Electromyogram and nerve conduction features of Hirayama disease / 解放军医学杂志

ABSTRACT

Objective To promote the understanding and diagnostic acuity of Hirayama disease by studying the features of electromyogram (EMG) and nerve conduction. Methods EMG was performed in 33 patients with Hirayama disease. Surface electrode was applied to examine the median nerve, cubital nerve, musculospiral nerve and part of the popliteal nerve, and the motor nerve conduction velocity (MCV), distal motor latency (DML) and the amplitude of compound muscle action potential (CMAP) were recorded. The sensory nerve conduction velocity (SCV) was also examined in the median nerve, cubital nerve and part of the sural nerve. Results The neurogenic abnormalities were detected in extremity muscles, with exception of brachioradial muscle, of upper limbs. In all the 33 patients damage was found on the illness-side and 97.0% on the contralateral side. One patient was found to have neurogenic abnormality of brachioradial muscle and 4 of proximal muscles, including 1 in whom muscle of lower limbs was involved. EMG abnormality rate of distal muscles (89.9%) was significantly higher than that of the proximal muscles of upper limbs (6.7%) and also muscles of lower limbs (1.7%). EMG also showed that there was delayed distal motor latency (DML) and decreased wave amplitude of compound muscle action potential (CMAP) in the nerves of upper limbs. statistically significant difference was found between the CMAP amplitude of affected limb (2.52?1.83mV) and the contralateral upper limb (9.82?3.57mV) by the detection of ulnar nerve conduction, while no difference and no nerve block were found between the DML of affected limb (4.25?1.33ms) and the contralateral upper limb (3.28?0.36ms). Conclusions Electrophysiological changes may be detected in some patients with subclinical Hirayama disease, of which the electrophysiological test is valuable in establishing early diagnosis.