4-AP Peripheral Nerve Crossover Trial

Inclusion Criteria: * Patients with trauma involving two or less limbs where the continuity of a given peripheral nerve or nerves is unclear on presenting physical examination. * Closed soft tissue envelope obscuring direct observation of the continuity of the affected nerve. * Cognitive ability to report sensory and motor deficit during examination. * Eligible for standard of care plan of monitoring vs surgical exploration of the nerve. * Adults subject aged 18-90 * Known limb trauma which resulted in nerve injury (aim 1) or post-operative/post intervention nerve injury (aim 2). * Ability to give written informed consent. * Availability for all testing days and main trial day. Exclusion Criteria: * Distracting injury which prevents adequate examination. * Plan for surgical exploration of the nerve during the ensuing 48 hours. * Plan for surgical exploration of the nerve as part of another surgical procedure within 48 hours of evaluation. * Intoxication during examination or evidence of cognitive deficit that emerges during examination. * History of multiple sclerosis, stroke or any other diagnosed neurological disorder * History of hypersensitivity to AMPYRA® or 4-aminopyridine * Current use of aminopyridine medications, including other compounded 4-AP * Renal impairment based on calculated GFR (GFR\<80 mL/min). This laboratory value is measured in all inpatient trauma patients as part of the standard of care. * History of difficult compliance with timely follow up or plan to seek care at another institution closer to home. * Patients outside the age range or unable to consent. * Patients with a known history of a seizure disorder (4AP overdose can, in selected cases, result in limited seizure activity). * Patients with a concomitant traumatic brain injury. * Patients unable to communicate return or loss of sensation. * Patients unable to exhibit motor control on the affected limb at baseline. * Patients unwilling to complete the study requirements. * Patients with injuries too extensive to isolate a single nerve(s) for testing. * Patients currently taking organic cat-ion transporter 2 (OCT2) inhibitors, e.g. Cimetidine. * Pregnancy, breastfeeding or incarcerated individuals.