Nerve conduction studies in the early diagnosis of amyotrophic lateral sclerosis and the importance of split-hand phenomenon

Abstract

Aim: The heterogeneity of the Amyotrophic Lateral Sclerosis (ALS) clinical phenotypes leads to difficulties in early diagnosis. The ‘split hand’ sign is defined as the thenar muscles that are more prominently affected by hypothenar. In this study, the results of the initial nerve conduction study of the patients were compared with those of the controls in order to increase the findings supporting early diagnosis. Material and Method: Seventy-five patients who were diagnosed with ALS in our clinic were included in the study. The initial ENMG findings of the patients were compared with those of 70 healthy controls: Distal motor latency (DML), the compound muscle action potential (CMAP) amplitude, velocity in the motor conduction of median, ulnar, peroneal and tibial nerves; distal latency, amplitude, velocity in sensorial conduction were evaluated. Ulnar/median DML and ulnar/median CMAP amplitude ratios were examined. Results: In ALS group, DMLs of the median, ulnar, peroneal, and tibial nerves were significantly longer, and CMAP amplitudes were significantly smaller than those of the controls. The sensory conductions of the median, ulnar, and sural nerves were not statistically different between the groups. The ulnar/median DML ratio of the patients was lower than the ratio of controls (0.73/0.80;p=0.003); while the ulnar/median CMAP amplitude ratio was greater (1.40/1.11; p=0.002). Conclusion: Prolonged DML and reduced amplitudes were observed in the motor nerve conduction of ALS patients in the early period. The results of the present study also support the presence of split-hand phenomenon even in early period of limb-onset ALS (both upper and lower). These findings suggest that nerve conduction studies and electrophysiologically detected split-hand sign are important clues for the early diagnosis of ALS in case of heterogeneous clinical phenotype.

Keywords

• amyotrophic lateral sclerosis
• split-hand
• nerve conduction study
• amyotrofik lateral skleroz
• sinir iletim çalışması
• ayrık el