Abstract
Hirayama disease, also called non-progressive juvenile muscular atrophy of distal upper limbs, is a type of cervical myelopathy associated with flexion movements of the neck. It is a type of benign motor neuron disease seen typically in young males in the age group of 15 to 25. The disease has an insidious onset with a stationary stage following a progressive phase. It is also called monomelic amyotrophy with patients usually presenting with insidious onset unilateral upper limb weakness and muscle wasting. A bilateral and asymmetrical presentation can be seen very rarely.A middle-aged male patient presented with bilateral asymmetrical upper limb weakness, muscle wasting involving forearm and hand muscles. Neurological examination showed bilateral upper limb weakness and muscle wasting involving forearm and hand muscles, with a classical pattern of muscle wasting in bilateral forearm muscles called oblique amyotrophy. A clinical diagnosis of Hirayama disease was made and the patient was sent to the radiology department for Magnetic Resonance Imaging of the cervical spine in flexion and neutral positions. The imaging findings were consistent with the clinical diagnosis of Hirayama disease with the presence of an abnormal “snake eye appearance”. The electrophysiological assessment done including the electromyography and nerve conduction studies were also consistent with the clinical diagnosis.“Snake eye appearance” on MRI in patients with Hirayama disease is associated with unfavorable outcomes and represents cervical myelopathy involving the anterior horn cells.
Highlights
Hirayama disease is an uncommon neurological entity and is a type of benign motor neuron disease
The patients are usually young males presenting with insidious onset of unilateral upper limb weakness with associated muscle wasting in the forearm and hand [1]
Magnetic Resonance Imaging (MRI) cervical spine in flexion and extension are the mainstay for radiological diagnosis showing prominent epidural space due to detachment of the posterior dura mater from the underlying lamina
Summary
Hirayama disease is an uncommon neurological entity and is a type of benign motor neuron disease. A clinical diagnosis of Hirayama disease was made and a contrast MRI of the cervicodorsal spine in neutral and flexion was done which showed an abnormal linear T1 hypo-intense (Figure 1a) and T2 hyperintense signal (Figure 1b) in the anterior spinal cord with “Snake Eye Appearance” (SEA) on axial T2-weighted image (Figure 1c). Sagittal T1 post-contrast image in flexion shows prominent enhancing posterior epidural space with a flow void (denoted by white arrow) He was asked to wear a cervical collar to stabilize the neck to reduce movements aggravating the symptoms. The patient developed pyramidal signs over a period of the 3 months and developed symptoms of cervical spondylosis
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