Hirayama Disease - A Variant of Motor Neuron Disease and Role of Flexion MRI in Diagnosis

Hirayama disease is a monomyelic variant of motor neuron disease (MND) and has distinctive features of male predominance, asymmetric involvement of upper extremities with a self limiting course. Flexion MRI (magnetic resonance imaging) forms the main stay for diagnosis of this condition. Here we report such an unusual case of Hirayama disease in a male patient of 20 years who presented with weakness and atrophy in right upper limb. Careful clinical examination will help to use the flexion MRI studies for the diagnosis of this condition as done in our case.