Nerve Transfers Plus Electrical Stimulation to Improve Hand Function in Cervical Spinal Cord Injury

Background:

Spinal cord injury (SCI) is a major problem facing the general public, with particular relevance for military personnel, given the high frequency of SCI in combat-related injuries. Nerve transfer surgery is one option for restoring function in cervical SCI patients that shows great promise. A nerve transfer involves sacrificing a working nerve that arises from a spinal cord segment above the zone of injury and connecting it to a non-working nerve to reinnervate a target muscle. Restoring hand function is consistently rated by SCI patients, including our lived experience consultants, as most important, even more important than walking or bowel/bladder control. Nerve transfer surgery has been shown to be effective in restoring hand function, but additional improvements are needed, especially for restoring grasp. Furthermore, pain is a significant problem in patients with cervical SCI, with an unmet need for options for treating pain in these patients. Peripheral nerve electrical stimulation has been shown to improve axonal regeneration, muscle reinnervation, and motor recovery and has been used to treat neuropathic pain. Thus, the use of peripheral nerve electrical stimulation has the potential to simultaneously improve motor and pain outcomes in cervical SCI patients undergoing nerve transfer surgery but has never been studied.

Objectives/Hypotheses:

The investigators hypothesize that brief intraoperative electrical stimulation of the donor nerves will result in improved motor outcomes compared to standard nerve transfer. We also hypothesize that placement of a temporary peripheral nerve stimulator for 60 days of postoperative electrical stimulation will result in improved pain outcomes compared to standard nerve transfer.

Specific Aim:

Compare motor and pain outcomes for nerve transfers in cervical spinal cord injury patients with and without peripheral nerve stimulation.

Study Design:

A single center, unblinded, single arm, non-randomized, observational design will be utilized. A total of 10 patients with cervical spinal cord injury classified as ASIA A or B, with International Standards for Neurological Classification of Spinal Cord Injury neurological level of injury C6 or C7 will be recruited and will undergo standard end-to-end nerve transfer surgery targeting restoration of finger extension (posterior interosseous nerve recipient) and finger flexion (anterior interosseous nerve recipient) according to standard clinical care. The test intervention will consist of intraoperative brief electrical stimulation of the donor nerves and postoperative electrical stimulation via a temporary, implantable peripheral nerve stimulator. Intraoperative brief electrical stimulation (BES) will be performed using a handheld nerve stimulator to stimulate the donor nerves at 2 mA with a 200 µs pulse duration for 10 minutes. The implantable peripheral nerve stimulator will be programmed to optimize postoperative pain control on an individualized basis. The peripheral nerve stimulator will be explanted after 60 days, as is intended for this device. The primary outcomes will be manual motor testing graded on the Medical Research Council (MRC) scale (0-5) for the extensor digitorum communis (EDC) and flexor pollicis longus (FPL) and the Numeric Rating Scale (NRS) for pain in the treated extremity (0-10). Patients will have a baseline preoperative electrodiagnostic study and functional electrical stimulation performed, with the decision for surgery occurring as part of standard clinical care. Assessments will occur preoperatively and postoperatively at 3, 6, 12, 24, and 36 months. The researchers will compare these data to a retrospective group of patients who underwent similar nerve transfer surgery without intraoperative or postoperative electrical stimulation.