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Imaging features and work up of Hirayama disease: A rare cause of cervical myelopathy 2012

General Spine

Udaykamal, Barad, MD
Annette, Douglas-Akinwande, MD, Non ASSR Member

Excerpta

Introduction:
Hirayama disease is benign nonprogressive disease which also termed as nonprogressive juvenile spinal muscular atrophy of the distal upper limbs, a kind of cervical myelopathy related to flexion movements of the neck ( 1,2,3,4) .
This disease affects predominantly males in either their 2nd or their early 3rd decade of life. After a period of initial deterioration, a stable stage is reached (5). Typical clinical features are muscular weakness and atrophy in the hand and forearm. Since the brachioradialis muscle is spared, the pattern of forearm involvement is also referred to as an oblique amyotrophy. We report the CT and MR findings in the case of Hirayama disease, a kind of cervical myelopathy related to flexion movements of the neck.

Purpose

Imaging features and work up of Hirayama disease: A rare cause of cervical myelopathy

Methods & Materials

Clinical features: 39-year- male presented with insidious onset of bilateral upper extremity weakness and atrophy of primarily the distal muscle groups including intrinsic hand muscles, wrist and finger extensors. The symptoms were started when he was 19 year old and initially involved right hand and forearm and then moved to left upper extremity. No family history of neuropathies, myopathies, or known autoimmune diseases. On neurological examination, diffuse atrophy of the both hand intrinsic muscles with severe weakness including inability to fully extend the knuckles of the both hand or fully extend the fingers. Intermittent fasciculations were noted throughout the intrinsic muscles of bilateral hand. The deep tendon reflexes were symmetrically normal without Babinski sign. Sensation to pin-prick, vibration, and joint position was intact. No extrapyramidal signs, Horner sign, or abnormalities in sweating and urination were noted. Electrophysiological examination: Electromyography showed very large, neurogenic type motor unit potentials in C6-C8 muscles bilaterally with infrequent fasciculations and fibrillation potentials. The findings were compatible with anterior horn cell disorders involving C6-8 levels of cord.

Results

Imaging: Nonflexion MR cervical spine revealed cord atrophy at C5-C6 and posterior wall of dural canal is in close contact with spinal canal. Midline sagittal T2 images showed area of high signal intensity possibly indicative of gliosis in atrophied segment of cervical spinal cord. Flexion MR cervical spine showed anterior shifting of the posterior wall of the dural canal at C5-6, which causes flattening of the lower cervical cord. Nonflexion CT of cervical spine revealed normal subarachnoid spaces while in flexion CT cervical spine showed enlargement of dorsal epidural venous plexus from C4-5 to T1-T2 with marked reduction in anterior subarachnoid space and ventral displacement of posterior dura resulting in spinal cord compression. He underwent C5-T1 posterior cervical laminectomies and C4-T2 fixation and fusion.

Conclusion

A good understanding of Hirayama disease is essential because early recognition and management can effectively halt the progressive deterioration. While a diagnosis of Hirayama disease is straight forward at flexion MR and CT imaging, the challenge for neuroradiologists is how to identify this condition on routine nonflexion CT or MR studies. Thus, in cases of adolescent onset of distal upper limb weakness, the finding of asymmetric cord. atrophy on routine nonflexion MR studies, especially at the lower cervical cord, should raise the suspicion of Hirayama disease. When this sign is seen, a flexion CT or MR with contrast study should be performed to confirm the diagnosis.

References/Financial Disclosures

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