Multiple Saccular Aneurysms of the Posterior Cerebral Artery With Mass Effect: A Case Report

Intracranial aneurysms are arterial dilatations most commonly located in the circle of Willis, characterized by a focal outpouching of the arterial wall. Posterior cerebral artery (PCA) aneurysms are very uncommon and, in very rare cases, may present as multiple lesions. They are particularly associated with mass effect due to their proximity to critical midbrain and thalamic structures. Despite their low frequency, they are clinically relevant due to their higher risk of rupture and potential for significant mass effect. We report the case of a 51-year-old postmenopausal female who presented with a 72-hour history of right upper limb monoparesis, progressing to right hemihypoesthesia, hemiparesthesia, ipsilateral facial involvement, gait disturbance, and transient conduction aphasia. Magnetic resonance angiography revealed two saccular aneurysms in the left PCA: one partially thrombosed aneurysm in the P2 segment measuring 14.8 × 10 mm (neck 6.4 mm) and another measuring 10.5 × 9.9 mm (neck 4.2 mm), both associated with significant mass effect and vasogenic edema involving the mesencephalon, cerebral peduncle, and ipsilateral ambient cistern. Due to the patient's autonomous decision and socioeconomic factors, conservative outpatient management was chosen following individualized assessment. Although microsurgical and endovascular options are generally preferred for PCA aneurysms considering their morphology, location, and institutional expertise, the final therapeutic decision was made through shared decision-making with the patient. The clinical presentation was consistent with a progressive and transient posterior circulation syndrome, secondary to a transient ischemic attack and vascular mass effect. Aneurysms in the posterior circulation can rarely affect language functions, as observed in this case with conduction aphasia. This case highlights the importance of early recognition of atypical presentations through appropriate clinical assessment and advanced imaging, allowing accurate diagnosis and timely therapeutic decision-making.