Electroencephalogram electrode

Abstract

Electroencephalogram electrode The present invention is related to an EEG measurement headset comprising a set of EEG electrode, each EEG electrode (1) comprising: - An enclosure (5) comprising side walls, a back wall and a front opening the enclosure (5) comprising a hydraulic inlet (6) connectable to an external electrolyte source; - An electrical contact (4) connected to a connection wire (2); - A water absorbent material (3) extending from the electrical contact (4) to the front opening; the headset comprising a rigid external shell (9,17) and an inner softer inflatable structure (8) supporting the electrodes of the set of electrodes.

Description

Electroencephalogram electrodeField of the invention

[0001] The present invention is related to an EEG electrode, a set of EEG electrode and a headset comprising a set of EEG electrode.Technical Background

[0002] Electroencephalography (EEG) is one of the most important imaging techniques for the detection of brain disorders due to its superior temporal resolution. It is in fact necessary for the diagnosis and management of multiple life-threatening neurological conditions such as seizures, status epilepticus, and acute brain injuries. However, despite the crucial role of EEG, it is not routinely performed in emergency and intensive care medical settings.

[0003] One of the reasons for this lies in the impractical use of EEG equipment. Furthermore, paramedics who provide medical care in these departments are not trained to place the electrodes. This also partially explains why continuous longterm EEG monitoring is hardly ever available for critically ill patients. This is especially the case in smaller or less specialized healthcare facilities and rural areas. As a result, there is often a significant delay in the initiation of EEG monitoring for unconscious acutely ill patients. Delay in diagnosis leads to delay in treatment and is associated with a higher risk of resistance to anti-seizure medication, longer hospital stays, and ultimately worse outcomes.

[0004] Traditional EEG setup is time-consuming. It involves the precise skull measurement and the placement of multiple electrodes on the patient's scalp according to the international 10-20 EEG recording montage. Since electrodes must be placed on hairy sites, this can be very challenging and time-consuming for the personnel. Then, in order to decrease the skin impedance to acceptable values below 20 kQ, these sites arerubbed with an abrasive paste that removes part of the outer skin called stratum corneum (SC). This layer is the main contributor to the skin impedance with a frequency response that ranges between 200 kQ and 200 Q at 1 Hz and 1 MHz respectively. The Ag / AgCI electrodes are then impregnated with an electrolyte gel that facilitates the transduction of ionic currents, which freely move through brain tissues and cerebrospinal fluid, into electronic currents. Eventually, the impedance of the different electrode-skin couples must be verified to guarantee homogeneous low values and good signal quality at every location. If it is not ensured, the personnel must identify the underlying issues and implement the proper corrective actions. Therefore, this installation process becomes impractical in emergent situations where time is a scarce resource.

[0005] Therefore, these time-consuming tasks require caregivers with experience in EEG. Specialized paramedics are usually present in the neurological service, but not in the emergency department or the ICU. Furthermore, in most hospitals, they are available during normal working hours but not at nights and weekends. Nowadays, the unavailability of trained medical personnel is one of the main impediments to 24 / 7 EEG coverage. This scarcity of human resources coupled to the time required to install the electrodes and achieve acceptable impedance values explain why critical neurological diagnosis is often delayed of several hours.

[0006] Another limitation of the current procedure is the inconvenience caused to the patient due to the abrasive paste and the electrolytic gel, which, in addition to being sticky and making the scalp dirty, can cause skin irritation or infection. A proper amount of gel must be applied, as an excess of it can form electrical bridges between electrodes, inducing a severe loss in spatial resolution. Additionally, once acceptable electrode impedances have been achieved, a countdown of a few hours begins until the gel dries, thus causing the transductive properties to disappear. Hence, gel-based electrodes are not practical for long-term measurements of 12 hours or more.

[0007] Emergent EEG is therefore expensive, as it involves considerable professional expertise to maintain a 24-hour EEG service. Consequently, its availability is often restricted due to the scarcity of technical expertise, administrative, and financialconstraints, despite having proved to be crucial in multiple emergent and critical medical indications.

[0008] To address these challenges, several solutions could be proposed. Developing portable, user-friendly EEG devices that can be rapidly deployed at the bedside by healthcare professionals with minimal training could significantly reduce setup times and make EEG more accessible.

[0009] Implementing these solutions could not only improve the speed and accuracy of neurological assessments in emergency and intensive care settings but could also lead to better patient outcomes through quicker therapeutic interventions. Moreover, streamlining EEG processes could potentially reduce the healthcare costs associated with the management of acute neurological conditions, making it a cost-effective improvement that benefits both patients and healthcare systems. Thus, the modernization and simplification of EEG technology and training are essential steps toward enhancing its utility in emergency neurological care.

[0010] The patent application CN 115736929 discloses an EEG headset comprising EEG electrodes. The disclosed headset is made of an elastic fabric on which the electrodes are supported by means of airbags placed between the fabric and the electrodes, each electrode having its own bag along with an individual pressure sensor.Summary of the invention

[0011] The present invention discloses an EEG measurement headset comprising a set of EEG electrode, each EEG electrode comprising:An enclosure comprising side walls, a backwall and a front opening the enclosure comprising a hydraulic inlet connectable to an electrolyte source;An electrical contact connected to a connection wire;A water absorbent material extending from the electrical contact to the front opening;the headset comprising a rigid external shell and an inner softer inflatable structure supporting the electrodes of the set of electrodes.

[0012] By rigid shell, it is meant a self-supporting structure (i.e., sufficiently rigid to support its own weight without apparent deformation). It can be a continuousclosed structure as in fig. 4, or an opened structure comprising beams supporting the inflatable structure as represented in Fig. 2 and 3.

[0013] Preferred embodiments of the present invention disclose at least one, or an appropriate combination of the following features:the hydraulic inlet is connectable to the external electrolyte source during use of said electrode without disconnection of a patient's scalp;the water absorbing material is selected from the group consisting of hydrogels, hydrophilic opened foam, textile and their combination;the water absorbing material comprises a hydrogel;the hydraulic inlet comprises a closing valve, said closing valve being electrically isolating when closed;the enclosure essentially consists of a soft material having a shore A hardness comprised between 20 and 80, preferably between 30 and 60.

[0014] The EEG headset advantageously comprises a hydraulic network for distributing aqueous solution to each of the EEG electrodes.

[0015] The EEG headset preferably comprises isolating valves for electrically isolating the electrodes from each other.

[0016] Advantageously, the isolating valves are located centrally, close to a single electrolyte source, all valves being controlled by a single command. By 'located centrally", it is meant that the valves are all located together nearby the single electrolyte source.

[0017] The EEG headset preferably comprises at least twenty-one electrodes preferably according to the 10-20 EEG recording standard.

[0018] Preferably, the EEG headset comprises an inflating valve connected to the inflatable structure and a security valve releasing pressure when the pressure inside the inflatable structure is higher than a predetermined value.

[0019] Advantageously, the inflatable structure is a single inflatable structure having a common pressure throughout the entire inflatable structure.Short description of the

[0020] Fig. 1 shows a cross section of an electrode according to the invention.

[0021] Fig. 2 shows an inside view of an example of a headset according to the invention.

[0022] Fig. 3 shows a wired view of an example of headset according to the invention

[0023] Fig. 4 shows another example of a headset according to the invention.

[0024] Fig. 5 shows an alternative enclosure comprising a distal hard part, and a proximal softer part.List of reference1: EEG electrode2: Connecting wire3: water absorbent material (such as a hydrogel)4: Electrical contact5: Enclosure6: hydraulic inlet7: isolating valve8: Inflatable structure9: rigid supporting structure10: Electrolyte feeding pipes11: central distribution valves12: electrolyte inlet13: Printed circuit board (PCB)14: chin strap15: pressure release valve16: air inlet17: rigid supporting helmet18: Distal partial enclosure19: Proximal partial enclosure (softer)Detailed description of the invention

[0025] The present invention uses an EEG electrode 1 comprising a flexible enclosure 5 preferably made of a polymer or elastomer with a hardness between 30A and 60A according to ASTM-412 (silicone or TPU for example) and made by injection molding or additive manufacturing. The polymer is preferably a thermoplastic material. It may optionally then be coated with silver paint or mixed with conductive fibers such as carbon for example. The enclosure must ensure the reliable assembly of two other electrode parts. The electrode may be fixed on a support that is a cap, or headset, helmet, headphones for instance. The securing is made through chemical or mechanical assembly or combination thereof. The electrode shape can be mainly cylindrical or with a curvature and increased contact surface (see figure 1).

[0026] The electrode further comprises a solid conductive EEG electrode 4, for example made of gold, silver, titanium or Ag / AgCl. It can also be a non-conductive material coated with a conductive layer such as gold or Ag / AgCl. This electrode 4 is inserted into the enclosure 5 either by injection overmolding, or by a mechanical or chemical assembly or a combination thereof. Its shape can be flat or cup-shaped, meshed or plain.

[0027] The electrode also comprises an aqueous solution absorbent 3 material that may or may not be conductive (ionically or electronically). It can be cotton, fabric and more particularly a hydrogel. It has a fixed geometry but has a certain flexibility. It can be cylindrical in shape, for example.

[0028] A hole measuring between 0.25 and 2 mm in diameter and passing through the enclosure allows a conductive electrolyte solution to be injected. The orifice can be radially or axially oriented. The hole is preferably connected to an inlet pipe 6.

[0029] Advantageously, the enclosure comprises a distal rigid cap 18, and a proximal softer skirt 19 improving water tightness and comfort of the electrode on the scalp.

[0030] Without being limitative for the present invention, the hydrogel can advantageously be made of a double interconnected network based on sodium alginate and a copolymer of acrylamide and of stearyl methacrylate, sodium chloride and sodiumdodecyl sulfate. The hydrogel is preferably obtained from a process comprising the steps of:Providing a mixture by mixing in an aqueous solution having a concentration of sodium chloride comprised between 0.1 and 1 mol / l:o an amount of surfactant in a weight of the aqueous solution comprised between 1 to 10 wt% in weight of water;o an amount of alginate comprised between 0.5 and 5 wt% in weight of water;o an amount of acrylamide comprised between 5 to 25 wt% in weight of water, wherein the weight ratio of alginate on acrylamide is comprised between 0.5:10 and 1:5;o an amount of alkyl-methacrylate, wherein the alkyl group is preferably linear and comprises 10 to 30 carbons, comprised between 0.5 and 5 mol% relative to the amount of acrylamide;o a thermal initiator;o and an accelerator;irradiating the mixture with UV light to initiate polymerization of a copolymer of acrylamide an alkyl-methacrylate;preferably incubating the irradiated mixture at a temperature comprised between 15°C to 70°C for at least 1 hour, preferably at least 10 hours at room temperature;soaking the irradiated and incubated mixture in a solution of a lithium salt having a concentration comprised between 1 mol / l and 12 mol / l, preferably between 1 mol / l and 6 mol / l.It can optionally embed PEDOT:PSS or glycerol. Before incubating, the irradiated mixture is preferably molded to conform the enclosure cavity. Alternatively, it can be molded in-situ or in dedicated intermediate molds. The assembly can rely on clipping, taper fitting, gluing, chemical treatment, chemical anchors.

[0031] The diameter of the electrode is preferably between 0.75 and 3 cm and the height is between 0.5 and 3 cm.

[0032] In typical use, several electrodes are secured on a patient scalp, forming an EEG measurement device with an electrical network with some spatial constraints.

[0033] A flexible printed circuit board (PCB) 13 may advantageously be used to connect the wires connecting the electrodes to the EEG machine. This allows to lighten the device for an improved comfort, while removing the need of untangling the wires.

[0034] Advantageously, in parallel to the electrical network, the EEG measurement device comprises a fluid distribution network able to distribute electrolytic fluid from one or several entries using injection means such as a syringe or a pump. The entries must be accessible when EEG measurement device is used (i.e. secured on a patient's head) and distribute the fluid to at least one semi-dry fluid absorbent electrode component (fabric, cotton or hydrogel for instance). Such distribution of fluid may improve the continuous measurement time by compensating the moisture lost by evaporation on the semi-dry electrode, thereby improving quality of the electrical contact.

[0035] Advantageously, the distribution channel network comprises isolating valves to avoid conducting channels between electrodes through the fluid distribution network during measurement. Said isolating valves may be disposed centrally (i.e. all valves being grouped together close to the electrolyte source), close to the injection means, or distributed close to each electrode.

[0036] The invention discloses an EEG headset supporting a plurality of semi-dry EEG electrodes. Preferably the EEG headset comprises at least 21 electrodes. It is intended to speed up and facilitate the installation process, while ensuring a reliable and accurate signal acquisition at every position. Those are defined by the internationally recognized 10-20 system that is the gold standard for clinical EEG recordings. The device hence enables to place in less than 10 minutes the 21 required electrodes, on the contrary of several quick and simple EEG products that only have a limited number of electrodes.

[0037] The EEG headset relies on an inflatable principle to evenly distribute the pressure to every electrode location. As such, several interconnected or separatedpneumatic beams are inflated with a pump to adjust the pressure and to secure the device on the patient's head. The pneumatic beams are preferably interconnected. Moreover, it avoids any excessive pressure point that would lead to discomfort when worn for longer duration recordings. A valve allows to inflate the device, while a security valve opens when the pressure is excessive to avoid damage to the device and any lesion for the patient.

[0038] The inflatable beams are either embedded into a semi-flexible supportive structure or secured inside it. The semi-flexible supportive structure has preferably the general shape of a headset or helmet. The semi-flexible structure is preferably multilayered and can be made of thermoplastic or neoprene or a combination thereof. The structure flexibility can be homogeneous or heterogeneous, as, for instance, a neoprene headset with supporting more rigid inserts.

[0039] The materials of the inflatable beams are preferably made of a layered combination of two materials. The outer layer is advantageously less extensible than the inner layer. As a result, the inner layer inflates more than the outer one. Those materials can be woven and non-woven thermoplastic polyurethane (TPU) or nylon or another thermoplastic. They are preferably flexible, water repellent, and weldable with a heat or gluing or chemical treatment process. The inner material is ideally soft and anti-static.

[0040] The electrodes are glued or mechanically or chemically secured into the EEG headset at the referenced positions. The name of the positions is written on the headset to allow lay users to identify each electrode when needed.

[0041] A removable chin strap can be connected to the headset for a more secured installation. It can be made of various flexible materials such as silicone or vulcanized rubber. An aesthetic layer made of textile or soft thermoplastic can be attached on the upper side of the headset through Velcro or another mechanical fixation system.

[0042] Preferably, there is no active component on the headset itself.

Claims

CLAIMS1. An EEG measurement headset comprising a set of EEG electrode, each EEG electrode (1) comprising:An enclosure (5) comprising side walls, a back wall and a front opening the enclosure (5) comprising a hydraulic inlet (6) connectable to an external electrolyte source;An electrical contact (4) connected to a connection wire (2);A water absorbent material (3) extending from the electrical contact (4) to the front opening;the headset comprising a rigid external shell (9,17) and an inner softer inflatable structure (8) supporting the electrodes of the set of electrodes.

2. The headset according to claim 1 wherein the hydraulic inlet (6) is connectable to the external electrolyte source during use of said electrode without disconnection of a patient's scalp.

3. The headset of any of the previous claims wherein the water absorbing material (3) is selected from the group consisting of hydrogels, hydrophilic opened foam, textile and their combination.

4. The headset according to claim 1 or 2 wherein the water absorbing material (3) comprises a hydrogel.

5. The headset according to any of the previous claims wherein the hydraulic inlet (6) comprises a closing valve (7), said closing valve (7) being electrically isolating when closed.

6. The headset according to any of the previous claims wherein the enclosure (5) essentially consists of a soft material having a shore A hardness comprised between 20 and 80, preferably between 30 and 60.

7. The headset according to any of the previous claims, comprising a hydraulic network for distributing aqueous solution to each of the EEG electrodes (1).

8. The headset according to claim 7 further comprising isolating valves (7,11) for electrically isolating the electrodes from each other.

9. The headset according to claim 8 wherein the isolating valves (11) are located centrally, close to a single electrolyte source, all valves being controlled by a single command.

10. The headset according to any of claims 7 to 9 comprising at least twenty-one electrodes (1).

11. The headset according to any of the previous claims comprising an inflating valve connected to the inflatable structure and a security valve releasing pressure when the pressure inside the inflatable structure is higher than a predetermined value.

12. The headset according to claim 11 wherein the inflatable structure is a single inflatable structure having a common pressure throughout the entire inflatable structure.

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