Neurophysiological phenotypes of pharmacoresistant temporal lobe epilepsy

Abstract

Patients with a drug-resistant form of epilepsy can be treated by neurosurgery through the destruction or separation of the epileptic focus. If the results of clinical, neuro-imaging and neurophysiological methods are discordant, then the localization of the epileptogenic zone is performed based on the results of long-term invasive monitoring of the bioelectrical activity of the cortex and deep structures of the brain. The aim of this work was the retrospective analysis of the results of invasive monitoring of the bioelectrical activity of the brain to clarify the mechanisms of the formation of patterns of interictal and ictal activity in structural epilepsy. The study included 35 patients (18 men, 17 women) with drug-resistant temporal lobe epilepsy, who were treated at the Polenov Neurosurgical Institute. The examination included video-EEG monitoring, long-term invasive monitoring of bioelectrical activity of the cortex, and deep brain structures. The patients were divided into two groups according to the type of surgical treatment: 1) micro-surgical resection of the epileptic focus, including the zone of structural changes (24 patients); 2) stereotactic destruction of the amygdala-hippocampal complex (6 patients). The follow-up of the outcomes of the surgical treatment took place over 2-3 years. Depending on the results of the surgical treatment, the patients were divided into two groups: 1) patients with a favorable outcome (Engel 1–2) — 15 patients and 2) patients with no positive dynamics and a relatively poor outcome (Engel 3–4) — 15 patients. The results obtained showed that the patterns of interictal and ictal activity in their totality determine the neurophysiology, i.e the phenotype of temporal lobe epilepsy, reflecting the interference of pathogenetic and sanogenetic mechanisms. The localization of the epileptogenic zone should be based on the cumulative assessment of interictal and ictal activity. The presence of more than one focus of interictal activity, the secondary spread of epileptiform activity from the primary focus, are prognostically unfavorable factors.