Rare Arterial Anomalies: Bilateral Posterior Inferior Cerebellar Artery Originating from the Posterior Meningeal Artery and Anterior Inferior Cerebellar Artery-posterior Inferior Cerebellar Artery Anastomosis.

Variations in the posterior inferior cerebellar artery are well-documented. However, bilateral posterior inferior cerebellar artery originating from the posterior meningeal artery is extremely rare, and no such cases have been previously reported. Anastomosis between the anterior inferior cerebellar artery and posterior inferior cerebellar artery is a rare arterial anomaly that may arise due to remnants of the primitive lateral basilovertebral anastomosis during embryonic development. A 61-year-old male presented with headache, vomiting, and left lower extremity ataxia. Brain magnetic resonance imaging revealed an acute infarction in the left medulla, and magnetic resonance angiography suggested a dissection of the left vertebral artery. Digital subtraction angiography revealed the posterior meningeal artery originating from the extracranial vertebral artery, supplying the bilateral posterior inferior cerebellar artery hemispheric branches. The original posterior inferior cerebellar artery from the distal vertebral artery supplied only the cerebellar vermis. Additionally, an anterior inferior cerebellar artery-posterior inferior cerebellar artery anastomosis was observed on the left side. This case highlights two rare arterial anomalies: bilateral posterior inferior cerebellar artery hemispheric branches originating from the posterior meningeal artery and an anterior inferior cerebellar artery-posterior inferior cerebellar artery anastomosis, offering insights into the embryologic development and unique vascular structures involved.