Atypical brainstem encephalitis: magnetic resonance imaging and oculographic features.

A 50-year-old woman had primary position upbeating nystagmus, abnormalities of the lower cranial nerves, mild cerebellar signs, and CSF lymphocytosis. CT and MRI showed enlargement of the pons. Eye movement recordings revealed impaired pursuit and optokinetic nystagmus, and visual-vestibular interactions were absent. The patient improved spontaneously.