Selective regeneration of sensory fibers following nerve crush injury

We investigated whether or not all classes of myelinated sensory fibers regenerate simultaneously after nerve crush injury and whether each parent fiber produces and maintains a regenerated branch. Electrophysiologic recordings were made from isolated lumbar dorsal root fibers in rats at various times after sciatic nerve crush injury. For all fibers that responded to electrical stimulation distal to the crush, the conduction velocity of the parent axon was established using the collision method. During the first few months following sciatic nerve injury, Aδ parent fibers were under-represented in the sample of successfully regenerated fibers. Only later did sprouts of the bulk of Aδ fibers grow out. In time, however, all fibers regenerated. Combined with histologic data indicating that fiber number was restored in the distal nerve stump, this finding indicated that after crush injury the majority of parent fibers maintained one, but only one, regenerated branch.