Diagnostic Usefulness of the Second Lumbrical and Interosseous Recording in Severe Carpal Tunnel Syndrome

J Korean Assoc EMG Electrodiagn Med 2009;11(2):73-77.
Published online December 31, 2009.

Abstract

Objective: The purpose of this study was to compare the diagnostic usefulness of various nerve conduction studies when the routine median motor and sensory responses are absent.
Method: Between January 2002 and March 2008, 30 hands of 25 patients were studied, with the medianmotor and sensory responses shown to be absent in the routine nerve conduction studies. We performedthree nerve conduction studies, median-radial latency difference to the thumb, median-ulnar latency differenceto the ring finger and the second lumbrical-interosseous latency comparison method.
Results: The subjects' (3 men and 27 women) ages ranged from 32 to 84 years. All hands had no mediansensory response to the thumb and the ring finger. 5 hands had no median motor response to the secondlumbrical muscle. 25 hands showed a significant prolongation of the lumbrical-interosseous latency difference(>0.4). In all the subjects, the needle EMG revealed abnormal spontaneous activity in the abductorpollicis brevis.
Conclusion: The lumbrical-interosseous latency comparison method is helpful in patients with severeCTS and with no median motor and sensory responses.

Key Words: Carpal tunnel syndrome, Electrodiagnosis, Median nerve, Nerve conduction, Muscles