Abstracts

Rationale: Epilepsy surgery planning in Tuberous Sclerosis Complex (TSC) is highly complex due to the presence of multiple cortical tubers, frequent occurrence of multiple seizure types and multifocal scalp EEG epileptiform activity. It has been however hypothesized that multifocal epilepsy in TSC may be an observed phenotype of a primary seizure focus driving a complex epileptic network. The aim of our study was to analyze clinical, EEG and neuroimaging markers of multifocality in pediatric TSC patients in relation to surgical approaches and outcome.Methods: 24 children with TSC who underwent excisional epilepsy surgery at Miami Children's Hospital were retrospectively studied. All subjects had available clinical, MRI, ictal SPECT, scalp and intracranial EEG, surgical as well as postsurgical seizure outcome data. Seizures were classified as uniform focal or multiple types/generalized. Diagnostic data were reevaluated and individual abnormities were classified as localized to one region/lobe or multilobar/multifocal. We then assessed whether brain tissue exhibiting abnormalities found by individual diagnostic tests was completely or incompletely surgically removed or not removed and related completeness of their resection to postsurgical seizure outcomes.Results: Seventeen patients underwent focal or one-lobe resections, 5 subjects had larger multilobar surgeries and only 2 children were operated on at 2 remote sites in the same hemisphere. Fourteen patients had long-term intracranial EEG prior surgery; remaining 10 subjects underwent one-stage resections with intraoperative electrocorticography. Ten patients have been seizure-free (SF) 2 years after the surgery; 14 subjects had less favorable outcomes (10 of them were significantly improved). Two children with a single large tuber have SF surgical outcomes. Postsurgical SF rates in patients regarded multifocal were as follows: 33% in 15 subjects with multiple/generalized seizure types; 28% in 18 children with multifocal/multiregional scalp EEG abnormities; 40% in 15 patients with nonlocalized/extensive ictal SPECT hyperperfusion zones and 25% in 12 subjects with multifocal/multiregional intracranial EEG findings. Complete removal of the SPECT hyperperfusion zone was achieved in 5 subjects; 3 of them have been rendered SF. Six of 7 children with completely removed brain regions of scalp EEG abnormity and 9 of 12 patients with completely excised cortical regions exhibiting significant intracranial EEG abnormalities are SF post surgery.Conclusions: TSC patients with signs of multifocality (based on seizure semiology and presurgical diagnostic work-up) are less likely to achieve complete postsurgical seizure freedom compared with subjects with better localized epileptogenic zones; however, not insignificant proportion of these complicated cases may be cured by one-site surgery. Complete surgical removal of significant intracranial EEG abnormalities is a strong predictor of favorable postsurgical outcome in TCS. Supported by MH CZ DRO, University Hospital Motol, Prague, Czech Republic 00064203 and IGA NT/11443-5.