[A case report of Bickerstaff brainstem encephalitis with attention to electronystagmographic findings]

We evaluated brainstem function by using electronystagmography in a 43-year-old woman with typical Bickerstaff brainstem encephalitis. She developed fever, drowsiness, total opthalmoplegia, swallowing disturbance, areflexia, and muscle weakness. On electronystagmography, eye-tracking test showed ataxic pattern with impaired smooth pursuit eye movement. The horizontal optokinetic nystagmus test showed diminished pattern. Caloric test revealed the vestibular hypofunction and the increase of caloric nystagmus on eye fixation. We considered these findings were attributed to the disturbance of pontine tegmentum, especially reticular formation. These findings were similar to those observed in patients with Fisher syndrome.