A Korean case of juvenile muscular atrophy of distal upper extremity (Hirayama disease) with dynamic cervical cord compression

Abstract

We present a Korean case of Hirayama disease with its typical neuroradiological findings of forward displacement of cervical dural sac and compression of the lower cervical cord during neck flexion. A 15-yr-old boy was presented with a one-year history of progressive weakness and atrophy affecting bilateral hands and forearms. The electrodiagnostic findings were compatible with the lesion of the anterior horn cells at the C7, C8, and T1 spinal segments. With neck flexion, cervical magnetic resonance imaging (MRI) showed the anterior shifting of the lower cervical dural sac resulting in the cord compression of those segments. Presumably, this disease might have been prevalent in Korea frequently under the diagnosis of "benign focal amyotrophy". In this regard, we discuss the clinical importance of cervical MRI with neck flexion and anticipate the increasing reports of the case substantiated by its characteristic radiological features.

Fig. 1

T2-weighted sagittal images in the neutral position reveals normal contour and signal intensity along the sixth to the eighth cervical segments without cervical cord compression.

Fig. 2

(A) On T2-weighted sagittal images in the anteflexed position, there is an anterior shifting of the posterior wall of the cervical dural sac below the third cervical vertebral level compressing the cervical spinal cord from the fifth cervical to the first thoracic vertebral levels (row of white arrows). (B) On enhancement, the widened posterior epidural space shows a homogenous strong enhancement with some signal flow void, suggesting a passively widened epidural venous plexus.

Fig. 3

(A) The T1-weighted axial image of the sixth cervical cord segment in the neutral position has a normal appearance. (B) There is a striking forward compression by the posterior dural sac in the enhanced axial image of the same cervical cord segment in the anteflexed position (white arrowheads).