Cortical dysplastic lesions in children with intractable epilepsy: role of complete resection

Object. The authors conducted a study to determine seizure-related outcomes in a group of pediatric patients with pathologically proven focal cortical dysplasia (FCD) treated by focal cortical resections and multiple subpial transections (MSTs). Methods. The authors performed a retrospective review of pediatric patients in whom surgery was conducted to treat medically refractory epilepsy secondary to cortical dysplasia between April 1989 and January 2001. Diagnostic studies included preoperative scalp electroencephalography (EEG), magnetic resonance (MR) imaging, positron emission tomography (PET), and magnetoencephalography (MEG). Intraoperative electrocorticography (ECoG) or extraoperative subdural grid EEG monitoring was performed in all patients. Seizure outcome was classified using the Engel scheme. The authors analyzed nine data points and compared these with seizure outcome, including seizure sermology, MR imaging, PET and MEG data, as well as location of resection, intracranial video-EEG findings, MSTs, postresection ECoG data, and histological findings. The authors analyzed data obtained in 39 children in whom the follow-up interval after epilepsy surgery was at least 18 months. Patients had suffered epilepsy for a mean of 7.7 years prior to surgical intervention and their mean age at treatment was 9.6 years (range 2 months-18 years). A good seizure-related outcome was demonstrated in 28 patients (72%), including 21 (54%) who were free of seizures (Engel Class I) and seven (18%) in whom seizures were rare (Engel Class II). In 11 patients seizure-related outcome was less favorable, including six (15%) with worthwhile improvement involving some seizures (Engel Class III) and five (13%) with no postoperative seizure improvement (Engel Class IV). There was no significant correlation between seizure outcome and data related to seizure characteristics, MR imaging, PET scanning, MEG, location of resection, intracranial video-EEG, postresection ECoG, and histological findings. Eight (50%) of 16 patients who underwent MSTs in addition to incomplete resection of FCD experienced a good outcome (Engel Class I and II). Twenty (87%) of 23 patients in whom resection of FCD was complete and in whom MSTs were not performed experienced a good seizure outcome (p < 0.05). Conclusions. Complete resection of FCD results in good seizure outcome in a majority of children. When conducted in conjunction with incomplete cortical resection, MSTs do not improve seizure outcome in patients with FCD. Focal cortical dysplasia located outside of eloquent cortex and complete excision of the lesion are the most important predictors of seizure outcome.