Focal white matter abnormalities related to neurocognitive dysfunction: an objective diffusion tensor imaging study of children with Sturge-Weber syndrome.

White matter (WM) loss is associated with cognitive impairment in Sturge-Weber syndrome (SWS). In this study, we evaluated if cognitive and fine motor abnormalities are associated with impaired microstructural integrity in specific WM regions in SWS. Fifteen children with unilateral SWS (age: 3-12.4 y) and 11 controls (age: 6-12.8 y) underwent diffusion tensor imaging. Tract-based spatial statistics was used for objective comparisons of WM fractional anisotropy (FA) and mean diffusivity (MD) between the two groups. In the SWS group, WM FA and MD values were correlated with intelligence quotient (IQ) and fine motor scores, with age as a co-variate. Bilateral, multilobar WM areas showed decreased FA, whereas significant MD increases were confined to small ipsilateral posterior regions in SWS children. IQ in the SWS group (range: 47-128) was positively correlated with FA in the ipsilateral prefrontal WM and inversely associated with MD in the ipsilateral posterior parietal WM. A negative correlation between fine motor function and MD was found in ipsilateral frontal WM encompassing motor pathways. Microstructural WM abnormalities occur not only ipsilateral but also contralateral to the angioma in unilateral SWS. Nevertheless, cognitive and fine motor functions are related to diffusion abnormalities in specific ipsilateral, mostly frontal, WM regions.