ABSTRACT
In adult mammals, including humans, the peripheral nervous system (PNS) is capable of regeneration following injury. The PNS consists of neural structures located outside the central nervous system (CNS), which is comprised of the brain and spinal cord. Unfortunately, CNS injuries rarely show a return of function, although recent studies suggest a limited capacity for recovery under optimal conditions. Neural regeneration is complicated by the fact that neurons, unlike other cell types, are not capable of proliferating. In successful regeneration, sprouting axons from the proximal nerve stump traverse the injury site, enter the distal nerve stump, and make new connections with target organs. Current surgical techniques allow surgeons to realign nerve ends precisely when the lesion does not require excision of a large nerve segment. Nerve realignment increases the probability that extending axons will encounter an appropriate distal neural pathway, yet the incidence of recovery in the PNS is highly variable, and the return of function is never complete. Surgical advances in the area of nerve repair seem to have reached an impasse, and biologic rather than technical factors now limit the quality of regeneration and functional recovery. The use of synthetic nerve guidance channels facilitates the study of nerve regeneration in experimental studies and shows promise in improving the repair of injured human nerves. Advances in the synthesis of biocompatible polymers have provided scientists with a variety of new biomaterials which may serve as nerve guidance channels, although the material of choice for clinical application has not yet been identified.
