Magnetic resonance imaging of thoracic epidural venous dilation in Hirayama disease.

Hirayama disease is a nonprogressive, asymmetric amyotrophy of the hands and forearms, possibly caused by compression of the lower cervical cord on neck flexion. The authors used phase-contrast MR angiography to study a patient with this disorder and observed abnormal spinal epidural venous dilation on neck flexion. In addition to mechanical compression of the lower cervical cord, venous congestion in the spinal canal may have a role in promoting anterior horn damage.