[A case of juvenile muscular atrophy of the upper limb with intraspinal cavity formation].

The patient was a 23-year-old man. He had no history of trauma in the head and neck. When he was 20 years old (in 1992), he noticed muscle atrophy and weakness in the right hand. In a hospital, he had cervical MRI study and other examinations. The diagnosis was juvenile muscular atrophy of the upper limb (Hirayama's disease). After that the symptoms became worse in the bilateral forearms and hands. The neurological examination showed severe atrophy in bilateral C7 to Th1 innervated muscles, right pyramidal sign, mild superficial and deep sensory disturbance in the dermatome of C7-Th1, and right Horner's sign. Cervical MRI and myelography revealed the atrophy of cervical cord and intraspinal cavity formations from C5 to Th1. We concluded that chronic and intermittent compression to cervical cord with flexion position made the cavities during the clinical course because these cavities were not found in the MRI taken in 1992.