[Cerebellar and brainstem hypoperfusion in Bickerstaff's brainstem encephalitis: a case report].

A 16-year-old healthy male experienced gastrointestinal symptoms and 9 days later developed fever, headache, numbness of the left hand, and disturbance of consciousness with rapid deterioration to a comatose state. These clinical symptoms resolved after treatment with steroid pulse, plasma exchange, and intravenous immunoglobulin. Along with the recovery, ophthalmoplegia and ataxia were observed. These symptoms and the detection of a high titer of serum anti-GQ1b immunoglobulin G autoantibodies led to the diagnosis of Bickerstaff's brainstem encephalitis (BBE). Brain 123I-IMP SPECT indicated hypoperfusion of the brainstem and bilateral cerebellar cortex during the acute phase, which increased during the recovery phase. This finding is indicative of reversible dysfunction in the cerebellar cortex and brainstem in the acute phase of BBE.