Premotor Potential Study for Diagnosis of Carpal Tunnel Syndrome.

INTRODUCTION The second lumbrical-interossei latency difference test (2LINT) is used frequently for electrodiagnosis of carpal tunnel syndrome (CTS). A premotor potential observed with 2LINT has been identified as a median-nerve sensory nerve action potential. We evaluated the utility of the premotor potential latency analysis (i.e., premotor potential study; PPS) for CTS electrodiagnosis. METHODS Sensitivity, specificity, and percentage "no evoked response" (%NER) values were compared prospectively among PPS, median-nerve sensory nerve-conduction studies (NCSs) for digits 1, 2, and 4, and palmar mixed NCS. RESULTS Sixty-four healthy control hands and 104 hands with CTS were enrolled in this study. PPS sensitivity was superior to other sensory/mixed NCSs (75% vs. 42%-62%). All NCS specificities were acceptable (95%-97%). The %NER of PPS was lower than that of other NCSs (13% vs. 25%-44%). CONCLUSION Premotor potential could be evoked in more CTS hands and was the most sensitive among median-nerve sensory and mixed NCSs. Therefore, we could use the 2LINT with PPS as median and ulnar motor NCS as well as median sensory NCS.