[Bickerstaff's brainstem encephalitis associated with nystagmus].

A 29-year-old man developed drowsiness, ophthalmoplegia and cerebellar ataxia following upper respiratory tract infection. We diagnosed the patient as having a Bickerstaff's brainstem encephalitis. There was upbeating nystagmus which appeared with upward gaze, and bilateral horizontal gaze-evoked nystagmus in both directions. On electronystagmography, eye-tracking test showed saccadic pattern with impaired smooth pursuit eye movement. The horizontal optokinetic nystagmus test showed diminution of response. These results suggested that brainstem and cerebellum were widely involved. Presence of nystagmus may help to speculate the lesion of Bickerstaff's brainstem encephalitis.