Patent Application: US-38004709-A

Abstract:
the invention described herein is a carbon nano - tube micro - electrode array relay system for providing nerve stimulation output and sensation input between proximal and distal ends of a damaged spinal cord . this device detects the signals coming from either end of a damaged spinal cord , amplifies them , and then stimulates the axons on the opposing side from which they were received . this device is intended to provide self - contained data relay for the goal of restoring function to a severed spinal cord . it is not intended for data output to an external source for analysis . this device is biocompatible and has a modular power system .

Description:
the device described herein is a nanotube micro electrode array relay system for providing nerve stimulation output and sensation input between proximal and distal ends of a severed spinal cord . the main components of this device are : proximal and distal microelectrode arrays ( 1 ) and their subsequent microcircuit boards ( 2 ), the inter array junction ( 3 ), modular power supply inputs ( 4 ), a biocompatible sheath ( 5 ), a biocompatible armature ( 12 ) with suturable sections ( 6 , 7 and 8 ) and grooves for cerebrospinal fluid flow ( 9 ), a tube to provide fluid flow through the spinal cord &# 39 ; s central canal ( 10 ), and the modular power supply ( 11 ). the nanotube microelectrode arrays of this device should be made using a combination of standard micro lithography techniques and chemical vapor deposition . assuming a minimum microelectrode diameter of 2 micrometers , a maximum electrode density of 5000 electrodes per centimeter could be attained . for the purposes of this device a minimum of 500 electrodes per square centimeter is required . these electrodes should be fabricated directly onto the microcircuit boards ( 1 ) that comprise the relay and amplification system . the relay and amplification system ( 2 ) functions thusly : when a voltage is generated between a pair of electrodes by a neuronal action potential , a micro switch is activated that closes a circuit which causes a micro capacitor to discharge a voltage of roughly 100 mv ( at the electrodes ), which passes through the inter array junction , across a pair of electrodes on the opposing surface and then back to the capacitor . each nanotube electrode has a partner electrode on the same array , across which voltages are detected or discharged , and a mirrored pair on the opposing array to which any signal received is transmitted . signal transmission in this device is bi - directional however micro diodes should be used to allow for unidirectional signal transmission at any one time . these components should be made using standard micro lithography , chemical vapor deposition and laser etching techniques . the microelectrode array ( 1 ) should be assembled on the same silicon dioxide microchip as the capacitor and switching components , however they should be on opposite surfaces of the microchip . contacts between the two electrode arrays and subsequent circuit systems should be achieved through the use of an inter array junction ( 3 ), into which connections from each array / circuit board pass . there must be a connection for each microelectrode to connect to its mirrored electrode . the junction may have a wider area than the microelectrode array to allow for physical support that may be needed for electrical contacts between opposing arrays . the function of the junction is to allow signals to be transferred between mirrored pairs of electrodes on either array . this junction should be manufactures with vertically aligned nano wires which securely contact nano wires coming from each microarray / auxiliary circuit complex . each array ( proximal and distal ) and its auxiliary components should be identical . these arrays , when placed with their microelectrodes facing away from each other , should be joined together at the inter array junction . this dual microarray system should be shaped to the cross - sectional dimensions of the spinal cord in the region of the spinal cord at which it would be placed . the preferred embodiment of this device would be such that arrays with different cross - sectional shapes would be made for each region of the spinal cord . these sets of devices with varying cross - sectional shapes would be made in different sizes to allow them to be used on a wide range of individuals with spinal cord damage at varying regions of the cord . passing through the center of the arrays , circuits and inter array junction , should be a biocompatible polyethylene tube ( 10 ), placed so that it mates on either side of the device with the central canal of the spine . this would allow for an unimpeded flow of cerebrospinal fluid through the device . power to this system should be provided through two leads ( 4 ) that pass from each circuit board , through the biocompatible housing of the device ( to be discussed below ), and into ports that allow for the connection of the modular power supply apparatus . four leads in total are needed , two for each array . the opposing arrays , microcircuits , and the inter array junction should all be contained within a biocompatible sheath . said sheath should be made of biocompatible polyethylene ( or a comparable material ) that is machined or molded using sterile , surgical grade , fabrication techniques . said sheath should have chamfers that fit around the perimeter of the micro electrode arrays . said sheath should be flexible enough to be fitted as a single piece around both arrays and auxiliary components and glued into place ( using a surgical grade epoxy or “ super - glue ” to provide a non degradable seal impenetrable to bodily fluids . said sheath must have sealed ports to allow for power supply leads to pass through it . over the sheath a biocompatible armature ( 12 ) should be fitted . it should be attached to the sheath using an appropriate adhesive or a mechanical connection . the functions of this armature are multifold . it must be biocompatible ( a thicker polyethylene or comparable material is appropriate ). it must have channels ( 9 ) through which cerebrospinal fluid can pass unimpeded . these channels may be simple longitudinally oriented grooves in the body of the armature to allow for fluid flow . it must have longitudinally oriented regions that allow for suturing ( 7 ) and / or tissue in - growth ( fabrics such as those used in arterial grafts are appropriate ). these regions may be fixed to the body of the armature using a chamfered channel travelling the length of the longitudinal suturing regions ( 7 ), along with an appropriate adhesive . these regions are meant to be sutured through the dura mater of the spinal cord . the armature must have a suturable region travelling the circumference of the openings into which the proximal and distal ends of the spinal cord pass ( 6 ). this suture ring is intended to affix the proximal and distal ends of a severed spinal cord to the device . this suture ring should not impede the flow of cerebrospinal fluid and should not extend to the distance ( measured from the central canal duct ( 10 ) outward ) of the longitudinally oriented suturing regions . these regions are intended to be sutured directly to the spinal cord or to the pia matter . these regions may be affixed to the armature by means of a chamfered channel travelling the circumference of the openings which accommodate the proximal and distal ends of a severed spinal cord , along with an appropriate adhesive . these channels should be oriented parallel to the spinal cord . the armature must have a suturable region travelling the circumference of the modular power supply port ( 8 ). this region is oriented perpendicularly to suturable region ( 6 ), and should travel the circumference of the region which allows for attachment of the modular power supply . this suturable region ( 8 ) is intended to affix the dura matter of the spinal cord around the circumference of the modular power supply attachment region . by doing so , the modular power supply ( 11 ), rests outside of the tissues sheathing the spinal cord , thereby allowing modular power supplies to be interchanged ( post - operatively ) without having to make an incision into the sheaths of the spinal cord . the armature must have ports to connect the power leads ( 4 ) leaving the inner sheath to the modular power supply ( 11 ). the armature , lastly , must have a means of securely attaching the modular power supply ( 11 ). the modular power supply ( 11 ) of this for this apparatus is any device that can fit in the attachment area of the armature and provide an appropriate power supply to the power leads ( 4 ) of the apparatus . the coupling between the device and the modular power supply should take place outside the dura matter of the spinal cord , into which the main body of the biocompatible armature is sutured . this should be affected by having the coupling area protrude dorsally from the main body of the device . this protrusion should be continuous with the biocompatible armature . this protrusion should have internally facing chamfers and be surrounded by a cuff of material capable of being sutured ( 8 ). the junction between the main device and the modular power supply can affected by any means capable of attaching the power supply adequately and that does not impede biocompatibility or implantability . the method of attaching the modular power supply pictured in fig1 is a pressure fitting , which would allow the modular power supply to be pushed into position and firmly held by the internal chamfer of the modular power supply attachment region . the power supply of this device is should be modular to allow for upgrades to the power supply system over the life of the implant without having to remove the main body of the device . the preferred method of powering this device would be a kinetic charger / rechargeable battery apparatus to generate power by means of body movement . other methods that can be utilized are an internal induction coil / rechargeable battery system that would be charged periodically with an external induction coil / rechargeable battery system linked to a generator ( solar / kinetic ), or to a stationary power source . these methods are preferable power solutions as they would provide unimpeded and ( largely ) self generated electrical power . other modular devices are acceptable so long as they provide an appropriate power supply , attach to the armature , and allow for uninterrupted power delivery . for this device to be implemented surgically , the region to be repaired must be prepped for the implant . preparation of the area requires that the damaged ends of the spinal cord must be cut so that they provide a flat plain perpendicular to the length of the cord . the vertebrae in the region to be repaired must also be immobilized ( temporarily or permanently , depending on consultation with a surgeon and the patients activity level ) using pre existing vertebral fusion / immobilization techniques . it should be implanted using appropriate microsurgery techniques . implementation of this device would be most favorable when coupled with physical therapy including biofeedback , exercise , and external stimulation of muscle groups . any post operative therapies should be discussed with a physician . reference to sequence listing , a table , or a computer program listing compact disc appendix ( 1 ) gasson , mark et . al . “ invasive neural prosthesis for neural signal detection and nerve stimulation .” international journal of adaptive control and signal processing . 19 . 5 ( 2004 ): 365 - 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