Bilateral cerebellar infarctions caused by a stenosis of a congenitally unpaired posterior inferior cerebellar artery

Bilateral symmetrical cerebellar infarcts in the territory supplied by the medial posterior inferior cerebellar artery (PICA) branches are extremely r are. In the few cases published, it has not been possible to clearly pinpoi nt the cause of this infarct pattern. The authors present the case history of a 58-year-old man who had acute headaches accompanied by pronounced rota tory vertigo with nausea and vomiting. The neurological examination reveale d bilateral cerebellar signs. Cranial magnetic resonance imaging showed bil ateral, nearly symmetrical infarcts in the territory of the medial branches of both PICAs. These bilateral PICA infarctions were caused by a stenosis of an unpaired PICA originating from the left vertebral artery supplying bo th cerebellar hemispheres.