Hirayama disease in a young Indonesian male: a case report.

Background: Hirayama disease (HD) is a rare, self-limiting lower motor neuron disorder predominantly affecting young males in Asia. It is caused by dynamic compression of the lower cervical spinal cord during neck flexion, resulting in ischemic injury to the anterior horn cells. Case Description: A 15-year-old Indonesian male presented with a 6-month history of progressive right upper limb weakness and muscle wasting without sensory deficits or spasticity. Electromyography (EMG) showed motor neurogenic changes with ongoing denervation and fasciculations in the right upper limb, with possible anterior horn cell (AHC) involvement. Cervical magnetic resonance imaging (MRI) in the neutral position appeared normal initially. However, a repeat dynamic MRI cervical spine demonstrated anterior displacement of the posterior dural sac and dilatation of the posterior epidural venous plexus from C3-6 with neck flexion, confirming the diagnosis of HD. The patient was managed conservatively with a hard cervical collar and physiotherapy. At 8 months' follow-up, symptoms continued to be stable with no further progression. Conclusions: Although rare, HD should be considered in adolescents presenting with unilateral distal upper limb weakness. It can often be underdiagnosed due to normal findings on neutral MRI cervical spine. As such, flexion imaging is essential for detecting the hallmark signs like anterior dural displacement and posterior epidural venous engorgement. With early recognition, conservative management with a cervical collar can halt disease progression and preserve neurological function.