Abstracts

Rationale: Sturge-Weber syndrome (SWS) is a clinical model of early, chronic brain ischemia of venous origin, often associated with epilepsy. In this study, we used high-resolution perfusion weighted MRI (HR-PWI) to test if there is a quantitative relationship between cerebral perfusion deficits and clinical seizure variables in children with SWS. Methods: Fifteen children with unilateral SWS (9 girls; age: 10 months - 10 years) prospectively underwent MR scanning including HR-PWI with a small voxel size of 1 1 4 mm³. Perfusion parameter maps of relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF) and mean transit time (MTT) were generated. rCBF, rCBV and MTT values in the subcortical white matter ipsilateral to the angioma, in regions affected by abnormal veins (pial angioma and deep veins), and in contralateral homotopic regions (avoiding the cortical surface, large vessels and ventricles) were measured. Asymmetry indices (AIs) for all three perfusion parameters were also calculated. All perfusion parameters ipsilateral to the angioma as well as perfusion AIs were correlated with seizure variables (age at epilepsy onset, duration of epilepsy, seizure frequency scores) using uni- and multivariate analyses. Results: Mean age at seizure onset was 1.4 years, mean duration of epilepsy was 3.0 years (range: 0-9.7 years), and seizure frequency varied from less than once a year to daily seizures (frequency scores ranging from 1-5, with a median of monthly seizures). CBF asymmetries varied between 39% and -82%, while CBV asymmetries varied between 69% and -67%; increased rCBF values (all >20% increases in the affected hemisphere; mean AI: 31% 5%) were seen in 5 children, while 9 children showed decreased perfusion (mean AI: -36% 24%) on the side of the angioma (one child had symmetric perfusion). Longer duration of epilepsy was related to lower rCBF and rCBV (but not MTT) values in the affected hemisphere (for rCBF AIs: r=-0.57, p=0.025; for rCBV AIs: r=-0.52, p=0.048; for ipsilateral rCBV values: r=-0.65, p=0.009). Both rCBF and rCBV asymmetries also showed an inverse correlation with seizure frequency scores in univariate analyses (p?0.01), and these correlations remained significant after epilepsy duration was controlled for (rCBF AI: r=-0.74, p=0.002; rCBV AI: r=-0.66, p=0.01). Age at epilepsy onset did not correlate with any perfusion variables. Conclusions: Both increased and decreased perfusion can occur in the affected hemisphere in children with unilateral SWS. Increased perfusion can be present during the early course of the disease, while long duration of epilepsy is often associated with severe hypoperfusion. The results also indicate a strong relationship between seizure frequency and decreased brain perfusion in SWS, regardless of epilepsy duration. Chronic hypoperfusion and tissue hypoxia may play a role in seizure generation in SWS; frequent seizures may further aggravate brain ischemia and contribute to disease progression.