Posterior inferior cerebellar artery aneurysm in the fourth ventricle: acute surgical treatment.

A case of an aneurysm of the posterior inferior cerebellar artery lying in the fourth ventricle is reported. The patient was surgically treated within a few hours after the onset of the subarachnoid hemorrhage by a microsurgical technique using direct exclusion of the aneurysm by a clip. The patient recovered completely following the operation.