G.P.292: Nerve ultrasonography and neurophysiological study in amyotrophic lateral sclerosis to assess distal motor dysfunction of median nerve

Abstract

In some patients with early stage of amyotrophic lateral sclerosis (ALS), distal motor latency (DL) prolongation without reductions of compound muscle action potential (CMAP) amplitude and motor conduction velocity (MCV) in median nerve is detected by nerve conduction study (NCS). It cannot be explained by axonal loss, and might be primary, specific lesion as the very early sign of ALS. Carpal tunnel syndrome may be complicated with ALS, or other disorders associated with ALS may occur. The aim of our study was to evaluate this pathogenesis generally by using NCS and nerve ultrasonography. Three individuals with ALS and 4 with CTS were examined nerve ultrasonography to measure the cross-sectional area (CSA) of their median nerve at wrist. NCS was also studied and we recorded DL, CMAP amplitude, sensory nerve action potential (SNAP) amplitude and sensory conduction velocity of median nerve at wrist in the patients of both groups. We compared the ALS group with the CTS group about these parameters. As for ultrasonography, no apparent abnormal findings were found in 2 CTS patients, and in other 2 CTS patients, median nerves were compressed at carpus part and enlarged at proximal to carpal tunnel. Though these findings were not found in all ALS patients, the CSA of the median nerve was smaller in the ALS patients than in the CTS patients. On the other hand, DL was prolonged in all ALS patients, CMAP amplitude was reduced in 2 out of 3 ALS patients. In 2 CTS patients, prolonged DL was found. One showed reduction of both CMAP and SNAP amplitude and the other showed only CMAP amplitude reduction. In other 2 CTS patients, NCS findings were normal. Nerve ultrasonography may demonstrates nerve atrophy in ALS even if NCS reveals similar findings to CTS and might contribute to the diagnosis of ALS in early stage.