Abstract
Background. In 30 % of cases with epilepsy, it qualifies as medically intractable and requires surgical treatment. The need for improvement of epilepsy surgery effectiveness demands updating of the preoperative assessment protocols. Intraoperative wide-range electrocorticography is a novel technique for defining resection volume in focal structural epilepsy. Combined analysis of high-frequency and epileptiform activity provides additional information and allows prognosticating of surgery outcome. However, consistent evaluation of intraoperative monitoring results is only possible when general anesthetic effect on brain electrical activity is taken into account.Objective. This study was aimed at evaluation of anesthetic gas sevoflurane effect on high-frequency brain electrical activity, recorded directly from the cortex or deep brain structures.Design and methods. Eight patients were included in this study (2 females, 6 males), aged 19 to 47, with a long-term epilepsy (disease duration 15 to 38 years). Prolonged electrocorticographic monitoring was indicated to these patients, combined with eloquent zones mapping in some cases. Patients were implanted with grid electrodes on frontal and temporal cortex, and deep brain Spencer electrodes into the mesial temporal lobe. Wide-range electrocorticography was recorded during slow-wave sleep and intraoperatively under sevoflurane anesthesia. Pathological high-frequency oscillations (pHFOs) rate was counted.Results. In seven patients pHFOs were recorded extraoperatively. Pathological HFO rate varied between 13 and 30 % (mean — 19 %). Distribution of pHFO did not change due to anesthesia effects. Mean background noise amplitude was significantly decreased intraoperatively (z = 2.45; p = 0.014). This effect facilitated visual marking of pHFOs. There were no trends in comparison between extraoperative and intraoperative pHFO rate.Conclusion. Well-controlled levels of general anesthesia obtained with sevoflurane (0,9-1,1 MAC) showed minimal effect on high-frequency brain electrical activity. This allows thorough analysis of wide-range electrocorticogiaphy without waking the patient and provides more information about the extension of the epileptogenic zone and its resection rate intraoperatively.
Highlights
In 30 % of cases with epilepsy, it qualifies as medically intractable and requires surgical treatment
Статистически значимые различия при сравнении параметров экстраоперационной и интраоперационной высокочастотной биоэлектрической активности получены для средней фоновой амплитуды (z = 2,45; p = 0,014)
Дальнейшие фундаментальные исследования могут быть сфокусированы на оценке изменений межнейронных связей под действием севофлурана при помощи количественного анализа высокочастотного компонента биоэлектрической активности
Summary
In 30 % of cases with epilepsy, it qualifies as medically intractable and requires surgical treatment. Список сокращений: ЗНП — зона начала приступа, ЗР — зона раздражения, МАК — минимальная альвеолярная концентрация, пВЧО — патологические высокочастотные осцилляции, ЭЗ — эпилептогенная зона, ЭКоГ — электрокортикография. Перспективной методикой локализации ЭЗ является широкополосная электрокортикография с регистрацией биоэлектрической активности головного мозга в диапазоне от 0,5 до 500 Гц [2]. Широкополосная ЭКоГ позволяет локализовать зону, генерирующую патологические высокочастотные осцилляций (пВЧО) [3]. Генерирующей пВЧО, ассоциировано с лучшими исходами хирургического лечения фокальной структурной эпилепсии [4].
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