Although the clinical manifestations such as drowsiness, brisk reflexes, extensor plantar responses and hemisensory disturbance usually are considered to suggest Bickerstaff's brainstem encephalitis (BBE) rather than Miller Fisher syndrome (MFS), the nosological relationship between BBE and MFS has yet to be established. Herein, we report upon a 58-year-old man who showed ophthalmoplegia, ataxia and consciousness disturbance. In the absence of any abnormality on brain MRI, electrophysiological studies and SPM analysis using (18)F-FDG PET showed evidence of brainstem and cerebellum involvements.