The Usefulness of Various Electrodiagnostic Parameters in Mild Carpal Tunnel Syndrome

J Korean Assoc EMG Electrodiagn Med 2008;10(2):135-143.
Published online December 1, 2008.

Abstract

Objectives: The purpose of this study is to evaluate the sensitivities and specificities of various electrodiagnosticparameters and to investigate the useful methods to increase the sensitivity in the electrodiagnosisof mild carpal tunnel syndrome (CTS).Methods: The 178 hands of 142 patients with mild CTS based on the Steven's electrodiagnostic criteriawere studied. We performed seven electrodiagnostic tests: distoproximal ratio in the second or third finger(M2DP, M3DP); median-radial latency difference to the thumb (MRLD); median-ulnar latency differenceto the ring finger (MULD); second lumbrical-interosseous motor latency difference (LILD); mediansensory-ulnar motor latency difference to the second or third finger (M2SUM, M3SUM). The sensitivityand specificity of each test were calculated.Results: The sensitivities of electrodiagnostic parameters were noted in the M2DP(98.9%),M3DP(98.9%), MRLD(87.6%), MULD(86.5%), M3SUM(74.2%), M2SUM(55.6%), LILD(54.5%).Among electrodiagnostic parameters, M2DP(49.0%) and M3DP(68.0%) revealed relatively low specificitiesthan others. Percentage of mild CTS hands which was abnormal at two differently combined electrodiagnostictest: in M2DP and M3DP(98.3%), M3DP and MULD(86.0%), M3DP and MRLD(81.5%),MRLD and MULD(79.2%), MULD and M3SUM(70.2%); in M3DP or LILD(100%), M3DP orM2SUM(100%), M3DP or MRLD(99.4%), M3DP or M2DP(99.4%), M3DP or MULD(99.4%), M3DPor M3SUM(99.4%).Conclusion: The most sensitive parameter was distoproximal ratio (M2DP, M3DP), as useful method inthe electrodiagnosis of mild CTS but it may cause greater reporting of false positive. Additional parametersincluding MULD, MRLD, LILD, M2SUM, M3SUM may be of value in the diagnosis of mild CTSpatients.

Key Words: Carpal tunnel syndrome, Electrodiagnosis, Parameters, Sensitivity