[MRI in flexed and extended positions for the diagnosis of cervical myelopathy in Hirayama's disease].

We report the case of a young man who presented with atrophy of the musculature of the right forearm and hand. The clinician suspected cervical myelopathy in Hirayama's disease on the basis of the findings at electromyography and recommended an MRI examination in both flexed and neutral position. The typical imaging findings for cervical myelopathy in Hirayama's disease were observed and the diagnosis was confirmed. The key findings for Hirayama's disease consist of asymmetrical medullary atrophy with involvement of the anterior horns, dorsal detachment of the dura mater, and dilatation of the epidural venous plexus.