Posterior fossa aneurysms

Abstract

Pertinent clinical data are presented from a series of 27 cases of aneurysm of the posterior fossa. The spectrum of clinical manifestations was generally similar to that presented by supratentorial aneurysms. The majority ruptured, 4 attained a large size to simulate posterior fossa tumor, and 1 patient was asymptomatic. Pneumo-encephalography demonstrated the mass of the aneurysm in 3 cases. Seventeen cases of ruptured aneurysm were identified by arteriography; 7 were operated and 9 were managed conservatively. Headache of a "vascular type, " xanthochromic spinal fluid, an episodic course, and a history of a previous "stroke" may help differentiate the large aneurysms from a tumor. Pneumoencephalography may demonstrate large aneurysms, but only vertebral arteriography can give a definitive diagnosis. In less than 1/3 of patients with ruptured infratentorlal aneurysms will the signs and symptoms suggest the site of the lesion. The most helpful signs include bilateral ocular paralysis, lower cranial involvement, crossed hemiparesis, and ataxia. Most cases will be identified only by the routine use of vertebral arteriography in the diagnostic study of subarachnoid hemorrhage. The mortality and morbidity are comparable to that resulting from ruptured supratentorial aneurysms. Surgery is feasible in a considerable number of cases, particularly if the aneurysm is located on the vertebral or posterior inferior cerebellar artery. The results of surgery in these lesions cannot be fully evaluated at this time.