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). However, there is ongoing debate about the most effective type of bypass surgery. 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 < .001, respectively). Hemodynamic outcomes showed significantly greater increases in acetazolamide-challenged cerebral blood flow (CBF) during short-term follow-up (P = .04) and in both basal CBF (CBF) and CBF 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.