Brachioradialis Involvement in Hirayama's Disease: An Atypical Presentation of a Rare Cervical Myelopathy.

Juvenile monomelic amyotrophy (JMA), also known as Hirayama's disease, is a rare cervical myelopathy that predominantly affects young Asian males. It is characterized by degeneration of anterior horn cells due to compression by the redundant dural sac. This study presents an atypical case of a 23-year-old Indian male who exhibited uncommon symptoms of JMA. The patient displayed progressive weakness and atrophy in the left forearm, including the usually spared brachioradialis muscle. Electrophysiological tests and MRI scans solidified the diagnosis of Hirayama's disease. After wearing a cervical collar for one year, the patient's condition stabilized, reinforcing the diagnosis. Unlike most JMA cases, this instance highlights the involvement of the brachioradialis muscle, underlining the variability in JMA presentations. A precise diagnosis is contingent upon clinical criteria, dynamic MRI, and electrophysiological findings. Recognizing these variations is crucial for early detection and appropriate management of the disease.