Hirayama Disease: Clinical, Radiological, and Electrophysiological Spectrum in a Case Series of Six Patients, Including a Radiologically Occult Variant

Abstract

Hirayama disease (HD) is a rare, benign, focal cervical myelopathy affecting predominantly young individuals, characterized by insidious onset of distal upper limb weakness and wasting involving C7-T1 myotomes. The objective of this case series was to describe the clinical, radiological, and electrophysiological spectrum of Hirayama disease, including bilateral and radiologically occult presentations, and their short-term clinical outcomes. This case series of six patients (5 males, 1 female) evaluated at a tertiary neurology centre, highlighting the clinical spectrum, imaging features, and electrophysiological findings of HD. Patients were aged 16-29 years and presented with painless, progressive distal upper limb weakness with variable unilateral or asymmetric bilateral involvement. The characteristic “oblique atrophy” pattern with sparing of brachioradialis was observed in all cases. Fasciculations and tremors were noted in a subset, and a history of cold-induced exacerbation of symptoms was frequently reported. One patient demonstrated a radiologically occult variant with normal dynamic MRI despite typical clinical and EMG features. Dynamic cervical spine MRI in flexion revealed anterior displacement of the posterior dura with lower cervical cord flattening in most patients. Electromyography consistently demonstrated chronic neurogenic changes in C7-T1 myotomes, occasionally with contralateral involvement. All patients were managed conservatively with cervical collar immobilization, restriction of neck flexion, and cold avoidance, with clinical stabilization during follow-up. This series highlights the heterogeneous presentation of HD, including bilateral and radiologically occult variants, and emphasizes the complementary role of dynamic MRI and EMG in diagnosis. Early recognition is essential to avoid misdiagnosis and ensure appropriate conservative management.