Retrograde changes in motor and sensory conduction velocity after nerve injury.

Nerve section is followed by a reduction of motor and sensory conduction velocity in the proximal segment of the injured nerve. This reduction of velocity is associated with retrograde changes in fiber size. If reinnervation does not occur within the next 1 1/2--2 years, retrograde degeneration of nerve fibers results, and the amplitude of the evoked nerve potential in the proximal segment of the injured nerve decreases. This retrograde degeneration is probably significant in view of the poor results frequently obtained after nerve transplantation which is carried out too late.