[Intraoperative electrically evoked nerve action potentials in ulnar entrapment syndrome]

Many attempts have been made in the past to find predictive factors concerning patients operated on because of ulnar nerve entrapment at the elbow. The factors most frequently discussed in the literature are the patient's age, the importance of the preoperative neurological deficit, the duration of symptoms, accompanying diseases as diabetes mellitus or alcoholism and preoperative electrophysiological findings (EMG and conduction velocity measurements). With the exception of the electrophysiological findings, which uniformly are considered to be without predictive value, all other factors mentioned above are discussed controversly. In 1972 Kline and Nulsen [12] have shown, that intraoperatively evoked nerve action potentials across a traumatic nerve lesion can provide information about nerve regeneration. This information helps to choose the appropriate surgical procedure namely either neurolysis or neuroma resection and grafting. However there are no reports dealing with this method in nerve entrapment syndromes. We present the results of 17 patients with ulnar nerve entrapment at the elbow. They were operated on in our hospital between 1989 and 1992 by simple decompression or by anterior transposition of the nerve. In each of them we tried to record electrically evoked nerve action potentials intraoperatively and compared preoperative clinical findings with the potentials recorded. Our main interest was to find out, if the potentials have any predictive value regarding the clinical outcome. In 16 of 17 patients we were able to record a reproducable nerve action potential. Amplitudes varied between 3.4 and 140 uV. Conduction velocities of the fastest fibers ranged from 17 to 71 m/s, while potential duration varied between 1.3 to more than 8 ms.(ABSTRACT TRUNCATED AT 250 WORDS)