Poster 105 Serial Nerve Conduction Studies in a Single Subject After Clinically Successful Carpal Tunnel Release

Objective: To perform serial nerve conduction studies (NCS) in a patient with clinically successful carpal tunnel release (CTR). Design: Preoperative and then prospective institutional review board approved testing of postoperative NCS performed included the median (digits 1-4) and ulnar sensory and median motor nerves. NCS were performed 4 days before surgery and at 1, 2, 3, 4, 5, 7, 9, 14, 20, and 25 weeks after surgery. Setting: An outpatient electromyography laboratory. Participants: A 54-year-old woman. Interventions: Not applicable. Main Outcome Measures: Median sensory nerve action potential (SNAP) onset and peak latencies, amplitudes, and distal motor latency and amplitude of the median nerve over time. Results: There was complete resolution of sensory symptoms on the same day as CTR. Post-CTR median (SNAP) onset and peak latencies gradually became normal. Pre-CTR digit 2 SNAP amplitude was low with wrist stimulation but seemingly normal when stimulating mid palm. Post-CTR median SNAP amplitude with wrist stimulation gradually improved, while amplitude with mid palm stimulation remained essentially unchanged. A decrease in the median distal motor latency was most prominent at 1 week after surgery, and, thereafter, it gradually improved. Conclusions: Despite sensory symptom resolution immediately after CTR, the median SNAP latency and amplitude improved gradually over months, in contrast to the median distal motor latency, which improved more rapidly in the first week and than later. The mechanism of improvement in median SNAP amplitude recording from digit 2 with wrist vs. mid palm stimulation may be due to remyelination and repair of apparent conduction block of the median sensory fibers rather than decreased temporal dispersion of the SNAP because the onset and peak SNAP latencies improved in parallel.