Arteriovenous malformations of the cerebellar vermis.

Fifteen cerebellar vermian arteriovenous malformations were surgically treated over a 7-year period. Intracranial hemorrhage was the presenting symptom in 73% of the cases and recurrent bleeding episodes occurred in 60%. Computed tomographic scans demonstrated the site of the malformation in 80% and documented the presence of intracerebral bleeding in all posthemorrhage patients. Angiography revealed two consistent patterns of arterial supply depending on the involvement by the malformation of the superior inferior cerebellar vermis. All lesions were surgically removed via a midline suboccipital posterior fossa microsurgical approach. Intraventricular extension of arteriovenous malformation was common, often in association with the choroid plexus of the 4th ventricle. Immediate postoperative angiography was used to document arteriovenous malformation removal. Three instances of unsuspected residual malformation were documented and required reexploration. The total operative mortality was 7%, and the neurological morbidity was 21%.