Pre-, intra-, and postoperative electrophysiologic analysis of the recovery of old injuries of the peripheral nerve and brachial plexus after microsurgical management.

This prospective electrophysiologic study compares the analysis of the pre-, intra-, and postoperative results of 38 surgically treated patients suffering from old injuries of the peripheral nerve (n=28) and brachial plexus (n=10). The period from injury until surgery for the peripheral nerve group ranged from 1.2 to 50 years and, in the brachial plexus group, from 1.2 to 12 years. A statistical electrophysiologic analysis was done: 1) to compare intraoperative amplitude and latency changes of the compound muscle action potential (CMAP) at commencement and on completion of surgery; 2) to compare amplitude and latency changes of CMAP and recruitment (voluntary muscle activity) prior to and 1 year after surgery. In the peripheral nerve group, intraoperative electrophysiologic recordings of CMAP showed a low amplitude at the onset of surgery and significant increase on completion of surgery after neurolysis (p=0.0001) with improvement of latency (p=0.001). The statistical analysis of recruitment of muscles showed a 60 percent improvement 1 year after neurolysis (27 patients) and good recovery after nerve graft (1 patient). There were no statistically significant differences in results in patients under 40 years of age, compared to those above 40 years of age. In the brachial plexus group, statistical analysis of recruitment showed voluntary muscle activity in 45 percent of muscles 1 year after neurolysis (7 patients) and in 42 percent of muscles after nerve graft and neurotization (3 patients). Intraoperative electrophysiologic findings provide useful information during surgery for old peripheral nerve and brachial plexus injury. Intraoperative and postoperative electrophysiologic analyses suggest that the viability of the old injured nerve tissue is longer than previously considered, thus providing a longer period of time in which nerve recovery can occur.