Hirayama Disease: A Rare Disease with Unusual Features

Abstract

Hirayama disease, also known as monomelic amyotrophy (MMA), is a rare cervical myelopathy that manifests itself as a self-limited, asymmetrical, slowly progressive atrophic weakness of the forearms and hands predominantly in young males. The forward displacement of the posterior dura of the lower cervical dural canal during neck flexion has been postulated to lead to lower cervical cord atrophy with asymmetric flattening. We report a case of Hirayama disease in a 25-year-old Indian man presenting with gradually progressive asymmetrical weakness and wasting of both hands and forearms along with unusual features of autonomic dysfunction and upper motor neuron lesion.

Figure 1

(a) Wasting of bilateral hands. (b) Wasting of the left forearm with sparing of brachioradialis muscle.

Figure 2

(a) MRI showing focal symmetrical atrophy of spinal cord with intramedullary T2 hyperintensity. (b) MRI showing forward displacement of the posterior subdural sac on flexion of neck, with prominent epidural space.