Methods, indications and validation of intraoperative nerve conductivity testing

During nerve surgery, electrodiagnostic methods are applied to assess the availability and viability of nerve fibers and to adjust operative measures accordingly. The validity of this procedure is verified by histology and by the outcome of the operation. This paper explains the techniques of intraoperative nerve action potential (NAP) and somatosensory evoked potential (SEP) recording, how to interpret the electrodiagnostic results, and describes both the special features and the limitations of the methods. We found reliable results of neurography, detecting the presence or absence of spontaneous nerve regeneration across a lesion in continuity months before the reinnervation reached its final target. Based on our results, we suggest that NAP recording of the exposed nerve can widely prevent unnecessary nerve or fascicle resection. Besides this important indication, the nerve function evaluation was successfully used in nerve surgery whenever the quality of the nerve parenchyma was crucial to the operative management. Further indications such as evaluating brachial plexus lesions and the condition of nerve roots, judging the proximal coaptation site in nerve reconstruction, tracing the site of a nerve lesion and identifying the pathophysiology of nerve malfunction are exemplified. Intraoperative nerve conductivity testing should not be considered as a replacement of but rather as a complement to preoperative clinical, electrophysiological and imaging evaluations and a thorough intraoperative morphological examination.