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 int raoperative electrically evoked nerve action potentials (NAPs) in the surgical treatment of traumatic peripheral nerve injuries (nerve lesio ns in continuity). METHODS: Sixty-four patients with 76 traumatic nerv e lesions in continuity were investigated intraoperatively by stimulat ing 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 lo ss of function (n = 33), the surgical procedure (external neurolysis, internal neurolysis, or nerve repair) was performed according to the m icroscopic aspect of the nerve and the result of the intraoperative el ectrophysiological testing. In cases (nerves) with incomplete loss of function (n = 43), the surgical procedure was performed solely accordi ng to the microscopic aspect of the nerve and independently from the r esult of the intraoperative electrophysiological testing. RESULTS: Of 43 nerves with incomplete loss of function, we were able to record rep roducible NAPs in 41 (95%) across the lesion site, thus demonstrating a high reliability of the method. Of 33 nerves with complete loss of f unction, a reproducible NAP could be recorded only in 3. Assuming an a xonotmetic lesion in regeneration, we did nothing else on the nerve wi th excellent clinical results (full recovery). Of the remaining nerves with no NAP, 24 showed a caliber shift of the nerve (in 20 cases a th ickening of the nerve, suggesting a neuroma in continuity). A grafting procedure was performed, and the histological evaluation revealed a n eurotmetic lesion. However, in six patients with no NAP, there was no clear caliber shift of the nerve. The epineurium was opened and an int ernal neurolysis performed showing fascicles in continuity. Three pati ents 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 regener ation. Thus, unnecessary further surgical procedures can be avoided. O n the other end of the spectrum, no recordable NAP together with a cal iber shift of the nerve (suggesting a neuroma in continuity) may facil itate the surgeon's decision for a grafting procedure without a time-c onsuming internal neurolysis. But there is also evidence from our data that not every nerve lesion in continuity without a NAP needs to be g rafted.