Chronic nerve health following implantation of femoral nerve cuff electrodes.
BACKGROUND
Peripheral nerve stimulation with implanted nerve cuff electrodes can restore standing, stepping and other functions to individuals with spinal cord injury (SCI). We performed the first study to evaluate the clinical electrodiagnostic changes due to electrode implantation acutely, chronic presence on the nerve peri- and post-operatively, and long-term delivery of electrical stimulation.


METHODS
A man with bilateral lower extremity paralysis secondary to cervical SCI sustained 5 years prior to enrollment received an implanted standing neuroprosthesis including composite flat interface nerve electrodes (C-FINEs) electrodes implanted around the proximal femoral nerves near the inguinal ligaments. Electromyography quantified neurophysiology preoperatively, intraoperatively, and through 1 year postoperatively. Stimulation charge thresholds, evoked knee extension moments, and weight distribution during standing quantified neuroprosthesis function over the same interval.


RESULTS
Femoral compound motor unit action potentials increased 31% in amplitude and 34% in area while evoked knee extension moments increased significantly (p < 0.01) by 79% over 1 year of rehabilitation with standing and quadriceps exercises. Charge thresholds were low and stable, averaging 19.7 nC ± 6.2 (SEM). Changes in saphenous nerve action potentials and needle electromyography suggested minor nerve irritation perioperatively.


CONCLUSIONS
This is the first human trial reporting acute and chronic neurophysiologic changes due to application of and stimulation through nerve cuff electrodes. Electrodiagnostics indicated preserved nerve health with strengthened responses following stimulated exercise. Temporary electrodiagnostic changes suggest minor nerve irritation only intra- and peri-operatively, not continuing chronically nor impacting function. These outcomes follow implantation of a neuroprosthesis enabling standing and demonstrate the ability to safely implant electrodes on the proximal femoral nerve close to the inguinal ligament. We demonstrate the electrodiagnostic findings that can be expected from implanting nerve cuff electrodes and their time-course for resolution, potentially applicable to prostheses modulating other peripheral nerves and functions.


TRIAL REGISTRATION
ClinicalTrials.gov NCT01923662 , retrospectively registered August 15, 2013.
['Freeberg|Max J|MJ|0000-0002-4976-5405', 'Pinault|Gilles C J|GCJ|', 'Tyler|Dustin J|DJ|', 'Triolo|Ronald J|RJ|', 'Ansari|Rahila|R|']
D000200:Action Potentials D000328:Adult D001696:Biomechanical Phenomena D004599:Electric Stimulation Therapy D004567:Electrodes, Implanted D004568:Electrodiagnosis D004576:Electromyography D005267:Femoral Nerve D006801:Humans D007717:Knee D008297:Male D053580:Muscle Strength D058117:Neural Prostheses D010243:Paralysis D010264:Paraplegia D011183:Postoperative Complications D013119:Spinal Cord Injuries
Chronic nerve health Spinal cord injury Electrical stimulation Electromyography Rehabilitation Electrodiagnostics and neuromuscular diseases peripheral nerve cuff electrodes