Abstract 65: Assessment Of MR Blood-Oxygen-Level-Dependent Cerebrovascular Reactivity Under General Anaesthesia In Children With Moyamoya

Abstract

Background: Moyamoya is a progressive arteriopathy condition characterized by steno-occlusion of the arteries of the circle of Willis. MRI performed with hypercapnic challenge can image blood-oxygen-level-dependent cerebrovascular reactivity (BOLD-CVR) thereby assessing cerebrovascular reserve. MRI studies of children <7 years of age, or with significant behavioural challenges require anesthesia. The purpose of this study was to validate the use of ventilator-induced hypercapnic challenge under general anaesthesia (GA). Methods: Children with moyamoya underwent two BOLD-CVR imaging in the same session under GA (GA-CVR). Differences in CVR estimates and intraclass correlation coefficient (ICC) between repeated scans were examined to determine repeatability across grey and white matter tissue and vascular territories. Bland-Altman plots were used to visulaize the overall variation between the scans. The associations with age, moyamoya types, and stroke presentation were also examined. Qualitative scoring by visual inspection was also conducted by trained neurologists. Results: Thirty-two paired GA-CVR studies (sixty-four scans in total) were analyzed (mean age: 7.07 (2.74 -17.95) years, 13 females). Forty-one percent (41%) were under 7 and 77%, under 10. No significant differences between repeated scans were found for any of the CVR estimates, when summarized by tissue and vascular territory. Of the paired studies, repeatability (ICC) for the whole-brain CVR estimates was excellent (≥0.74) in 14 (43.8%), good (≤0.59, >0.74) in 7 (21.9%), fair (≤0.41, >0.59) in 6 (18.8%) and poor (<0.41) in 5 (15.6%). Bland-Altman plots illustrated the overall variation of whole-brain CVR within 95% confidence interval level. Repeatability indices were not affected by children’s age and other clinical factors. On qualitative scoring, the Cohen weighted kappa showed substantial agreement in both right (0.75) and left (0.81) hemispheres. Conclusion: Our study support the clinical use of GA-CVR across all ages and disease conditions. The GA-CVR provides a feasible, repeatable, and reliably interpretable tool for the assessment of cerebrovascular reserve of very young and behaviourally challenged children with moyamoya.