Ruptured Posterior Inferior Cerebellar Artery Aneurysm Presenting With Cerebellar Intraparenchymal and Intraventricular Hemorrhage: A Case Report.

Aneurysmal subarachnoid hemorrhage (aSAH) may present with intraparenchymal and intraventricular extension, particularly in posterior circulation aneurysms, which warrants careful evaluation for secondary causes, including an underlying macrovascular lesion. We report the case of a 39-year-old woman who presented with a sudden-onset severe headache, nuchal pain, and transient loss of consciousness. Initial non-contrast cranial computed tomography demonstrated a dominant left cerebellar intraparenchymal hemorrhage with subarachnoid and intraventricular extension, accompanied by acute hydrocephalus. Given the patient's age, clinical presentation, and hemorrhage pattern, computed tomography angiography was performed and revealed a ruptured wide-neck saccular aneurysm of the left posterior inferior cerebellar artery (PICA) with multiple daughter sacs. The patient underwent successful endovascular coil embolization, preserving parent vessel patency, and made a complete neurological recovery. This case highlights a recognized but high-risk presentation of aneurysmal subarachnoid hemorrhage with cerebellar parenchymal extension and reinforces the importance of early vascular imaging in younger patients and in posterior fossa hemorrhage patterns. Prompt diagnosis and timely aneurysm securing remain critical determinants of the outcome.