Percussive injury to peripheral nerve in rats.

Weights were dropped on rat sciatic nerves. Teased fibers and light and electron micrographs of nerves removed between 10 minutes and 2 weeks later were examined. Axonal alterations were seen 10 minutes after injury, and subsequently interruption of axonal continuity with preservation of the basal lamina was apparent. Dissolution of myelin began within 30 minutes and progressed. At 14 days, a segment of some large fibers was devoid of myelin and, by 2 weeks, remyelination had commenced. Demyelination of significant number of fibers was always accompanied by Wallerian degeneration of other fibers of the same nerve. Percussive injury of nerves caused a mixed lesion in which the early and late pathological features were clearly distinguishable from those following crush or compression by a cuff. Any explanation of the transient interruption of function that has been described following such an injury is at present speculative.