"Top of the basilar" syndrome.

Infarction of rostral brainstem and cerebral hemispheral regions fed by the distal basilar artery causes a clinically recognizable syndrome characterized by visual, oculomotor, and behavioral abnormalities, often without significant motor dysfunction. Rostral brainstem infarction produces oculomotor and pupillary signs that are identical to those in thalamic hemorrhage. Somnolence, vivid hallucinations and dreamlike behavior may also accompany rostral brainstem infarction. Temporal and occipital infarctions are frequently accompanied by hemianopia with distinctive characteristics, fragments of the Balint syndrome, amnestic dysfunction, and agitated behavior. The "top of the basilar" syndrome is most often due to an embolus.