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Biomedical subjects

G A Shchekut'ev

Publications and source records attributed to G A Shchekut'ev.

At least 19 recordsLinked to original sources
PubMed1979

[Spectral and integral-temporal analysis of cerebral evoked potentials in epilepsy patients].

Changes in the spectral and integral-temporal characteristics of evoked potentials (EP) to flashes, were studied in 17 epileptic patients and 20 normals. The analysis of EP was done on a background recording and after a 2-minute hyperventilation. It was demonstrated that an epileptization of the brain according to the integral indices of EP is expressed by an increase in the square response, duration of EP (an increase in the duration of the system return to a state of equilibrium), by a higher level of residual noise in a discharge of EP, as well as by an increase in the negative part of EP and a larger instability of responses. The spectral content of EP in epileptic patients demonstrates an increase in amplitude maxima, especially within theta = psi delta ranges. Hyperventilation in epileptic patients evokes a pronounced synchronization of brain bioelectric activity, which leads to a drop of the response intensity and an increase in the level of residual noise in a discharge of EP. The data obtained suggest that the proposed method of EP analysis may be effective in the determination of the intensity in the focus of epileptical activity, as well as in the study of the function of inhibitory mechanisms of convulsive discharges.

Electroencephalography↗
PubMedDate not supplied

[Motor responses in transcranial magnetic stimulation and somatosensory evoked potentials in patients with pain syndromes].

The main goal was to evaluate the motor and somatosensory systems by recording evoked motor responses (EMRs) during transcranial magnetic stimulation (TMS) and somatosensory evoked potentials (SEPs) in patients with neurogenic pain syndromes before and after implantation of the systems for chronic antipain epidural stimulation. Fifteen patients with neurogenic pain syndromes and a control group of 15 apparently healthy examinees were examined. The patients were found to have a significant reduction in the motor thresholds of EMRs during TMS and an increase in the amplitude of EMRs after implantations of the systems. There were no significant changes in the amplitude-time characteristics of short SEPs as compared to the healthy examinees and after implantation of the systems. Analysis of the amplitude-time characteristics of long SEPs in these patients revealed a significant increase in the amplitude of the component P250 as compared to the normal values and its decrease after implantation of the systems.

Evoked Potentials, Somatosensory↗
PubMedDate not supplied

[A dipole localization method in analyzing the auditory brain-stem evoked potential].

The localization of generators of brainstem auditory evoked response (BAER) has been studied in one patient using the method of dipole localization based on the spatial distribution of BAER over the surface of the head. It has been found that in formation of all BAER waves the activity of several generators overlaps. It is especially marked for the peaks I', II', III and III'--their potential distribution can not be described by single-dipole model, thus preventing the defining of their generation site. Distribution of potential for other peaks corresponds to the single-dipole model. The coordinates of the equivalent sources of these peaks are in the vicinity of the auditory structures: I--near the distal part of the auditory nerve, II--near the auditory nerve in the place of its entering the brainstem, V--near contralateral auditory pontine structures, V--near lateral lemniscus while V', VI and VI'--near mesencephalic auditory structures.

Adolescent↗
PubMedDate not supplied

[Diagnosis of lesions of the central nervous system in patients with systemic lupus erythematosus].

A total of 60 patients with systemic lupus erythematosus (SLE) were under observation; 36 of them had clinical symptoms of the CNS affection and 25 persons included into the control group exhibited no psychic disorders during the clinical examination. Besides, routine clinico-laboratory examinations accepted in rheumatology, the patients were subjected to cranial computer tomography (CT), electroencephalography, examination of cerebral hemodynamics with a radionuclide partechnetate 99mC as well as to psychological testing. Neuropsychic disorders developed during the first four years after the onset of the disease and are grouped in the following way: neurological, border-line, neuropsychic, affective, psychotic, intellectual-mnestic. Moderate affection of the CNS in SLE is characterized by a complex of subjective and objective symptoms: headache, deterioration of memory, insomnia, vertigo, irritability, depressed mood, assymetry of the face innervation, coordinatory disorders. Diffuse widening of the subarchnoidal space, diffuse cerebral changes, interhemispheric assymetry of the venous and arterial phases of cerebral circulation: the most peculiar symptoms of the CNS affection in SLE according to CT and EEG and radionuclide studies of cerebral hemodynamics. Focal changes in the CNS were observed in 50% of the patients with neuropsychic disorders.

Adolescent↗
PubMedDate not supplied

[Monitoring somatosensory evoked potentials during surgery of cerebral vessels].

In 43 patients serial SSER recordings were made during operations for the clipping of arterial aneurysms of cerebral vessels performed under controlled arterial hypotension. SSER recordings during the preliminary phase of the operation showed an average decrease in the response amplitude of 20% during trepanation and a reduction (by 23% of the initial value) during the phase of arterial hypotension. The response recovered to 84% of its initial level by the moment of the beginning of the operation. There was no statistically significant relationship between serial SSER parameter values during arterial pressure reduction and the duration or degree of hypotension. The results testify to the higher information content of such SSER parameters as the amplitude of the first positive complex, as compared with latency criteria and in particular the CCT. It has also been found that a significant increase in the information value of the SSER for the evaluation of ischemia effect on the brain function may be obtained by synchronous stimulation of both arms and registration of cortical responses from both hemispheres.

Adolescent↗
PubMedDate not supplied

[The locked-in patient and the characteristics of the electrical activity of his brain].

"Locked-in" state differs from the known states characterized by the motor activity blockade, preservation of conscience of speech contact, despite the fact that connection with outer world during this state is limited only by vertical movements of eyes and eyelids in response to speech signals. Three "locked-in" men were studied at different stages of development of this state. Spectral-coherent analysis of the EEG was conducted. The most typical for the developed state of the "locked-in" man is a uniform change of the intercentral EEG relations. In the motor areas of the cortex alpha-activity and its links are not formed (coherence in alpha-range is zero) while high and low frequencies are coherent. In the visual areas, in contrast, the alpha-rhythm is coherent. Distinct interhemispheric asymmetry of coherent connections appears. In the right hemisphere a decrease of coherence level is sharp and even, in the left one--in occipito-temporal parts the level remains close to norm, while in the frontal parts of the cortex it decreases.

Alpha Rhythm↗
PubMedDate not supplied

[Short-latency evoked potentials in evaluation of the severity and localization of traumatic lesions of the brain].

Acoustic stem evoked potentials (ASEP) and early components of somatosensory evoked potentials (SSEP) were studied in 36 patients with craniocerebral trauma and compared with those of normal individuals. The results demonstrate the advantages of using SSEP for appraising the patients' condition. This is manifested by the fact that the ASEP parameters do not correlate with the clinical data on the severity of the patients' condition (Glasgow scale) and the indices of the outcome scale, while, in contrast, the SSEP parameters are in good correlation with the clinical findings.

Adolescent↗
PubMedDate not supplied

[Changes in evoked potentials to light in the presence of lesions of the diencephalic and brainstem regions of the human brain].

Evoked potentials (EPs) to light were studied in groups of patients with tumours of basal-diencephalic localization (24 patients) and at the brain-stem level (24 patients), in comparison with 11 normal subjects. In the first group, a decrease of amplitude and increase of response duration were found in the frontal cortical areas, with simultaneous reduction of intrahemispheric differences due to decrease of low-frequency components in the EP spectra by amplitude in fronto-central parts, and of alpha- and beta-frequencies in the occipital parts of the hemispheres. EP changes resulting from brain-stem tumors were more expressed than in the case of cerebellar tumors. In patients with foci causing a pronounced irritation of the brain-stem, a decrease in responses amplitude was observed accompanied by an amplitude lowering of delta- and theta-frequencies in EPs-spectra in the frontal, central and temporal leads, with no changes in the occipital leads. The obtained data testify to functional inequivalence and independence of different EP frequency components suggesting that the methods of studying the EP frequency structure are informative and efficient.

Adolescent↗
PubMedDate not supplied

[Monitoring of short latent evoked potentials during brain stem surgery].

The studies were carried out in 33 patients with intrastem volumetric tumors. In 6 patients the monitoring was impossible because of technological problems. Somatosensory evoked potentials (SSEP) were recorded in 10 and acoustic stem evoked potentials (ASEP) in 18 out of 27 patients and the findings correlated to changes in the neurological status on day 1 postoperation. In 3 out of 9 patients operated on in a sitting posture SSEP monitoring during the main stage of the operation became impossible because the response disappeared due to an air layer above the parietal cortex. Transitory or constant changes in SSEP at the stage of tumor removal were detected in 5 patients. In 9 patients intraoperative changes in ASEP were recorded. False-positive results of ASEP monitoring were obtained in 4 cases. In 2 cases a discrepancy between intraoperative changes of SSEP and the postoperative neurologic deficit were detected. The authors discuss the technological and methodological problems of intraoperative monitoring of evoked potentials and approaches to solution of these problems.

Adolescent↗
PubMedDate not supplied

[Somatosensory evoked potentials in the evaluation of the effectiveness of intensive therapy of ischemic complications in neurosurgical patients].

Nineteen patients with ischemic disorders of brain circulation were examined. All of them were in a critical state and in need of intensive vasoactive therapy. Somatosensory evoked potentials (SSEP) were examined in both hemispheres in all of them, this being followed by monitoring on the side of the predominant involvement. Simultaneously with monitoring, vasoactive therapy was started, beginning from rheological agents. Electro-physiologic assessment of the efficacy of vasoactive drugs in this group of patients revealed that the time course of SSEP helps predict the disease outcome, detect the reaction to a specific vasoactive agent, and choose the appropriate scheme of intensive care.

Adolescent↗
PubMedDate not supplied

[Intraoprative identification and monitoring of motor structures of the brain stem].

The purpose of this work was to evaluate the method of identification of motor structures of the bottom of the IV ventricle in order to find the zone through which it is possible to safely approach the bulky formation and to assess the efficacy of subsequent monitoring of these structures for the prevention of their intraoperative injury. Fourteen patients with bulky tumors of the caudal portions of the brain stem aged 4 to 57 were examined. Motor structures of the brain stem (nerves VII or IX, X, and XII, depending on the site of injury) were identified by direct electrostimulation of the surface of the rhomboid fossa and recording of the motor functions by mechanography of EMG. The results indicate that intraoperative identification of motor structures followed by monitoring thereof is a useful instrument which helps reduce the surgical risk of injuring these structures during surgery on the brain stem.

Adult↗