Usefulness of Median-Radial Latency Difference to the Thumb in the Diagnosis of Mild Carpal Tunnel Syndrome

J Korean Assoc EMG Electrodiagn Med 1999;1(1):19-25.
Published online January 1, 1999.

Abstract

Objective : To investigate the sensitivity of median-radial latency difference to the thumb compared with other conventional electrodiagnostic parameters, to determine the significance of each of these techniques in the early diagnosis of mild carpal tunnel syndrome(CTS). Method : Fifty four hands of thirty persons with clinical diagnosis of CTS were included in this study. Patients were categorized into 3subgroup I(54 hands), total patients with clinical symptoms and signs suggestive of CTS; group II(27 hands), mild CTS(e.q. normal median motor and sensory latency with clinical synptoms); group III(13 hands), CTS with peripheral polyneuropathy. We performed five electrodiagnostic test; that is, median motor distal latency(MMDL), median sensory peak latency(MSPL), sedian sensory peak latency wrist-to-palm(MSPL, W-P), median-radial latency difference to the thumb(MRLD) and median-ulnar latency difference to the ring finger(MULD), We also compared these data with those of the age-matched normal cintrol group IV(58 hands). Results : There were significant delays in five electrodiagnostic parameters in group I compared with those of control group IV(p<0.05). MRLD was significantly delayed in group I, group II(p<0.05) and group III(p<0.01)compared with group IV. In all 3 patient groups, MSPL W-P was the most sensitive parameter. Especially in group II, MRLD was more sensitive than MULD. In group II, combination of MRLD and MSPL W-P had sensitivity of 77.8% Conclusion : We concluded that MRLD is one of sensitive indicators in the diagnosis of mild CTS and combination of MRLD and MSPL W-P may be of value in early screening for a mild CTS.

Key Words: Carpal tunnel syndrome(CTS), Median-radial latency difference