Electrophysiological differences between Hirayama disease patients with diffuse neurogenic damages on electromyography and patients with amyotrophic lateral sclerosis

Abstract

Objective To compare the electrophysiological features between Hirayama disease (HD) patients with diffuse neurogenic damages on electromyography (EMG) and patients with amyotrophic lateral sclerosis (ALS). Methods The data of 83 patients who were diagnosed with HD based on electromyographical findings collected from April 2006 to January 2016 were reviewed to find patients with diffused neurogenic damages on EMG. Two ALS patients who were sex- and disease duration-matched were chosen as controls for every HD patient. Results Eight of 83 HD patients (9.6%) were found to have diffuse neurogenic damages on EMG. Compared with the ALS controls ((38.6±4.2) years old), the HD group were younger ((17.5±2.4)years old, t=12.92, P<0.01), had fewer cases with involvement on both sides (1/8 vs 12/16, P=0.008), and fewer cases with decreased amplitude of the median nerve compound muscle action potential (CMAP; 1/8 vs 15/16, P<0.01). The ulnar/median CMAP ratio was lower (0.66(0.29, 0.79)vs 1.83(1.20, 3.82), Z=124.0, P<0.01), the spontaneous potential of the upper limbs was less (abductor digiti minimi Z=60.5, P=0.003; extensor digitorum communis Z=36.0, P=0.019), and the duration of motor unit potential in the sternocleidomastoid muscle had less increase (33%(31%, 50%) vs 52%(43%, 58%), Z=103, P=0.016) in HD patients compared with ALS. Conclusion The pathogenic mechanism of HD with diffuse neurogenic damages on EMG remains unclear, but above-mentioned electrophysiological differences might be helpful to the differential diagnosis of the two diseases. Key words: Hirayama disease; Amyotrophic lateral sclerosis; Electromyography