Brain damage and IQ in unilateral Sturge-Weber syndrome: support for a "fresh start" hypothesis

Abstract

We tested the hypothesis that extent of severe hypometabolism measured by fluorodeoxyglucose PET has a U-shaped (nonlinear) relationship to IQ in children with unilateral Sturge-Weber syndrome. Thirty-five consecutive children (age range: 30-153 months) with Sturge-Weber syndrome and unilateral brain involvement were enrolled in the study. Participants underwent cognitive assessment and interictal fluorodeoxyglucose PET scans. Regression analyses tested whether a quadratic model best accounted for the relationship between extent of severe cortical hypometabolism and IQ, controlling for seizure variables. A significant quadratic relationship was found between IQ and extent of severe (but not total) hypometabolism. Seizure variables also contributed significant variance to cognitive functions. Results suggest that intermediate size of severe hemispheric hypometabolism is associated with the worst cognitive outcomes, and small or absent lesions, with the best cognitive outcomes. Children in whom a very large extent of the hemisphere is severely affected are likely to have relatively preserved cognitive function.

Figure 1

Scatter plots of extent of severe hypometabolism on FDG PET and VIQ and PIQ. The plots show the curvilinear (quadratic) relationships between extent of severe hypometabolism and verbal and nonverbal cognitive outcome. Both the linear and quadratic effects are significant for both VIQ and PIQ.

Figure 2

FDG PET images showing (a) 12 year old male with 77% extent of severe hypometabolism in the affected hemisphere, VIQ=83; and (b) a 12 year old female with 46% extent of severe hypometabolism, VIQ=59.

Figure 3

Scatter plots of extent of overall hypometabolism on FDG PET and VIQ and PIQ. The plots show the linear relationships between extent of overall (mild and severe) hypometabolism and verbal and nonverbal cognitive outcome. Only the linear effects are significant in each plot.