Value of Median Nerve Residual Latency and Terminal LatencyIndex as Electrodiagnostic Tools in Diagnosis of Carpal Tunnel Syndrome

Abstract

C arpal tunnel syndrome (CTS) occurs as the result of compression of the median nerve in the carpal tunnel of the wrist, and is most commonly seen as an entrapment neuropathy, especially in women. It is possible to make a diagnosis with symptoms and findings, but the clinical findings almost always need to be confirmed by electrophysiological examinations. Conventional nerveconduction studies (NCS) are used for the diagnosisof CTS, but none of the electrophysiologicaltests on its own has sufficient sensitivity andspecificity for the diagnosis of CTS. The mostcommonly preferred traditional electrophysiologicalmethods in the diagnosis of CTS are mediansensory nerve conduction, median motor distallatency, comparison of median and ulnar nervesensory conduction, and comparison of fourthfinger median-ulnar peak latency. Terminal latencyindex (TLI) and residual latency (RL), calculatedfrom distal motor latency, distal distanceand proximal motor conduction velocities, areelectrophysiological parameters used to identifyabnormalities in the distal segment of the motornerve.