Direct STA-MCA Bypass in Moyamoya Disease: Predicting Post-Operative Symptomatic Contralateral Stroke Using Clinical Characteristics and Angiographic Collateralization Patterns

Background: Moyamoya disease (MMD) is a rare cerebrovascular disorder marked by internal carotid artery narrowing, collateral neovascularization, and symptomatic cerebral ischemia. Select patients can benefit from direct bypass (STA-MCA bypass) by restoring blood flow to hypoperfused territories. Symptomatic contralateral stroke (CS) following STA-MCA bypass is a devastating, poorly understood complication. We investigate clinical and radiographic risk factors influencing CS incidence after bypass surgery.

Methods: A retrospective review of bilateral MMD patients undergoing STA-MCA bypass at our institution (2018-2022) included demographic details, comorbidities, average pre-operative systolic blood pressure (SBP), post-operative SBP goals, and angiographic patterns. Pre-operative diagnostic angiograms were analyzed for collateral vascular patterns. Post-operative clinical course was recorded. Statistical analyses employed parametric and non-parametric tests for small sample size.

Results: Six of 39 patients (15.4%) experienced CS post-bypass. No baseline demographic differences were identified between patients with and without CS. CS patients had higher pre-operative SBP (146.2 vs. 131.1, p<0.05), were more likely to have post-operative SBP goals below their average pre-operative SBP (66.7% vs 15.2%, p=0.018) and had longer time from symptom onset to surgery (51.8 vs 13 months, p=0.039). There were no differences in specific angiographic patterns in either hemisphere for CS patients versus those without CS though overall contralateral Suzuki grade was higher in CS patients (p<0.05).

Conclusions: CS patients following bypass had significantly higher pre-operative SBP, post-operative SBP goals below their average pre-operative SBP, and longer time from symptom onset to surgery compared to patients without CS. Patient-specific post-operative SBP management and timely surgical revascularization are crucial for preventing CS in MMD patients undergoing STA-MCA bypass.