ABSTRACT
BACKGROUND AND PURPOSE: We report decremental responses to repetitive nerve stimulation (RNS) in 11 patients diagnosed with X-linked spinobulbar muscular atrophy (X-SBMA). METHODS: The compound muscle action potential (CMAP) of the right abductor digiti minimi (ADM) and trapezius (TZ) in response to a 3-Hz stimulation of the ulnar nerve at the wrist and accessory nerve at the neck were recorded by surface electrodes. RESULTS: A decremental response to RNS was observed in 90.9% of the TZ muscle and 27.2% in the ADM muscle of patients with X-SBMA. CONCLUSION: These electrophysiological features of X-SBMA are considered to be useful for diagnosis of X-SBMA. Furthermore, the waning phenomena that mostly appeared in the TZ muscle and increment of CMAP in RNS after the exercise also suggest a unique manifestation in X-SBMA.