[A case of juvenile-type distal and segmental muscular atrophy of upper extremities (Hirayama disease) with the isolated cervical fusion at the C3-C4 levels].

The case, 29-year-old male, had suffered from muscular weakness and atrophy of the bilateral forearms and hands with tremor of the bilateral fingers for about 13 years. A neurological examination showed normal muscle-stretch reflexes and no sensory disturbances. A cervical spinogram revealed a fusion at the C3-C4 levels and mild spondylotic changes. We clinically diagnosed him as juvenile-type distal and segmental muscular atrophy of upper extremities (Hirayama disease) with the isolated congenital cervical fusion. Magnetic resonance imaging demonstrated an enlargement of the anterior epidural space from the C4-C5 levels to the Th 1-Th 2 levels. This abnormal epidural space showed relatively high signal intensity partially with low signal intensity on the T2 weighted spin-echo image and decreased in signal on the T1 weighted spin-echo image. And the dural sac was shifted backward and narrowed. And the soft discs was slightly protruded at the level of C4-5, C5-6 and C6-7. These findings suggest the over swelling and the delayed blood flow of the internal vertebral venous plexus. In this case, the degeneration of the cervical spine and soft disc derived from the congenital cervical fusion seems to have caused the internal vertebral venous plexus congestion and then have damaged the anterior horn cells.