Sensitivity of Multi-electrodiagnostic Parameters in Carpal Tunnel Syndrome: Usefulness of residual latency

ABSTRACT

This prospective study following American Association of Electrodiagnostic Medicine recommended criteria in the diagnosis of Carpal Tunnel Syndrome(CTS) evaluated the sensitivity of multi-electrodiagnostic parameters and usefulness of residual latency in CTS. In 45 symptomatic hands of 26 patients with clinical diagnosis of CTS, 8 electrodiagnostic parameters-median motor distal latency, median motor residual latency, median sensory onset latency, median sensory peak latency, median to ulnar sensory onset latency difference(digit 4), median to ulnar sensory peak latency difference(digit 4), median to radial sensory onset latency difference(digit 1), median to radial sensory peak latency difference(digit 1)-were compared to the normative data obtained from the age-matched control group. In 31 CTS hands without polyneuropathy, median to ulnar sensory latency difference(digit 4), median to radial sensory latency difference(digit 1), median sensory peak latency have same sensitivity(71.0%). In 8 CTS hands with delayed proximal median motor nerve conduction velocity which were indiscernible from polyneuropathy in routine nerve conduction study, residual latency was more sensitive than median to ulnar sensory latency difference and median to radial sensory latency difference. Sensitivity difference between sensory onset latency and sensory peak latency was negligible in the electrophysiologic diagnosis of CTS. We concluded that residual latency measurement was a very useful and convenient method in the diagnosis of CTS, especially in the patients with delayed proximal median motor conduction velocity.