Extracranial posterior inferior cerebellar artery aneurysm causing isolated intraventricular hemorrhage: a case report.

The authors report the unusual case of an aneurysm arising on an extracranial loop of the left posterior inferior cerebellar artery (PICA). The computed tomographic scan showed an isolated hemorrhage in the lateral ventricles, and the lesion was recognized 1.5 cm below the foramen magnum at the level of the atlas. The literature concerning peripheral PICA aneurysms is reviewed and the clinical and radiological features of these lesions are discussed. A tendency for subarachnoid bleeding from distal PICA aneurysm ruptures to spread into the ventricular system is suggested. The diagnosis of distal PICA aneurysm should also be considered in cases of isolated intraventricular hemorrhage without obvious parenchymal or subarachnoid hemorrhage. The need for four-vessel angiography when studying patients suffering from a subarachnoid hemorrhage is stressed.