Abstracts

Rationale: Malformations of cortical development (MCD) are common in pediatric epilepsy surgery patients but have not been well studied clinically. This study examined the concordance of histopathology subtypes and clinical markers such as IQ, seizure outcome (Engel at one year post surgery), and post-operative quality of life using an established MCD classification system (Palmini et al., 2004). Methods: A surgical series of 30 patients (mean age = 9.8, SD = 4.7; median age of onset = 3.5 years) was reviewed, including 24 children with MCD and/or focal cortical dysplasia (FCD). The sample included 14 children with histopathologically confirmed FCD IA or IB, 7 children with FCD IIA or IIB, 3 children with heterotopia only, and 6 children with dysembryoplastic neuroepithelial tumours (DNT). IQ was measured with Wechsler scales; for children who were too low-functioning to take part in formal testing, IQ was estimated based on developmental or adaptive measures (N = 5). Post-operative quality of life was measured with the global scale from the Impact of Child Neurological Disability scale. Results: Histopathology subtype did not fully predict clinical outcome: over half of children with FCDs involving severe architectural and cytological abnormalities (FCD IIA and IIB) were cognitively normal (57%), while the mildest MCD category (heterotopia only) had some of the most cognitively delayed children (2/3 with moderate to severe delay). Most children in the FCD I category did not have cognitive disabilities (69%) and most had Class I seizure outcome (69%). The DNT group had excellent seizure and cognitive outcomes (5/6 Class I; all normal IQ). Across subtypes, IQ was a significant predictor of Class I outcome (r = -.41, p = .04). Children with IQs above the cutoff for cognitive disability were 6 times more likely to attain a Class I outcome (Odds ratio = 6.5, CI = 1.1 - 39.6) than children with cognitive disabilities, and good quality of life occurred frequently in this group (77%). High quality of life was less frequent in children with cognitive disabilities, but was not negligible (40%). Younger age at onset and normal MRI were both significant predictors of worse seizure outcome (r = -.54, r = -.44, p < .02). Conclusions: Our results indicate that a majority of children with surgically treated FCDs are cognitively normal, while some children with milder forms of cortical malformation (heterotopia only) may present with severe cognitive delays. Normal IQ appears to be a marker of Class I outcome, but children with low cognitive levels may still enjoy good quality of life after epilepsy surgery.