Combined Treatment of Large Fusiform A2 Aneurysm with End-to-Side Extended Superficial Temporal Artery–A3 Bypass Using Contralateral Superficial Temporal Artery Interposition Graft and Endovascular Aneurysm Trapping: A Case Report and Literature Revi

<b>Background:</b> A2 fusiform aneurysms present certain management difficulties with conventional microsurgical or endovascular approaches due to the circumferential morphology, deep location within the interhemispheric fissure, and narrow surgical corridor. <b>Methods:</b> We present a case of a large (>10 cm) fusiform aneurysm in the right A2 segment treated with a combined method consisting of an extended superficial temporal artery to A3 bypass using a contralateral superficial temporal artery interposition graft and subsequent endovascular trapping of the aneurysm. To treat the aneurysm, endovascular trapping following revascularization was planned. During surgery, as the left A3 segment was not available, a superficial temporal artery to A3 bypass was performed. The right frontal branch (donor) was extended with the left frontal branch as a free interposition graft (end-to-end anastomosis) and then anastomosed with the right A3 segment (end-to-side anastomosis). At 6 days after surgery, after confirming the good patency of the bypass graft, endovascular aneurysm trapping was performed. <b>Results:</b> At 8 days after surgery, the patient was discharged without any neurologic deficits. Follow-up digital subtraction angiography at 12 months after surgery showed the good patency of the bypass graft with complete occlusion of the aneurysm. <b>Conclusions:</b> Our case demonstrates the feasibility and effectiveness of a combined microsurgical-endovascular approach as a management strategy for deeply located A2 fusiform aneurysm. When in situ bypass is not possible, an extended superficial temporal artery donor may be considered.