Cognitive and motor outcomes in children with unilateral Sturge–Weber syndrome: Effect of age at seizure onset and side of brain involvement

Purpose: Most children with Sturge–Weber syndrome (SWS) develop seizures that may contribute to neurocognitive status. In this study, we tested the hypothesis that very early seizure onset has a particularly detrimental effect on the cognitive and/or motor outcomes of children with unilateral SWS. We also tested whether side of SWS brain involvement modulates the effect of seizure variables on the pattern of cognitive abnormalities. Methods: Thirty-four children (22 girls; mean age 6.1 years) with unilateral SWS and history of epilepsy in a longitudinal cohort underwent neurological and cognitive evaluations. Global intelligent quotient (GIQ), verbal intelligent quotient (VIQ), nonverbal intelligent quotient (IQ), and motor function were correlated with epilepsy variables, side and extent of brain involvement on magnetic resonance imaging (MRI). Results: Mean age at seizure onset was 1.3 years (0.1–6 years) and mean IQ at follow-up was 86 (45–118). Age at seizure onset showed a logarithmic association with IQ, with maximum impact of seizures starting before age 1 year, both in uni- and multivariate regression analyses. In the left SWS group (N = 20), age at seizure onset was a strong predictor of nonverbal IQ (p = 0.001); while early seizure onset in the right-hemispheric group had a more global effect on cognitive functions (p = 0.02). High seizure frequency and long epilepsy duration also contributed to poor outcome IQ independently in multivariate correlations. Children with motor involvement started to have seizures at/before 7 months of age, while frontal lobe involvement was the strongest predictor of motor deficit in a multivariate analysis (p = 0.017). Conclusion: These findings suggest that seizure onset prior to age 1 year has a profound effect on severity of cognitive and motor dysfunction in children with SWS; however, the effect of seizures on the type of cognitive deficit is influenced by laterality of brain involvement.