Ruptured Aneurysm in AICA-PICA Complex Managed with Endovascular Coiling

Introduction The Anterior Inferior Cerebellar Artery‐Posterior Inferior Cerebellar Artery (AICA‐PICA) complex refers to an arterial anomaly in which a single vessel supplies both the AICA and PICA territories. This variant has a prevalence of up to 20%. Despite its relatively high occurrence, aneurysms associated with the AICA‐PICA complex are rare. The rupture of aneurysms arising from such vascular anomalies can be challenging to detect on CT angiography (CTA). Digital subtraction angiography (DSA) can provide superior visualization and aid in both diagnosis and management. Purpose We present a case of a ruptured aneurysm located at the distal AICA‐PICA complex with hemorrhagic complications. The vascular anomaly was not well demonstrated on CTA but was further delineated by DSA and subsequently treated with embolization. Materials and Methods A 59‐year‐old woman with no significant medical history presented with the sudden onset of a severe headache, rated 9/10 in intensity. She also reported neck pain, neck stiffness, sweating, and nausea with vomiting. A non‐contrast head CT revealed subarachnoid hemorrhage within the peri‐mesencephalic, peri‐pontine, and pre‐medullary cisterns. Additionally, there was intraparenchymal hemorrhage in the left cerebellum, intraventricular hemorrhage extending into both lateral ventricles, and mild hydrocephalus of the left lateral ventricle. CTA identified an oval‐shaped aneurysm with a 3.5 mm long axis at the pontomedullary cerebellar junction, likely originating from the distal PICA. External ventricular drainage was placed, followed by emergent DSA. In contrast to the CTA findings, DSA revealed a bilateral AICA‐PICA variant with basilar artery fenestration proximal to its origin. A ruptured aneurysm was identified at the apex of the left AICA‐PICA complex, with a clot at the dome measuring 3.75 mm × 2.7 mm × 2.11 mm and a neck measuring 1.596 mm. Results Endovascular coiling was performed using two coils placed in a “dumbbell” configuration to secure the aneurysm. Post‐intervention, the patient gradually improved with intensive care monitoring and was discharged without residual deficits. Conclusion Infratentorial hemorrhages are less common than supratentorial bleeding. Infratentorial subarachnoid hemorrhages may result from venous sources, aneurysmal rupture, or trauma. In cases involving rare vascular variants, DSA provides superior diagnostic accuracy compared to CTA. Interventional management, such as embolization, can lead to favorable clinical outcomes.