[A case of syringomyelia with proximal dominant muscle weakness and without superficial sensory disturbance].

A 43-year-old woman had noticed muscular weakness in her arms for four years before her admission. Muscle weakness and atrophy were prominent in the bilateral deltoid muscles, but muscular strength was almost unimpaired in the bilateral forearms and intrinsic muscles. There was no sign of sensory impairment except vibratory sensation. EMG revealed neuropathic NMU. X-P of the cervical spine showed enlargement of the spinal canal diameter, and MRI of the spinal cord revealed a large syrinx. On the basis of metrizamide CT and cranial MRI, a diagnosis of syringomyelia with Chiari malformation (type I) was made. Despite the presence of a large syrinx extending from C 1 to Th 11, the only detectable neurological sign was proximal weakness of the upper extremities simulating myopathy.