Penfield Lecture. A quarter century's experience with intraoperative nerve action potential recording.

The rationale, basic considerations, and technique of intraoperative nerve action potential (NAP) recording have been reviewed. Experience using this technique in several thousand patients over a 25 year period has been summarized. The most frequent serious nerve injury is one that leaves it in continuity. Resection of such a lesion that is regenerating does the patient a great disservice as does exploration without repair of one with little or no potential for useful spontaneous recovery. The frequency of lesions in continuity as well as the difficulties in evaluating them in the early months by electromyography let alone by surgical inspection has led to the development of intraoperative NAP recording. Where neurolysis was based on a recordable NAP across a lesion in continuity, 93% recovered good function. Where resection of the lesion was based on absence of an NAP, the injury was, without exception, neurotmetic and/or one with poor potential for useful recovery without repair. Some lesions had an NAP across their lesion but a portion of the cross-sectional area appeared more seriously injured. By use of NAP recordings, a split repair was done and usually with good results.