On the issue of the electroencephalographic phenomenon «burst-suppression»: variants of outcomes and possible neurophysiological mechanisms

Objective: to evaluate the indicators of electrical activity of the brain using frequency- spectral analysis and data of three- dimensional localization of sources of pathological activity for an approach to the analysis of possible neurophysiological mechanisms of the brain of patients whose EEG recorded the phenomenon of ‘burst- suppression’. Material and methods: 45 electroencephalograms recorded in 22 patients (average age 51.05; 11 women, 11 men) were analyzed. In 12 patients, the EEG study was performed in dynamics from 1 to 8 times. At the time of the first registration, the ‘burst- suppression’phenomenon was recorded in the EEG of all patients. The level of wakefulness of all patients, with the exception of patients who were under anesthesia, was 3 points on the Glasgow coma scale. EEG recording was performed on electroencephalographs ‘Encephalan- EEGR-19/26’, ‘Mitsar- EEG-10/70–201’, ‘Mitsar- EEG-SmartBCI’, ‘Neuron- Spectrum-5’and ‘Neuron- Spectrum-65’in accordance with the International scheme of arrangement of electrodes 10–20 %. A frequency- spectral analysis of the power of the ‘burst’and ‘suppression’periods was carried out — the fast Fourier transform method was used. The program ‘BrainLoc 6.1’(Russia) was used for localization of equivalent dipole sources of pathological electrical activity of the ‘burst’period. Results: during the first EEG recording, the ‘burst- suppression’phenomenon was recorded in all patients. In seven patients, the ‘burst’period in the ‘burstsuppression’phenomenon was visually represented by slow-wave oscillations, in 15 patients, the ‘burst’periods resembled epileptiform discharges. In frequency- spectral analysis EEG in all patients in the ‘burst’period, the dominance of the power of slow-wave oscillations (mainly in the delta range) was noted. According to the program ‘BrainLoc 6.1’, equivalent dipole sources of pathological activity of the ‘burst’period were recorded at the level of the thalamus, in the medio- basal parts of the frontal and temporal lobes on both sides. A favorable outcome of the ‘burst- suppression’phenomenon was observed in only five patients of 22, all other patients had an unfavorable outcome. Conclusion: a favorable outcome of the ‘burst- suppression’phenomenon was observed only in patients under sevorane anesthesia and in some patients after acute poisoning with drugs that affect the central nervous system, while patients after brain anoxia had an unfavorable outcome. In prognostic terms, our data are comparable to the literature data. The changes revealed during the frequency-spectral analysis of the EEG in the form of the dominance of the power of slow-wave oscillations (mainly in the delta range), as well as the localization of the supposed generators of electrical activity in the ‘burst’ period at the level of the thalamus, in the mediobasal parts of the frontal and temporal lobes (according to the ‘BrainLoc 6.1’program), may to some extent be consistent with the data of experimental works and mathematical models of the ‘burst–suppression’phenomenon If the ‘burst- suppression’ phenomenon is detected during EEG registration, it is advisableto conduct a dynamic EEG study or EEG monitoring.