[A case of flexion myelopathy presenting juvenile segmental muscular atrophy of upper extremities--a successful treatment by cervical spine immobilization].

A 24-year-old man was well until 1982, when he noticed weakness and atrophy of right arm especially those of biceps muscles. These symptoms did not progress until 1988. In 1988 weakness of left elbow flexion appeared and he was admitted to our hospital. On examination, he had weakness and atrophy of both upper extremities. Fasciculation was noticed in the proximal part of right arm. When his head was bent forward, dysesthesia appeared around radial side of his arm. There were no long tract sign or objective sensory loss. EMG showed neurogenic change over both his upper extremities. In plain cervical roentgenogram there existed abnormal kyphosis of cervical vertebrae. In MRI imaged with his neck flexed, cervical cord was compressed by the posterior surface of 4th cervical vertebral body, which corresponded to the top of cervical kyphosis. Based on these signs and examinations, a diagnosis of flexion myelopathy was made. Spinal immobilization by wiring and bone graft implantation ranging from C2 to C6 was performed to limit the range of anterior nuchal flexion. After this operation, improvement of muscle strength along with the disappearance of dysesthesia on neck flexion was observed. Clinically, this case closely resembles to juvenile type of distal and segmental muscular atrophy of upper extremities (Hirayama type). From our study, pathomechanism of this case seems to be a flexion myelopathy at C4 level. This view is supported also by the good recovery after the operation. This case suggests that nonprogressive atrophy of upper extremities due to flexion myelopathy can be successfully treated by cervical spine immobilization.