[Comparison of electrocorticographic patterns with focal cortical dysplasia types in children with epilepsy].

OBJECTIVE: the objective of the study was to determine significant differences in electrocorticographic patterns for various types of focal cortical dysplasias. MATERIAL AND METHODS: 42 patients diagnosed with drug-resistant focal epilepsy were operated on at the Burdenko Neurosurgical Institute in the period from 2006 to 2013. Patients who were histologically diagnosed with focal cortical dysplasia (FCD) and underwent video-electroencephalography and electrocorticography were analyzed. RESULTS: The classification of epileptiform patterns proposed by Palmini in 1995 was used. The sporadic epileptiform activity pattern was predominant in electrocorticographic studies. The continued pattern was more frequent in the case of type II focal cortical dysplasias (FCDs), both combined and isolated; burst and sporadic activity patterns prevailed in combinations in the case of type III FCDs. A uniform distribution of all pattern types of the epileptiform activity was observed in type I FCDs. The data are statistically significant for groups with sporadic and continued patterns. CONCLUSION: The continued epileptiform activity pattern is predominant in type II focal cortical dysplasia that corresponds to the most pronounced epileptogenesis processes of brain tissue with the presence of pathological forms of neurons. A uniform pattern distribution is observed for type I FCD. Patterns of the epileptiform activity and sporadic spike bursts are predominant in the case of type III FCDs. The sporadic activity is likely to be non-specific and almost uniformly distributed in all types of cortical dysplasias.

[The comparative analysis of changes of short pieces of EEG at perception of music on the basis of the event-related synchronization/desynchronization and wavelet-synchrony].

The going of present pilot study is an analysis of features changes of EEG short pieces registered from 32 sites, at perception of musical melodies healthy examinees depending on logic (cognizance) and emotional (it was pleasant it was not pleasant) melody estimations. For this purpose changes of event-related synchronization/desynchronization, and also wavelet-synchrony of EEG-responses at 31 healthy examinees at the age from 18 till 60 years were compared. It is shown that at a logic estimation of music the melody cognizance is accompanied the event-related desynchronization in the left fronto-parietal-temporal area. At an emotional estimation of a melody the event-related synchronization in left fronto - temporal area for the pleasant melodies, desynchronization in temporal area for not pleasant and desynchronization in occipital area for the melodies which are not causing the emotional response is typical. At the analysis of wavelet-synchrony of EEG characterizing jet changes of interaction of cortical zones, it is revealed that the most distinct topographical distinctions concern type of processing of the heard music: logic (has learned-hasn't learned) or emotional (it was pleasant-it was not pleasant). If at an emotional estimation changes interhemispheric communications between associative cortical zones (central, frontal, temporal), are more expressed at logic - between inter - and intrahemispheric communications of projective zones of the acoustic analyzer (temporal area). It is supposed that the revealed event-related synchronization/desynhronization reflects, most likely, an activation component of an estimation of musical fragments whereas the wavelet-analysis provides guidance on character of processing of musical stimulus.

[Long-latency components (N100, N200 and P300) of acoustic evoked potentials in prediction of mental recovery in severe traumatic brain injury].

The authors analyzed correlations of amplitude and latency levels of N100, N200 and P300 components of acoustic evoked potentials (AEP) registered during sonic stimulation and counting of target-oriented stimuli in 22 patients in vegetative state and mutism as an outcome of traumatic brain injury. Results were analyzed with association of electrophysiological findings with data of diffusion-tensor MRI. 55 healthy volunteers were included into control group. It is described that patients in vegetative state with formal recovery to the level of clear consciousness develop all three components of AEP in response to target-oriented tone. The instruction "to counts" leads to their better development. Patients with restoration to minimal level of consciousness produce all components during audition of sounds and only N100 and N200 in response to standard tone after instruction "to count". It is discovered that levels of amplitude have bigger correlation according to Spearman's criterion with outcome in comparison to latency. There changes are more prominent in N100 and N200 components rather in P300. In addition, after instruction "to count sounds" the registered changes between stages of vegetative state and mutism are significant for leads of left hemisphere, and during audition of sounds--for sagittal leads. The study showed correspondence of acquired changes with MRI data. Chronic unconscious state is associated with changes in corpus callosum (degeneration fibers) and corticospinal tracts in the brainstem. The data are discussed in light of hypothesis of the role of morphofunctional disconnections (brainstem-thalamus and interhemispheric) in impairment of attention and in genesis of different forms of posttraumatic unconscious state.

[Amplitude-time parameters of long-latency components (N1, N2 and P300) of acoustic evoked potential of healthy examinees of young and mature age].

The aim of study was to track a cumulative changes of amplitude-time parametres of components N1, N2 and P300 of acoustic evoked potential in experimental situations different in complexity (at the account and listening of sounds) and to compare the received distinctions at examinees of young and mature age. ERP were recorded at 12 healthy subjects from 18 to 22 ages and 12 subjects from 32 to 59 ages. The two-stimuli oddball paradigm was used. It is revealed that components N1, N2 and P300 recorded in the situation of the listenings of sounds without any preliminary instruction do not differ at persons of young and mature age. At examinees of younger age the biger amplitude of component N1 is noted at the account of sounds in comparison with listening whereas the latency of the one do not change depending on complexity of the task. It is shown that component N2 has stability of latency in relation to age and an experimental situation. The amplitude of component N2 is above at the account of sounds in both age groups. The amplitude-time parametres of component P300 do not differ at examinees of different age in a problem of listening of sounds. The revealed features of components N1, N2 and P300 at examinees of young and mature age in experimental situations different in complexity, allow to assume that with the years at the person adaptive mechanisms which allow carrying out successfully of the task.

[Changes in brain bioelectrical activity during xenon anesthesia in neurosurgical patients].

Xenon is a promising anesthetic agent in neurosurgery. However, there is now little evidence on the effect of xenon at anesthetic concentrations on brain electrical activity, which limits its use in neurosurgical patients. Changes in brain bioelectrical activity were studied in patients with skull base tumors before surgery (conscious ones) and at different stages of xenon anesthesia (after denitrogenization, at 50% xenon concentration in the circuit, at 65% xenon concentration in the circuit, during steady-state xenon anesthesia, and after hyperventilation). EEG during xenon anesthesia was similar to that during propofol anesthesia; a circuit xenon concentration (50 or 65%) and a ventilation mode had no considerable impact on EEG. Xenon did not induce paroxysmal activity. The findings suggest that the use of xenon anesthesia in neurosurgical patients is safe in terms of its impact on brain bioelectrical activity.

[Dynamics of P300 component of acoustic evoked potential in postraumatic unconsciousness].

In order to reveal features of the brain reactions to external stimuli in the course of consciousness recovery after a severe craniocerebral injury, component P300 of acoustic evoked potential was analyzed in 9 patients with chronic and 32 patients with reversible unconsciousness. In patients with chronic unconsciousness, P300 parameters displayed a linear correlation with the current functional state. However, this component remained significantly different from its normal shape and varied only in a narrow range. In patients with reversible unconsciousness, time course of changes in amplitude and latency between recovery stages was of linear character with a tendency to normalization. The findings suggest that, in reversible unconsciousness states, processing of sensory information at different recovery stages may be performed with various functional systems that determine varying quality of processing, whereas changes in chronic unconsciousness are caused by a decrease in the number of active elements within the same functional system.

[Component P300 of acoustic evoked potential in patients with local brain lesion]. / Komponent P300 akusticheskogo vyzvannogo potentsiala u bol'nykh s ochagovym porazheniem golovnogo mozga.

The aim of the study was a comparative analysis of spatial-temporary organization of P300 acoustic evoked potential (AEP) in patients with local lesions of the brain stem, frontal and temporal structures in the situations of "passive" listening to sounds and their active recognition (a count). Specific changes of P300 parameters were distinguished in each group. The peak-temporary P300 parameters--latency increase, decrease of amplitude and tendency to the decrease of half-cycle--were similarly changed, irrespective of brain damage topography. A degree of the changes correlated with a level of functional acoustic evoked potential decompensation. In relation to pathologic process location, the topographical P300 AEP features were more specified, comparing to peak-temporary parameters. An existence of two systems for P300 generation at "active" counting and "passive" listening was suggested. In "passive" listening, a response is mostly determined by intact left frontal lobe and middle-stem structures but in "active" counting--by intact right frontal lobe or lobes and limbic system structures (hippocampus).

[Characteristics of the spatio-temporal organization of the P300 component of AEP during the "active" and "passive" stimulus perception in healthy subjects]. / Osobennosti prostranstvenno-vremennoi organizatsii komponenta P300 AVP pri "aktivnom" i "passivnom" vospriiatii stimula u zdorovykh ispytuemykh.

The concern of the work was in detection and analysis of P300 component of the acoustic evoked potential in healthy subjects in different experimental situations. During counting the rare sounds, P300 was most pronounced in the frontocentral and parietooccipital areas mainly of the left-hemisphere. The response shape was correlated with characteristics of the basic rhythm of the background EEG. Responses of simple and complex shapes were distinguished. The simplest responses were recorded in subjects with hypersynchronous alpha-rhythm. Analysis of three-dimensional dipole source localization showed that structures of the brainstem, limbic system, and frontal lobes participate in generation of the wave. In all the subjects, the decisive role in response generation was played by the brainstem structures. In persons with hypersynchronous alpha-rhythm, the contribution of the frontal lobes was less pronounced. During "passive" listening of sounds, P300 parameters significantly differed from those observed during counting only in 46% of cases (in persons having no hypersynchronous alpha-rhythm). A simplification of the response shape during "passive" listening was observed in these cases, the area of the maximal response expression was shifted to symmetrical areas of the right-hemisphere, the number of dipole sources reduced due to a decrease in the contribution of the frontal and limbic structures into the response generation.

[Visual evoked potentials and the P300 component in different courses of the posttraumatic vegetative state]. / Zritel'nye vyzvannye potentsialy i komponent P300 pri raznom techenii posttravmaticheskogo vegetativnogo sostoianiia.

The late latency components of visual evoked potentials (VEP) and the component P300 AEP were analyzed to evaluate their informative value in the process of mental function restoration in patient after long-term traumatic coma. VEP components with latencies of 70 to 320 msec were studied in 24 patients. Topographical mapping of the power of the study VEP components and components P300 was made by the peak amplitude. Long-term VEP components and component P300 were examined by the method of three-dimensional localization of equivalent dipole sources. In 16 patients with positive tendencies in the condition there was a stable localization of the maximum VEP power in the parietal, sagittal, and occipital regions, component P300 showed its maximum amplitude in the central and parietal regions in the left hemisphere. Eight patients with negative tendencies in the status had the maximum VEP and component P300 in the frontal and temporal regions, predominantly in the right hemisphere. The paper shows it important to evaluate not only time-amplitude parameters and analyzes the tomographic features of its formation in dynamics.

[Foci of pathological activity in the human brain and their influence on the spatial-temporal relationships of the EEG]. / Ochagi patologicheskoi aktivnosti v golovnom mozge cheloveka i ikh vliianie na prostranstvenno-vremennýe otnosheniia EEG.

EEGs of 51 patients with focal brain lesions (tumor localized in brain hemispheres) were analyzed. Coherence functions were calculated between the EEG recorded from the intact and lesioned hemispheres and three-dimensional analysis of the delta-wave "source" localization was conducted. The revealed delta-wave "sources" localized in the perifocal region of the lesioned hemisphere demonstrated its dynamic properties and a tendency for fluctuations. Changes in the delta-wave "source" pattern were correlated with the EEG coherence values neither in the lesioned nor in the intact hemisphere. The focus of pathological activity produced the changes in EEG coherence and its interhemispheric asymmetry. In the majority of cases (72%), the mean level of intrahemispheric coherence at the side ipsilateral to the pathological focus was lower than the normal mean level, and the mean level of EEG coherence in the intact hemisphere was increased.

[The P300 component of the auditory evoked potential in the posttraumatic vegetative state]. / Komponent P300 akusticheskogo vyzvannogo potentsiala v posttravmaticheskom vegetativnom sostoianii.

The dynamic studies of P300 component of the acoustic evoked potential were conducted in 12 patients in posttraumatic state of the autonomic system. The amplitude and time parameters of P300 were analyzed, its spatial distribution over the cortex, and features of generation. The obtained results were compared with the normative data. Significant changes in P300 in comparison with the normal characteristics were revealed in patients with the absence of conscious mental activity. These changes were maximally expressed when the state of patients was irreversible. In case of patients' outcome from the studied state the amplitude-temporal and topographic response characteristics tended to normalization but did not reach it completely. The obtained results allow us to consider the P300 component as one of the most informative indices in consciousness recovery after severe brain injury.

[The electroencephalographic correlates of a disorder in higher cortical functions in local lesions of the hypothalamic area]. / Elektroéntsefalograficheskie korreliaty narusheniia vysshikh korkovykh funktsii pri lokal'nykh porazheniiakh gipotalamicheskoi oblasti.

In order to reveal correlations between disturbances in higher cortical functions and characteristics of electrical activity 70 patients with pathological foci in the hypothalamic regions were examined using computer data processing. Destruction of the normal intercentral relations between EEG rhythms develops under the influence of the hypothalamic focus. The process builds up with the aggravation of cortical disorders (mnestic, emotional-affective, consciousness oppression with sleep inversion). General decrease of EEG coherence is observed with the highest destruction of correlations in the frontal cortical areas. The structure of high-frequency alpha-rhythm becomes deranged even in slight cortical disorders, its coherence decreases predominantly in the frontal cortical areas. With intensification of the pathological process in the focus, the stage of delta-rhythm coherence increase is observed and at the background of general destruction of correlations new, pathological intercentral relations develop. Using a BRAINLOC computer technique "sources" of the delta- and theta-activity have been localized in the medio-basal brain regions. The area of localization is specific for hypothalamic lesions. The "source" is mostly expressed in the slightest pathology of higher cortical functions. With aggravation of the process in the hypothalamic pathological focus and further derangement in the cortical functions expression of the "sources" reduces up to their complete disintegration in coma.