Presentation
Hand and forearm muscle weakness and atrophy. Electromyogram suspected for injuries at levels C7 and T1 myotomes.
Patient Data
Neutral position: shows minor focal atrophy of the spinal cord at C6 - T1 levels, with no signal abnormality on sagittal T2W/STIR.
Flexion position:
there is a forward migration of the posterior wall of the dura mater which leads to the reduction in the AP diameter of the cord compared to the neutral position and compression of the lower cervical spinal cord
the posterior epidural space is enlarged with flexion and is seen as a crescent. This expanded posterior epidural space shows high signal intensity on T2W/STIR sequences and vividly enhances on T1 post-contrast images with marked epidural flow voids
Case Discussion
This case demonstrates the typical MRI findings of Hirayama disease.
Hirayama disease typically affects young males in their 20s. Clinical symptoms are weakness and atrophy of the distal upper extremity muscles.
MRI in the neutral position can show focal atrophy and signal abnormality of the lower cervical spinal cord. MRI in a flexion position is the key to diagnosis and demonstrates forward migration of the posterior wall of the dura mater and an enlarged, crescent-shaped and enhancing posterior epidural space.
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