[An Extracranial Aneurysm in the Distal Posterior Inferior Cerebellar Artery Located at the Tonsillomedullary Segment:Case Report and Review of the Literature].

We report a rare case of subarachnoid hemorrhage(SAH)due to ruptured extracranial aneurysm originating at the caudal loop of the left posterior inferior cerebellar artery(PICA). A 50-year-old woman presented with severe headache and mild consciousness disturbance. Computed tomography(CT)revealed SAH and intraventricular hemorrhage.