Electrode array configured to wrap around and stimulate the spinal cord

Abstract

A method for treating intractable pain via electrical stimulation of the spinal cord. Remote, non-contact stimulation of a selected region of spinal cord is achieved by placement of a transceiver patch directly on the surface of that region of spinal cord, with said patch optionally being inductively coupled to a transmitter patch of similar size on either the outer or inner wall of the dura surrounding that region of the spinal cord. By inductively exchanging electrical power and signals between said transmitter and transceiver patches, and by carrying out the necessary electronic and stimulus signal distribution functions on the transceiver patch, the targeted dorsal column axons can be stimulated without the unintended stray stimulation of nearby dorsal rootlets. Novel configurations of a pliable surface-sheath and clamp or dentate ligament attachment features which realize undamaging attachment of the patch to the spinal cord are described.

What is claimed: 
     
         1 . An electrode array configured for delivering electrical stimulation directly to the spinal cord of a subject from inside the dura surrounding the spinal cord, wherein the array comprises:
 (1) a curved backing having a curvature that is contoured to match the curvature of the spinal cord;   (2) a plurality of electrodes projecting from inside the curvature of the backing, positioned so as to directly engage the spinal cord when the curved backing is conformed to the spinal cord; and   (3) one or more flexible attachment arms configured for wrapping around at least part of the circumference of the spinal cord inside the dura, thereby securing the electrodes in contact with the spinal cord;   wherein the electrode array has a sufficiently thin profile and configuration such that when the array of electrodes is secured in direct contact with the pial surface of the spinal cord, a CSF filled space is maintained between the electrode array and the dura.   
     
     
         2 . An electrode array configured for delivering electrical stimulation directly to the spinal cord of a subject from inside the dura surrounding the spinal cord, wherein the array comprises:
 (1) a body configured to lie against the spinal cord inside the dura;   (2) a flexible band having a distal end and a proximal end, attached through the proximal end to the body; and   (3) a plurality of electrodes;   wherein the body and the flexible band combine to form a substrate with a length that matches the circumference of the spinal cord and is configured such that the distal end of the flexible band can be passed around the circumference of the spinal cord and secured to an opposing edge of the substrate, whereupon the substrate completely encircles the spinal cord;   wherein the electrodes are distributed along the substrate such that when the array is secured around the spinal cord inside the dura, the electrodes surround and are in contact with the spinal cord; and   wherein the electrode array has a sufficiently thin profile and configuration such that when the array of electrodes is secured in direct contact with the pial surface of the spinal cord, a CSF filled space is maintained between the electrode array and the dura.   
     
     
         3 . The electrode array of  claim 1 , comprising a plurality of flexible attachment arms projecting from the backing and configured to wrap around the spinal cord circumferentially in opposite directions. 
     
     
         4 . The electrode array of  claim 3 , wherein at least some of the electrodes are positioned inside and along the arms. 
     
     
         5 . The electrode array of  claim 1 , wherein the one or more flexible attachment arms are sized to only partly encircle the spinal cord, and have a mechanical compliance such that once conformed to the spinal cord, the electrode array is secured in position. 
     
     
         6 . The electrode array of  claim 1 , wherein the curved backing is sufficiently elastic to expand and contract with spinal cord movement. 
     
     
         7 . The electrode array of  claim 1 , wherein individual electrodes in the array are flexibly mounted to the backing by a soft resilient material, thereby allowing each electrode to move relative to the backing. 
     
     
         8 . The electrode array of  claim 1 , wherein the backing has a thickness of 0.5 mm or less. 
     
     
         9 . The electrode array of  claim 1 , further comprising penetrating electrodes projecting from inside the curvature of the backing, configured to penetrate into the spinal cord, thereby accessing an internal target subregion within the spinal cord. 
     
     
         10 . The electrode array of  claim 1 , further comprising a signal receiver disposed along the backing of the array and configured to receive energy wirelessly from a signal generator located outside an external surface of the patient's dura. 
     
     
         11 . An assembly for treating pain or other neurological condition in a patient, comprising the electrode array of  claim 2 , and a means for securely connecting the distal end of the flexible band to an opposing edge of the array so that the array stays in position around the circumference of the spinal cord at a target location. 
     
     
         12 . A system for treating pain or other neurological condition in a patient, comprising the electrode array of  claim 1 , and circuitry that is configured to deliver electrical stimulation to the spinal cord by way of the electrodes. 
     
     
         13 . The system of  claim 12 , wherein the circuitry comprises a signal generator suitable for providing energy to the electrode array from outside the patient's dura, and a conductor extendable through the patient's dura to convey energy from the generator to the electrode array. 
     
     
         14 . A system for treating pain or other neurological condition in a patient, comprising the electrode array of  claim 2 , and circuitry that is configured to deliver electrical stimulation to the spinal cord by way of the electrodes. 
     
     
         15 . The system of  claim 14 , wherein the circuitry comprises a signal generator suitable for providing energy to the electrode array from outside the patient's dura, and a conductor extendable through the patient's dura to convey energy from the generator to the electrode array. 
     
     
         16 . A method for preparing a patient for spinal cord stimulation with the electrode array of  claim 1 , comprising:
 implanting the electrode array inside the dura of the subject such that the electrodes in the array are placed in direct contact with the pial surface of the subject's spinal cord at a position from which to deliver electrical stimuli to a target subregion of the spinal cord; and   securing the electrode array so that it stays in place against the spinal cord as the spinal cord moves inside the dura.   
     
     
         17 . A method for preparing a patient for spinal cord stimulation with the electrode array of  claim 2 , comprising:
 implanting the substrate around the patient's spinal cord inside the dura such that the electrodes contact the spinal cord at a target subregion;   connecting the distal end of the flexible band to an opposing side of the substrate, thereby completely encircling the spinal cord and securing the electrode array so that it stays in place against the spinal cord as the spinal cord moves inside the dura.   
     
     
         18 . A method of stimulating the spinal cord of a subject using the electrode array of  claim 1 , comprising delivering electrical stimuli to a target subregion of the spinal cord from the electrode array secured against the subject's spinal cord inside the dura. 
     
     
         19 . A method of stimulating the spinal cord of a subject using the electrode array of  claim 2 , comprising delivering electrical stimuli to a target subregion of the spinal cord from the electrode array secured against the subject's spinal cord inside the dura. 
     
     
         20 . The method of  claim 18 , which is a method of treating spinal cord injury.