Retrograde slowing of conduction in sensory axons central to a sciatic nerve neuroma.

We have plotted the time-course of retrograde slowing of impulse conduction velocity in myelinated afferent fibers after sciatic nerve transection and ligation, using compound action potential recordings, and samples of single afferent fibers. Conduction slowed rapidly during the first few weeks postoperative, and then the rate of slowing declined, approaching an asymptote after about 5 months. There was no indication of recovery. The initial decline in conduction velocity that follows nerve crush was similar to that following nerve transection. Upon regeneration, however, conduction velocity returned to near baseline values. Afferent fibers in the neighboring posterior biceps nerve share conduction pathways, dorsal root ganglia, and spinal terminal fields with sciatic nerve afferents, but their conduction velocity was not reduced following sciatic nerve injury.