Intra-individual comparison of long-term outcomes between combined and indirect bypass surgery in adult moyamoya disease

PURPOSE Bypass surgery is regarded as the standard treatment option for symptomatic and hemodynamically unstable moyamoya disease (MMD), but controversy exists regarding which type of bypass surgery is most effective. We aimed to analyze the long-term outcomes of combined and indirect bypasses for MMD patients through intra-individual comparisons. METHODS Of the 896 patients who underwent 1084 bypass surgeries between 2007 and 2021, 24 patients with MMD who underwent combined bypass on one side and indirect bypass on the other side were ultimately enrolled in this study. Clinical, angiographic and hemodynamic outcomes were retrospectively evaluated. RESULTS Three asymptomatic strokes (12.5%) occurred within 30 postoperative days in each group. Postoperative strokes after 30 days occurred in 3 patients (12.5%) with 3 hemorrhagic events and 1 cerebral infarction, only in indirect bypass, while no stroke occurred in hemispheres treated with combined bypass. The revascularization area relative to supratentorial area was significantly greater in combined bypass than in indirect bypass, both in short-term and long-term periods (64.9% versus 43.9% in short-term and 75.7% versus 54.9% in long-term; P  < 0.001, respectively). Hemodynamic outcomes showed significantly greater increases in acetazolamide-challenged cerebral blood flow (CBF _acz ) during short-term follow-up (P = .04) and in both basal CBF (CBF _bas ) and CBF _acz during long-term follow-up (P = .014 and P = .009, respectively) in combined bypass than in indirect bypass. CONCLUSION Combined bypass may be a more effective treatment option for MMD based on its higher revascularization area and favorable hemodynamic results compared to indirect bypass in the same patient.