Abstracts

Rationale: Epilepsy is a leading cause of morbidity in children with Tuberous Sclerosis Complex (TSC). Despite several specific challenges to epilepsy surgery planning in TSC population, a significant proportion of patients (>60%) could become seizure-free with proper surgical candidate selection. Variable predictors of favorable/unfavorable postsurgical outcome have been reported. We analyzed a large surgical series of pediatric TSC patients in order to identify prognostic factors crucial for selection of these subjects for epilepsy surgery. Methods: 33 children with TSC who underwent resective epilepsy surgery at Miami Children's Hospital between 1994 and 2010 were retrospectively reviewed. Only patients who had a definite diagnosis of TSC and known seizure outcome at two years after surgery were selected. A total of 29 clinical, neuropsychological, EEG, MRI and surgical variables were analyzed and related to surgical outcomes. Fisher's exact test was used to examine the significance of associations between the variables and seizure outcomes. The association strength was expressed by Quetet-Yule coefficients. Results: 18 patients (55%) have been seizure-free two years after the (final) surgery. Seizure outcome in remaining subjects was classified as follows: Engel II in five patients (15%), Engel III in four patients (12%) and Engel IV in six patients (18%). For the purpose of the study, these 15 subjects were pooled into "non-seizure-free" group. The following predictors of seizure-free outcome were demonstrated: (1) complete removal of the epileptogenic tissue detected by both MRI (i.e., one large tuber or a region with several tubers supposed to represent the epileptogenic zone) and intracranial EEG (i.e., brain tissue exhibiting significant intracranial EEG abnormalities as defined previously); (2) occurrence of regional scalp interictal and ictal EEG patterns; (3) agreement of interictal and ictal EEG localizations; (4) incidence of simple partial seizures; (5) presence of preoperative hemiparesis; and (6) one-stage surgery (without previous long-term invasive EEG). Other factors such as age at seizure onset, incidence of infantile spasms, duration of epilepsy, seizure frequency, mental retardation, number of brain regions affected by tubers as well as extent of resections did not influence outcome. Conclusions: The size of the data set, all collected at one institution, enabled to distinguish clinically important variables influencing surgical outcome in children with intractable epilepsy due to TSC. Our findings may assist in the surgical management of these patients.