364 Bypass Surgery for Moyamoya Vasculopathy: Predictors of BOLD MRI Revascularization Response

INTRODUCTION: Revascularization surgery in Moyamoya vasculopathy (MMV) has been shown to reduce stroke and symptom recurrence. Most studies examining revascularization outcomes are based on surrogates like clinical response or angiography. These surrogates are not direct measures of tissue level perfusion. Blood oxygenation-level dependent (BOLD) MRI imaging provides a tissue-level measure of cerebral hemodynamics. METHODS: We conducted a retrospective cohort study of patients who underwent revascularization surgery for MMV. All patients received pre-operative and 1-year BOLD MRI scans. The primary outcomes were changes in two cerebrovascular reactivity (CVR) measures, CVRDelay and CVRMax, calculated using our group’s methodology (Watchmaker et al, Neurosurgery 2019). The primary exposures were donor STA graft length and diameter. Diameter was evaluated distal to the STA bifurcation for single-vessel grafts, and proximal for combined grafts. Secondary exposures included age, post-operative hypertension, smoking status, and surgery type. Linear regression and Wilcoxon rank-sum tests were used. RESULTS: There were 45 patients with 68 total operated hemispheres. Magnitude of CVR change (ΔCVR) was highly dependent on pre-operative CVR; correspondingly, all analyses were adjusted by pre-operative CVR. STA length was associated with superior revascularization in terms of CVRMax (p=0.001) but not in terms of CVRDelay. STA diameter did not affect revascularization at a statistically significant level. Current smoking status (CVRDelay, p=3.6x10-4) and older age (CVRMax, p=5.7x10-4) were associated with poor revascularization. Neither having hypertension in the post-operative period nor surgery type were associated with revascularization outcomes. CONCLUSIONS: We conducted the first analysis of clinical factors influencing MMV revascularization that examines tissue-level cerebral hemodynamic outcomes. Longer STA donor grafts improved revascularization, but STA diameter did not. Surgery type did not influence revascularization. BOLD MRI represents a non-invasive measure of evaluating revascularization in MMV with tissue-level granularity.