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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 diseaseis 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.

Background. After-discharge (AD) activity is a pattern that differs from background corticography, represented by rhythmic stereotypical slow waves and/or repetitive spike discharges with ≥1 Hz frequency, recorded after cessation of electrical stimulation and lasting for more than 2 seconds. Despite the accumulated experience in the field of intraoperative neuromonitoring, there is no unified protocol for high-frequency stimulation of cortical functional areas (FAs) upon the AD event.Objective: to demonstrate a need to change the intraoperative FAs mapping protocol in patients with brain tumor on awakening in cases of AD recording.Material and methods. Two clinical cases of awake surgical functional mapping followed by resection of the brain tumor are presented. Multimodal monitoring included high-frequency stimulation according to the approved intrahospital protocol with maximum stimulation force of auditory-speech zones of 2.5 mA, electrocorticography, and subcortical dynamic mapping.Results. In the first case, AD was registered while FAs mapping in a patient with a history of one epileptic seizure, upon reaching the maximum stimulation force of 2.5 mA, that was replaced by recording focal epileptiform activity with the following evolution to ictal generalized event and development of intraoperative convulsive seizure. In the second patient with a history of recurrent epileptic seizures, AD with spatiotemporal evolution of the pattern development of clinical ictal event was registered with stimulation at 2.5 mA. In both cases, the appearance of AD required to change mapping protocol with a stepwise decrease in stimulus strength to obtain cortical FAs data.Conclusion. Registration of AD is the basis for changing the protocol of high-frequency cortical stimulation in surgical treatment of brain tumor FAs.

Background. Cerebral ischemia induced by transient middle cerebral artery occlusion is one of the most popular ischemic stroke models used to evaluate drug candidates with neuroprotective properties. The possibilities of combining this model with neurophysiological techniques (e.g., electroencephalography, electrocorticography, evoked potential registration, etc.) to assess the effectiveness of novel pharmacotherapeutic strategies appear to be of great interest to current biomedical research.The aim. Identifying specific changes in somatosensory evoked potentials occurring after cerebral ischemia induced by middle cerebral artery occlusion in rats.Materials and methods. A total number of 18 white outbred male rats were randomized into 3 groups by 6 animals in each: 1) control (presumably healthy animals); 2) ischemia-30 (30-minute middle cerebral artery occlusion); 3) ischemia-45 (45-minute occlusion). At post-surgery day 7, cortical responses to sequential electrical stimulation of left and right n. ischiadicus were registered. N1, P2, N2, P3, and N3 peak latencies and amplitudes, peak-to-peak interval durations and amplitudes were calculated. Spearman’s rank correlation coefficients were used to assess the relationship between ischemia duration and evoked potential parameters, and the Chaddock scale was used to qualitatively evaluate the strength of correlations.Results. The rats subjected to cerebral ischemia demonstrated a decrease in some of the peak amplitudes of the ipsi- and contralateral somatosensory potentials evoked by n. ischiadicus stimulation. In the injured hemisphere, decreased P2 and N3 peak and P3–N3 interval amplitudes were registered ipsilaterally, and decreased P3 peak amplitudes and N2–P3 interval durations were observed contralaterally.Conclusions. The obtained data suggest that somatosensory evoked potential registration and analysis can be used to evaluate the functional state of central nerve tracts in rats subjected to cerebral ischemia.

Introduction.The frequency of adverse outcomes in patients with severe traumatic brain injury (TBI) exceeds 25%. Epileptic seizures and vasospasm, in the absence of pathogenetic treatment, cause irreversible brain damage and thus complicate the course of severe TBI. Bedside electroencephalography (EEG) is traditionally used to diagnose these conditions. However, its low spatial resolution when recording from the scalp and a large number of artefacts that make it challenging to analyse the data. Materials and methods.Electrocorticography (ECoG) monitoring was performed using subdural electrodes implanted in the traumatic brain lesion during TBI surgery in 11 patients during the acute period of severe TBI. All patients were concurrently monitored using scalp EEG with subdermal needle electrodes. Results.Analysis of scalp recordings showed frequency disturbances and oscillation asymmetry in all patients, while sporadic epileptiform activity and rhythmic and periodic patterns were detected in 18% and 64% of subjects, respectively. Analysis of invasive EEG showed sporadic epileptiform activity in 27% of patients, while rhythmic and periodic patterns were present in 91%. Moreover, epileptiform activity was registered only by the subdural leads in 3 patients. The total percentage of subjects in whom we registered clinical and electrographic signs of convulsive and non-convulsive status epilepticus using EEG and ECoG was 55%. We found indirect EEG signs of slow-spreading cortical depolarization in one patient whose level of consciousness was coma, followed by an electrographic pattern of status epilepticus on ECoG. Conclusion.ECoG recording, while patients with severe TBI are in the intensive care unit, increases the diagnostic capabilities of this method, allowing electrographic seizures to be recorded more often and more accurately, but also to detect indirect signs of slow-spreading cortical depolarization using standard EEG amplifiers. Electrode implantation during TBI surgery is safe and does not significantly change the surgical approach.

Aim. In the brain of mammals and humans, several widespread neuronal networks are capable of generating spontaneous rhythmic activity. Among them is the thalamo-cortical network, which involves neurons of the thalamus (diencephalon) and in the neocortex and characterized by hierarchical organization. The thalamo-cortical network generates alpha rhythms with a frequency of about 8...14 Hz. Various neurological and psychiatric disorders are known to associate with similar disturbances of thalamo-cortical rhythms, i.e. the thalamo-cortical dysrhythmia. In particular, absence epilepsy, a non-convulsive form of epilepsy caused by disturbances of the thalamo-cortical system. Absence seizures involve brief and sudden lapses of consciousness (i.e., the state of «absence») associated with high-amplitude spike-wave discharges in the encephalogram. The current paper describes morphology of the thalamo-cortical system and diagnostic principles of the thalamo-cortical dysrhythmia. Methods. WAG/Rij rats with genetic predisposition to absence epilepsy were used as a model of the thalamo-cortical dysrhythmia. Electrical brain activity was recorded from the surface of neocortex using implanted electrodes (electrocorticogram, ECoG). Time-frequency analysis of rhythmic activity in ECoG was performed using continuous wavelet transform and the fast Fourier transform. Results. The following hallmarks of the thalamo-cortical dysrhythmia were defined. (1) During the slow-wave sleep, the spectral power in ECoG was shifted from slow to fast frequencies. (2) Short-lasting episodes of 3...12 Hz rhythmic activity with the amplitude maximum in delta (3...4 Hz) and theta (5...9 Hz) ranges were present in the frontal ECoG. (3) The so-called «pro-epileptic» 5...9 Hz oscillations were present in the frontal ECoG. Conclusion. The most pronounced manifestation of the thalamo-cortical dysrhythmia was found in ECoG during the slow-wave sleep. The dysrhythmic mechanism mostly affected short-lasting slow-wave oscillations with a frequency of 3...4 Hz and 5...9 Hz in combination with disturbances of the time-frequency structure of ECoG.

Objective: To search for correlations between intraoperative electrocorticographic data and seizure control after the multiple hippocampal transections (MHT) in patients with symptomatic pharmacoresistant medial temporal lobe epilepsy., Material and Methods: Six patients underwent MHT nearby the hippocampus. The left dominant hemisphere was affected in all cases. Patients had normal memory function. Follow up was 18 to 24 months. Scalp electroencephalogram (EEG) and electrocorticography (ECoG) were intaoperatively recorded. Transections of the hippocampus were performed until ECoG epileptiform discharges stopped., Results: Seizure control was achieved in five patients. Synchronous epileptiform activity disappeared in the hippocampus in all patients after MHT. Complete disappearance of epileptiform activity in the hippocampus and basal cortex was demonstrated in 2 cases. The epileptiform activity remained in the basal cortex in 3 patients., Conclusions: Using the method of hippocampal transections it was possible to achieve the disappearance of synchronous epileptic activity in the hippocampus in all patients. It is correlated with good outcome in 5 out of 6 cases. Preservation and even arising of spiking in the basal temporal cortex are not a risk factor for maintaining seizures after complete resection of the epileptogenic substrate in the temporal lobe and hippocampal transections. A decrease in the background epileptiform activity on the scalp EEG was observed in 4 of 5 cases after the resection of the pathological substrate, uncus and amygdala.

Background: Non-invasive EEG reveals epileptogenic zone in 70% of patients. In other cases, invasive EEG monitoring is indicated. Various implantation strategies and techniques of intracranial EEG (icEEG) potentially provide different outcomes. Choosing the optimal icEEG technique may be challenging., Objective: To analyze the results of icEEG in adults with temporal lobe epilepsy and to determine the algorithm for selection of optimal invasive EEG technique., Material and Methods: The study included 82 patients with temporal lobe epilepsy who underwent invasive EEG. Effectiveness of invasive EEG was determined by detection of epileptogenic zone and post-resection outcomes. Postoperative results were analyzed throughout more than 6-month follow-up period using the Engel grading system. Statistical analysis was conducted using the Fisher's exact test., Results: Epileptogenic zone was revealed in 72 (88%) cases. Invasive EEG was supplemented by another modality in 3 (4%) patients. Mean follow-up period after resection was 17 months in 45 patients. Favorable outcomes were achieved in 31 (69%) cases. Statistical analysis showed that identification of epileptogenic zone depends existing of lesion and symptoms of seizures. Selection algorithm for optimal technique of invasive EEG was determined considering own results and literature data., Conclusion: Invasive EEG results and post-resection outcomes demonstrated favorable efficacy of original algorithm. The last one may be used in decision-making on optimal technique of invasive EEG in adults with temporal lobe epilepsy.

Objective: Surgery is the first-line treatment option in children with FCD and refractory epilepsy, but the rate of success and patient numbers who became free of seizures vary widely from series to series., Study Aims: To elicit variables affecting the outcome and predicting achievement of the long-term seizure-free status., Material and Methods: One hundred sixty-nine children with cortical dysplasia and DR-epilepsy underwent surgery Preoperative evaluation included prolonged video-EEG and MRI (in all patients) and neuropsychological testing when possible. Fourteen patients underwent invasive EEG, fMRI and MEG were used also in some cases. Including 27 repeat procedures the list of overall 196 surgeries performed consists of: cortectomy (lesionectomy with or without adjacent epileptogenic cortices) – in 116 cases; lobectomy – in 46; and various disconnective procedures – in 34 patients. Almost routinely employed intraoperative ECOG (134 surgeries) was combined with stimulation and/or SSEP in 47 cases to map eloquent cortex (with CST-tracking in some). A new permanent and not anticipated neurological deficit developed post-surgery in 5 cases (2,5%). Patients were follow-upped using video-EEG and MRI and FU which lasts more than 2 years (median – 3 years) is known in 56 cases. Thirty-two children were free of seizures at the last check (57,2% rate of Engel IA). A list of variables regarding patients’ demography, seizure type, lesion pathology and localization, and those related to surgery and its extent were evaluated to figure out anyone associated with favorable outcome., Results: Both Type II FCDs and their anatomically complete excision are positive predictors for favorable outcome and achievement of SF-status (p<0,05). Residual epileptic activity on immediate post-resection ECOG do not affect the outcome., Conclusion: Patients with Type II FCD, particularly with Type IIb malformations are the best candidates for curative surgery, including cases with lesions in brain eloquent areas. Kids with Type I FCD have much less chances to become free of seizures when attempting focal cortectomy. However, some of them with early onset catastrophic epilepsies may benefit from larger surgeries using lobectomy or various disconnections.

Introduction: Glioneuronal tumors (GNT) are usually found in children (less than 1.5% of all neoplasms of the brain). With rare exceptions, they are benign and usually manifest only by epilepsy, which is quite often resistant to treatment with AE drugs. Tumor removal usually helps to cope with epileptic seizures, however, a number of issues regarding diagnosis and surgical treatment (interpretation of morphological data and classification, epileptogenesis and topography of the epileptogenic zone, the value of intraoperative invasive EEG and the optimal volume of resection) remain debatable., Aim: To describe the morphology, electro-clinical picture and MR-semiology in patients with gloneuronal brain tumors, as well as to analyse the results of their surgical treatment and the factors determining its outcome., Material and Methods: 152 children with a median age of 8 years were treated surgically (There were 64 gangliogliomas, 73 DNT, 15 cases where the tumor classification failed - GNT NOS). In children under 2 years of age, temporal localization of the tumor prevailed. In 81 cases, ECoG was used during the operation. Surgical treatment complications: transient neurological deficit (in 15 cases); hematomas removed without consequences (in 2 cases), infectious (osteomyelitis of bone bone flap in 2 cases). We analyzed: the age of the epilepsy onset (median - 4 years 7 months) and its duration (median - 23.5 months), the type of seizures, as well as the features of MR-semiology and morphology of tumors and adjacent areas of the brain. The volume of tumor resection was verified by MRI (in 101 cases) and CT (in each case). The follow-up was collected through face-to-face meetings, with repeated video EEG and MRI, as well as telephone interviews. We studied the effect of a number of parameters characterizing the patient and features of his/her operation on the outcome of treatmen., Results: Among 102 patients in whom the follow-up history is one year or more (median - 2 years), a favorable outcome (Engel IA) was observed in 86 of them (84%); 55 of them (54%) at the time of the last examination stopped drug AE treatment. Radical tumor removal and younger age at the time of surgery were statistically significantly associated with a favorable result., Conclusion: In children with gloneuronal brain tumors, removal of the tumor is effective and relatively safe in the treatment of symptomatic epilepsy. Radical tumor resection and earlier intervention are the most important prerequisites for a favorable outcome and persistent remission of seizures.

Objective: Epilepsy is a frequent clinical manifestation of cavernous malformations (CMs) of the mediobasal temporal region (MBTR). Surgical removal of CMs is an excellent technique for treating associated epilepsy and may range from pure lesionectomy to tailored resection of the temporal lobe., Purpose: The study purpose was to determine the optimal surgical management for epilepsy in patients with CMs of the MBTR., Material and Methods: We retrospectively analyzed the clinical data, neuroimaging findings, surgical techniques, and surgical outcomes in 11 patients with epilepsy and CMs of the MBTR. All patients underwent video-electroencephalography, magnetic resonance imaging, and computed tomography in the pre- and postoperative periods. Nine patients underwent preoperative implantation of foramen ovale electrodes. In all cases, surgery was accompanied by electrocorticography (ECoG)., Results: CMs were located in the anterior MBTR in 7 cases, anterior and middle thirds of the MBTR in 1 case, middle third in 2 cases, and middle and posterior thirds in 1 case. In 8 patients, preoperative monitoring revealed a seizure onset area in the MBTR. These patients underwent cavernomectomy with ECoG-guided resection of the hemosiderin ring and adjacent tissue using the pterional (4 cases) or supracerebellar transtentorial approach (4). In 3 cases, anterior temporal lobectomy with cavernomectomy was additionally used due to spreading of pathological activity to the lateral temporal neocortex. Seizure control after surgery was excellent in 7 patients (class 1 ILAE) and good in 4 (class 2 ILAE)., Conclusion: Surgery in patients with epilepsy caused by CMs of the MBTR should be performed based on non-invasive and invasive presurgical evaluation. If the seizure onset area is located in the MBTR, lesionectomy with ECoG-guided resection of the adjacent temporal cortical areas can be performed using the pterional or supracerebellar transtentorial approach. Lateral spread of epileptic activity requires cavernomectomy and anterior temporal lobectomy.