['Several studies have shown a significant amplitude decrement in compound muscle action potentials (CMAPs) on repetitive nerve stimulation (RNS) of muscles involved in amyotrophic lateral sclerosis (ALS). In ALS, muscle wasting preferentially affects the thenar muscles (APB) rather than the hypothenar muscles (ADM).', 'We performed RNS studies in the APB and ADM muscles of 32 ALS patients to determine whether the effect of RNS differs between the median and ulnar nerves.', 'The decremental responses to RNS were greater in the APB than in the ADM. Reduced CMAP amplitude was negatively correlated with CMAP decrement in median but not in ulnar nerves.'] Is significant CMAP decrement by repetitive nerve stimulation more frequent in median than ulnar nerves of patients with amyotrophic lateral sclerosis?