Aberrant conduction in human peripheral nerve: ephaptic transmission?

Later motor responses were recorded from the foot muscles of patients with neuropathy after stimulation of the posterior tibial nerve at the ankle. The latencies were too short to involve the spinal cord, but latencies were reduced by more proximal stimulation, indicating that the pathway begins with proximal conduction. The response differed from previously reported "axon reflexes," because it appeared on supramaximal stimulation. It was attributed to reflection of an impulse at a discontinuity of the myelin sheath. In 2 of 32 subjects, stimulation of the medial plantar nerve in the great toe resulted in reproducible motor responses with latencies of 37 and 38 msec in the flexor hallucis brevis. Ephaptic transmission was implied.