The use of the signal averaging computer for evaluation of peripheral nerve problems

Utilization of signal averaging computers to analyze evoked nerve potentials generated by an electrical stimulus is a useful adjunct to clinical evaluation. Currently, somatosensory evoked responses are useful for the evaluation of the peripheral nerve with suspected compression syndromes, neuropathies of unknown etiologies, post-traumatic injuries, neuromas-in-continuity, and brachial plexus injuries. Further refinements in the system will result in increased clinical application of this useful modality. Present data indicate that neuromas with a conduction velocity of less than 10 meters per second or an amplitude of less than one fourth of normal should be considered unfavorable neuromas, and if clinically correlated, resection and repair anticipated. Conduction velocity slowing of greater than 20 meters per second across a potential site of compression neuropathy at the wrist using short-segment study should also be viewed as undesirable and will usually correlate with clinical findings on an abnormal von Frey test. The somatosensory response in compression neuropathy usually correlates better with the clinical finding than with an EMG.