Postoperative perfusion volume on territorial arterial spin labeling provides an exploratory risk signal for cerebrovascular autoregulation failure after moyamoya revascularization: a prospective physiological study.

Background: Cerebral hyperperfusion syndrome (CHS) after revascularization for moyamoya disease (MMD) represents a failure of cerebrovascular autoregulation-a system-level vascular physiological process. Non-invasive tools to quantify autoregulatory reserve and support early risk stratification remain limited. This study aimed to evaluate whether postoperative perfusion volume measured by territorial arterial spin labeling (tASL) provides an exploratory risk signal for cerebrovascular autoregulation failure after MMD revascularization and to identify candidate physiological factors associated with this complication. Methods: This prospective cohort study enrolled 116 adult MMD patients who underwent combined revascularization (suprasylvian approach, n=60; infrasylvian approach, n=56). All patients underwent 3D pseudo-continuous arterial spin labeling (3D-pCASL) preoperatively and postoperatively, and tASL on postoperative day 1. Postoperative perfusion volume and regional cerebral blood flow (CBF) were quantified. Firth's penalized multivariable logistic regression was used to evaluate candidate factors associated with autoregulation failure (CHS) while avoiding statistical overfitting due to rare events (13 CHS cases). Receiver operating characteristic analysis determined exploratory threshold values. CHS was diagnosed contemporaneously during hospitalization by integrating new neurological symptoms, blood-pressure/hemodynamic context, and ASL evidence of focal postoperative hyperperfusion. Results: In the Firth penalized multivariable model, hypertension and Stage IV angiographic disease were associated with postoperative CHS, while Stage V showed a positive but statistically imprecise estimate. Age and tASL-derived postoperative perfusion volume showed exploratory ROC signals, with cutoffs of 61 years and 104.45 cm³, respectively. The suprasylvian approach showed a numerically higher early CHS rate than the infrasylvian approach (16.7% vs. 5.4%; Fisher exact P = 0.077), while showing higher regional CBF at postoperative day 30 and lower postoperative mRS scores at POD30. The low overall CHS incidence (13/116, 11.2%) should be interpreted in the context of standardized inpatient monitoring and active postoperative blood-pressure management. Conclusion: Quantitative tASL perfusion volume provides a non-invasive, exploratory physiological marker of postoperative cerebrovascular autoregulatory stress after MMD revascularization. In this cohort, the suprasylvian approach was associated with greater POD30 CBF improvement and lower POD30 mRS scores, but also a numerically higher early CHS rate; these findings should be interpreted as early postoperative associations rather than evidence of long-term surgical superiority. The 104.45 cm³ tASL threshold requires internal and external validation before it can be used as a stand-alone clinical decision rule.