Abstracts

Rationale: Focal cortical dysplasia (FCD) is now recognized as the major cause of focal intractable epilepsy in childhood. Several variables have been reported to be significant predictors of favorable postsurgical outcome in pediatric patients with FCD. The aim of our study was to analyze electro-clinical, imaging, neuropsychological, surgical and histopathological data in relation to seizure outcome in order to identify prognostic factors crucial for selection of pediatric patients with FCD for epilepsy surgery.Methods: We retrospectively evaluated a cohort of 149 patients with histologically confirmed mild malformations of cortical development (mMCD) or FCD. Subjects with other migrational disorders such as tuberous sclerosis complex, polymicrogyria and nodular heterotopia were excluded. All subjects were followed for at least two years after the surgery; 113 subjects had at least five years of postoperative follow-up. The contribution of 28 clinical, EEG, MRI, neuropsychological, surgical and histopathological parameters to seizure outcome was evaluated.Results: At two years after surgery, proportions of patients in individual outcome categories were as follows: Engel I, 55%; Engel II, 12%; Engel III, 9%; Engel IV, 24%. The completeness of surgical resection defined as complete removal of the structural MRI lesion (if present) and the cortical region exhibiting prominent ictal and interictal abnormalities on intracranial EEG was the single most important predictor of favorable postsurgical seizure outcome. There were non-significant trends towards better outcomes in patients with normal intelligence, with FCD type II and patients undergoing hemispherectomy. Other factors such as age at seizure onset, duration of epilepsy, seizure frequency, associated pathologies including hippocampal sclerosis, extent of EEG and MRI abnormalities and extent and localization of resections did not influence outcome. 25% of patients have changed seizure status after the second postoperative year. Anticonvulsant medication was discontinued in 14% of patients at the end of follow-up.Conclusions: The ability to localize and fully excise the entire region of dysplastic cortex is the most powerful predictor of seizure outcome in pediatric FCD patients. Unlike several previous reports, we did not find a significant correlation between other presurgical, surgical and histopathological variables and seizure outcome. Unfavorable surgical outcome is mostly caused by overlap of dysplastic and eloquent cortical regions. Supported by Grant IGA NR/8843-4.