US20080234791A1 - Spinal cord implant systems and methods - Google Patents

Abstract

A system for transferring spinal cord signals comprises a superior electrode and an inferior electrode. The superior electrode interfaces with a first portion of a spinal cord of a human body; and the inferior electrode interfaces with a second portion of the spinal cord. The superior electrode has at least one superior contact for receiving signals from the first portion of the spinal cord to transmit to the inferior electrode; and the inferior electrode has at least one inferior contact for transmitting signals received from the superior electrode to the second portion of the spinal cord.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of U.S. Provisional Patent Application No. 60/881,056 filed on Jan. 17, 2007, the entirety of which is incorporated by reference herein.
BACKGROUND
• Neural interfaces have emerged as possible interventions to reduce the burden associated with some neurological diseases, injuries, and disabilities, such as spinal cord injuries which can cause reduced sensation and mobility by damaging the nerve pathways between the brain and the rest of the body. Many neural interfaces take advantage of cortical plasticity, which is the brain's ability to reorganize its functions and their locations within the brain in response to chronic changes in the received sensory information.
• Researchers have considered implanting electrode devices to detect nerve signals or stimulate nerves. For example, signals detected in the brain or peripheral nervous system may be used to help control devices outside the body, such as cursors on a computer screen or prostheses; cochlear implants for the deaf stimulate auditory nerves in response to sounds; and stimulation of the spinal cord has been considered for restoring genitourinary and bowel motor functions. Studies of spinal cord recording include:
• • Borisoff J. F., McPhail L. T., Saunders J. T., Birch G. E., Ramer M. S.,Detection and classification of sensory information from acute spinal cord recordings. IEEE Transactions on Biomedical Engineering. 53 (8):1715-9, 2006.
  • Sahin M.,Information capacity of the corticospinal tract recordings as a neural interface. Annals of Biomedical Engineering. 32 (6):823-30, 2004.
  • Patton H. D. and Amassian V. E.,Single and multi unit analysis of cortical stage of pyramidal tract activation. Journal of Neurophysiology. 17:345-63, 1954.
• For persons suffering from paralysis due to spinal cord injury, attempts to restore motor function have relied on retraining any undamaged nerve pathways and stimulating nerves with signals generated independently of brain signals. Studies of spinal cord stimulation include:
• • Philip Troyk, Martin Bak, Joshua Berg, David Bradley, Stuart Cogan, Robert Erickson, Conrad Kufta, Douglas McCreery, Edward Schmidt, and Vernon Towle.A Model for Intracortical Visual Prosthesis Research. Artificial Organs. 27 (11): 1005-1015, 2003.
  • Jonathan Coulombe, Sylvain Carniguian, and Mohamad Sawan,A Power Efficient Electronic Implant for a Visual Cortical Neuroprosthesis, Artificial Organs. 29 (3):233-238.2005.
  • Rajiv Saigal, Costantino Renzi, and Vivian K. Mushahwar,Intraspinal Microstimulation Generates Functional Movements After Spinal-Cord Injury, IEEE Transactions on Neural Systems and Rehabilitation Engineering, Vol. 12, No. 4, 2004.
  • Victor Pikov and Douglas B. McCreery,Mapping of Spinal Cord Circuits Controlling the Bladder and External Urethral Sphincter Functions in the Rabbit. Neurourology and Urodynamics 23:172-179 (2004).
  • Douglas McCreery, Victor Pikov, Albert Lossinsky, Leo Bullara, and William Agnew,Arrays for Chronic Functional Microstimulation of the Lumbosacral Spinal Cord. IEEE Transactions on neural systems and Rehabilitation, Vol. 12, No. 2, 2004.
  • Changfeng Tai, August M. Booth, Charles J. Robinson, William C. de Groat, and James R. Roppolo,Isometric Torque About the Knee Joint Generated by Microstimulation of the Cat L6Spinal Cord. IEEE Transactions on neural systems and Rehabilitation, Vol. 7, No. 1, 1999.
  • Lisa Guevremont, Costantino G. Renzi, Jonathan A. Norton, Jan Kowalczewski, Rajiv Saigal, and Vivian K. Mushahwar,Locomotor-Related Networks in the Lumbosacral Enlargement of the Adult Spinal Cat: Activation Through Intraspinal Microstimulation. IEEE Transactions on neural systems and Rehabilitation, Vol. 14, No. 3, 2006.
  • Changfeng Tai, August M. Booth, Charles J. Robinson, William C. de Groat, and James R. Roppoloa,Multi-joint movement of the cat hindlimb evoked by microstimulation of the lumbosacral spinal cord. Experimental Neurology 183 (2003) 620-627.
  • M. M. Pinter, F. Gerstenbrand, and M. R. Dimitrijevic,Epidural electrical stimulation of posterior structures of the human lumbosacral cord:3. Control of Spasticity. Spinal Cord (2000) 38, 524-531.
  • B. Jilge, K. Minassian, F. Rattay, M. M. Pinter, F. Gerstenbrand, H. Binder, M. R. Dimitrijevic.Initiating extension of the lower limbs in subjects with complete spinal cord injury by epidural lumbar cord stimulation. Exp Brain Res (2004) 154: 308-326
  • K. Minassian, B. Jilge, F. Rattay, M. M. Pinter, H. Binder, F. Gerstenbrand and M. R. Dimitrijevic,Stepping-like movements in humans with complete spinal cord injury induced by epidural stimulation of the lumbar cord: electromyographic study of compound muscle action potentials. Spinal Cord (2004) 42, 401-416.
• However, these stimulation therapies may not be effective for persons suffering from complete spinal cord injuries, when no motor function or sensation remains below the injury site, or for restoring more complex motor functions and skills such as standing up and walking. Therefore, a need remains for a device that enhances or restores motor function for persons suffering from spinal cord injuries, including more severe injuries such as complete spinal cord injuries.
SUMMARY
• A system for enhancing or restoring motor function for a person suffering from spinal cord injury may detect nerve signals and stimulate nerves based on the detected signals. In particular, electrode devices may be implanted in the spinal cord that are in communication with each other and capable of detecting signals and/or stimulating the spinal cord. The electrode devices may interact with processors separate from the electrode devices that may process signals, generate stimulation signals, and offer a user interface with which to modify processor or electrode device settings.
• In one aspect of the invention, a system for transferring spinal cord signals includes a superior electrode for interfacing with a first portion of a spinal cord of a human body and an inferior electrode for interfacing with a second portion of the spinal cord. The superior electrode has at least one superior contact for receiving signals from the first portion of the spinal cord to transmit to the inferior electrode. The inferior electrode has at least one inferior contact for transmitting signals received from the superior electrode to the second portion of the spinal cord.
• In one embodiment, the inferior electrode has at least one inferior contact for receiving signals from the second portion of the spinal cord to transmit to the superior electrode; and the superior electrode has at least one superior contact for transmitting signals received from the inferior electrode to the first portion of the spinal cord. Any superior contacts or inferior contacts may be individually addressable.
• In another embodiment, the superior electrode penetrates the first portion of the spinal cord and the inferior electrode penetrates the second portion of the spinal cord. The first portion of the spinal cord is within a superior segment of the spinal cord that is anatomically intact and in contact with the brain of the human body. The second portion of the spinal cord is within an inferior segment of the spinal cord that is anatomically intact and separate from the superior segment.
• In another embodiment, the system includes a plurality of superior electrodes for interfacing with the first portion of the spinal cord and a plurality of inferior electrodes for interfacing with the second portion of the spinal cord.
• In another embodiment, the system includes a superior backing coupled to the plurality of superior electrodes to form an array and an inferior backing coupled to the plurality of inferior electrodes in an array. The superior backing and the inferior backing may be curved to match a curvature of the spinal cord, implanted within a subdural space of the spinal cord, and/or composed of bio-compatible materials. The superior and/or inferior backing may measure between about 0.5 cm and about 3 cm along either an axis substantially parallel to the spinal cord or an axis substantially perpendicular to the spinal cord.
• In another embodiment, the superior electrode and the inferior electrode are along a first lateral side of the spinal cord. A second superior electrode and a second inferior electrode may be along a second lateral side of the spinal cord.
• In another embodiment, the superior electrode and the inferior electrode are along a dorsal side of the spinal cord.
• In another embodiment, the system includes processing circuitry for processing signals transferred between the superior electrode and the inferior electrode. The processing circuitry may includes an amplifier for amplifying received signals, a power supply for generating power for the processing circuitry, a stimulator for sending stimulation signals, a switching matrix for selectively coupling an electrode to the stimulator, a processor for modifying signals, a programming interface for modifying the processor and for interfacing with a programming device external to the human body, a wireless transmitter for wirelessly transmitting the signals received from a portion of the spinal cord, and a wireless receiver for wirelessly receiving signals transmitted by the wireless transmitter. The power supply may be external to a dura of the spinal cord; and the processing circuitry may be implanted within a subdural space of the spinal cord.
• In another embodiment, the system includes a superior wire coupled to the superior electrode and an inferior wire coupled to the inferior electrode. The superior wire and the inferior wire may be implanted within a subdural space of the spinal cord.
BRIEF DESCRIPTION
• In the detailed description which follows, reference will be made to the attached drawings, in which:
• FIG. 1 depicts an exemplary spinal cord transfer interface system, according to one aspect of the invention;
• FIGS. 2A and 2B depict dorsal views of an exemplary spinal cord implant, according to one aspect of the invention;
• FIG. 3 depicts an exemplary spinal cord implant similar to the spinal cord implant ofFIG. 2, according to one aspect of the invention;
• FIGS. 4A and 4B depict dorsal views of an exemplary spinal cord implant, according to one aspect of the invention;
• FIG. 5 depicts a dorsal view of an exemplary electrode assembly implanted dorsally in a subdural space of a spinal cord, similar to electrode assemblies depicted inFIGS. 4A and 4B, according to one aspect of the invention;
• FIG. 6 depicts an oblique dorsal view of an exemplary electrode assembly implanted dorsally in a section of spinal cord, according to one aspect of the invention;
• FIG. 7 depicts a cross-sectional view of an exemplary spinal column of a patient in which a spinal cord implant may be disposed;
• FIG. 8 depicts a cross-sectional view of an exemplary electrode assembly implanted dorsally in a spinal cord, similar to the electrode assembly depicted inFIG. 6, according to one aspect of the invention;
• FIG. 9 depicts a cross-sectional view of an exemplary electrode assembly implanted dorsally in a section of a spinal cord, according to one aspect of the invention;
• FIG. 10 depicts a cross-sectional view of an exemplary electrode assembly implanted laterally in a section of a spinal cord, similar to electrode assemblies depicted inFIG. 3, according to one aspect of the invention;
• FIG. 11 depicts a portion of an exemplary electrode that may be used in the electrode assemblies described herein, according to one aspect of the invention;
• FIGS. 12 and 13 depict block diagrams for exemplary processing circuitry that may be used in a spinal cord transfer interface system, according to some aspects of the invention;
• FIG. 14 depicts an exemplary electrode assembly employing electrodes similar to that depicted inFIG. 11, according to one aspect of the invention; and
• FIG. 15 depicts an exemplary substrate portion of an electrode assembly, according to one aspect of the invention.
DETAILED DESCRIPTION
• Systems and methods for transferring signals from one portion of the spinal cord to another are provided. Signals may be generated or detected via electrode assemblies implanted in the spinal cord. Detected signals may be processed via a processor implanted in the body or external to the body, allowing a user to modify the processing of the signals. Signals to be transmitted on the spinal cord may be generated based on the detected signals.
• FIG. 1 depicts an exemplary spinal cordtransfer interface system100 according to one embodiment of the invention. The spinal cordtransfer interface system100 includes asuperior electrode assembly102 and aninferior electrode assembly104 each implanted in thespinal cord120 of apatient122 having aspinal cord injury124, aremote device106 for interfacing with and modifying theelectrode assemblies102 and104, and acomputer108 for interfacing with and modifying theremote device106.
• Thesuperior electrode assembly102 is implanted in a region of thespinal cord120 superior to any site ofinjury124 on thespinal cord120, and is capable of receiving signals from the patient's brain. The signals are transmitted, potentially wirelessly, to theinferior electrode assembly104 which is located inferior to a site ofinjury124 on thespinal cord120 and stimulates thespinal cord120 based on the signals received from thesuperior electrode assembly102. In addition, theinferior electrode assembly104 can receive signals that originated from the peripheral nervous system and transmit, potentially wirelessly, the signals to thesuperior electrode assembly102, which in turn can stimulate thespinal cord120 to send signals to the brain. Processing circuitry located at thesuperior electrode assembly102, located at theinferior electrode assembly104, and/or elsewhere implanted in the body of the patient can process the signals received by thesuperior electrode assembly102 and/or theinferior electrode assembly104 to aid in generating signals with which to stimulate thespinal cord120. Thesuperior electrode assembly102 and theinferior electrode assembly104 are described further below.
• Theremote device106 is capable of altering settings of the processing circuitry to modify how the processing circuitry processes received signals and generates signals for stimulation. Theremote device106 includes aprocessing interface118 that when placed on the patient adjacent to the processing circuitry serves to wirelessly communicate the desired alterations to the processing circuitry. Theprocessing interface118 receives the desired alterations via awire110 attached to thehousing112 of theremote device106. Thehousing112 includes user interface features, such as adisplay114 andbuttons116, that allow a user to select alterations. For example,certain buttons116 may correspond to specific actions, such as standing or sitting up, that the patient would like to perform.Other buttons116 may correspond to increasing or decreasing the intensity or strength of stimulating signals. Other user interface mechanisms such as dials, switches, or touch-screens may also be included in theremote device106. Theremote device106 may be used by the patient or by someone else who is aiding the patient to perform or learn certain activities, possibly as part of a physical therapy regimen. In the case where processing circuitry is located at both thesuperior electrode assembly102 and theinferior electrode assembly104, theremote device106 may be connected via wire to a second processing interface (not depicted) similar to theprocessing interface118 depicted. Theprocessing interface118 may be placed adjacent to one of the electrode assemblies while the second processing interface is placed adjacent to the other electrode assembly to simultaneously communicate with processing circuitry at both locations.
• Theremote device106 may have a port with which to connect to acomputer108. Thecomputer108 may reprogram thebuttons116 of theremote device106 to correspond to different actions or to improve the efficacy of the settings corresponding to certain actions. In one embodiment, theprocessing interface118 may receive signals from the processing circuitry that originated either from the brain or the peripheral nervous system, which are then transmitted to the remote device, which in turn transmits the received signals to thecomputer108 for storage, inspection, and/or to assist in determining how best to process the received signals to generate stimulation signals. Different options for processing the received signals may be stored on the remote device and assigned todifferent buttons116. Stimulation signals may be generated by the computer and transmitted via theremote device106 to theprocessing interface118, which transmits the stimulation signals to the appropriate electrode assembly to stimulate the spinal cord.
• FIGS. 2A and 2B depict dorsal views of an exemplaryspinal cord implant200 having asuperior electrode assembly202, aninferior electrode assembly204, andprocessing circuitry206, and implanted in a patient having a spinal cord injury approximately near theT6 vertebra212 or theT7 vertebra214. Thesuperior electrode assembly202 and theinferior electrode assembly204 are disposed approximately near theT5 vertebra216 and theT8 vertebra218, respectively. Other injury sites along thespinal cord220 may also benefit from a spinal cord implant system as described herein, where the superior electrode assembly is typically implanted superior to any injury site while the inferior electrode assembly is typically implanted inferior to any injury site.
• Thesuperior electrode assembly202 and theinferior electrode assembly204 each have at least one electrode array, in this casesuperior electrode arrays202aand202bandinferior electrode arrays204aand204b. Each electrode array has an electrode backing attached to a plurality of electrodes that pierce thespinal cord220 to receive and/or transmit signals, which are described further below. Thesuperior electrode arrays202aand202bare attached to and communicate signals via asuperior wire208 that is connected to theprocessing circuitry206. Similarly, theinferior electrode arrays204aand204bare attached to and communicate signals via aninferior wire210 that is also connected to theprocessing circuitry206. Theelectrode arrays202a,202b,204a, and204b,processing circuitry206, andwires208 and210 are all implanted in a subdural space, which is accessed by first performing a laminectomy, a surgical procedure to access the spinal cord dorsally by removing the lamina of the vertebrae, and then slicing open the dura mater to expose the subdural space. After implanting theassemblies202 and204, thewires208, and210, and theprocessing circuitry206, the dura mater may be sewn closed to prevent leakage of cerebrospinal fluid. In this embodiment, in which wires are used to communicate signals between superior andinferior electrode assemblies202 and204, it can be necessary to remove the lamina of all vertebrae between the superior andinferior electrode assemblies202 and204.
• FIG. 3 depicts an exemplaryspinal cord implant300 similar to thespinal cord implant200 ofFIG. 2, also having asuperior electrode assembly302 comprising twosuperior electrode arrays302aand302b, aninferior electrode assembly304 comprising twoinferior electrode arrays304aand304b, andprocessing circuitry306 connected to thesuperior electrode assembly302 and theinferior electrode assembly304 via asuperior wire308 and aninferior wire310, respectively. Each electrode array includes a plurality ofelectrodes312 disposed substantially parallel to one another and attached to a backing, namelysuperior backings314aand314bandinferior backings316aand316b, which can be made of any substantially rigid biocompatible material such as platinum-iridium or surgical grade stainless steel with a suitable coating like Silastic. Theelectrodes312 when implanted pierce through thespinal cord318, with each electrode having a plurality of contacts. Thesuperior electrode assembly302 and theinferior electrode assembly304 are each depicted relative to a section ofspinal cord318, and in particular their respective electrodes are shown as potentially piercing thespinal cord318 laterally. In another embodiment, the electrodes pierce thespinal cord318 laterally at sections of thespinal cord318 free fromnerves322. Theprocessing circuitry306 has ahousing320 which can be made of platinum-iridium or surgical grade stainless steel with a suitable coating like Silastic, or any other biocompatible material.
• FIGS. 4A and 4B depict dorsal views of an exemplaryspinal cord implant400 having asuperior electrode assembly402 and aninferior electrode assembly404 implanted in a patient having a spinal cord injury approximately near at least one of the T7 throughT12 vertebrae406. Thesuperior electrode assembly402 and theinferior electrode assembly404 are disposed approximately near theT6 vertebra408 and theL1 vertebra410, respectively. Other injury sites along thespinal cord412 may also benefit from a spinal cord implant system as described herein, where the superior electrode assembly is typically implanted superior to any injury site while the inferior electrode assembly is typically implanted inferior to any injury site.
• Thesuperior electrode assembly402 and theinferior electrode assembly404 each have an electrode array, in this casesuperior electrode array402aandinferior electrode array404a. Each electrode array has an electrode backing attached to a plurality of electrodes that pierce thespinal cord412 to receive and/or transmit signals, which are described further below. Thesuperior electrode assembly402 and theinferior electrode assembly404 communicate signals wirelessly and are each implanted in a subdural space, which is accessed by first performing a laminectomy, a surgical procedure to access thespinal cord412 dorsally by removing the lamina of the vertebrae, and then slicing open the dura mater to expose the subdural space. After implanting theassemblies402 and404, the dura mater may be sewn closed to prevent leakage of cerebrospinal fluid. In this embodiment in which the signals are communicated wirelessly between the superior and inferior implantation sites, it can be necessary to remove the lamina of only the vertebrae at the implantation sites. For example,FIGS. 4A and 4B depict theT6408 andL1410 vertebrae after having had laminectomies performed, while the interveningvertebrae406 remain intact.
• FIG. 5 depicts a dorsal view of anexemplary electrode assembly500 implanted dorsally in a subdural space of aspinal cord502, similar to eithersuperior electrode assembly402 orinferior electrode assembly404 both depicted inFIGS. 4A and 4B. Theelectrode assembly500 can include a wireless receiver and/or transmitter and processing circuitry that can be reprogrammed using a processing interface similar toprocessing interface118 ofFIG. 1. To access the section of thespinal cord502 in which theelectrode assembly500 is implanted, a laminectomy, which removes the lamina, has been performed to thevertebra504 immediately adjacent to the relevant section of thespinal cord502. The removal of the lamina facilitates transcutaneous communication between the processing circuitry and theprocessing interface118, which in use is placed externally on the surface of the skin. In addition, thedura mater506 has been cut open and pulled back to expose the subdural space in which theelectrode assembly500 is implanted.
• FIG. 6 depicts an oblique dorsal view of anexemplary electrode assembly600 implanted dorsally in a section ofspinal cord602 of a patient, which can be either a superior electrode assembly or an inferior electrode assembly. Theelectrode assembly600 includes anelectrode backing604 disposed under thedura mater606, a power supply608 disposed outside thedura mater606, and processing circuitry contained within the housing for theelectrode backing604 and/or within the housing for the power supply608. Theelectrode backing604 is attached to a plurality of electrodes (not depicted) that pierce thespinal cord602 to receive signals from and/or transmit signals to thespinal cord602. The signals are generated and/or processed by the processing circuitry, which is powered by the power supply608. As the power supply608 may need replacement more often than the other parts of theelectrode assembly600, the power supply608 is implanted externally to thedura mater606. Implants outside thedura mater606 are typically easier to access than any subdural implant which over time may develop scarring that further inhibits removal of the subdural implant. In one embodiment, the housing of the power supply608 includes flanges which may be sewn to thedura mater606 to secure the power supply608 substantially near the rest of theelectrode assembly600. The processing circuitry can include wireless receivers and/or transmitters to communicate with another electrode assembly and/or a processing interface placed adjacent to theelectrode assembly600 and external to the skin of the patient.
• FIG. 7 depicts a cross-sectional view of an exemplaryspinal column700 of a patient in which a spinal cord implant may be disposed according to one aspect of this invention. Thespinal column700 comprises avertebra702 through which runs aspinal canal704 in which resides aspinal cord706. Thespinal cord706 has adura mater708, namely a tough outer layer that surrounds the rest of thespinal cord712 and is separated from the rest of thespinal cord712 by asubdural space710 containing cerebrospinal fluid. The rest of thespinal cord712 includes the nerves of the central nervous system. Thevertebra702 includes a section of bone posterior to thespinal cord706 known as thelamina714 of thevertebra702. A procedure well-known in the art, known as a laminectomy, can remove thelamina714.
• FIG. 8 depicts a cross-sectional view of anexemplary electrode assembly800 implanted dorsally in aspinal cord802 of a patient, similar to theelectrode assembly600 depicted inFIG. 6 and which can be either a superior electrode assembly or an inferior electrode assembly. Theelectrode assembly800 includes anelectrode backing804 disposed within thedura mater806 of thespinal cord802 and in asubdural space812, a power supply808 disposed outside thedura mater806, and processing circuitry contained within the housing for theelectrode backing804 and/or within the housing for the power supply808. Theelectrode backing804 is attached to a plurality ofelectrodes810 disposed substantially parallel to one another and that pierce the innerspinal cord814 to receive signals from and/or transmit signals to nerves contained within the innerspinal cord814. The signals are generated and/or processed by the processing circuitry, which is powered by the power supply808. As the power supply808 may need replacement more often than the other parts of theelectrode assembly800, the power supply808 is implanted externally to thedura mater806. Implants outside thedura mater806 are typically easier to access than any subdural implant which over time may develop scarring that further inhibits removal of the subdural implant. In one embodiment, the housing of the power supply808 includes flanges which may be sewn to thedura mater806 to secure the power supply808 substantially near the rest of theelectrode assembly800. The processing circuitry can include wireless receivers and/or transmitters to communicate with another electrode assembly and/or a processing interface placed adjacent to theelectrode assembly800 and external to the skin of the patient. Thevertebra816 surrounding the section ofspinal cord802 depicted inFIG. 8 has had its lamina removed to allow access to thespinal cord802, as shown by theempty space818 located posterior to theelectrode assembly800.
• FIG. 9 depicts a cross-sectional view of anexemplary electrode assembly900 implanted dorsally in a section of aspinal cord902 of a patient to whichnerves920 are connected. Theelectrode assembly900 is similar to theelectrode assembly600 depicted inFIG. 6 and can be either a superior electrode assembly or an inferior electrode assembly. Theelectrode assembly900 includes anelectrode backing904 disposed within thedura mater906 of thespinal cord902 and in asubdural space912 of thespinal cord902, apower supply908 disposed outside thedura mater906, and processing circuitry contained within the housing for theelectrode backing904 and/or within the housing for thepower supply908. Theelectrode backing904 is attached to a plurality ofelectrodes910 disposed substantially parallel to one another and that pierce the innerspinal cord914 to receive signals from and/or transmit signals to nerves contained within the innerspinal cord914. In particular, each electrode has a plurality of contacts along a substantial portion of its length, where each contact is individually addressable, which allows each contact to receive or transmit a signal independently of all other contacts. The width of theelectrode backing904 and the lengths of theelectrodes910 are selected such that the electrodes are in contact with as many sections of the innerspinal cord914 as possible so that signals may be received from or transmitted to as many sections of the spinal cord as possible. The signals are generated and/or processed by the processing circuitry, which is powered by thepower supply908. As thepower supply908 may need replacement more often than the other parts of theelectrode assembly900, thepower supply908 is implanted externally to thedura mater906. Implants outside thedura mater906 are typically easier to access than any subdural implant which over time may develop scarring that further inhibits removal of the subdural implant. In one embodiment, the housing of thepower supply908 includes flanges which may be sewn to thedura mater906 to secure thepower supply908 substantially near the rest of theelectrode assembly900. The processing circuitry can include wireless receivers and/or transmitters to communicate with another electrode assembly and/or a processing interface placed adjacent to theelectrode assembly900 and external to the skin of the patient.
• FIG. 10 depicts a cross-sectional view of anexemplary electrode assembly1000 implanted laterally in a section of aspinal cord1002 of a patient, similar to either thesuperior electrode assembly302 or theinferior electrode assembly304 depicted inFIG. 3. Theelectrode assembly1000 includeselectrode backings1004aand1004bdisposed within thedura mater1006 of thespinal cord1002 and in asubdural space1012 of thespinal cord1002,power supplies1008aand1008bdisposed outside thedura mater1006, and processing circuitry contained within the housings for theelectrode backings1004aand1004band/or within the housings for thepower supplies1008aand1008b. Theelectrode backings1004aand1004bare each attached to a plurality ofelectrodes1010 disposed substantially parallel to one another and that pierce the innerspinal cord1014 to receive signals from and/or transmit signals to nerves contained within the innerspinal cord1014. In particular, each electrode has a plurality of contacts along a substantial portion of its length, where each contact is individually addressable, which allows each contact to receive or transmit a signal independently of all other contacts. The widths of theelectrode backings1004aand1004band the lengths of theelectrodes1010 are selected such that the electrodes are in contact with as many sections of the innerspinal cord1014 as possible so that signals may be received from or transmitted to as many sections of the spinal cord as possible. The signals are generated and/or processed by the processing circuitry, which is powered by the power supply,1008aor1008b, closest to its corresponding electrode backing,1004aor1004b, respectively. As thepower supplies1008aand1008bmay need replacement more often than the other parts of theelectrode assembly1000, thepower supplies1008aand1008bare implanted externally to thedura mater1006. Implants outside thedura mater1006 are typically easier to access than any subdural implant which over time may develop scarring that further inhibits removal of the subdural implant. In one embodiment, the housings of thepower supplies1008aand1008bincludes flanges which may be sewn to thedura mater1006 to secure thepower supplies1008aand1008bsubstantially near the rest of theelectrode assembly1000. The processing circuitry can include wireless receivers and/or transmitters to communicate with another electrode assembly and/or a processing interface placed adjacent to theelectrode assembly1000 and external to the skin of the patient.
• FIG. 11 depicts a portion of anexemplary electrode1100, similar to theelectrodes810,910, and1010 depicted inFIGS. 8,9, and10, respectively, that may be used in the electrode assemblies described above. Theelectrode1100 has a plurality ofcontacts1102 dispersed over its surface, where eachcontact1102 may be individually addressable. Thecontacts1102 may be made of platinum-iridium, or any other conductive, biocompatible, corrosion-resistant material.Electrode1100 may be made via a deposition method and may range from about 100 to 200 microns indiameter1104.
• FIG. 14 depicts anexemplary electrode assembly1400, similar to the electrode assemblies described above, that employs a plurality ofelectrodes1402 similar toelectrode1100, according to some aspects of the invention. Theelectrodes1402 may have approximately a uniform length or may range in length. In some embodiments, theelectrodes1402 each have a length corresponding to a region of the spinal cord. For example, electrodes in contact with the conus region, when implanted, may have a length between about 1.5 cm and about 2 cm, while electrodes in contact with the thoracic region, when implanted, may have a length around 1 cm.Electrodes1402 are attached to asubstrate1404 and may be spaced up to 500 microns apart from one another. In some embodiments, thesubstrate1404 may have a depth ranging between about 1 mm and about 3 mm. The edges of thesubstrate1404 may be rounded.Substrate1404 may include processing circuitry for receiving and/or transmitting signals from theelectrodes1402 and communicating with devices external to the body in whichelectrode assembly1400 is implanted, such as the devices described above with respect toFIG. 1.FIG. 15 depicts anexemplary substrate1500, similar to thesubstrate1404 ofFIG. 14, havingprocessing circuitry1502 formed thereon, according to some aspects of the invention. Theprocessing circuitry1502 may includecharge amplifiers1504,memory1506, and aprocessor1508, and may be in communication with acoil1510 for receiving and/or transmitting signals, such as radio frequency signals.
• FIGS. 12 and 13 depict block diagrams for exemplary processing circuitry that may be used in a spinal cord transfer interface system, according to some aspects of the invention.FIG. 12 depicts a block diagram forexemplary processing circuitry1200 capable of processing and transferring signals from superior electrodes, such as those in thesuperior electrode assemblies102,202,302, and402 described above, to inferior electrodes, such as those in theinferior electrode assemblies104,204,304, and404 described above.Exemplary processing circuitry1300 ofFIG. 13 may, in addition, process and transfer signals from the inferior electrodes to the superior electrodes.
• Theprocessing circuitry1200 includessuperior processing circuitry1202, a portion of which may be implanted near the superior electrodes, andinferior processing circuitry1204, a portion of which may be implanted near the inferior electrodes. Thesuperior processing circuitry1202 receives asignal1206 from the superior electrodes and includes anamplifier1208 for amplifying the receivedsignal1206, asignal processor1210 for processing the signal output by the amplifier, and atransmitter1212 for transmitting the signal output by thesignal processor1210 to theinferior processing circuitry1204. Thesuperior processing circuitry1202 may include aprogramming interface1214 for modifying thesignal processor1210 and apower supply1216 for powering thecircuitry1202. Theinferior processing circuitry1204 receives asignal1218 from thesuperior processing circuitry1202 via areceiver1220, which outputs the receivedsignal1218 to astimulator1222 for generating a signal to be transmitted via the inferior electrodes. Theinferior processing circuitry1204 may include aprogramming interface1224 for modifying thestimulator1222 and apower supply1226 for powering thecircuitry1204. The programming interfaces1214 and1224 allow a user to alter how theprocessing circuitry1200 transfers signals received at the superior electrodes to the inferior electrodes. Such altering may occur during a physical therapy session and in response to feedback from a patient in which the superior and inferior electrodes are implanted.
• Turning toFIG. 13, theprocessing circuitry1300 includessuperior processing circuitry1302, a portion of which may be implanted near the superior electrodes, andinferior processing circuitry1304, a portion of which may be implanted near the inferior electrodes. Thesuperior processing circuitry1302 receives a signal from the superior electrodes and includes anamplifier1308 for amplifying the received signal, asignal processor1310 for processing the signal output by the amplifier, and atransceiver1312 for transmitting the signal output by thesignal processor1310 to theinferior processing circuitry1304. Thetransceiver1312 may also receive signals from theinferior processing circuitry1304 and transmit them to astimulator1328 for generating a signal to be transmitted via the superior electrodes. Aprogramming interface1314 may modify thesignal processor1310 and/orstimulator1328, allowing a user to alter how theprocessing circuitry1300 transfers signals between the superior and inferior electrodes. A switchingmatrix1330, in communication with the superior electrodes,amplifier1308, andstimulator1328, determines whether the superior electrodes are receiving signals, which are transmitted to theamplifier1308, or transmitting signals from thestimulator1328. Apower supply1316 powers thesuperior processing circuitry1302.
• Theinferior processing circuitry1304 is similar to thesuperior processing circuitry1302. Atransceiver1320 receives a signal from thesuperior processing circuitry1302 and outputs the received signal to astimulator1322 for generating a signal to be transmitted via the inferior electrodes. Theinferior processing circuitry1304 may also receive signals from the inferior electrodes which are then amplified by anamplifier1332, whose output signal is processed by asignal processor1334 to generate a signal to transmit to thesuperior processing circuitry1302 via thetransceiver1320. Aprogramming interface1324 may modify thestimulator1322 and/orsignal processor1334, allowing a user to alter how theprocessing circuitry1300 transfers signals between the superior and inferior electrodes. A switchingmatrix1336, in communication with the inferior electrodes,amplifier1332, andstimulator1322, determines whether the inferior electrodes are receiving signals, which are transmitted to theamplifier1332, or transmitting signals from thestimulator1322. Apower supply1326 powers theinferior processing circuitry1304.
• Altering how theprocessing circuitry1300 transfers signals via theprogramming interfaces1314 and1324 may occur during a physical therapy session and in response to feedback from a patient in which the superior and inferior electrodes are implanted. Thetransceivers1312 and1320 may transmit and receive signals via a wire or wirelessly.
• Following implantation of electrode assemblies of a transfer interface in an injured spinal cord, processing circuitry of the electrode assemblies, such asprocessing circuitry1200 and1300 described above, may be programmed and/or altered to determine how signals will be transferred between superior and inferior electrodes of the transfer interface. The programming may occur over a number of physical therapy sessions with the patient, according to a predetermined procedure for evaluating electrodes and signals received or stimulated thereon. In some embodiments, a procedure first evaluates electrodes by determining which electrode contacts are functional and active, and then devises algorithms for translating recorded signals into stimulation signals corresponding to specific body movements. An exemplary procedure for electrode evaluation and algorithm programming follows:
• I. Superior electrode assembly cord recording evaluation
• A. Evaluate each electrode for function
  • i. Impedance testing
    • a. Use the ground plane on the electrode array backing as the reference
    • b. Evaluate each electrode by passing a 1 μA signal through it. (Note this signal may depend upon the electrode area and shape).
      • 1. The electrode will be considered active if its impedance at 30 Hz, 250 Hz, and 1 KHz is within the design specifications of the electrode manufacturer.
      • 2. If the electrode impedance is outside of the operational range it will be conditioned using a conditioning pulse defined by the electrode manufacturer.
        • a. The electrode will be tested again at the three impedance values.
        • b. If the electrode remains outside of specifications it will be removed from the grid by setting a software flag to disable the switching matrix from activating this electrode.
    • c. This impedance test will automatically be run at least once daily.
  • ii. Recording field evaluation
    • a. The patient will be asked to try to make specific movements in their lower extremities.
      • 1. Example Movements
        • a. Each side separately
        •  i. Dorsal Flexion
        •  ii. Planter Flexion
        •  iii. Wiggle the toes
        •  iv. Knee Flexion
        •  v. Knee Extension
        •  vi. Hip Flexion
        •  vii. Hip Extension
        • b. Bilateral
        •  i. Stand up on toes
        •  ii. Roll over
        •  iii. Sit up
        •  iv. Walk
        •  v. Jump
        •  vi. Stand on one leg
        •  vii. Stand on the other leg
        •  viii. Sway back and forth
      • 2. For each movement, which will be evaluated 20 times for 5 consecutive days, the software will store the following from each electrode contact
        • a. Rectified and integrated activity
        •  i. Over the complete event
        •  ii. Over short time intervals (e.g., 50 millisecond blocks)
        • b. Firing rate (zero crossing)
        •  i. Over the complete event
        •  ii. Over short time intervals
        • c. Spectral bands
        •  i. Over the complete event
        •  ii. Over short time intervals
      • 3. With the stored data the following analyses will be performed within each movement pattern and across each pattern to differentiate electrode activation patterns for each movement
        • a. Cluster analysis
        • b. Correlation analysis
        • c. Spectral and cross-spectral analysis
        • d. Bispectral analysis
      • 4. Electrodes will be given a weighted score between zero and 100 for each test and evaluation. The goal is for the cluster analysis of the rectified and integrated data to be the primary measure for movement detection, although the frequency analysis may be used for determining walking.
  • iii. All analysis will be performed on an external computer and software that is connected to the patient via a wireless radio frequency transmitter/receiver system.
  • iv. Once all weightings have been established for each of the evaluations they will be downloaded to the on-board processor for real-time recording evaluation.
• B. Inferior electrode assembly stimulation evaluation
  • i. Impedance testing will be performed in a method similar to that described in I.a.i.2.
  • ii. This testing procedure will be performed in two phases. Phase I will evaluate each individual stimulating electrode. Phase II will evaluate groups of electrodes.
  • iii. For phase I, pairs of sterile needled electrodes or small surface gold cup electrodes will be placed in (or on the surface) of the leg muscle as follows:
    • a. 1 pair in the Adductor Hallucis
    • b. 1 pain in the Abductor digiti minimi
    • c. 1 pair in the Flexor hallucis brevis
    • d. 1 pair in the flexor digitorum brevis
    • e. 1 pair in the abductor hallucis
    • f. 2 pairs in the flexor hallucis longus
      • 1. 1 pair 3 cm distal to the center of the muscle
      • 2. 1 pair 3 cm proximal to the center of the muscle
    • g. 1 pair in the flexor digitorum longus
    • h. 1 pair in the soleus
    • i. 1 pair in the lateral head of the gastrocnemius
    • j. 1 pair in the medial head of the gastrocnemius
    • k. 1 pair in the biceps femoris
    • l. 1 pair in the semitendinosus
    • m. 1 pair in the anterior tibialis
    • n. 1 pair in the extensor digitorum brevis
    • o. 1 pair in the vastus medialis
    • p. 1 pair in the vastus lateralis
    • q. 1 pair in the vastus intermedius
    • r. 1 pair in each of the posterior spinal muscles below the level of the stimulation
    • s. 1 pair in the gluteus maximus
    • t. 1 pair in the rectus femoris
    • u. 1 pair in the iliopsoas
    • v. 1 pair in the adductor longus
  • iv. Stimulation will then be done at a frequency of 2.4 Hz and a pulse width of 200 microseconds.
  • v. Amplitude will be slowly raised from 0 μA to 100 μA.
    • a. The level of each EMG activation will be noted.
    • b. Flags will be set in the software relating the level of stimulation and the muscle stimulated for each active contact.
II. Translation of Data
• A. The software will be programmed with the muscle and level table that was determined from the above tests.
  • i. The software will then be used to translate the recorded fields that were determined by looking at the weights of maximal activation with a desire to move.
  • ii. This will then activate the appropriate switching matrix on the stimulation side
  • iii. Stimulation weights will then be applied by setting the appropriate current levels for stimulation at each switch
  • iv. Stimulation will then be activated to move the appropriate muscle groups.
  • v. During the desire for more complex movements motor programs will be activated.
  • vi. These programs can be activated by:
    • a. An external device the patient can use and control by hand
    • b. A long term goal is to have the system automatically determine the activity via the recorded signals.
• B. For safety purposes the system will have to evaluate external electrical influence and reject them—this will be part of an on board coil to pick up signals that are large and external and put the system in a safe mode.
  III. A secondary goal is to have recording electrodes placed inferior to the injury site and stimulation electrodes placed superior to the injury site for sensation transfer
• A. If these secondary electrodes are added evaluation of the system will be performed as follows.
  • i. Sensations will be evaluated by testing each dermatomal level with
    • a. Light touch—a brush
    • b. Pressure
    • c. Cold
    • d. Heat
    • e. Needle stick
  • ii. Fields will be determined in a manner similar to the cranial electrode motor testing in part I.A.ii
  • iii. Stimulation of each superior sensation electrode will be tested individually and the patient will respond by verbalizing what they feel.
• Described herein are exemplary embodiments of the invention that are presented for purposes of illustration and not of limitation. Applicants consider all operable combinations of the embodiments disclosed herein to be patentable subject matter.

Claims (22)

1. A system for transferring spinal cord signals, comprising:

a superior electrode for interfacing with a first portion of a spinal cord of a human body; and

an inferior electrode for interfacing with a second portion of the spinal cord, wherein

the superior electrode has at least one superior contact for receiving signals from the first portion of the spinal cord to transmit to the inferior electrode, and

the inferior electrode has at least one inferior contact for transmitting signals received from the superior electrode to the second portion of the spinal cord.

2. The system ofclaim 1, wherein

the inferior electrode has at least one inferior contact for receiving signals from the second portion of the spinal cord to transmit to the superior electrode, and

the superior electrode has at least one superior contact for transmitting signals received from the inferior electrode to the first portion of the spinal cord.

3. The system ofclaim 1, further comprising processing circuitry for processing signals transferred between the superior electrode and the inferior electrode.

4. The system ofclaim 1, wherein

the at least one superior contact for receiving signals is individually addressable, and

the at least one inferior contact for transmitting signals is individually addressable.

5. The system ofclaim 2, wherein

the at least one inferior contact for receiving signals is individually addressable, and

the at least one superior contact for transmitting signals is individually addressable.

6. The system ofclaim 1, wherein the superior electrode penetrates the first portion of the spinal cord and the inferior electrode penetrates the second portion of the spinal cord, wherein

the first portion of the spinal cord is within a superior segment of the spinal cord, said superior segment being anatomically intact and in contact with a brain of the human body; and

the second portion of the spinal cord is within an inferior segment of the spinal cord, said inferior segment being anatomically intact and separate from the superior segment.

7. The system ofclaim 1, further comprising:

a plurality of superior electrodes for interfacing with the first portion of the spinal cord; and

a plurality of inferior electrodes for interfacing with the second portion of the spinal cord.

8. The system ofclaim 7, further comprising

a superior backing coupled to the plurality of superior electrodes to form an array, wherein the superior backing is curved to match a curvature of the spinal cord, and

an inferior backing coupled to the plurality of inferior electrodes in an array, wherein the inferior backing is curved to match a curvature of the spinal cord.

9. The system ofclaim 8, wherein at least one of the superior backing and the inferior backing measures between about 0.5 cm and about 3 cm along an axis substantially parallel to the spinal cord.

10. The system ofclaim 8, wherein at least one of the superior backing and the inferior backing measures between about 0.5 cm and about 3 cm along an axis substantially perpendicular to the spinal cord.

11. The system ofclaim 1, the superior electrode and the inferior electrode being along a first lateral side of the spinal cord.

12. The system ofclaim 11, further comprising a second superior electrode and a second inferior electrode, the second superior electrode and the second inferior electrode being along a second lateral side of the spinal cord.

13. The system ofclaim 1, the superior electrode and the inferior electrode being along a dorsal side of the spinal cord.

14. The system ofclaim 8, wherein the superior backing and the inferior backing are implanted within a subdural space of a spine containing the spinal cord.

15. The system ofclaim 3, wherein the processing circuitry includes:

an amplifier for amplifying received signals; and

a power supply for generating power for the processing circuitry.

16. The system ofclaim 15, the power supply being external to a dura of the spinal cord.

17. The system ofclaim 3, wherein the processing circuitry includes:

a stimulator for sending stimulation signals; and

a switching matrix for selectively coupling an electrode to the stimulator.

18. The system ofclaim 3, wherein the processing circuitry includes:

a processor for modifying signals; and

a programming interface for modifying the processor and for interfacing with a programming device external to the human body.

19. The system ofclaim 3, wherein the processing circuitry includes:

a wireless transmitter for wirelessly transmitting the signals received from a portion of the spinal cord; and

a wireless receiver for wirelessly receiving signals transmitted by the wireless transmitter.

20. The system ofclaim 3, wherein the processing circuitry is implanted within a subdural space of a spine containing the spinal cord.

21. The system ofclaim 1, further comprising a superior wire coupled to the superior electrode and an inferior wire coupled to the inferior electrode, wherein the superior wire and the inferior wire are implanted within a subdural space of a spine containing the spinal cord.

22. The system ofclaim 8, wherein the superior backing and the inferior backing are composed of bio-compatible materials.

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