B53-08 Emergent Bypass After Failed Flow Diversion for Giant MCA (Middle Cerebral Artery) Aneurysm in a Young Adult

Abstract Introduction Giant intracranial aneurysms (25 mm) represent 5% of cerebral aneurysms and are associated with high rupture risk and surgical complexity, especially when involving critical vessels like the Middle Cerebral Artery (MCA). Most arise at the MCA bifurcation, often in older women. Presentation in younger patients is rare, and management requires a nuanced, multidisciplinary approach. While flow diversion offers a less invasive option, complications may necessitate urgent surgical intervention. Description A 24 year old male with facial trauma history and retained maxillary hardware presented with progressive left facial swelling. CT imaging revealed facial abscess and an incidental 2.6 cm aneurysm of the left MCA M1 segment. Further imaging confirmed a complex aneurysm involving MCA, internal carotid artery (ICA), and Anterior Cerebral Artery (ACA) branches. He underwent endovascular placement of a flow-diverting stent, which was complicated by M2 thrombosis and device migration into the aneurysm sac. Emergent left craniotomy, Superficial Temporal Artery (STA) - MCA bypass, and aneurysm clipping were performed. Postoperatively, he developed right hemiplegia. MRI showed acute infarcts in the left basal ganglia and periventricular white matter. Repeat DSA confirmed bypass patency and partial aneurysm filling via contralateral flow. Over 22 days, the patient improved steadily. By two months he had mild expressive aphasia and right-sided weakness. At 8 months, MRA showed stable aneurysm with near complete neurological recovery. Discussion This case highlights the challenges of managing giant MCA aneurysms, particularly in anatomically complex or surgically unfavorable cases. Though endovascular therapy is often preferred, complications like thrombosis and device migration may require urgent surgical rescue. Microsurgical bypass remains a vital tool for maintaining cerebral perfusion in such scenarios. Careful preprocedural planning, imaging, and multidisciplinary coordination are essential for optimal outcomes. This abstract is funded by: none