RELATIVE DEAFNESS (bradyacusia) — the hearing disorder complicating speech communication of people in life on production and public life.
The hearing disorder (see) causing T., can vary from its insignificant decrease to almost total loss adjoining on deafness (see). Border between heavy T. and is defined deafness by various researchers on - a time-noma. Most of them considers that unlike deafness at T. ability of perception of the speech remains; carry to it also those cases when the speech is perceived only during the strengthening by its special means.
It is considered to be that T. 2 — 3% of the population with the noticeable deviations from these figures in the different countries depending on klimatogeografichesky features and social living conditions of the population suffer on average. In the Soviet Union considerable decrease in the general prevalence of T is observed. due to reduction of incidence hron. purulent average otitis (see) and children's infections; at the same time owing to increase in average life expectancy of the population forms T accrue., inherent to advanced age (see the Presbyacusis), and also the forms connected with broad use of the pharmaceuticals having side ototoksichesky effect, and noise influence (see the Surdomutism).
On localization of the defeat which caused a hearing disorder, T. divide on conductive, a cut disturbances of the sound carrying out system, and pretseptiv-ny (or neurosensory), caused by direct damage of a touch epithelium of a kortiyev of body are the reason (spiral body, T.) and the formations of the acoustic analyzer located above (see). On a wedge, to a current distinguish acute and chronic T. On extent of decrease in hearing of T. subdivide on easy (the I degree), average (the II degree), heavy, later cover T. passes into deafness (the III degree).
Conductive T. most often (at children in 80% of cases) it was caused by catarral or purulent average otitis, at Krom functional and organic damages of the main structures of a middle ear (see) and toxic, action of the inflammatory center on receptor formations of a snail are usually noted (see. Inner ear). Thanks to effective methods of treatment the frequency of developing of purulent average otitis and its effects decreased, and it lost value of the main reason for T.; however T. on this soil and in sovr. to practice has still considerable distribution. Other frequent reason of conductive T. the otosclerosis is (see).
Neurosensory T. approximately in 30% of cases is a consequence acute inf. diseases (flu, meningitis, epidemic parotitis, scarlet fever, infectious hepatitis, etc.). Among causative agents of these diseases one are capable to strike preferential touch epithelium of a kortiyev of body (see), others — fibers before - a door and cochlear nerve and ganglionic cells, the third — vascular educations. A big role in development of T. plays ability inf. agents and their toxins to get through a blood-brain barrier (see) also the gematolabirintny barrier. At epidemic cerebrospinal meningitis (see. The meningococcal infection) usually develops a bilateral purulent labyrinthitis (see) with simultaneous defeat of a trunk of an eighth cranial nerve and its kernels. At epidemic parotitis (see Parotitis epidemic), the virus to-rogo possesses high neuro tropnostyyu, T. or deafness develop, as a rule, on one party. T. at flu it is connected with expressed vazo-and neyrotropnostyo a virus. The changes in an inner ear and retroko-hlearny educations occurring at flu can lead to manifestations of T, various on weight., up to unilateral full deafness. At infectious hepatitis the main reason of T. disturbance of permeability is (see) vascular walls of a labyrinth and their atony.
In modern a wedge, practice in quality etiol. factor of neurosensory T. the great value got side ototoksichesky effect of pharmaceuticals, especially antibiotics of an aminoglikozidny row (Neomycinum, Kanamycinum, gentamycin, Monomycinum) and tetracycline group (chlortetracyclin, etc.), diuretics (ethacrynic to - that), and also quinine, salicylates, etc. In a pathogeny of such ototoksichesky action the large role is played by disturbance of permeability of a gematolabirintny barrier with the subsequent injury of receptors (see) inner ear. Considerable changes of dystrophic character happen in cells of a vascular stripe of a cochlear labyrinth. At the same time in cellular formations of an inner ear destruction of mitochondrions and ribosomes with the subsequent disturbance of protein metabolism, decrease in energy resources and increase in permeability of membranes is observed. Changes in distribution of potassium ions and sodium on both sides of cellular membranes are the cornerstone of ototoksichesky effect of Acidum etacrynicum (see).
Important etiol. factor of neurosensory T. impact of production noise (see) and vibrations is (see), to-rye cause dystrophic changes in voloskovy cells and further — in fibers of an eighth cranial nerve and cells of a spiral ganglion of a snail (see. Acoustic injury, Vibrotrauma). Among other prof. of the factors promoting development of T., it should be noted intoxication lead. manganese, mercury, etc.
At Menyer's disease (see Meunier-ra, a disease) T. it is caused by supertension in endolimfati-chesky space — an endolymph-tichesky hydrodog. At the same time considerable changes undergo voloskovy and other cells of a kortiyev of body. T. has non-constant character (so-called fluctuating T.), what is connected with pristupoobrazny disease. T. at Meunier-ra disease
the wedge, manifestations of T has nek-ry audiological signs, various options inherent to also conductive T. Sushchestvuyut., what reflects a variety of the reasons and mechanisms of its development. Distinguish acute and hron. current of T. At an acute current of T. arises suddenly and more often has unilateral character. As a rule, decrease in hearing is accompanied by a sonitus (see), is frequent — dizziness and nausea (see). Extent of decrease in hearing quickly reaches a maximum with the subsequent its recovery. More rare, napr, at Menyer's disease, an acoustic injury, vascular disorders, T. gets hron. current; hearing continues to worsen steadily.
Hron. current of T. it is observed considerably more often than acute. It is peculiar, e.g., to professional T., to age decrease in hearing, T., caused by an otosclerosis, hron. purulent and adhesive average otitis, etc. In most cases in conductive T. initially hearing on sounds low decreases (bass T.), and then gradually and high frequency. Similar dynamics of decrease in hearing is inherent to damages of a middle ear, but in nek-ry cases it is observed at tumors of a mostomozzhechkovy corner, limited serous meningitis. At neurosensory T. at first perception of sound waves of high frequencies decreases (diskantovy T.), and during the progressing of process and average frequencies. At the mixed T. the neurosensory component arises more often for the second time therefore decrease in acoustical sensitivity happens at first on waves of low, and then high frequencies. At conductive T. perception of sound waves of those frequencies decreases, to-rye get into an acoustic organ by air conductivity at preservation of datum level of hearing on the tones which are carried out through bones of a skull; at neurosensory T. the hearing disorder equally concerns both air, and bone sound transmission. All this receives reflection in a configuration and dynamic range of audiometric curves (see Audiometriya).
Division of T. on reversible (T. at a mental injury, an acute edema of a labyrinth, an acute inflammation of a middle ear), stable (T. because of ototoksichesky action of antibiotics, postinfectious, inborn and hereditary) and progressing (professional T., caused by noise and vibration) is conditional since the mixed forms or substitution in course of disease of one form another are had. So, T., developing as a result of an injury, it is characterized by positive or negative dynamics in the beginning, and further it is stabilized; professional noise and vibration T. progresses only at the continuing influence of pathogenic factors, but becomes stable after the termination of their action.
Diagnosis is based on data a wedge, inspections of the patient, and also an otoskopiya (see), researches by means of the live speech, tuning forks and an audiometriya. Great value for diagnosis of T. at children the objective and game audiometriya has (see). To early diagnosis apply additional researches — definition of hearing thresholds in expanded frequency range and measurement of acoustical sensitivity to ultrasound.
Definition of degree of T. is based on data of a tone audiometriya, and the borders of degrees of T offered by different researchers. considerably vary. JI. W. Neumann (1961) in size of an average hearing loss on tones 500, 1000, 2000 and 4000 Hz carries to relative deafness of the I degree a hearing loss apprx. 40 to, the II degrees — apprx. 65 dB,
the III degree — apprx. 80 dB; the big hearing loss is regarded by it as deafness.
In surdologichesky practice apply a technique of definition of degree of T. by comparison of size of loss of tone hearing to extent of perception of the live speech. On extent of perception of the speech carry those cases when informal conversation is perceived from distance from 6 to 4 m, the II degree —
from 4 to 1 m, the III degrees — from 1 m to
25 cm to relative deafness of the I degree; if informal conversation is perceived from distance less than 25 cm, it is considered that T. borders on deafness. Dissociation of tone and speech hearing allows to reveal the main component T. With the same purpose investigate perception and legibility of the so-called sensibilized speech (i.e. speeches with distortions) filtering of its separate components, etc. For identification of damages of receptors of a snail and differentiation they with retrocochlear defeats are used by methods of a superthreshold audiometriya — definition of a phenomenon of acceleration of increase of loudness (see Hearing). In modern a wedge, practice in audiol. diagnosis with success methods of an objective audiometriya in the form of registration of the cortical and stvolomozgovy signals caused by a difference of acoustical potentials, measurements of an acoustic impedance (see), elektrokokhleografiya are implemented.
For differential diagnosis of forms T. widely use ultrasound (see). B. M. Sagalovich with sotr. it is established that the human ear can perceive ultrasound with a frequency up to 225 Committee of Civil Initiatives at its bone carrying out. Hearing thresholds of ultrasound accrue with increase in its frequency and exceed thresholds of all tones of usual sound range. Acoustical perception of ultrasound arises at its intensity in limits to the 100-th shares of watt on 1 cm2. The greatest acoustical effect is shown at the placement of a radiator on zaushny area of the head and on the centerline of a forehead, the smallest — on area of a backbone. The arising effect reminds feeling of high frequencies of usual sound range. Ultrasound badly or at all is not differentiated on frequency, but well differentiated on intensity. It gives the chance rather precisely to measure hearing thresholds of ultrasound.
During the studying of perception of ultrasound with a hearing disorder find natural features of such perception at various forms T in people.: at conductive T. (otosclerosis) thresholds of perception remain normal or close to norm, there is a noticeable gap in perception of a sound at bone and its air carrying out; at neurosensory T. thresholds of perception sharply raise up to its full loss, perception of a sound at bone and its air carrying out is broken almost to the same extent. Such research at atypical forms T is especially important. (cochlear form of an otosclerosis, secondary cochlear neuritis). At asymmetrical decrease in hearing definition of ultrasonic thresholds is at a loss in connection with impossibility to muffle better the hearing ear. In such cases paramount value gets a research of lateralization of ultrasound.
Treatment can be conservative (kofoterapiya) and operational (kofokhirurgiya). Conservative treatment of T. includes medicamentous therapy and physical methods of influence. At conductive T. treatment needs to be begun with sanitation of upper respiratory tracts. The effect of treatment in many respects depends on recovery or improvement of functions of an Eustachian tube (see. Acoustical pipe), especially at T. because of acute and hron. exudative average otitis. In practice pneumo - and vibromassage of a tympanic membrane (see the Pneumomassage), ear inflation was widely adopted (see).
From physiotherapeutic methods the electrophoresis of potassium iodide and enzymes (see the Electrophoresis), and also diadynamic currents are effective (see. Impulse currents). In treatment of exudative average otitis effectively transtubarny introduction of corticosteroids and antibiotics, meatotim-panalny introduction or endaural-ny electrophoresis of a lidaza. At hron. purulent average otitis it is recommended after removal of contents from a drum cavity to enter antiseptic agents, alcohol-soluble antibiotics, corticosteroids, Dimexidum, antihistamines, etc. Afterwards carry out a myringoplasty (see). In some cases intranasal novocainic blockade gives effect (see). Treatment of neurosensory T. less effectively, than conductive. It consists in use of a wide range of means — vasodilating, anticoagulants, vitamins of group B (at a presbyacusis also of vitamins A and E), ascorbic to - you, neurosin, biol. stimulators (e.g., an apilak), pyrogenal, methyluracil, nek-ry amino acids (cysteine), the means increasing energy balance in cells (ATP), nitrate of strychnine, antikholinesterazny means (Galantaminum, prozerin), the hyposensibilizing means, Unithiolum, cytochrome C, and also in use of hyper baric oxygenation (see), etc.
Operational treatment is applied at conductive T. (see Hearing a beam-shayushchiye of operation). It includes various types of a tympanoplasty (I eat.) and stapedoplasties (see the Otosclerosis).
The forecast at conductive T. rather favorable. Good results at T. because of an otosclerosis, adhesive average otitis and nek-ry forms hron. purulent average otitis gives operational treatment. The forecast at neurosensory T. much worse.
Prevention consists of elimination of the factors which are negatively influencing function of hearing (e.g., profvrednost, irrational use of the antibiotics and other pharmaceuticals possessing ototoksichesky action), and that is especially important, identifications of the earliest forms T., when it is still possible to prevent development of the expressed changes of hearing.
The special attention is required by identification and treatment of T. at children since the hearing disorder at them affects development of the speech. In this regard enormous value is gained by medical examination of children and teenagers with the lowered hearing (see Medical examination). Problems of education and training of hard of hearing and deaf children develop a surdology (see the Audiology) and a surdopedagogika (see). In practical work the surdoterapevtichesky equipment (see) and hearing aid (see) by means of hearing aids is widely used (see).
See also Surdomutism. Bibliography: Neumann L. W. Development of the theory and practice of education and training of children with shortcomings of hearing of the USSR, Vestn. otorinolar., No. 2, page 57, 1970; With and Galo in and the p B. M. Some results and perspectives of studying of acoustical perception of ultrasound in an experiment and clinic, in book: Aktualn. vopr. audiol. and an otiatria, under the editorship of N. A. Bobrovsky, etc., page 7, M., 1964; Sagalovich B. M. and Pokra of K. P valov. Thresholds of acoustical perception of ultrasound at various forms of relative deafness and their differential and diagnostic value, Shurn. ushn., nose. and throats, Bol., No. 3, page 30, 1964; Relative deafness, under the editorship of N. A. Preobrazhensky, M., 1978; Hechinashvi-l and S. N. Questions of an audiology, Tbilisi, 1978, bibliogr.; Physiological measures of audio-vestibular system, ed. by L. J. Bradford, N. Y., 1975. See also
bibliogr. to St. Surdomutism, Deafness, Hearing.
N. A. Preobrazhensky; B. M. Sagalovich