Hirayama disease.

This article discusses three patients with likely Hirayama disease. They have no other significant past medical history and no personal or family history of other neurological disorders. Hirayama disease is a form of cervical myelopathy attributed to forward displacement of the posterior cervical dural sac on neck flexion with resultant cord compression and/or venous congestion. It is characterized by a pure motor focal amyotrophy in the distribution of C7, C8 and T1 spinal segmental-innervated muscles and differs from other motor neuron diseases by virtue of its ultimately non-progressive course.