A 33-yr-old male presenting with neck pain and bilateral upper limb weakness 

Hirayama disease, also known as juvenile muscular atrophy of the distal upper extremity is a benign focal amyotrophy of the distal upper limbs involving C7, C8, and T1 segmental myotomes with sparing of the brachioradialis and proximal muscles of the upper limb innervated by C5–6 myotomes. This disease affects predominantly males in either their 2nd or their early 3rd decade of life. Typical clinical features are muscular weakness and atrophy in the hand and forearm. There is unilateral involvement in the majority of patients, but asymmetric and symmetric bilateral involvement are also observed. Dynamic spinal cord compression at neck flexion with forward displacement of the posterior dura is an important finding in the diagnosis of this disease. A tight dural canal during flexion of the neck is due to a disproportional length between the vertebral column and the dural canal. Asymmetric cord thinning with or without signal changes of cord in young adults showing distal upper limb atrophy warrants reporting radiologist to acquire MR images in neck flexion to diagnose Hirayama disease. Early recognition of this condition is necessary, because avoidance of neck flexion can stop the progression of this disease. Since the progressive stage is expected to cease in a few years, application of a cervical collar for 3– 4 years has been advocated. In selected patients, surgical management includes cervical decompression and/or fusion with or without duraplasty.