Introduction:Hirayama disease, also referred to as monomelic amyotrophy, is an uncommon, non-progressive form of cervical myelopathy that predominantly occurs in adolescent and young adult males. Clinically, it presents with a gradual onset of unilateral or asymmetric weakness and muscle atrophy in the distal upper limb, without affecting sensation or the pyramidal tract. Hirayama disease is thought to arise from intermittent spinal cord compression that occurs during neck flexion, leading to ischemic injury of the anterior horn cells. Magnetic resonance imaging (MRI), particularly in the flexed neck position, is essential for confirming the diagnosis and differentiating it from other disorders affecting motor neurons.
Objective: This study aims to assess the characteristic MRI findings in 15 young patients with clinical suspicion of Hirayama disease, emphasizing the importance of dynamic imaging in its diagnosis.
Materials and Methods: A retrospective study was conducted on cervical spine MRI scans of 15 patients (aged 15-35 years) with clinical suspicion of Hirayama disease. Both neutral and flexion MRI sequences were analyzed for spinal cord atrophy, dural displacement, epidural space changes, venous plexus prominence, and signal abnormalities.
Results:In 13 patients, MRI scans obtained with the neck in a neutral position demonstrated localized thinning and volume loss of the lower cervical spinal cord.Flexion MRI demonstrated anterior shifting of the posterior dural sac in all patients, along with a prominent crescent-shaped enhancing posterior epidural space in 12 cases, suggestive of venous plexus engorgement. All participants showed evidence of posterior dural detachment. Flow voids in the posterior epidural space were detected in 11 patients, and subtle T2 hyperintensity within the spinal cord during flexion—suggestive of potentially reversible ischemic changes—was noted in 4 individuals.
Conclusion: Flexion cervical spine MRI is essential in diagnosing Hirayama disease, revealing dynamic spinal changes not visible on neutral imaging. Recognizing these characteristic features can facilitate early diagnosis, allowing timely intervention to prevent progression and improve patient outcome.
International Journal of Radiology and Diagnostic Imaging
