The relation of changes in intraoperative EEg and ECog with age, anamnesis duration and outcome of surgical treatment in children with symptomatic epilepsy

   Aim. To reveal relation of change in intraoperative electroencephalography (EEG), electrocorticography (EсoG) with age of patients, the anamnesis duration, localization and type of pathology, the result of treatment.
   Materials and methods. 64 patients with symptomatic epilepsy operated at N.N. Burdenko National Medical Research Center of Neurosurgery of the Ministry of Health of Russia from 2010 to 2016. 28 males, 36 females, age from 3 months to 18 years, on average 7,2 years. The pathology localization: temporal – 21 cases, occipital and parietal – 18, frontal – 25. Pathomorphology: 12 patients with focal cortical dysplasia (FCD) I, 20 patients with FCD II, 5 patients with FCD III, 4 patients with tuberous sclerosis, 20 patients with low grade tumors, and 3 cases else. The duration of disease
is from 61 to 5081 days. Catamnesis (follow-up) ranged from 364 to 1877 days. There was four criteria for including patients in research: intraoperative EEG, presence of initial and control registration of EсoG, follow-up above 364 days. There are three hallmarks selected as significant concerning the efficiency of neurophysiological monitoring: 1) the positive changes in scalp EEG: decrease of interhemispheric asymmetry due to reduction of slow activity on the side of pathology; significant reduction of the unilateral epileptiform activity on the side of pathology and bilateral if exist; 2) the positive changes in EсoG: significant reduction of the regular epileptiform activity; 3) the absence or existence of residual epileptiform activity in adjacent to resected pathology sites. The statistical processing carried out with application of a Stat10 package.
   Results. The more expressed positive dynamics of EEG were revealed in patients of smaller age already during operation. A correlation was found between the age of patients and the positive dynamics of intraoperative EEG. An inverse correlation was found between the duration of the disease and the positive dynamics of the scalp EEG during surgery (p = 0.1560). The EEG changes during surgery were shown more often with reduction of the seizure anamnesis. There was found out that residual epileptiform activity on ECoG occurred more often at patients with longer anamnesis of a disease and at patients with frontal localization of pathology. The residual epileptiform activity on ECoG was registered more often at patients with preservation of seizures (outcomes 2, 3, 4, 5 ILAE).
   Conclusions. During resective interventions for symptomatic epilepsy in children the probability of positive changes was the more, the younger the patient was. Intraoperative ECoG is one of the useful tools in epilepsy surgery, but it does not definitely determine success. There was no statistically significant relationship between the presence of residual epileptiform signs on the ECoG in the cortex adjacent to the removal area and the outcome of surgical treatment for seizures. Patients in follow-up had three times fewer seizures in the absence of residual epileptiform activity on the ECoG of adjacent to the resected areas of the cortex. The dependence is statistically insignificant. Removal of FCD type III and tumors is accompanied by a more complete elimination of epileptiform activity than FCD I, the level of statistical significance of p = 0.0305.

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