Familial monomelic amyotrophy (Hirayama disease): two brothers with classical flexion induced dynamic changes of the cervical dural sac.

Sir, In Hirayama disease or monomelic amyotrophy (MMA), dynamic changes of the cervical dural sac and spinal cord associated with neck flexion have been suggested to cause transient cord compression. This finding has not been reported in familial MMA. Two brothers were clinically evaluated and underwent magnetic resonance imaging (MRI) of the spinal cord. They were born to nonconsanguineous parents and had classical manifestations of MMA of the upper limb. Both demonstrated presence of characteristic flexion induced dynamic changes of the cervical dural sac with enhancing posterior epidural space. This observation among familial MMA has not been reported till date.