Application of nerve action potential(NAP)of ulnar nerve in the forearm in diagnosis of mild cubital tunnel syndrome

Objective To explore the most sensitive electrophysiological parameters for diagnosis of cubital tunnel syndrome.Methods Data of electrophysiologieal tests of 32 cases of mild cubital tunnel syndrome collected from October 2005 to March 2006 were analysed.Results For those diagnosed as cubital tunnel syndrome,50% had reduction of motor nerve conduction velocity(MNCV)in ulnar nerve at the elbow. 40.6% had reduction of sensory nerve conduction velocity(SNCV)and sensory nerve action potential(SNAP) amplitude from little finger to wrist.The positive rate of amplitude reduction of ulnar nerve action potential (NAP)in the forearm was 87.5%.The abnormal rate of short segment conduction time(SSCT)of the ulnar nerve across the elbow was about 59.4%.The positive results in needle EMG was 3.1%.Conclusion Amplitude reduction of ulnar nerve NAP(wrist to elbow)≥50% that of the contralateral side is one of the most sensitive parameter for diagnosis of early cubital tunnel syndrome.