Abstract 64: Diffusion Tensor Imaging Suggests Decreased Axonal Myelination in Children with Moyamoya Without Stroke

Introduction: Moyamoya is a progressive cerebrovascular disease leading to arterial stenosis of the circle of Willis. Using diffusion tensor imaging (DTI), adults with moyamoya have significantly decreased white matter fractional anisotropy (FA) compared to controls even when conventional imaging is normal. This raises concern for under recognized white matter injury. Children with moyamoya have been shown to have significantly increased whole brain apparent diffusion coefficient (ADC) values. However, to our knowledge the involvement of specific white matter tracts in children with moyamoya, relevant to specific cognitive domains, has not been evaluated. Methods: We present a cohort of 16 children with moyamoya with 25 affected hemispheres without stroke compared to 25 children controls. We analyzed DTI data using unscented Kalman filter (UKF) tractography and extracted major white matter pathways with a fiber clustering method. We compared the FA, ADC, AD, and RD globally as well as within each white matter tract using ANOVA. Results: Age and sex were not significantly different between children with moyamoya and controls. For all white matter tracts, children with moyamoya had significantly lower FA (-7.0%, p=0.04) as well as higher ADC (5.7%, p=0.002) and RD (9.5%, p=0.002). AD was also higher but not significant (2.3%, p=0.21). Specific white matter tracts that were significantly affected included: inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, superior longitudinal fasciculus and thalamo-frontal tract (Table 1). Discussion: Lower FA with higher ADC and RD is consistent with decreased axonal myelination. Tracts in watershed regions were especially affected in children with moyamoya. These findings are also consistent with concerns that children with moyamoya are chronically hypoperfused. In conclusion, future research is needed to determine whether these findings are reversible.