Minimally invasive two-dimensional grid electrode

A system for deploying an electrode array at a target location through a hole formed in the patient's cranium. The system includes an array of electrodes attached to a substrate and an inserter attached to the substrate and/or the array of electrodes. The inserter, substrate and array of electrodes are configured into a first compressed state and are positioned within the lumen of a cannula. Using the cannula, the system is inserted through the hole, the cannula is then removed, and the inserter is used to transition the substrate and electrode array from the first compressed state to a second uncompressed state, thereby deploying the array of electrodes at the target location.

FIELD

The present specification is related generally to the field of electrodes. More specifically, the present specification is related to a compressible multi-contact electrode that can be inserted through an access hole via a surgical procedure, expanded to its full dimensions, verified as to position and location prior to completion of the surgical procedure, and preferably extracted via the same access hole.

BACKGROUND

Surgical treatment for epilepsy is being utilized more often when drug medical therapy fails to control the disease. Evaluation prior to surgery involves conducting direct brain recordings to verify that the epileptic focus is treatable. This type of evaluation is well understood by those of ordinary skill in the art.

Typically, hundreds of electrodes are needed to thoroughly map the brain. The electrodes employed may be in arrays, for example an 8×8 array with 64 contacts. To implant these electrode arrays, a section of skull is removed (skull flap) to allow placement of the electrodes, as shown inFIG. 1. Referring toFIG. 1, the electrodes are in a grid array100and are typically thin and flexible. Some electrodes or a portion of the electrode array100will be placed at the location of the skull flap, and other electrodes will be tucked between the skull and the brain over surfaces that are not directly exposed. To remove the electrode arrays, another surgical procedure is needed. The risks, costs and discomfort for these procedures are significant.

Other electrodes employed may be strip electrodes or needle-like depth electrodes. Strip electrodes may be inserted radially through burr holes, which are typically on the order of 2 cm in diameter. Depth electrodes may be inserted through small drill holes in the skull and removed without anesthesia.

Further, the placement of electrodes is important for interpreting electrode signals that are generated. The desired electrode locations are usually well defined and may be on the surface of the scalp, in or on the brain, or at some other location on the body. Depth electrodes and grid electrodes consist of multiple electrodes in a matrix, where the expected geometric relation of each input to all other inputs within the matrix is known. In complex cases with multiple grids or multiple depth electrodes, the locations of each individual or group of electrodes is either part of the surgical planning or is noted during the surgery. A placement error will lead to either confusion because the testing results do not make sense or worse—a mistaken conclusion that can affect treatment and outcome.

What is needed is a compressible grid electrode that can be compressed, folded, or otherwise modified in shape to allow for insertion and that is configured to subsequently unfolded when in the proper location. What is also needed is a folding grid electrode that is configured to be inserted into a relatively small access hole that can be expanded to its full dimension, that can be verified as to position and location prior to completion of the surgical procedure, and that can be extracted via the same access hole.

SUMMARY

The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods, which are meant to be exemplary and illustrative, and not limiting in scope. The present application discloses numerous embodiments.

The present specification discloses a system for deploying an electrode array at a target location within a patient's cranium through a hole formed in the patient's cranium, the system comprising: a substrate; an array of electrodes attached to the substrate; an inserter attached to the substrate, wherein the inserter, the substrate, and the array of electrodes are configured in a first compressed state and wherein the inserter is configured to expand from the first compressed state to a second uncompressed state; and a cannula configured to accommodate the inserter, the substrate and the array of electrodes in the first compressed state and configured to release the inserter, the substrate and the array of electrodes through the hole and within the patient's cranium at the target location.

Optionally, in the first compressed state, the substrate and array of electrodes have a width that is less than a width of the substrate and array of electrodes in the second uncompressed state.

Optionally, the array of electrodes comprises a plurality of contacts having associated lead wires, and wherein each of said lead wires are connected to a terminal on an electrical device.

Optionally, the system further comprises an actuator coupled to the inserter. Optionally, the actuator is configured to be accessible outside the patient's cranium and further configured such that, when a force is applied to the actuator, in a first direction, the inserter expands, thereby causing the inserter, the substrate, and the array of electrodes to be in the second uncompressed state. Optionally, the actuator is configured to be accessible outside the patient's cranium and further configured such that, when a force is applied to the actuator, in a second direction, the inserter compresses, thereby causing the inserter, the substrate, and the array of electrodes to be in the first compressed state.

Optionally, the inserter comprises at least a first spring element and a second spring element, wherein a distal end of the first spring element is attached to a first edge of the substrate, wherein a distal end of the second spring element is attached to a second edge of the substrate, and wherein the first edge opposes the second edge. Optionally, a proximal end of the first spring element and a proximal end of the second spring element are connected to a common member.

Optionally, the inserter comprises a multi-segmented cantilever coupled to a first and a second actuator. Optionally, the multi-segmented cantilever is configured to expand when the first actuator is pulled in a first direction and the second actuator is pushed in an opposing second direction.

Optionally, the substrate has a tapered proximal portion configured to facilitate ease of extraction of the substrate through the hole.

Optionally, the cannula includes a mark to facilitate a proper orientation of a contact surface of the array of electrodes during release of the inserter, the substrate and the array of electrodes.

Optionally, the cannula has an ovoid cross-section and is curved along its length.

Optionally, the cannula includes a port configured to provide compressed gas to generate a brain-cranium gap for inserting the cannula through the hole.

Optionally, the cannula further accommodates a front-pointing viewing element and at least one illuminator.

The present specification also discloses a method of deploying an electrode array at a target location within a patient's cranium through a hole formed in the patient's cranium, the method comprising: obtaining an electrode array system, wherein the electrode array system comprises a cannula having a lumen, a substrate, an array of electrodes attached to the substrate, and an inserter attached to the substrate, wherein the substrate, the array of electrodes, and the inserter are positioned in the lumen in a first compressed state; inserting the cannula through the hole; sliding the cannula backwards while positioning the inserter, the substrate, and the array of electrodes at the target location; and causing the inserter, the substrate and the array of electrodes to transition from the first compressed state to a second uncompressed state at the target location.

Optionally, in the first compressed state, the substrate and array of electrodes have a width that is less than a width of the substrate and the array of electrodes in the second uncompressed state.

Optionally, the array of electrodes comprises a plurality of contacts having associated lead wires and wherein each of said lead wires are connected to a terminal on an electrical device.

Optionally, the method further comprises causing the inserter, the substrate and the array of electrodes to transition from the first compressed state to the second uncompressed state by moving an actuator attached to the inserter. Optionally, the actuator is configured to be accessible outside the patient's cranium and further configured such that, when a force is applied to the actuator, in a first direction, the inserter expands, thereby causing the inserter, the substrate, and the array of electrodes to be in the second uncompressed state. Optionally, the actuator is configured to be accessible outside the patient's cranium and further configured such that, when a force is applied to the actuator, in a second direction, the inserter compresses, thereby causing the inserter, the substrate, and the array of electrodes to be in the first compressed state.

Optionally, the inserter comprises at least a first spring element and a second spring element, wherein a distal end of the first spring element is attached to a first edge of the substrate, wherein a distal end of the second spring element is attached to a second edge of the substrate, and wherein the first edge opposes the second edge. Optionally, a proximal end of the first spring element and a proximal end of the second spring element are connected to a common member.

Optionally, the inserter comprises a multi-segmented cantilever coupled to an actuator. Optionally, the multi-segmented cantilever is configured to expand when the actuator is pulled in a first direction and configured to contract when the actuator is pulled in a second direction.

Optionally, the method further comprises causing the inserter, the substrate and the array of electrodes to transition from the second uncompressed state to the first uncompressed state at the target location. Optionally, the inserter, the substrate and the array of electrodes transitions from the second uncompressed state to the first uncompressed state by moving an actuator in physical communication with the inserter. Optionally, the method further comprises removing the cannula and the inserter through the hole. Optionally, the method further comprises extracting the array of electrodes through the hole.

Optionally, the method further comprises verifying a physical position of at least one of the inserter, the substrate or the array of electrodes within the patient's cranium.

The present specification also discloses a method of deploying an electrode array at a target location onto a patient's cortex through a burr hole formed on the patient's cranium, the method comprising: inserting a cannula through said burr hole, said cannula accommodating an inserter and an array of electrodes, wherein said inserter and array of electrodes are in a first state; sliding the cannula backwards while positioning said inserter and array of electrodes in said first state at said target location; causing said array of electrodes to be in a second state at said target location; and verifying said positioning of said inserter and array of electrodes at said target location.

Optionally, the method further comprises removing the cannula and the inserter through the burr hole. Optionally, the method further comprises extracting the array of electrodes through the burr hole.

Optionally, in said first state, the inserter and array of electrodes are compressed.

Optionally, in said second state, the array of electrodes is expanded.

The present specification also discloses a system for deploying an electrode array at a target location onto a patient's cortex through a burr hole formed on the patient's cranium, the system comprising: an array of electrodes formed on a substrate; an inserter attached to the array of electrodes, wherein the inserter and array of electrodes are configured into a first state; and a cannula, wherein the cannula accommodates the inserter and array of electrodes in said first state, and wherein the cannula is inserted through the burr hole to deploy the array of electrodes at the target location in a second state.

Optionally, in said first state, the inserter and array of electrodes are compressed.

Optionally, in said second state, the array of electrodes is expanded.

Optionally, the array of electrodes comprises a plurality of contacts having associated lead wires, wherein said lead wires are bundled into at least one pigtail.

Optionally, an actuator is coupled to the inserter. Optionally, application of a force on the actuator in a direction causes the inserter to be expanded, thereby causing the array of electrodes to be in said second state.

Optionally, the cannula and the inserter are removed from the burr hole after the array of electrodes is deployed in said second state.

Optionally, the array of electrodes is removed through the burr hole using said at least one pigtail.

Optionally, the inserter comprises a multi-segmented cantilever coupled to an actuator.

The present specification also discloses a method of deploying an electrode array at a target location onto a patient's cortex through a burr hole formed on the patient's cranium, the method comprising: inserting a cannula through said burr hole, said cannula accommodating an inserter and an array of electrodes, wherein said inserter and array of electrodes are in a first state; and sliding the cannula backwards while positioning said inserter and array of electrodes in said first state at said target location.

Optionally, the method further comprises causing said inserter and array of electrodes to be in a second state at said target location.

Optionally, said second state is caused by activating an actuator coupled to said inserter.

Optionally, the method further comprises verifying said positioning of said inserter and array of electrodes at said target location.

Optionally, the method further comprises removing the cannula and the inserter through the burr hole.

Optionally, the method further comprises extracting the array of electrodes through the burr hole.

The present specification also discloses a method of deploying an electrode array at a target location onto a patient's cortex through a burr hole formed on the patient's cranium, the method comprising: inserting a cannula through said burr hole, said cannula accommodating an inserter and an array of electrodes, wherein said inserter and array of electrodes are in a first state; sliding the cannula backwards while positioning said inserter and array of electrodes in said first state at said target location; causing said array of electrodes to be in a second state at said target location; and verifying said positioning of said inserter and array of electrodes at said target location.

Optionally, the method further comprises removing the cannula and the inserter through the burr hole.

Optionally, the method further comprises extracting the array of electrodes through the burr hole.

Optionally, in said first state, the inserter and array of electrodes are compressed.

Optionally, in said second state, the array of electrodes is expanded.

The aforementioned and other embodiments of the present shall be described in greater depth in the drawings and detailed description provided below.

DETAILED DESCRIPTION

The term ‘user’ is used interchangeably to refer to a surgeon, neuro-physician, neuro-surgeon, neuro-physiologist, technician or operator of an electroencephalogram or electroencephalography (EEG) system and/or other patient-care personnel or staff.

A “computing device” is at least one of a cellular phone, PDA, smart phone, tablet computing device, patient monitor, custom kiosk, or other computing device configured to execute programmatic instructions. It should further be appreciated that each device and monitoring system may have wireless and wired receivers and transmitters capable of sending and transmitting data. Each “computing device” may be coupled to at least one display, which displays information about the patient parameters and the functioning of the system, by means of a graphical user interface (GUI). The GUI also presents various menus that allow users to configure settings according to their requirements. The system further comprises at least one processor to control the operation of the entire system and its components. It should further be appreciated that the at least one processor is capable of processing programmatic instructions, has a memory capable of storing programmatic instructions, and employs software comprised of a plurality of programmatic instructions for performing the processes described herein. In one embodiment, the at least one processor is a computing device capable of receiving, executing, and transmitting a plurality of programmatic instructions stored on a volatile or non-volatile computer readable medium. In addition, the software comprised of a plurality of programmatic instructions for performing the processes described herein may be implemented by a computer processor capable of processing programmatic instructions and a memory capable of storing programmatic instructions.

“Electrode” refers to a conductor used to establish electrical contact with a nonmetallic part of a circuit. EEG electrodes are small metal discs usually made of stainless steel, tin, gold or silver covered with a silver chloride coating. They are typically placed on the scalp on predetermined locations. “Depth electrodes” are made of thin wires, are configured to record seizures which may start deep in the brain, and are typically inserted into the brain parenchyma. “Strip and grid electrodes” are conductors that are positioned, implanted or embedded within a thin sheet of plastic and are typically configured to be placed on a surface of the brain.

In the description and claims of the application, each of the words “comprise” “include” and “have”, and forms thereof, are not necessarily limited to members in a list with which the words may be associated. It should be noted herein that any feature or component described in association with a specific embodiment may be used and implemented with any other embodiment unless clearly indicated otherwise.

As used herein, the indefinite articles “a” and “an” mean “at least one” or “one or more” unless the context clearly dictates otherwise.

The present specification is directed towards electrodes and inserters, together referred to as an “electrode system”, configured to allow for insertion of a compressible grid electrode, in a compressed configuration, through a relatively small hole, which can then be expanded to position an array of contacts over the surface of the brain. In some embodiments, the hole is dime-sized. In some embodiments, a diameter of the hole ranges between 2 mm and 30 mm, preferably 10 mm to 20 mm, and any numerical increment therein. The system can then use an electrode location system to verify that the grid electrode is properly positioned during the surgery. The grid electrode may be removed without additional surgery in an antiseptic environment.

FIG. 2Aillustrates an assembly of an electrode system200, with electrode array202in compressed form and housed in a cannula204, in accordance with some embodiments of the present specification. The electrode system200comprises an inserter201attached to the electrode array202. The electrode system200is in compressed form and contained within the cannula204, wherein the cannula204is stiff enough to be inserted into a desired location and depth of a patient's skull or cranium. In embodiments, the electrode array202comprises a distal end202aand a proximal end202b.

In an embodiment, the electrode array202is a grid electrode and consists of an array of contacts203, each of which has a lead wire207(visible inFIG. 2C). The lead wires207are bundled into one or more pigtails208and terminated in a multi-contact connector. A pigtail is defined as a short length of wire that connects, at one end, to a terminal on an electrical or computing device and, at the other end to circuit wires. Within or alongside the compressed electrode array202is a guide wire206. In an alternate configuration, a plunger may follow the lead wires207to the proximal end202bof the compressed electrode array202. Operationally, after the cannula204has been inserted into a patient's skull, the cannula is pulled back to thereby release the compressed electrode array202at the desired location. The guide wire206or the plunger is then used to keep the electrode array202at the desired location and depth. The electrode system200also includes, in some embodiments, an actuator210described in greater detail below.

FIG. 2Bis an illustration of the electrode system200ofFIG. 2A, with electrode array202in compressed form and removed from the cannula204, in accordance with some embodiments of the present specification. The electrode array202is shown in a compressed configuration with the array of contacts203and the lead wires (or electrode leads)207bundled into at least one pigtail208. The electrode leads are flexible and resist breakage when the electrode array202is compressed and uncompressed.

In embodiments, the electrode array202is attached or coupled to a substrate220having length and/or width dimensions of 2 cm to 15 cm in an uncompressed form. The substrate220of the electrode array202is of sufficient strength and flexibility so that the array202will not fragment during insertion or removal. In some embodiments, if necessary, reinforcing filaments can be added to the substrate which will effectively distribute the forces that come into play during compression and release of the electrode array202. In embodiments, the substrate is biocompatible for temporary implantation and can be sterilized. In various embodiments, the substrate220is made of flexible biocompatible material such as silicone rubber and with conductive contacts as are currently used for grid electrodes such as stainless steel, platinum or carbon. The geometry can be variable both in size and shape as is currently supported by invasively placed cortical grid electrodes. The contacts may also be placed asymmetrically to accommodate optimal spring positions and to allow ease of placement and removal.

In various embodiments, the electrode array202is compressed into a plurality of configurations such as, but not limited to, a first configuration wherein the array202is rolled up, a second configuration wherein the array202is folded in an accordion-like manner, a third configuration wherein the array202is compressed in a serpentine manner, a fourth configuration wherein the array202is squeezed in a tube-like manner or in other ways or configurations that combine or are different from these four exemplary configurations.

Also shown inFIG. 2Bis the inserter201in compressed form along with an actuator210. A compressed assembly200aof the inserter201and the electrode array202is also shown. In the compressed form, the inserter201has dimensions of 2 cm to 15 cm long and less than 1 cm in width. In various embodiments, the inserter201is attached or coupled to the electrode array202and/or the substrate220using any attachment means known in the art. In some embodiments, in a compressed state, the substrate220, in combination with the electrodes/contacts203, the inserter201and the lead wires207, have dimensions that are less than the dimensions of the substrate, electrode/contacts, and lead wires in an uncompressed state.

FIG. 2Cis an illustration of the electrode system200ofFIGS. 2A and 2B, in uncompressed or expanded form, in accordance with some embodiments of the present specification. As described earlier, the grid electrode array202consists of an array of contacts203, each of which has a lead wire207. The lead wires207are bundled into one or more pigtails208and terminated in a multi-contact connector. The pigtails208pass through the patient's skull and skin and the connector is external to the patient. In some embodiments, the grid electrode array202may be fabricated on the substrate220which is thin and flexible and which conforms to the surface of the patient's brain when applied, and which can be compressed or folded into a tube-like structure for insertion.

An uncompressed or unfurled configuration200bof the inserter201and the electrode array202is also shown. The unfurling of the electrode array202requires it to roll across or slide across the surface of the patient's brain. In embodiments, this is accomplished in a plurality of ways depending on the compression method and the shape or configuration of the final compressed grid array202. In various embodiments, a scissors action, a fluid filled hydraulic system built into the grid array202, a multi-segmented cantilevered action, or a spring which is gradually released as the cannula204is retracted is used to accomplish the unfurling. In other embodiments, the grid202comprises a shape-memory material that expands once the cannula204is retracted from the compressed assembly of the electrode array202and inserter201. In some embodiments, a combination of these unfurling systems is used.

The inserter201is also shown in uncompressed form in theFIG. 2C, which employs a mechanical actuator210to unfurl the compressed electrode system200a(shown inFIG. 2B) into an uncompressed state200bfor placement on the surface of a patient's brain, in accordance with some embodiments of the present specification. In some embodiments, as shown inFIG. 2C, the actuator210is coupled to a collapsible as well as expandable structure211(for example, a multi-segmented cantilever). In some embodiments, a force applied on the actuator210in a first direction causes the structure211to expand (thereby causing the attached electrode array202to also unfurl) while a force applied on the actuator210in a second direction (opposite to the first direction) causes the structure211to collapse or compress.

FIG. 2Dshows an exemplary inserter201dconfigured in the form of a multi-segmented cantilever or scissors jack mechanism, in accordance with some embodiments of the present specification. Configuration265shows the inserter201din a fully compressed state, configuration267shows the inserter201din a partially expanded state while configuration269shows the inserter201din a fully expanded state. The scissors jack mechanism of the inserter201dcomprises a plurality of segments250coupled together via a plurality of hinges252that allow flexible expansion or compression of the segments250. First and second sliding joints254,255enable portions of the coupled segments250to slide up or down along first and second bars257,258during expansion or compression of the segments250, respectively. The inserter201dalso comprises a proximal actuator260and a distal actuator262to enable modulation of the inserter201dinto expanded or compressed states. During operation, a user pulls the distal actuator262down (or holds stationary) and pushes the proximal actuator260up thereby applying opposing forces to the proximal and distal hinges252and expanding the scissors jack mechanism laterally.

FIG. 3is a flow chart describing exemplary steps for inserting, expanding, verifying, and extracting the electrode system, in accordance with some embodiments of the present specification. At step305, an insertion, access or burr hole is formed or created in a patient's skull or cranium at a desired location and of a desired depth so as to enable access to a surface of the patient's brain or cortex. At step310, an assembly of an inserter attached to an electrode array is compressed and slid or inserted into the access or burr hole through a cannula. At step315, the cannula is slid back leaving the compressed assembly of the electrode array and the inserter in place.

At step320, the electrode array is uncompressed, unfurled, deployed or expanded over the surface of the patient's brain or cortex and at the desired location or position. In some embodiments, the electrode array is unfurled by applying a force, in a direction, to an actuator coupled to the inserter wherein the inserter is a multi-segmented cantilever. In some embodiments, the electrode array is unfurled by a scissors action of the actuator or inserter. In some embodiments, the inserter is a hydraulically actuated system built into the electrode array wherein actuation of the hydraulic pressure causes the electrode array to unfurl. In some embodiments, the inserter is embodied as a spring that is gradually released as the cannula is retracted. In some embodiments, the inserter and/or the grid electrode array comprises a shape-memory material that expands passively causing the electrode array to unfurl.

At step325, the location or position of the deployed or unfurled electrode array is verified to ensure that the location or position is indeed the intended, targeted or desired position. At step330, the inserter is removed and/or released through the burr hole. In some embodiments, the inserter is a hydraulically actuated system wherein the associated hydraulic pressure is released for removal of the inserter. Finally when desired, at step335, the electrode array is removed or extracted through the burr hole by teasing it out using at least one pigtail of the electrode array. In embodiments, the flexible substrate of the electrode array will collapse in on itself and exit via the insertion path and insertion or burr hole.

FIG. 4illustrates exemplary steps for inserting the electrode system into a burr hole, in accordance with some embodiments of the present specification. At step405, a cannula404, comprising a compressed assembly of an inserter401attached to an electrode array402, is inserted into a burr hole403formed in the cranium of a patient. At step410, the cannula404is slid back, through the burr hole403, leaving the compressed assembly of the inserter401and the electrode array402in position at a desired or target site on the patient's brain or cortex407. At step415, the electrode array402is deployed, uncompressed or unfurled by activating an actuator411coupled to the inserter401. Finally, after deployment, at step420the inserter401and the cannula404are removed through the burr hole403, leaving the electrode array402deployed on the patient's brain or cortex407.

FIG. 5illustrates exemplary steps for verifying electrode placement using excitation and field measurements, in accordance with some embodiments of the present specification. For verification, a plurality of surface electrodes505are placed on a patient's scalp507such that the surface electrodes505are over the expected, intended, desired or target location where the electrode array502is supposed to have been implanted and deployed over the surface of the patient's brain or cortex511. In other words, the surface electrodes505are located directly over the electrode array502such that they overlap or are mutually parallel with the patient's skull in between. Lead wires from the electrode array502are bundled into at least one pigtail515and are in electrical communication with an EEG amplifier520. The surface electrodes505are in electrical communication with an electrical pulse generator510that causes pulsed electric field to be generated across the plurality of surface electrodes505.

The pulsed electric field generated across the plurality of surface electrodes505is detected as a signal by each implanted grid electrode (of the electrode array502). The location of each grid electrode is calculated from such signal using an inverse localization and statistical comparison to an expected, intended, desired or target location.

FIG. 6Aillustrates an assembly of an electrode system600in compressed form and housed in a cannula604along with a visualization or imaging system630, in accordance with some embodiments of the present specification. The electrode system600comprises an inserter601attached to an electrode array602. The electrode system600is in compressed form and contained within the cannula604, wherein the cannula604is stiff enough to be inserted into a desired location and depth of a patient's skull or cranium. In embodiments, the electrode array602comprises a distal end602aand a proximal end602b.

In an embodiment, the electrode array602is a multi-contact grid electrode consisting of an array of contacts603, each of which has a lead wire607(visible inFIG. 6C). The lead wires607are bundled into one or more pigtails608and terminated in a multi-contact connector. Within or alongside the compressed electrode array602is a guide wire606. In an alternate configuration, a plunger would follow the lead wires607to the proximal end602bof the compressed electrode array602. Operationally, after the cannula604has been inserted into a patient's skull, it is pulled back, releasing or unfurling the compressed electrode array602using the guide wire606or the plunger to keep the electrode array602at the desired location and depth. The electrode system600also includes, in some embodiments, an actuator610.

In some embodiments, as shown inFIG. 6A, the cannula604may have a circular cross-section and a straight elongate body. However, in alternate embodiments, as shown inFIG. 6E, the cannula604bmay have an ovoid or oblong cross-section605and may be curved along its length to transit a surface of the brain around a curvature of the brain. In some embodiments, as shown inFIG. 6E, a port640in the cannula604amay provide compressed gas to generate a brain-cranium gap for inserting the cannula604aand visualizing the insertion and deployment trajectory.

In some embodiments, the visualization or imaging system630comprises a front-pointing viewing element632to visualize and image, based on its field of view, insertion and deployment of the electrode array602into the patient's skull and at least one illuminator634for illuminating a field of view of the front-pointing viewing element632. In some embodiments, the front-pointing viewing element632is a digital camera comprising a front-pointing image sensor such as, but not limited to, a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS) image sensor.

In embodiments, the front-pointing viewing element632is positioned at a distal tip of an elongated sheath633. During deployment, the elongated sheath633is inserted through a proximal end of the cannula604such that the front-pointing viewing element632lies within, proximal or protrudes a distal end of the cannula604.

In an embodiment, the front-pointing viewing element632is mounted on a circuit board, which supplies it with necessary electrical power, and in an embodiment, generates still images and/or video feeds captured by the image sensor. In one embodiment, the circuit board is connected to a set of electrical cables (not shown) which are threaded through a channel running through the elongated sheath633. The set of electrical cables emanate from a proximal end of the sheath633for connection to a computing device and associated display, monitor or screen. In various embodiments, the computing device is configured with hardware and/or software to receive and process image and/or a video feed acquired by the front-pointing viewing element632and display the image and/or video feed on an associated display, monitor or screen. In an embodiment, the front-pointing viewing element632has a lens assembly mounted on top of it and provides the necessary optics for receiving images. In one configuration, the lens assembly includes a plurality of lenses, static or movable, which provide a field of view ranging from 90 degrees to 180 degrees.

In some embodiments, the at least one illuminator634may include a light-emitting diode (LED), which may be a white light LED, an infrared light LED, a near infrared light LED, an ultraviolet light LED or any other LED. In such embodiments, the at least one LED may be coupled to the same circuit board on which the front-pointing viewing element632is mounted and positioned proximate the front-pointing viewing element632. In some embodiments, the at least one illuminator634may be a fiber optic illuminator that transmits light generated from remote sources. In such embodiments, the fiber optic illuminator is inserted through the cannula604and positioned next to the front-pointing viewing element632.

During deployment, the at least one illuminator634(that is, the LED or the fiber optic illuminator) together with the front-pointing viewing element632are inserted through the proximal end of the cannula604so as to lie proximate or protrude the distal end of the cannula604. In various embodiments, the visualization or imaging system630(that is, the front-pointing viewing element632and the at least one illuminator634) rests in the cannula604during insertion, but may be protruded beyond the distal end of the cannula604after the cannula604is positioned for deployment—as can be seen inFIG. 6D. In some embodiments, the contents (that is, the visualization or imaging system630and the electrode system600) of the cannula604are stacked such that the visualization or imaging system630can be deployed first. The imaging system620once deployed can be moved laterally to provide clearance for the electrode system600. This allows more room (or clearance) for the electrode system600without increasing the cross-sectional size of the cannula604while also allowing visualization of the deployment. Once the electrode system600is fully deployed the front-pointing viewing element632fits again through the cannula604along with electrode leads or lead wires when the cannula604is removed.

FIG. 6Bis an illustration of the electrode system600ofFIG. 6A, with the electrode array602in compressed form and removed from the cannula604, in accordance with some embodiments of the present specification. The electrode array602is shown in a compressed configuration with the array of contacts603and the lead wires (or electrode leads)607bundled into at least one pigtail608. The electrode leads are flexible and resist breakage when the electrode array602is compressed and uncompressed.

In embodiments, the electrode array602is attached or coupled to a substrate625having dimensions of 2 cm to 15 in an uncompressed form. The substrate625of the electrode array602is of sufficient strength and flexibility so that the array602will not fragment during insertion or removal. In some embodiments, if necessary, reinforcing filaments can be added to the substrate which will effectively distribute the forces that come into play during compression and release of the electrode array602. In embodiments, the substrate625is biocompatible for temporary implantation and can be sterilized.

In various embodiments, the substrate625is made of flexible biocompatible material such as silicone rubber and with conductive contacts as are currently used for grid electrodes such as stainless steel, platinum or carbon. The geometry can be variable both in size and shape as is currently supported by invasively placed cortical grid electrodes. The contacts may also be placed asymmetrically to accommodate optimal spring positions and to allow ease of placement and removal. The plurality of electrodes or contacts603are distributed across the substrate625. Each electrode or contact, of the plurality of electrodes or contacts603, has dimensions of 0.1 mm to 10 mm. In some embodiments, the electrodes or contacts603are preferably distributed such that there is at least 1 electrode or contact603for every 0.1 mm2to 20 mm2of the substrate625. In various embodiments, the electrodes or contacts603are attached or coupled to the substrate625using any attachment mechanism known in the art.

In various embodiments, the electrode array602is compressed into a plurality of configurations such as, but not limited to, a first configuration wherein the array602is rolled up, a second configuration wherein the array602is folded in an accordion-like manner, a third configuration wherein the array602is compressed in a serpentine manner, a fourth configuration wherein the array202is squeezed in a tube-like manner or in other ways or configurations that combine or are different from these three exemplary configurations.

Also shown inFIG. 6Bis the inserter601in compressed form along with the actuator610. In various embodiments, the inserter601is removably attached or coupled to the electrode array602and/or the substrate625. In some embodiments, in a compressed state, the substrate625, in combination with the electrodes/contacts603, the inserter601and the lead wires607, have dimensions that are less than the substrate625and electrodes/contacts603in uncompressed form.

FIG. 6Cis an illustration of the electrode system600ofFIGS. 6A and 6B, in uncompressed or expanded form, in accordance with some embodiments of the present specification. As described earlier, the grid electrode array602consists of an array of contacts603, each of which has a lead wire607. The lead wires607are bundled into one or more pigtails608and terminated in a multi-contact connector. The pigtails608pass through the patient's skull and skin, via a burr hole, and the multi-contact connector is external to the patient. In some embodiments, the grid electrode array602is fabricated on the substrate625which is thin and flexible so as to conform to the surface of the patient's brain when applied, and which can be compressed, rolled or folded into a tube-like structure for insertion.

An uncompressed or unfurled configuration601bof the inserter601is also shown wherein the inserter601is embedded/built into, coupled or attached to the flexible substrate625that supports the grid electrode array602. Unfurling or unfolding of the electrode array602requires it to roll across or slide across the surface of the patient's brain. In accordance with an aspect of the present specification, the inserter601is embodied as a spring which is gradually released as the cannula604(FIG. 6A) is retracted thereby unfurling the electrode array602.

The inserter601embodied as one or more springs, shown in uncompressed form inFIG. 6C, also employs a mechanical actuator610to aid unfurling of the compressed electrode system600(FIG. 6B) into an uncompressed state600b(FIG. 6C) for placement on the surface of a patient's brain, in accordance with some embodiments of the present specification. The actuator610is held in place when the cannula604(FIG. 6A) is retracted and subsequently released from the spring for removal of the actuator610.

In some embodiments, referring back toFIG. 6C, a proximal portion615of the substrate625has a tapered shape to facilitate ease of movement through the burr hole during retraction of the cannula604(FIG. 6A). Additionally, in some embodiments, the electrode contacts603as well as the inserter610, embodied as one or more springs, are also distributed on the substrate625in a tapered configuration to facilitate ease of movement of the electrode system600through the burr hole during retraction of the cannula604(FIG. 6A).

The spring actuated embodiment expands towards its pre-compressed position taking the electrode substrate along. As shown inFIG. 6C, the actuator610is coupled to a collapsible or expandable spring (or inserter601).

In some embodiments, the spring is left in place within the substrate625along with the electrode array602upon deployment in the patient's brain and provides a collapsing mechanism when the electrode array602is removed (such as by teasing and tugging at the at least one pigtail608). In alternate embodiments, the spring can be pulled out or released from the substrate625once the electrode array602is deployed and its desired placement is confirmed.

Referring again toFIG. 6C, in some embodiments, a distribution of the plurality of electrodes or contacts603on the substrate625may be asymmetrical as locations of the contacts603may be required to be shifted to avoid overlap with spring locations.

In various embodiments, the spring (inserter601) may be configured in a plurality of forms.FIG. 7shows first, second and third configurations701a,701b, and701cof a spring functioning as an inserter, in accordance with some embodiments of the present specification. In the first configuration701a, the spring comprises a plurality of separate spring elements705. In the second configuration701b, the spring comprises a plurality of hybrid elements such that at least one sequential or child spring element710may be attached or branch off along a length of at least one preceding or parent spring element705.

In the third configuration701c, the spring is shown incorporating first and second features that enable modulation or adjustment of the spring constant of the spring. In embodiments, the spring constant of each spring element705may be adjusted for its position along the grid electrode array. In some embodiments, this is accomplished by adding a first feature in the form of S-curves715to one or more spring elements705. In some embodiments, this is accomplished by incorporating a second feature that deals with modifying or changing a geometry720(comprising, cross-sectional shape and/or size/radius) along a length of one or more spring elements705. It should be appreciated, that attaching at least one child spring element710to at least one parent spring element705, as shown in the second configuration701b, also enables modulation of the spring constant. In some embodiments, contacts are placed asymmetrically to accommodate optimal spring positions and to allow ease of placement and removal.

While the illustrations of the first, second and third configurations701a,701b,701care of relatively simple spring geometries, it should be noted that in various alternate embodiments the spring geometries may be more complex to optimize both the unfolding process and to reduce forces and risk of injury. It should be appreciated, however, that in a preferred embodiment, there is at least one first spring element having a distal end in physical communication with a first corner or edge of the electrode array (such as the left side) and at least one second spring element having a distal end in physical communication with a second corner or edge of the electrode array (such as the right side) where 1) the first corner or edge is positioned opposite the second corner or edge, 2) the distal end of the at least one first spring element is configured to move separate and distinct from the distal end of the at least one second spring element, preferably in an opposing direction, and 3) a proximal end of the at least one first spring element and the at least one second spring element are connected to a common member. It should further be appreciated that additional spring elements may be attached to areas of the electrode array proximate the first corner or edge and proximate the second corner or edge where each of those additional spring elements are attached, at a proximal end, to the same common member.

In embodiments, the spring elements705,710and features715,720may be fabricated from materials such as, for example, plastic, metal or carbon fiber. In embodiments, tips725of the spring elements705,710are embedded/built into, attached or coupled to the electrode substrate (substrate625ofFIG. 6C), and the tips725themselves are shaped, such as for example with a ball end or a substantially spherical or bulbous end, to reduce risk of injury to the brain tissue. In some embodiments, the spring is left in place within the substrate along with the electrode array upon deployment in the patient's brain and provides a collapsing mechanism when the electrode array is removed. In alternate embodiments, the spring can be pulled out or released from the substrate once the electrode array is deployed and its desired placement is confirmed.

FIG. 8is a workflow describing exemplary steps for inserting, expanding, verifying, and extracting the electrode system, in accordance with some embodiments of the present specification. At step805, an insertion, access or burr hole801is formed or created in a patient's skull or cranium802at a desired location and of a desired depth so as to enable access to a surface of the patient's brain or cortex803.

At step810, a cannula811is inserted through the hole801with the help or guidance of a visualization or imaging system812comprising a front-pointing viewing element (such as a digital camera) and at least one illuminator (such as an LED of a fiber optic illuminator). In some embodiments the cannula811may have a circular cross-section and a straight elongate body. However, in alternate embodiments, the cannula811may have an ovoid or oblong cross-section and may be curved along its length.

At step815, in some embodiments, an assembly816of an inserter attached to an electrode array is compressed or collapsed and slid or inserted into the access or burr hole801through the cannula811. In alternate embodiments, a compressed assembly816of the inserter attached to the electrode array along with the visualization or imaging system812is prepackaged or stacked within the cannula811and ready for deployment. In some embodiments, the inserter is embodied in the form of a collapsible or expandable spring. A plurality of lead wires or electrode leads emanating from a plurality of electrode contacts of the electrode array, are bundled together into at least one pigtail817. In some embodiments, the cannula811includes an orientation mark or indicator (at distal and/or proximal ends of the cannula811) so that a proper contact surface or side of the electrode array is deployed with contacts against the brain or cortex803when uncompressed. This is advantageous since the surfaces of the electrode array are not reversible. In alternate embodiments, where the cannula811is curved along its length, the orientation mark or indicator is not required as the bearing of the contact surface or side of the electrode array is implied to be a concave side of the cannula811. Accordingly, the assembly816within the cannula811is prepackaged such that the contact surface or side of the electrode array resides towards the concave side of the curved cannula811.

At step820, the cannula811is slid back and partially withdrawn leaving and exposing the assembly816of the electrode array and the inserter in place. As the cannula811is withdrawn, the compressed assembly816expands, unfurls or unfolds due to a recoiling or releasing action of the spring (inserter) thereby unfurling the electrode array over a surface of the patient's brain or cortex803. In some embodiments, a guide wire821is utilized to keep the assembly816at the desired location and depth while the cannula811is being retracted, slid back or withdrawn. It should be appreciated that pushing on or holding the guide wire821in place, while the cannula811is being retracted, keeps the electrode array and the inserter in place and enables the spring inserter to un-compress or unfurl and spread the electrode array.

At step825, the location or position of the deployed or unfurled electrode array is verified to ensure that the location or position is indeed the intended, targeted or desired position. In embodiments, verification of the deployment is performed visually (using the visualization or imaging system812) and/or electrically. For electrical verification, a plurality of surface electrodes826(shown in the figure associated with step805) are placed on the patient's scalp such that the surface electrodes826are over the expected, intended, desired or target location where the electrode array is supposed to have been implanted and deployed over the surface of the patient's brain or cortex803. Lead wires from the electrode array, bundled into at least one pigtail817, and are in electrical communication with an EEG amplifier. The surface electrodes826are in electrical communication with an electrical pulse generator that causes pulsed electric field to be generated across the plurality of surface electrodes826. The pulsed electric field generated across the plurality of surface electrodes826is detected as a signal by each implanted grid electrode (of the electrode array). The location of each grid electrode is calculated from such signal using an inverse localization and statistical comparison to an expected, intended, desired or target location.

At step830, the cannula811is completely withdrawn or retracted leaving the assembly816at the target location. As shown, the pigtail817extends from the hole801. Finally when desired, at step835, the assembly816is removed or extracted through the hole801by teasing it out using the at least one pigtail817of the electrode array. In embodiments, the flexible substrate of the electrode array and the inserter, embodied in the form of the spring, will collapse in on itself and exit via the insertion path and insertion or burr hole801.

The above examples are merely illustrative of the many applications of the system and method of present specification. Although only a few embodiments of the present specification have been described herein, it should be understood that the present specification might be embodied in many other specific forms without departing from the spirit or scope of the specification. Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the specification may be modified within the scope of the appended claims.