Arteriovenous malformations of the posterior fossa: clinical presentation, diagnostic evaluation and surgical treatment.

Infratentorial arteriovenous malformations represent only some 5-7% of malformations in major series. Since 1977 thirty-two patients with intracranial, intradural malformations of the brain stem or cerebellum have been evaluated by the Division of Neurological Surgery of The University of Texas Health Science Center at Dallas. Thirty of these patients have undergone surgical treatment. Twenty-three patients presented with intracranial hemorrhage which was recurrent in eleven cases. Nine patients were evaluated due to progressive brain stem or cerebellar deficits. A history of progressive deficits was unusual in the group that presented with hemorrhage and a prior or subsequent hemorrhage was rare in the patients initially evaluated due to progressive deficits. Seventeen of these malformations were located in the vermis, seven within the cerebellar hemisphere, two in the tonsil, two in the cerebellar-pontine angle, and four within the brain stem. Operative intervention was directed at primary resection in fifteen cases, staged resection in seven cases, embolization and resection in five cases, and evacuation of hematoma in three patients. Operative mortality in this surgical series was 7% with significant morbidity in 13%. Application of modern microsurgical techniques to the removal of arteriovenous malformations of the posterior fossa may result in improvement over the natural history of the disease process, especially in those patients who present with hemorrhage.