White matter volume as a major predictor of cognitive function in Sturge-Weber Syndrome

Objective: To assess the role of gray and white matter volume loss vs seizures in cognitive impairment of children with Sturge-Weber syndrome with unilateral involvement. Design: Patients were enrolled in this prospective cohort during a period of 3 years. Setting: Pediatric neurology clinic with national referral through the Sturge-Weber Foundation. Participants: Twenty-one children (age range, 1 year 6 months to 10 years 4 months) with unilateral Sturge-Weber syndrome. Main Outcome Measures: Cortical gray matter and hemispheric white matter volumes were measured on segmented volumetric magnetic resonance imaging and correlated with the age of the participants. Global intellectual function (IQ) was correlated with magnetic resonance imaging and seizure variables in both univariate and multivariate analyses. Results: Both gray and white matter volumes showed an age-related linear increase. Tissue volumes on the side of the angioma showed a positive correlation with IQ after controlling for age in univariate regression analyses (white matter, r=0.71, P<.001; gray matter, r=0.48, P=.03), while seizure variables did not correlate with IQ (P>.1). A multivariate regression showed that hemispheric white matter volume ipsilateral to the angioma was an independent predictor of IQ (R= 61, P=.006), which also showed a negative correlation with age (R=-0.52, P=.022) but no correlation with gray matter volumes. Conclusions: Early hemispheric white matter loss may play a major role in cognitive impairment in children with Sturge-Weber syndrome. Future therapeutic approaches should aim at preserving white matter integrity in addition to seizure control to improve cognitive outcome.