Radiological and Electrophysiological Correlates of Disease Progression in Patients with Hirayama Disease

Background and Objectives: To correlate the distribution of neurogenic motor unit potentials in the upper limb (s) and the extent of anterior displacement of the cervical duramater on neck flexion with the progression of weakness/atrophy in Hirayama disease. Methods: Consecutive patients with distal Hirayama disease were classified as distal group (neurogenic potential in C7–T1 innervated muscles), proximal (neurogenic potentials C5–T1 muscles), and contralateral group (neurogenic potentials in contralateral hand/arm). Based on the extent of anterior dural displacement on neck-flexed cervical magnetic resonance imaging, patients were classified as anterior dural displacement across the C5 vertebra and anterior dural displacement at C5 vertebra and below. The disease progression at 1 year was correlated with the distribution of neurogenic potentials and the extent of anterior dural displacement. Results: Twenty-eight patients (mean age, 17.41 ± 2.30 years; all males) were included. Eleven (39.2%), 17 (60.7%), and 22 (78%) patients were in proximal, distal, and contralateral groups, respectively. Twenty-three (82%) had anterior dural displacement across the C5 vertebra, whereas 5 (17%) had anterior dural displacement at C5 vertebra and below. Ipsilateral disease progression was seen in 15 (53%) and contralateral progression in 25 (89%) (new onset in 7 [25%]). No patient showed progression in shoulder/arm muscles. The proximal group had a significantly larger extent of anterior dural displacement. However, there was no correlation of disease progression with either the distribution of neurogenic motor unit potentials or the extent of cervical dural displacement on neck flexion. Conclusions: The extent of anterior dural displacement on neck flexion and neurogenic motor unit potentials in proximal, distal, or contralateral upper limb did not correlate with progression of muscle weakness/atrophy in Hirayama disease at 1 year.