The effectiveness of cortico-cortical evoked potential in detecting seizure onset zones

Objective The aim of the study was to evaluate the parameters for localizing the seizure onset zone in refractory epilepsy patients using cortico-cortical evoked potentials (CCEP). Methods Fifteen patients (nine females) with medically refractory partial epilepsy underwent stereo electro encephalography (SEEG) in Tsinghua University Yu-Quan Hospital from 2015 to 2016. Clinical semiology and, scalp electroencephalography (EEG) findings were analyzed during phase I preoperative evaluation. During phase II evaluation, localization of seizure onset zone (SOZ) was analyzed using SEEG by experienced epileptologists. Meanwhile, the cortico-cortical evoked potential (CCEP) paradigm was tested in all patients in phase II. The value of root-mean-square (RMS) of CCEPs amplitude from 7 ms to 300 ms after stimulation was analyzed to quantify the response. Results RMS of CCEPs amplitude in SOZ was higher than in seizure propagation zone (SPZ) (P < 0.05) and non-seizure onset zone (NSOZ) (P < 0.05). RMS of CCEPs amplitude in SOZ was higher than in NSOZ in epilepsy patients with secondary generalized tonic-clonic seizures (SGTCS) (N = 6, P < 0.05); The RMS of CCEPs amplitude in SOZ was strikingly higher than SPZ in the repetitive spiking (RS) onset pattern, and the difference was significant (N = 5, P < 0.01). Conclusions This data indicated that CCEP response is enhanced in SOZ despite different seizure types (with or without SGTCS). CCEP may be an effective method to locate SOZ.