State Institution "A. I. Kolomiychenko Institute of Otolaryngology of the National Academy of Medical Sciences of Ukraine", Kyiv
Introduction. Acoustic trauma, influence of sounds of high intensity can cause specifiс disorders in the hearing system. While getting combat acoustic trauma both peripheral and central parts of the hearing analyzer can be damaged. Also, the effect of noise, sounds of high intensity not only on the structures of the hearing system but on the whole body of a suffered person should be taken into consideration. Therefore, in the acoustic trauma not only auralics manifestations (related to the state of different parts of the hearing system) are taken place, but, also, expressed extraauralic disorders (on the side of organs and systems, not directly related to structures of the hearing system, but the state of which influence on the hearing function ).
In the first place it concerns the central nervous and cardiovascular systems (mostly cerebral blood circulation). Therefore, it is expedient to study the functional state of the CNS in patients with acoustic trauma.
Purpose of the research – to find changes in the state of bioelectric activity of brain by records of the electroencephalography (EEG) in servicemen which have got combat acoustic trauma in the zone of the anti-terroristic operation (АТО).
Materials and methods. We have selected a group of 50 combatants among all examined persons with acoustic trauma and asimetric sensorineural disorders and a descending type of the curve. A methodology of the work included conducting electroencephalography with the computer electroencephalograph of the "DХ-systems" Company. Electrodes were laid in such way as to equally cover the frontal, parietal and cervical areas of both hemispheres, according to the procedure of applying electrodes "10–20", recommended by the International Federation of Electroencephalography.
Results and discussion. According to the EEG records of the examined servicemen with acoustic trauma, irritative changes were found both in the background record and under the functional loads, especially under hyperventilation of different degree. The most frequent there were found: the expressed disorganization and desynchronization of rhythms, a tendency to smoothing or absence of zonal discrepancies, the availability of sharp peaks and potentials, "acceleration" of the basic rhythms, predominance of the β-rhythms in the structure of the bioelectric activity and signoficant part of weak Δ- and θ-rhythms. Tht overall decline in the bioelectric activity of brain was recorded in the part of patients, expressed in different degree, especially in the temporal lead. These changes were mainly of cerebral (generalized) character and more expressed in patients with more significant disorders in the hearing analyzer. In many cases there were observed asymmethric biocurrents, mainly in postfrontal, temporal and parietal leads, especially in those cases, when patients had asymmethric disorders in the hearing system with a considerable difference in the indicators on both sides. There were also often observed splashes of hypersynchronous activity in persons with combat acoustic trauma, including slow-wave elements, pointing to considerable predominance of processes of excitation in the deep brain structures. In the considerable part of patients with acoustic trauma the irritation of cortical, diencephalic, diencephalic-brain stem or brain mediobasal structures were found. On the whole, in all examined servicemen with acoustic trauma, processes of excitation are prevailing, and it is necessary to pay attention to this when prescribing the treatment. According to the analysis of he quantitative indicators of the EEG it was found, that in comparison to the data of the control group there was a significant difference (Р < 0,05) in the presence of the basic rhythms of the EEG in the examined patients with acoustic trauma not only in th temporal and occipital but, also, in the frontal leads. So, in the background record of the EEG at the normal value of the percentage of α-rhythm in the control group (62,5 ± 4,6) % in temporal and (64,3 ± 4,8) % in occipital leads, in the group of patients with acoustic trauma the corresponding indicators were (45,4 ± 3,7) and (48,9 ± 3,9) % respectively, that was significantly (Р < 0,05) lower. So, for example, in persons of the examined group of patients with acoustic trauma changes in the EEG showed the significant increase of the presence of β-rhythm in the background record in temporal and parietal leads up to (29,1 ± 2,8) and (27,2 ± 2,7) % with the control value (20,3 ± 2,1) % (16,8 ± 2,0) % respectively (Р < 0,01). While analyzing the presence of α-rhythm (dominant rhythm of the normal EEG picture) a considerable decrease in it's percentage, deformation of the basic rhythm and a weak reaction on the functional loading were found in the mentioned leads. Especially illustrative was the analysis of the slow-wave activity (θ- and Δ-rhythm) in patients with acoustic trauma, that exceeded the indicators of the control group considerably, especially in the frontal leads, pointing to the growth of th functional changes in the the central nervous system, exactly in deep brain structures. Thus, in the frontal leads in such patients the increase of the percentage presence of Δ-rhytm was found (14,3 ± 1,5) % in the background record, (14,8 ± 1,6) % in the photostimulation and (15,1 ± 1,5) % in hyperventilation (Р < 0,01), sgnificantly more than in the norm. Also, the illustrative is a growth in the percentage of the presence of θ-rhytm in patients with combat acoustic trauma during hyperventilation in temporal and occipital leads to (16,5 ± 2,3) and (14,5 ± 2,0) %, respectively (Р < 0,05), which is significantly higher in comparison with the control values. So, considarable changes in the brain bioelectric activity, mainly of irritative character with irritations in deep parts of the brain, were recorded in the examined persons with acoustic trauma got in real combat conditions. The conducted analysis of the EEG in persons with acoustic trauma got in the zone of the АТO points to the presence of expressive functional changes on the side of the central nervous system.
Conclusions. The conducted analysis of the EEG in persons with acoustic trauma got in the zone of the AТО, shows the presence of considerable functional changes in the central nervous system. By the records of the EEG in the examined servicemen with acoustic trauma, irritative changes were found both in the background record and at the functional loads, especially under hyperventilation, expressed in a different degree. The most expressed significant changes in the examined persons with acoustic trauma were the reduction of α-rhytm and the growth of β-rhytm and slow wave activity in the frontal, temporal and occipital leads, in comparison to the indicators of the control group. In the complex examination of servicemen with acoustic trauma with the purpose of the detailed estimation of extraaural changes, it is expedient to conduct studies of the functional state of the CNS by the EEG records.The account of the data of the complex study of brain bioelectric activity by the EEG recods, makes it possible to objectively estimate the extraaural disorders and promote a purposeful prescription of treatment to patients with acoustic trauma got in the zone of АТО, thus increasing it's efficiency.
Key words: sensorineural hearing loss, acoustic trauma, auditory analyze, bioelectric activity of brain, electroencephalography
ORCID ID of co-authors and their contribution to the preparation and writing of the article:
Shidlovskaya T.A. (ORCID ID 0000-0002-7894-359X) - Definition of the purpose and design of the study, registration of the OAU, analysis of OAU registration data, analysis of the obtained results, formation of conclusions;
Petruk L.G. (ORCID ID 0000-0002-1261-7054) - selection of patients for examination, conducting of clinical studies, review of literature, statistical processing of the obtained results in accordance with generally accepted methods of mathematical variation statistics, analysis of the obtained data, formation of conclusions, design of the article.