Investigation of the correlation of preoperative clinical and imaging findings with electrophysiological findings in patients with epilepsy due to focal cortical dysplasia

Objective: The patients who had epilepsy surgery for pathologically proven focal cortical dysplasia (FCD) were retrospectively evaluated for scalp EEG. It is aimed to classify and discuss EEGs findings in different pathological subtypes. Methods: The study included 19 refractory epilepsy patients who underwent surgery between 1999 and 2017 at the Istanbul Faculty of Medicine. Demographic data and preoperative tests such as scalp video EEGs and invasive EEGs were evaluated retrospectively. Postoperative outcomes was evaluated according to the Engel classification. Results: 36.8% of the patients were female The mean age was 21.89 ± 14.64 years. Type Ia in 36.8%, type Ib in 21.1%, type IIa in 21.1%, type IIb in 15.7% and type IIIa FCD in 5.3% was found. Type I was determined as 57.9%, type II was 36.8% and type III FCD was 5.3%. In the scalp EEGs, rhythmic activity was observed in 31.6% (n = 6, Type I = 3, Type II = 3) of the patients. 37.5% (n = 3) of the patients with focal spike activity were type I, 50% (n = 4) were type II, 12.5% (n = 1) were type III. One patient had Frontal Intermittent Rhythmic Activity (FIRDA), one patient had Electrical Status Epilepticus in Slow Sleep (ESES), two patients had "burst suppression", one patient had "switch of" sign. A small number of patients did not constitute a statistical group. Conclusion: We did not find any distinctive electropyshiologic features in FCD and types of FCD. The incidence of REDs did not differ between types. The frequency of localized focal spikes was higher in type II than type I Key Words: Focal cortical dysplasia, epilepsy surgery, EEG, pathological subtypes, preoperative evaluation