical window by the daughterboard. The optoelectronic device 816 is also perpendicular to the optical axis of the lead channel. Daughterboard 814 further comprises a processor 803, as will be further described. Daughterboard 814 is held in place by the standoffs and connected to a main circuit board 818 by a ribbon cable 807, which provides power to the daughterboard and communicates control signals as required.

[0071] A main circuit board 818 is disposed within the IPG casing by the isolation and is operatively connected to the battery, the capacitor, the contacts of the leads, and the daughter board.

[0072] A main circuit board 818 receives data inputs from the daughter board and generates stimulation pulses of varying frequency, pulse width, and amplitude based on signals from the daughter board. The stimulation pulses are sent to the lead contacts for transmission to the electrodes. The daughter board generates control signals for the main circuit board by sending light pulses from the light emitters and receiving and interpreting signals from the photodetectors, as will be further described. The main circuit board is also operatively connected to a secondary inductive coil 809 and an RF antenna 811.

[0073] The main circuit board includes a processor and a signal generator that allows signals to be communicated to an external receiving device via an RF antenna 811. In a preferred embodiment, the main circuit board and the RF antenna are used to communicate a warning signal from the daughter board when the emitter current reaches a maximum value, as will be further described.

[0074] A capacitor 810 is connected to a battery 808 and stores energy from the battery to generate the stimulation pulses. In a preferred embodiment, battery 808 is a rechargeable lithium ion battery. Battery 808 is inductively charged via a secondary inductive coil 809 disposed around the battery on one interior surface of the IPG casing. The main circuit board controls the recharging duty cycle.

[0075] 9A and 9B, in a preferred embodiment, the optical window 900 is a polished rectangular single crystal alumina (sapphire) or polycrystalline alumina ceramic. It is ceramic brazed to the IPG case 901 in the header bay. Niobium is used as a metal-to-ceramic filler material. In a preferred embodiment, the alumina is 94% brazed to Fe-29Ni-10Co internally at about 1000° C. The optical window 900 is brazed to the IPG case 901 along the window braze joint 906 using a hermetic braze fillet 904. Although the optical window 900 and IPG case 901 are shown coplanar in FIG. 9B, they may alternatively be stacked or overlapped.

[0076] 10A and 10B, in another embodiment, an optical window 1000 is overlaid on the outside of an IPG case 1001 adjacent to the header bay. In this embodiment, the IPG case 1001 includes four (4) waveguides 1008. The waveguides are holes in the header bay wall that allow red or infrared light to transmit through the optical window along the optical axis of each lead channel and into the interior of the IPG casing. Optical window 1000 is sealed to the IPG case using brazing, soldering, epoxy or other suitable means along window joint 1006.

[0077] 11A, 11B, 11C and 11D, in another preferred embodiment, pane 1104 comprises a flat sapphire rectangle approximately 1 mm thick. Four light guides 1106 are fused to the pane using ceramic welding. In another embodiment, the pane and the light guides are integrally formed from the same crystal structure. Each light guide includes an internally reflective iris 1108. The iris is a cylindrical hole concentrically aligned with the optical axis of the lead channel. Aperture pane 1104 is laser welded to IPG casing 1101 along weld joints 1102.

[0078] When assembled, each of the optical waveguides passes through hole 1110 into the interior of the IPG casing. In a preferred embodiment, each optical waveguide is adjacent to an optoelectronic device on the daughter board that is secured to the IPG casing, as described above. In practice, the iris is important to prevent light loss between the optical fibers of the leads and the optoelectronic device.

[0079] 12A, 12B, and 12C, the daughter board 814 is preferably a double-sided PC board supporting optoelectronic devices 1204, 1205, 1206, and 1270, connector 1210, and processor 1208. Processor 1208 draws power from the battery and is supplied with on-board memory containing instructions for its operation. The optoelectronic devices are positioned in quadrants adjacent to the proximal face of the optical window. Each quadrant is separated by an optically opaque light baffle 1212. In a preferred embodiment, the baffle is a "cross-shaped" PVC isolation approximately 1-2 mm high, coated on its outer surface with a reflective layer such as Ti02, and glued to the daughter board with a suitable adhesive. Each of the optoelectronic devices is positioned to be aligned perpendicular to the optical axis of one lead channel to maximize either the transmission or reception of light from the optical fibers positioned in the lead channels. In a preferred embodiment, the optoelectronic devices 1204, 1205, 1206, and 1207 and the optical baffle 1212 are integrated into one or more application specific integrated circuits (ASICs).

[0080] A connector 1210 links a daughter board 814 to the main circuit board of the IPG device. A processor 1208 is electrically connected to the optoelectronic device through the daughter board as necessary to communicate electrical signals to the processor.

[0081] In one embodiment, the optoelectronic device 1204 is a light emitter and the optoelectronic devices 1205, 1206, and 1205 are light detectors.

[0082] In another embodiment, optoelectronic devices 1204 and 1206 are light emitters and optoelectronic devices 1205 and 1206 are light detectors.

[0083] The wavelength of the emitter ranges from visible red to infrared, or about 620 to 1700 nanometers. The emitter can be either single wavelength or multiple wavelengths. For example, the emitter can be a high speed single wavelength infrared emitting diode with a wavelength of 850 nm, such as part number VSMY1850 available from Vishay Intertechnology, Inc., Malvern, Pennsylvania. Alternatively, the emitter can be a multi-chip emitter capable of emitting wavelengths of 670 nm, 770 nm, 810 nm, 850 nm, and 950 nm, such as part number MTMD6788594SMT6 available from Marktech Optoelectronics, Inc., Latham, New York. Alternatively, the emitter and detector can be integrated into a single ASIC, such as ADPD144RI from Analog Devices, Inc., Norwood, Massachusetts.

[0084] 12D, a preferred embodiment of a coupling configuration between the optical leads and the optical emitters in a surgical lead is described. Emitter 1292 is optically coupled to central fiber 1215 of surgical lead 1211. Detector 1290 is optically coupled to lead 1213 of surgical lead 1211. Detectors 1294 and 1296 are connected to leads 1217 and 1219, respectively.

[0085] 12D, a preferred embodiment of a coupling configuration between the optical leads and the optical emitters in a surgical lead is described. Emitter 1292 is optically coupled to central fiber 1215 of surgical lead 1211. Detector 1290 is optically coupled to lead 1213 of surgical lead 1211. Detectors 1294 and 1296 are connected to leads 1217 and 1219, respectively.

[0086] Referring to FIG. 12E, a graph showing the light output from a side ignition fiber of a surgical lead and the input current to the corresponding emitter over time is illustrated.

[0087] The light output over time is shown by the curve labeled "a". It can be seen that the light output of fiber 1215 degrades over time due to microfractures of the fiber and other degradation of optical components within the surgical lead. The degradation of the optical performance of fiber 1215 is monitored over time by processor 1208 by reading the voltage signal from detector 1296, which receives light from fiber 1215 reflected by the spinal cord. Processor 1208 is programmed to counteract the degradation of the light output by increasing the current to emitter 1204 according to curve "b". As can be seen, increasing the current to emitter 1204 maintains the light output of fiber 1215 at a consistent level as shown by curve "c" in the figure.

[0088] 12F, an automatic adjusting emitter current program for adjusting the light output from an emitter fiber is described. In a preferred embodiment, said program is a series of instructions resident in said memory of processor 1208.

[0089] In step 1262, the program is started.

[0090] In step 1264, the processor sets the output current to emitter 1292. In a preferred embodiment, the emitter current is set to the minimum requirement to produce a readable signal at detectors 1290 and 1296.

[0091] At step 1266, the processor reads the voltage at detector 1294. At step 1268, the voltage level is stored in memory. At step 1270, the processor 1208 sends a signal to the main circuit board 818 to begin a stimulation program. The main circuit board responds by sending the appropriate stimulation signal to the leads.

[0092] In step 1272, the processor 1208 determines whether the self-timer has expired. If so, the program proceeds to step 1274. If not, the program returns to step 1270.

[0093] In step 1274 , the processor 1208 reads the detector voltage at the detector 1294 .

[0094] In step 1276, the processor compares the current detector voltage to the detector voltage stored in the memory. If the current detector voltage is less than the stored detector voltage, the process proceeds to step 1278. If not, the program returns to step 1270.

[0095] In step 1278, processor 1208 increases the emitter current to emitter 1204. In a preferred embodiment, the emitter current is increased by 1 / 100 of the maximum allowed emitter current.

[0096] In step 128, the processor determines whether the emitter current is set to the maximum allowed. If so, the program moves to step 1282. If not, the program returns to step 1274.

[0097] In step 1282, the processor sends a signal to the main circuit board, which communicates it via the RF antenna to an external receiver, indicating that the maximum emitter current has been reached. The program then returns to step 1270.

[0098] 12G, 12H, and 12I, an alternative embodiment of the daughterboard 814 will now be further described.

[0099] Daughterboard 1201 is a composite optoelectronic device comprised of optoelectronic devices 1250 and 1252, connector 1254, and signal processor 1209. The optoelectronic devices are arranged adjacent and parallel to the optical window. In a preferred embodiment, each optoelectronic device is separated by an optically opaque light baffle 1251. In a preferred embodiment, baffle 1251 is a reflective or opaque rectangular PVC standoff bonded to the daughterboard as previously described.

[0100] A connector 1254 links the daughter board 1201 to the main circuit board of the IPG device. A processor 1209 is electrically connected to the opto-electronic device through the daughter board as required and communicates external signals to the signal processor. The daughter board communicates with the main circuit board through connector 1254.

[0101] 12J, a preferred embodiment of a coupling configuration between the optical leads and the optical emitters in a surgical lead is described. The emitter 1293 is optically coupled to the central fiber 1225 of the signal lead 1221. The detector 1291 is optically coupled to the lead 1223 of the signal lead 1221. The emitter 1295 is optically coupled to the central fiber 1227, and the detector 1297 is connected to the lead 1229. In this configuration, the dual optical reflectance measurement channels facilitate stereo detection of the spinal cord position in the sagittal and coronal planes, as previously described in U.S. Patent Nos. 8,239,038, 8,543,213, 9,132,273, and 9,656,097 to Wolf II.

[0102] 13A-13G, a preferred embodiment of a percutaneous lead 1400 is described.

[0103] 13A and 13B, a preferred embodiment of a lead body 1402 comprises a generally hollow tube terminated in a transmissive window 1409. In a preferred embodiment, the lead body is comprised of a flexible polymer such as Pellethane 55-D, or a similar biocompatible polymer. The lead body is preferably a multi-lumen extrusion available from Zeus Industrial Products, Inc. of Orangeburg, South Carolina, USA.

[0104] A transparent window 1409 is a hollow cylinder fused to the end of the flexible lead body surrounding a diffusion cavity 1430. In a preferred embodiment, the window is a suitable optically transparent material such as thermoplastic polyurethane. The transparent window 1409 is terminated by a lid 1425. The lid 1425 includes an internal reflective surface 1403 that faces the diffusion cavity 1430. In a preferred embodiment, the internal reflective surface is a titanium dioxide coating.

[0105] A stylet channel 1405 extends from the transmission window to the proximal end of the lead body. The stylet channel serves two purposes: to house a pointer stylet for use during placement of the lead during surgery, and to house a housing and optical fiber post-surgery, as will be further described. In a preferred embodiment, the stylet channel 1405 is lined with a polytetrafluoroethylene (PTFE) lining 1407 that extends the length of the lead body to a transmission window 1409. The very low surface friction provided by the carbon-fluorine bonds of the PTFE facilitates manual insertion of the stylet and the optical fiber. The lining does not extend into the diffusion cavity where the side firing portion of the optical transmission fiber resides to enhance light transmission.

[0106] A metallic anchor ring 1410 is disposed at the proximal end of the lead body. The anchor ring is generally cylindrical and permanently attached to the exterior of the lead body proximal to the lead contacts. Eight cylindrical proximal metallic contacts 1408a, 1408b, 1408c, 1408d, 1408e, 1408f, 1408g, 1408h are fixed to the exterior of the lead body at equal axial distances along the lead body and positioned to electrically contact the coil spring of the header.

[0107] Similarly, eight cylindrical distal metal electrodes 1406a, 1406b, 1406c, 1406d, 1406e, 1406f, 1406g, 1406h are provided at the distal end of the lead body. Each of the distal lead contacts is permanently affixed to the outer surface of the lead. The distal lead contacts are equally spaced along the lead body proximal to the optical window.

[0108] The lead body further includes eight radially oriented lumens 1431a, 1431b, 1431c, 1431d, 1431e, 1431f, 1431g, and 1431h. Conductors 1420a, 1420b, 1420c, 1420d, 1420e, 1420f, 1420g, and 1420h are disposed within the lumens and extend from their respective proximal contacts to the distal electrodes. In a preferred embodiment, the conductors are constructed of MP35N or another conductive material that is similarly resistant to corrosion. Each of the conductors connects exactly one proximal contact to one paired distal electrode.

[0109] Referring now to FIG. 13C, a cross-sectional view of an alternative embodiment of a lead body 1450 is illustrated.

[0110] Lead body 1450 has nine radially oriented lumens, 1449a, 1449b, 1449c, 1449d, 1449e, 1449f, 1449g, 1449h, and 1449i. Conductors 1451a, 1451b, 1451c, 1451d, 1451e, 1451f, 1451g, 1451h and ground line 1451i are disposed in the lumens. Ground line 1451i extends from the proximal end of the lead body to the transmission window. Ground line 1451i is electrically connected to the anchor ring 1410. When the anchor screw engages anchor ring 1410, the ground lead is connected directly to the IPG ground through the anchor block or through a ground connection through the header. The ground line can be used to supplement the electrical shielding of the electrode array contacts to enhance MRI compatibility.

[0111] In another preferred embodiment, the lead body can incorporate a non-metallic shielding layer 1496 connected to ground wire 1451i to further enhance MRI capabilities. In a preferred embodiment, the shielding layer is formed by carbon fiber infused onto the surface of the lead body. In another preferred embodiment, a low friction layer 1493, such as PTFE, is included on the exterior of the lead body to aid in placement of the lead during surgery.

[0112] 13D and 13E, a fiber optic subassembly 1419 includes a ferrule 1412 and an optical fiber 1418.

[0113] The ferrule 1412 is generally a ceramic cylinder. The ferrule 1412 includes an integrally formed alignment tip 1413. The alignment tip 1413 is a chamfer formed in the ferrule at a chamfer angle 8, preferably about 135° to 150°. In a preferred embodiment, the chamfer angle 8 coincides with the chamfer angle 735 of the center face 716 so that when the ferrule is attached to the header, there is elastic compression of the ferrule by the polymer lead body. When attached, the positive stop of the ferrule by the ferrule center face 716 prevents pressure from being applied to the fiber or the optical window 718 sealed by the ferrule. A hole 1415 is in the center of the ferrule 1412 and extends the entire length of the ferrule. In a preferred embodiment, the diameter of the hole closely matches the diameter of the optical fiber. In a preferred embodiment, the ferrule 1412 is made of polished ceramic, preferably zirconia, or other MRI compatible material.

[0114] A ferrule 1412 is disposed at the proximal end of the optical fiber 1418. The optical fiber 1418 includes a terminal reflector 1414 and a side-firing fiber portion 1416 at its distal end, and a polished optical tip 1411 at its proximal end. The optical fiber 1418 is preferably constructed of a polymethylmethacrylate core with a fluorocarbon coating having a diameter of approximately 250-400 micrometers. In a preferred embodiment, the fiber also includes a low friction layer 1447, preferably made of PTFE. During use, the low friction layer aids in the insertion of the fiber into the stylet lumen.

[0115] Optical fiber 1418 includes a reflector 1414 at its distal end. The reflector prevents axial emission from the fiber and improves radial dispersion of light. Thus, the reflector improves optical signal strength and reduces power consumption. Ideally, the reflector consists of a layer of titanium dioxide that is heat polished and then coated onto the end of the fiber.

[0116] Side-ignition fiber section 1416 is disposed within diffusion cavity 1430, adjacent lid 1425, and is typically approximately 5 mm in length. Side-ignition fiber section 1416 is formed by modifying the coating of the optical fiber. The coating can be modified using femtosecond laser etching, mechanical abrasion, or alternative methods to achieve radial leakage of light.

[0117] A polished optical tip 1411 is disposed at the proximal end of the optical fiber. Polished optical tip 1411 is preferably a heat polished surface perpendicular to the optical axis of the fiber. Optionally, a convex lens can be attached to the proximal end of the fiber to focus light into and out of the fiber, as will be further described.

[0118] 13E, a fiber optic subassembly 1419 is placed in the stylet channel 1405. The outer diameter of a ferrule 1412 is smaller than the outer diameter of the lead body 1402, but larger than the diameter of the stylet channel 1405, such that the lead body acts as a stop for the ferrule.

[0119] In one embodiment, a fiber optic subassembly 1419 is placed in the stylet channel after surgical placement of the lead body in vivo, as further described.

[0120] One such suitable medical grade adhesive is preferably an optically clear, biocompatible epoxy sealant such as EPO-TEK® MED-353ND by Epoxy Technology, Inc. of Billerica, Massachusetts, USA. In this case, polished optical tip 1411 is ground flush with alignment tip 1413.

[0121] 13F, an alternative embodiment of the fiber optic subassembly 1419 will be described.

[0122] The lead body 1401 includes a stylet channel 1405 having an optical axis 1421. The lead body incorporates a proximal contact, a distal electrode, and a dielectric as previously described. The stylet channel 1405 terminates in a fulstral conical flare 1482. The fulstral conical flare 1482 is coaxial with the optical axis 1421. The inclination angle β of the fulstral conical flare ranges from about 135 degrees to about 150 degrees.

[0123] In a preferred embodiment, the lead channel has a diameter approximately 15-20% larger than the optical fiber to allow the fiber to travel within the channel. The optical fiber 1444 is preferably a plastic fiber, as previously described. The optical fiber 1444 includes an end reflector 1446 and a side firing portion 1445, as previously described.

[0124] Optical fiber 1444 is proximally terminated by a convex lens 1452. Convex lens 1452 is made of a polished ceramic material, such as sapphire, that is secured to the optical fiber using a suitable optically clear adhesive. In another embodiment, the lens is integrally formed with the transmitting fiber. In another embodiment, the optical fiber is polished flat and does not incorporate a lens.

[0125] Collet 1457 includes a collet body 1453. Preferably, collet body 1453 is constructed from a ceramic material, such as zirconia, or another MRI compatible material. Alignment tip 1454 is a chamfer integrally formed at the distal end of said collet body. Alignment tip 1454 forms a bevel angle γ of approximately 135 degrees. In a preferred embodiment, angle γ coincides with angle β of full-strand conical flare 1482.

[0126] A lens shield 1469 is integrally formed with the proximal end of the collet body 1453. It is designed to act as a stopper to prevent the optical fiber from colliding with the optical window of the IPG body. Lens shield 1469 further includes a frustoconical lens opening 1468 ducted to collet chamber 1456. The frustoconical lens opening is coaxial with the collet chamber and has an inclination angle δ with the collet chamber of about 175 degrees. The frustoconical lens opening 1468 serves to focus light towards the optical window.

[0127] 13G, the proximal end of the optical fiber is shown disposed within collet chamber 1456. Lens 1452 does not extend beyond lens shield 1469. The fiber is secured to the collet chamber with a suitable epoxy.

[0128] An optical fiber 1418 is disposed in the stylet channel 1405 of the lead body 1401. A frustoconical flare 1482 helps guide the insertion of the optical fiber into the lead channel. The interface of the frustoconical flare 1482 and alignment tip 1454 also serves to center the optical fiber 1444 and lens 1452 on axis 1421. The outer diameter of a collet 1457 is smaller than the outer diameter of the lead body 1401 but larger than the diameter of the stylet channel 1405 so that when the lead is inserted into the header, the lead body acts as a stop for the collet and the side firing portion of the fiber is adjacent to the optical window.

[0129] A preferred embodiment of an optical threading component 1460 will now be described with reference to Figures 13H-13K. Inserting the optical fiber into the stylet channel of the lead can be difficult due to the small size of the fiber and the small diameter of the stylet channel. Similarly, during surgery, replacing a stylet within the stylet channel can be difficult. These difficulties are exacerbated by the need for speed, dexterity, and vision. Improper insertion of the optical fiber can lead to damage to the fiber, causing breakage or premature deterioration of the fiber. Similarly, improper stylet insertion can put the lead body at risk. The optical fiber threading component solves these and other problems.

[0130] The optical threading part 1460 includes a guide body 1497. The guide body is cylindrical with a diameter of about 1 cm and is constructed from thermoplastic. The part is preferably formed using either injection molding or additive manufacturing; other manufacturing methods will suffice. The guide body 1497 is generally cylindrical and is constructed from two opposing half-cylinders 1461 and 1462.

[0131] The optical threading piece 1460 includes a frustoconical lead centering surface 1463 at its distal end. The frustoconical lead centering surface 1463 is coaxial with the axis 1421. The frustoconical lead centering surface 1463 is adjacent a cylindrical alignment surface 1467. The cylindrical alignment surface 1467 forms an alignment cavity 1498. The frustoconical lead centering surface 1463 forms an inclination angle τ of about 135° with the cylindrical alignment surface 1467. The alignment cavity has a diameter that is generally equal to the diameter of the lead body 1402. The alignment cavity terminates in a stop surface 1466. The stop surface 1466 is a generally annular ring formed perpendicular and coaxial with the axis 1421.

[0132] Adjacent and ducted to the alignment cavity 1498 is a generally cylindrical fiber alignment duct 1499. The fiber alignment duct 1499 is coaxial with the axis 1421. The diameter of the fiber alignment duct is generally the same as the diameter of the stylet channel 1405 in the lead body 1402.

[0133] The fiber alignment duct 1499 is adjacent to and ducted with the frusto-conical fiber optic centering surface 1465. The frusto-conical fiber optic centering surface 1465 forms an inclination angle η of about 135° with the fiber alignment duct 1499. The frusto-conical fiber optic centering surface 1465 is coaxial with the axis 1421.

[0134] Half-cylinder 1461 includes alignment pegs 1474, 1470, and 1472. Half-cylinder 1462 includes alignment recesses 1475, 1471, and 1473. Alignment peg 1474 is diametrically opposed to alignment recess 1475. Alignment peg 1470 is diametrically opposed to alignment recess 1471. Alignment peg 1472 is diametrically opposed to alignment recess 1473. The respective diameters of alignment recesses 1475, 1471, and 1473 are such that alignment pegs 1474, 1470, and 1472 are secured by a press fit. As will be described further, the use of the alignment pegs and recesses allows the half-cylinder to be easily assembled, used, and disassembled after use.

[0135] In use, optical threading assembly 1460 aligns lead body 1402 and fiber optic subassembly 1419 along axis 1421. Lead body 1402 is aligned using fulstral conical lead centering surface 1463 and held in position within alignment cavity 1498 by alignment surface 1467 and stop surface 1466. Fiber optic subassembly 1419 is aligned using fulstral conical centering surface 1465 and moved through fiber alignment duct 1499 into the stylet channel of the lead body.

[0136] Similarly, a stylet can be placed in the stylet channel in place of the optical fiber.

[0137] The surgical lead is comprised of two or more multi-duct leads with integrated optical fibers depending on the number of electrodes in the array and the desired number of optical reflectance measurement channels. The multi-duct leads can be organized into emitter and detector lead pairs. Typically, surgical leads comprised of two multi-duct leads incorporate one optical reflectance measurement channel, whereas surgical leads comprised of four multi-duct leads incorporate two optical reflectance measurement channels. A surgical lead with two multi-duct leads with integrated optical fibers can determine the sagittal spinal position, whereas a surgical lead with four multi-duct leads with integrated optical fibers can determine the sagittal and coronal spinal position.

[0138] Referring now to FIG. 14A, a preferred embodiment of a surgical lead 1500 will be described.

[0139] The electrode array 1500 is comprised of an integrated flexible panel 1502. The panel 1502 is preferably a medical grade inert polymeric material such as Pellethan 55-D. The flexible panel 1502 houses multi-duct leads 1506, 1510, 1514, and 1518. In a preferred embodiment, the multi-duct leads are sealed within the body of the flexible panel. Each of the multi-duct leads 1506, 1510, 1514, and 1518 includes a central lumen 1595, 1596, 1597, and 1598, respectively. Each central lumen includes a light transmitting fiber 1541, 1543, 1545, and 1547, respectively. Each light transmitting fiber terminates at the distal end of a side firing fiber optic portion 1535, 1536, 1537, and 1538, respectively. The side ignition fiber optic segments are constructed as previously described, with each side ignition fiber optic segment disposed adjacent a distally disposed optical window 1533, 1532, 1531, and 1530, respectively.

[0140] Panel 1502 further includes electrode arrays 1504, 1508, 1512, and 1516 disposed on adjacent multi-duct leads 1506, 1510, 1514, and 1518, respectively. In a preferred embodiment, each of electrode arrays 1504, 1508, 1512, and 1516 includes eight electrodes embedded in said panel and having exposed surfaces on the exterior of said panel. Each of multi-duct leads 1506, 1510, 1514, and 1518 incorporates eight electrical conductors that extend the length of said panel and said multi-duct lead, as previously described. Each electrode is connected to exactly one lead contact via said conductors of said lead body. Electrode array 1504 is connected to lead contact 1507. Electrode array 1508 is connected to lead contact 1511. Electrode array 1512 is connected to lead contact 1515. The electrode array 1516 is connected to lead contacts 1519. In a preferred embodiment, the electrodes are constructed from a platinum-iridium alloy (nominal 90% / 10% to 80% / 20%).

[0141] Each of the multi-duct leads 1506, 1510, 1514, and 1518 terminates in a ferrule 1505, 1509, 1513, and 1517, respectively. In a preferred embodiment, the ferrules are bonded to fibers as previously described.

[0142] 14B and 14C, each of the electrode arrays 1504, 1508, 1512, and 1516 is connected via electrical connections 1519, 1521, 1523, and 1525 to one of conductor bundles 1540, 1542, 1544, and 1546, respectively, which contain the individual conductors radially separated as previously described. The side ignition fiber portions separate from the multi-duct lead and are spaced apart from the conductor bundles in connecting tubes 1580, 1581, 1582, and 1583, respectively.

[0143] Panel 1502 includes optical reflectors 1550, 1551, 1552, and 1553, adjacent side-firing optical fiber portions 1535, 1536, 1537, and 1538, respectively. The optical reflectors are preferably semi-cylindrical or parabolic and flexible. In a preferred embodiment, optical reflectors 1550, 1551, 1552, and 1553 are constructed from a non-conductive material polymer, such as Pellethan-55D, coated with a non-conductive reflective surface, such as titanium dioxide. This material operates at desired wavelengths from red to infrared and can be applied as a paint or film. The reflection improves optical efficiency by redirecting radially generated light from the emitter fiber portion to the optical window, or by reflecting incident light from the optical window to the detector fiber portion.

[0144] Panel 1502 further comprises a lattice shield 1526. Lattice shield 1526 is typically comprised of a flat flexible film that interdigitates with the polymeric material of the lead body. In a preferred embodiment, lattice shield 1526 is coated with a reflective material such as titanium dioxide (Ti02) adjacent to the optical fibers. The lattice shield is included within the panel adjacent each of conductor bundles 1540, 1542, 1544, and 1546 and generally extends the length of the panel.

[0145] In one embodiment, the lattice shield is constructed of a conductive material, such as carbon nanofiber, and acts as a heat sink, drawing heat away from the electrode contact array and dispersing it back. In another embodiment, as shown in FIG. 13C, each of the leads 1518, 1514, 1510, and 1506 includes a ground terminal. A ground wire 1451i connects the lattice shield 1526 to the anchor ring at the proximal end of the lead. The anchor ring is connected to an IPG ground terminal. This configuration provides optimal electrical shielding for MRI compatibility.

[0146] Referring now to FIG. 15A, a preferred embodiment of a surgical lead 1600 will be described.

[0147] The surgical lead 1600 is comprised of an integrated flexible panel 1602. In a preferred embodiment, the flexible panel 1602 is a medical grade inert flexible polymeric material as previously described. Integrated within said flexible panel are multi-duct leads 1608 and 1610. Each of the multi-duct leads 1608 and 1610 includes a central lumen 1698 and 1699, respectively. The central lumen includes an optical fiber 1611 and 1612, respectively. Each optical fiber terminates in a side ignition optical fiber portion 1618 and 1619, respectively. The side ignition optical fiber portions are configured as previously described. Each side ignition optical fiber portion is disposed adjacent an optical window 1621 and 1620, respectively. In a preferred embodiment, each of the optical windows is an integrally formed optically transparent region of the flexible panel 1602.

[0148] Panel 1602 further includes electrode arrays 1604 and 1606. Each of electrode arrays 1604 and 1606 includes eight electrodes embedded in the surface of said panel 1602 and having exposed surfaces on the exterior of said panel. In a preferred embodiment, said electrodes are a platinum-iridium alloy. As previously described, each of said electrodes is connected to exactly one lead contact via said conductor of said multi-duct lead body. Electrode array 1604 is connected to lead contact 1630. Electrode array 1606 is connected to lead contact 1632.

[0149] Each of the multi-duct leads 1608 and 1610 terminates in a ferrule 1690 and 1691, respectively, which are attached and coupled to the optical fibers as previously described.

[0150] 15B, the conductors of the multi-duct lead body are separate from side-ignition fiber optic portions 1618 and 1619 of optical manifolds 1653 and 1652, respectively. Each of electrode arrays 1604 and 1606 is connected via electrical connections 1650 and 1651, respectively, to the conductors of one of conductor bundles 1640 and 1642.

[0151] Panel 1602 further comprises a grid shield 1614. The grid shield 1614 comprises a generally flat flexible film integrally formed with both of the flexible panels. As previously mentioned, the grid shield may be coated with a reflective material adjacent to the optical fibers. As previously mentioned, the grid shield may be connected to a ground contact for further connection to the IPG ground.

[0152] Panel 1602 further includes reflectors 1616 and 1625 disposed adjacent side-ignited fiber optic sections 1618 and 1619, respectively. In a preferred embodiment, the reflectors are generally semi-cylindrical or parabolic. In another embodiment, the reflectors are flat flexible panels. The reflectors serve to reflect light emitted from the side-ignited fiber sections out of an optical window and to focus incident light from the optical window onto the fiber for transmission to a detector within the IPG.

[0153] 16A, 16B and 16C, an alternative embodiment of a surgical lead 1700 is described. The integrated panel 1702 is generally flat, polymeric and rectangular, as previously described. Integrated within the integrated panel 1702 are multi-duct leads 1718, 1720 and 1722 with optical fibers 1736, as previously described. Each of the multi-duct leads has a proximal electrical contact that is individually connected to an electrode array 1712, 1714 and 1716 via a conductor, as previously described. The integrated panel 1702 further has an optical window 1709 integrated into said panel adjacent side ignition fiber portions 1730, 1732 and 1734, as previously described.

[0154] The composite reflector 1710 is comprised of a plurality of alternating parabolic surfaces, such as parabolic surfaces 1750, 1752, and 1754, and flat interstitial surfaces, such as surfaces 1756 and 1758. The parabolic and flat surfaces are preferably comprised of a flexible inert plastic with sufficient rigidity to sustain moderate bending. In a preferred environment, polyvinyl chloride is used. The inner surfaces 1751, 1753, and 1755 of the parabolic surfaces and the inner surfaces 1757, 1759 of the flat surfaces are all coated with a reflective material, such as titanium dioxide. The inner surfaces 1751, 1753, and 1755 are disposed adjacent side ignition fiber portions 1730, 1732, and 1734 and serve to function as previously described.

[0155] In another preferred embodiment, composite reflector 1710 is grounded to the IPG case via a conductor in one of the multi-duct leads, as previously described.

[0156] 17A and 17B, an alternative embodiment of a surgical lead 1800 is further described.

[0157] The integrated panel 1802 is generally flat, polymeric, and rectangular, as previously described. The integrated panel 1802 includes electrode arrays 1810 and 1812 connected to multi-duct leads 1814 and 1818, as previously described. The integrated panel 1802 further includes integrally formed multi-duct leads 1814, 1816, and 1818, as previously described. Each of the multi-duct leads 1814, 1816, and 1818 includes an optical fiber 1850 with a side-ignition fiber portion 1820, 1822, and 1824. Each optical fiber 1850 is positioned to terminate in a right angle prism, such as right angle prisms 1804, 1806, and 1808, which are positioned to direct light from optical windows 1811, 1813, and 1817 to the optical fibers, or from the optical fibers to the optical windows, as the case may be.

[0158] Referring now to FIG. 18, a method 1900 for placing a surgical lead will be described.

[0159] In step 1902, a laminectomy is performed at the level of the segment that corresponds to the somatic distribution of the patient's pain.

[0160] Electrodes are placed in the spinal canal at step 1904. Typically, the electrodes are placed in the dorsal epidural space by manually inserting the electrode array into the laminotomy space.

[0161] At step 1906, the electrodes are secured to fascia, ligaments, or adjacent bone.

[0162] At step 1908, an incision is made for the IPG.

[0163] At step 1910, the lead is tunneled subcutaneously from the electrode insertion site to the IPG pocket.

[0164] At step 1914, the multiduct lead is secured to the IPG header. If the fiber is not secured to the multiduct lead, it may be inserted and secured in this step, as described below. In practice, the lead body including the fiber subassembly is threaded into the appropriate lead channel, bringing the proximal lead contact into electrical contact with the canted coil spring of the lead channel. The multiduct lead advances within the lead channel until the multiduct lead body encounters a full-stretch conical centering surface 724 that guides it along a cylindrical alignment surface 726 until it engages a stop surface 730 of an anchoring chamber 728. At the same time, the ferrule is advanced within the alignment cylinder 712 until it encounters a ferrule centering surface 716. The ferrule centering surface 716 aligns the optical fiber in the buffer gap 734 with the optical window in the IPG casing adjacent the composite optoelectronic device 740. The multi-duct lead is secured in the lead channel by advancing anchor screw 708 using a torque limiting ratchet until it engages anchor ring 1410 .

[0165] In step 1916, the IPG is placed in the pocket.

[0166] In step 1918, the procedure ends.

[0167] With reference to FIG. 19, a preferred method 2000 of percutaneous lead placement is described.

[0168] In step 2002, a Tuohy needle and needle stylet are inserted into the spinal canal at the appropriate segment level.

[0169] In step 2004, the needle stylet is removed from the lumen of the Tuohy needle.

[0170] In step 2006, the percutaneous lead with attached stylet guide is inserted into the inner diameter of the Tuohy needle.

[0171] In step 2008, the percutaneous lead is guided to an appropriate location within the spinal canal using the stylet guide under fluoroscopy.

[0172] In step 2010, the stylet guidewire is removed from the stylet channel.

[0173] In step 2012, the optical fiber is inserted into the stylet channel, as previously described.

[0174] In step 2014, the Tuohy needle is removed, leaving the lead in place.

[0175] In step 2016, the proximal end of the percutaneous lead is secured to the IPG header, as previously described.

[0176] Next, with reference to FIG. 20, the step 2012 of securing the optical fiber in a stylet channel of a lead will be further described.

[0177] In step 2102, the semi-cylindrical sections 1461 and 1462 are aligned with the percutaneous lead body. In step 2104, the semi-cylindrical sections 1461 and 1462 are assembled by press-fitting. In step 2106, the proximal end of the percutaneous lead body is inserted into the alignment cavity of the threaded part, guided by the fulcrum conical lead centering surface 1463. Alignment surface 1467 aligns the multi-duct lead body with alignment cavity 1498.

[0178] In step 2108, the optical fiber 1418 is inserted into the fiber alignment duct 1499, guided by the fulcrum conical fiber optic centering surface 1465. The optical fiber is then inserted into the stylet channel 1405 of the multi-duct lead body 1402 of the threaded component.

[0179] In step 2110 , the ferrule 1412 is threaded onto the optical fiber 1418 .

[0180] In an alternative embodiment, a stylet is placed into the fiber alignment duct and the stylet channel at this step, in which case the method ends here.

[0181] In step 2112, the threaded component is disassembled.

[0182] In step 2114, the half cylinder is removed from the assembled lead body and optical fiber.

Claims

1. 1. An implantable pulse generator and communication system, comprising: a non-metallic implantable pulse generator casing implanted subcutaneously; an internal processor contained within said casing; a battery contained in the casing and operably connected to the processor; a secondary charging coil contained in the casing and operably connected to the processor; a transcutaneous external processor; a primary charging coil adjacent to the secondary coil and operably connected to the external processor; a charging signal generated by the external processor and transmitted to the primary charging coil; having the charging signal is received by the secondary charging coil; the internal processor adapts the charging signal to charge the battery. Implantable pulse generator and communication system.

2. 10. The implantable pulse generator and communication system of claim 1, further comprising: a first RF antenna included in the casing and operably connected to the internal processor; a second RF antenna operably connected to the external processor; having the internal processor generates a radio signal including a data stream; the wireless signal is transmitted by the first RF antenna; the second RF antenna is adapted to receive the wireless signal and transmit the signal to the external processor; Implantable pulse generator and communication system.

3. 10. The implantable pulse generator and communication system of claim 1, wherein the casing is glass.

4. 10. The implantable pulse generator and communication system of claim 1, wherein the casing is ceramic.

5. 10. The implantable pulse generator and communication system of claim 1, wherein the casing is alumina.

6. 10. The implantable pulse generator and communication system of claim 1, wherein the casing is zirconia.

7. 10. The implantable pulse generator and communication system of claim 1, wherein the casing is sapphire.

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