Adjunctive Procedures for Median Nerve Decompression in Carpal Tunnel Syndrome An Intraoperative Somatosensory Evoked Potential Study.

The objective of this study was to determine the role of ad- junctive surgical procedures on the median nerve for carpal tunnel syndrome as measured by somatosensory evoked potentials (SEPs) on the nerve. Fifty-five median nerves in 47 patients were studied. In each patient, a base-line SEP was recorded in the operating room prior to incision and then intraoperatively following each of three sequential pro- cedures: division of the transverse carpal ligament, an epi- neurolysis of the nerve, and finally, either an epineurotomy or epineurectomy that we refer to as a "limited internal neu- rolysis" since it did not involve any intraneural dissection of fascicles. Comparison of the baseline mean SEP latency for the median nerve, referred to as N19 (negative polarity = 19 msec), showed a statistically significant improvement following each of the three procedures. The average reduc- tion of latency after ligament release alone was 1.52 msec, and the total improvement in latency from baseline through limited internal neurolysis was 4.72 msec. Our study showed that epineurolysis followed by a limited internal neurolysis using either an epineurotomy or epineurectomy produced a significant electrophysiologic improvement in the median nerve. There was no significant difference when comparing epineurotomy and epineurectomy.