Efficacy and safety of flow diverters for middle cerebral artery bifurcation aneurysms: a retrospective dual-center study

Purpose To evaluate the efficacy and safety of flow diverters (FDs) for the treatment of middle cerebral artery (MCA) bifurcation aneurysms. Methods This retrospective, dual-center study enrolled 29 patients with unruptured MCA bifurcation aneurysms treated with flow diverters (FDs) between January 2021 and December 2024. Clinical outcomes were assessed using the modified Rankin Scale (mRS), where scores of 0–2 indicated a favorable functional outcome. Aneurysm occlusion was evaluated at the 6-month follow-up using the O’Kelly-Marotta (OKM) grading scale on digital subtraction angiography (DSA). Procedure-related complications, including in-stent stenosis (ISS), were systematically recorded. Results All 29 aneurysms were successfully treated with FD, with no technical failures, in-stent thrombosis, cerebral hemorrhage, or ischemic events observed during the perioperative period. No patients developed new neurological deficits before discharge. All patients were followed up via telephone and outpatient visits after discharge. Six-month angiographic follow-up was performed in all 29 patients by DSA. The follow-up duration ranged from 6 to 43.2 months. At the final follow-up, one patient developed vertigo and a transient episode of left limb weakness more than 2 months after treatment. The mRS score was 0 in 28 patients and 1 in one patient. The 6-month angiographic outcomes were: OKM Grade A in 1 patient (3.4%), Grade B in 5 (17.3%), Grade C in 7 (24.1%), and Grade D in 16 (55.2%). ISS was observed in 3 patients (10.3%): one moderate proximal, one moderate mid-stent, and one diffuse severe stenosis. The overall procedure-related complication rate was 3.4% (1/29), with a mortality rate of 0%. The probability of achieving complete occlusion was >88.8% for necks ≤ 3.0 mm, compared to >53.3% for necks between 3.0–5.0 mm. Conclusion Our findings suggest that the use of FDs is an effective and safe therapeutic option for MCA bifurcation aneurysms. A neck diameter ≤ 5.0 mm was associated with a higher likelihood of complete occlusion; this association requires external validation.