Hirayama Disease: Latest Insights into an Intriguing Disorder

Hirayama disease (HD) is a cervical flexion-induced myelopathy that causes asymmetrical distal upper limb atrophy and weakening. It usually affects males, with onset in early adolescence, and progression occurs over 3-5 years, resulting in irreversible functional deficits. In addition to classical HD, several rarer phenotypes are described, including distal bimelic amyotrophy, lower limb, proximal, and upper motor neuron variants. Dynamic flexion magnetic resonance imaging is critical in the diagnosis, with distinctive characteristics such as significant epidural flow voids and anterior displacement of the posterior dural sac involving lower cervical segments, with sensitivity and specificity of 93% and 98%, respectively. In progressive cases, apart from conservative management with a cervical collar, surgical management is considered early, with the ideal approach being anterior cervical discectomy and fusion with plating. This review aims to address the latest insights in the pathophysiology, HD variants, spine imaging, and various surgical procedures in the management and prevention of serious residual limb weakness.