Value of nerve action potentials in the surgical management of traumatic nerve lesions.

OBJECTIVE: The goals of the study were to investigate the value of intraoperative electrically evoked nerve action potentials (NAPs) in the surgical treatment of traumatic peripheral nerve injuries (nerve lesions in continuity). METHODS: Sixty-four patients with 76 traumatic nerve lesions in continuity were investigated intraoperatively by stimulating and recording NAP from the whole nerve across the suspected lesion site. Among the 76 nerves (nerve lesions) were 43 with incomplete and 33 with complete loss of function. In cases (nerves) with complete loss of function (n = 33), the surgical procedure (external neurolysis, internal neurolysis, or nerve repair) was performed according to the microscopic aspect of the nerve and the result of the intraoperative electrophysiological testing. In cases (nerves) with incomplete loss of function (n = 43), the surgical procedure was performed solely according to the microscopic aspect of the nerve and independently from the result of the intraoperative electrophysiological testing. RESULTS: Of 43 nerves with incomplete loss of function, we were able to record reproducible NAPs in 41 (95%) across the lesion site, thus demonstrating a high reliability of the method. Of 33 nerves with complete loss of function, a reproducible NAP could be recorded only in 3. Assuming an axonotmetic lesion in regeneration, we did nothing else on the nerve with excellent clinical results (full recovery). Of the remaining nerves with no NAP, 24 showed a caliber shift of the nerve (in 20 cases a thickening of the nerve, suggesting a neuroma in continuity). A grafting procedure was performed, and the histological evaluation revealed a neurotmetic lesion. However, in six patients with no NAP, there was no clear caliber shift of the nerve. The epineurium was opened and an internal neurolysis performed showing fascicles in continuity. Three patients had good and three had partial (but useful) recovery. CONCLUSIONS: In nerve lesions in continuity with complete loss of nerve function, intraoperative NAPs are able to detect axonotmetic lesions in regeneration. Thus, unnecessary further surgical procedures can be avoided. On the other end of the spectrum, no recordable NAP together with a caliber shift of the nerve (suggesting a neuroma in continuity) may facilitate the surgeon's decision for a grafting procedure without a time-consuming internal neurolysis. But there is also evidence from our data that not every nerve lesion in continuity without a NAP needs to be grafted.

[Significance of distal motor latency after carpal tunnel operation]. / Zur Bedeutung der distalen motorischen Latenz nach Karpaltunneloperationen.

Motor distal latency (MDL) is one of the most important parameters in the electrodiagnosis of carpal tunnel syndrome (CTS). In a retrospective study of 1816 open surgical decompressions for CTS, a total of 612 postoperative motor nerve conduction measurements on 485 hands could be evaluated. In patients with good or satisfactory results after carpal tunnel release, an average improvement of MDL of 1.0 ms after 9-13 days, and of 2.2 ms after 1 year and longer was found. The individual motor nerve conduction improvement was in close correlation with the extent of preoperative prolongation of the MDL. Whereas relief of symptoms can be noted almost immediately, prolonged latencies often do not return to normal, even when the study is done a year later. Of the 10 patients with persisting symptoms, four had a new postoperative impairment of MDL, and also four had a marked improvement, whereas it remained unchanged in two. Patients with severe recurrent CTS presented in 11 out of 31 cases with an improved MDL from 0.3 ms to 3.0 ms in comparison to the initial preoperative evaluation; in 6 hands MDL was unchanged, further prolongation up to 2.0 ms was seen in 6 cases and marked worsening with new loss of motor response had to be noted in 8 hands at repeat electrodiagnosis. In 33 cases of postoperative reflex sympathetic dystrophy, an improvement of MDL from 0.3 ms to 3.3 ms (mean 1.7 ms) was observed in 22 hands and dissolution of a preexisting motor conduction block in three others, whereas two remained unchanged (without motor response) and an electrophysiological impairment was found only in six hands. Three of them presented with a further prolongation of MDL from 0.3 to 1.0 ms and a new loss of response was noted in the remaining three. In conclusion, postoperative motor nerve conduction studies may assess a favorable course following carpal tunnel release. However, they are often not helpful when surgical results are unsatisfactory, and indication for repeat surgical decompression should be based merely on clinical symptoms.

[Intraoperative electrically evoked nerve action potentials in ulnar entrapment syndrome]. / Intraoperativ elektrisch evozierte Nervenaktionspotentiale beim Ulnarisrinnensydrom.

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)