Effectiveness of intraoperative electrocorticography with symptomatic epilepsy associated with brain tumors

Abstract

Intraoperative electrocorticography had become the “gold standard” in surgery of intrahemispheric brain tumors associated with epilepsy. Glioblastomas and oligodendrogliomas are more frequently accompanied by epileptic seizures than other brain tumors. The primary goal of intraoperative electrocorticography is to define the focus of epileptic activity that needs to be totally resected in order to achieve the best possible seizure outcome. Electrocorticography is a highly effective method (more than 70%) in localizing the focus of epileptic activity, especially when associated with a temporal lobe tumor. However, electrocorticographic recording in frontal lobe tumor turns out to be less effective. Intraoperative electrocorticography is recorded in the presence of factors affecting the activity of neocortical neurons. Based on the results of intraoperative electrocorticography only in 45–55% of the cases persistent epileptic activity of high occurrence rate is recorded allowing the clarification of epileptic focus location and its resection within the limits of physiologic permissibility. However, it remains unspecified whether the fact of low occurrence rate of the epileptic activity or even the absence of such activity is clinically relevant. Epileptiform discharges in the preresection electrocorticography recorded in 33 (53%) cases, in the postresection electrocorticography in 10 (23,6%) patients sporadic epileptiform discharges or alternate patterns were recorded. Based on the results of postoperative electrocorticography in 4 (6%) of the cases focal epileptic activity was recorded with underlying gross diffuse changes of bioelectric activity. Probably, acquisition of epileptic activity of low occurrence rate during intraoperative electrocorticography is influenced by factors including but not limited to the neurosurgical intervention.

Keywords

intraoperative electrocorticography / epileptic syndrome / neurophysiological monitoring / brain tumors / effectiveness / tumor-related epilepsy / epileptic activity rate / alternate pattern / epileptic zone resection

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