The median nerve terminal latency index in carpal tunnel syndrome: a clinical case selection study

The terminal latency index (TLI) adjusts the distal motor latency (DL) for the terminal distance and the proximal nerve conduction velocity. We prospectively studied 66 patients in order to assess the sensitivity of the median nerve TLI for the diagnosis of carpal tunnel syndrome (CTS). Clinical and electrophysiological evaluations were completed by separate, blinded examiners. Based on the clinical diagnosis, 54 patients were judged to have CTS (CTS group) and 12 were believed not to have CTS. Control data were obtained from 38 healthy hands. The mean TLI was 0.26 +/- 0.04 in the CTS group and 0.43 +/- 0.04 in the control group (P < 0.001). The sensitivity of the TLI was 81.5%. The TLI was statistically better than the median motor DL and sensory peak latency (PL) to the second digit. The TLI was always abnormal when the median mixed-nerve palmar latency was abnormal. In three cases from the CTS group, the TLI was the only abnormal electrophysiological parameter. The median TLI is a useful, sensitive electrodiagnostic parameter for CTS.