564 CT Perfusion–Based Risk Prediction of Cerebral Hyperperfusion Syndrome After Direct Bypass in Moyamoya Disease: A Meta-Regression Study

INTRODUCTION: Moyamoya disease (MMD) is a rare, progressive steno-occlusive cerebrovascular disorder that often necessitates direct bypass surgery but carries the risk of postoperative cerebral hyperperfusion syndrome (CHS), a potentially devastating complication. While computed tomography perfusion (CTP) parameters are emerging as potential predictors of CHS, their utility remains underexplored. This study contributes a novel, multivariate meta-regression assessing the prognostic value of preoperative and postoperative CTP parameters, as well as differential changes, in predicting CHS among adult patients with MMD undergoing direct STA-MCA bypass. METHODS: A PRISMA-compliant systematic review was conducted in MEDLINE and Embase databases through December 2024. Studies included reported CTP parameters relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), relative mean transit time (rMTT), and relative time-to-peak (rTTP), as well as postoperative CHS incidence. Among 138 citations screened, 34 underwent full-text review, and 9 studies representing 746 patients met criteria and were included. To standardize data from studies lacking relative CTP or contralateral values (n = 4), raw perfusion parameters were converted to relative values (rCTP) using standardized contralateral values derived from a previous study in adult MMD patients undergoing combined bypass (Zhang et al.). Primary analyses were conducted with a multivariate meta-regression random effect model; sensitivity analyses excluded studies with calculated relative values, hemorrhagic MMD only, or mixed direct and indirect bypass cases. RESULTS: Preoperatively, elevated rCBF (β = 0.0982, p = 0.0411) and reduced rCBV (β = -0.0687, p = 0.0105) were significantly associated with increased CHS incidence, while rMTT and rTTP were not. Postoperative CTP parameters showed no significant association with subsequent CHS development in isolation; however, lack of ample improvement or, possibly, reductions in ΔrCBF were significantly associated with CHS (β = -0.0479, p = 0.0234). Sensitivity analyses confirmed the robustness of preoperative rCBV and ΔrCBF, except when those studies reporting calculated rCTP values were excluded; preoperative rCBF did not maintain significance under any sensitivity analysis. CONCLUSIONS: CTP parameters including elevated preoperative rCBF, reduced preoperative rCBV, and lack of ample increase in ΔrCBF are potential predictors of CHS in adult patients undergoing direct STA-MCA bypass for MMD. These findings support the integration of CTP data into perioperative risk assessment and monitoring protocols. Further study is required to generate more robust and individualized predictive models.