[Bickerstaff's brainstem encephalitis with one-and-a-half syndrome].

We presented a case of Bickerstaff's brainstem encephalitis. A 50-year-old woman developed semicoma, external ophthalmoplegia, hyporeflexia, extensor plantar responses. A high titer of anti-GQ1b IgG antibody was detected in her acute phase serum. Auditory brainstem response suggested the presence of brainstem lesion. Although MRI and CSF showed no abnormality, one-and-a-half syndrome was observed during the clinical course, suggesting involvement of the pontine tegmentum. She received steroid pulse-therapy and symptoms disappeared completely. Our case suggested that anti-GQ1b IgG antibody might relate to the pathogenesis of intramedullary as well as extramedullary lesions.