Diagnosis of hearing loss in children

It is quite easy to detect hearing loss and deafness in adults. Most of the methods they use are based on the subject's responses to sounds of certain tones and frequencies, as well as speech, given by a tuning fork or through headphones. The curve derived from these subjective responses characterizes the state of the auditory function. However, these so-called psychophysical methods can be used in children no earlier than 4-5 years of age: at an earlier age, a child, as a rule, is not able to give a correct answer. Meanwhile, it is precisely at this and even earlier ages that there is an urgent need to detect hearing loss, since it is most closely related to the development of the speech function and intelligence of the child.

It is known that 80% of hearing impairments occur in children at the age of 1-2 years. The main problem is that late diagnosis of hearing loss leads to untimely treatment, and therefore to late rehabilitation, delayed speech development in the child. Modern concepts of deaf-pedagogical work and hearing aids are based on an earlier start of training. The optimal age is considered to be 1-1.5 years, but if this time is missed, which happens with every third child, it is much more difficult to teach speech, and the child has a higher chance of becoming deaf-mute. In this multifaceted problem, one of the most important issues is the early diagnosis of hearing loss, which is the field of activity of a pediatrician and otolaryngologist. Until recently, this task remained an almost insoluble problem. The main difficulty lies in the need to conduct an objective study based not on the child's answers, but on other criteria that do not depend on his consciousness.

Method of unconditional responses

The first group of such methods is simple, but, unfortunately, very inaccurate. Hearing is determined based on the occurrence of unconditional reflexes in response to sound stimulation. Based on a variety of reactions (increased heart rate, pulse rate, respiratory movements, motor and vegetative responses), it is indirectly judged whether the child can hear or not. Some scientific studies show that even the fetus from about 20 weeks reacts to sounds by changing the rhythm of heart contractions. Very interesting data suggesting that the embryo hears the frequencies of the speech zone better. On this basis, a conclusion is made about the possible reaction of the fetus to the mother's speech and the beginning of the development of the psycho-emotional state of the child during pregnancy.

The main contingent for using the unconditional response method are newborns and infants. A hearing child should respond to sound immediately after birth, already in the first minutes of life. Various sound sources are used for the study: sounding toys pre-calibrated with a sound meter, rattles, musical instruments, simple devices - sound reactometers, sometimes narrow-band and broadband noise. The sound intensity is different, the general principle is that the older the child, the lower the sound intensity is needed to detect a reaction. Thus, at 3 months, a reaction is caused by an intensity of 75 dB, at 6 months - 60 dB, at 9 months, 40-45 dB is enough to cause a reaction in a hearing child. It is very important to conduct and correctly interpret the results of the method: the study should be carried out 1-2 hours before feeding, since later the reaction to sounds decreases. The motor reaction may be false, i.e. not to sounds, but simply to the doctor's approach or the movements of his hands, so some pauses should be made each time. To exclude false positive reactions, a two- or three-fold identical response can be considered reliable. The use of a specially equipped crib for hearing testing eliminates many errors in determining the unconditional reaction.

The most common and studied types of unconditional responses are the cochleopalpebral (blinking in response to sounds) and cochleopapillary reflexes (pupil dilation), motor orientation reflexes, and disturbances in the inhibition rhythm of the sucking reflex. Some responses can be objectively recorded, such as changes in the lumen of blood vessels (plethysmography), heart rhythm (ECG), etc. What are the positive aspects of this group of methods? They are simple, accessible in any conditions, and therefore can be widely used in the medical practice of a neonatologist and pediatrician. However, their disadvantages should also be taken into account. Firstly, high sound intensity and strict adherence to the research rules are necessary to exclude false positive responses, mainly in case of unilateral hearing loss. Thus, we can clarify only one question: does the child hear (without characterizing the degree of hearing loss and its nature). Although this is also extremely important. Using this technique, one can try to determine the ability to localize the source of a sound, which normally develops in children as early as 3-4 months.

The group of methods of unconditioned reflexes can be widely used in practical work for screening diagnostics, especially in risk groups. If possible, all newborns and infants in the maternity hospital should undergo such examinations and consultations, but they are considered mandatory only for the so-called risk groups for hearing loss and deafness. These include:

• causes affecting the hearing function of the fetus during pregnancy (congenital hearing loss and deafness ); toxicosis, threat of miscarriage and premature birth, Rh-conflict between mother and fetus, nephropathy, uterine tumors, maternal diseases during pregnancy, primarily rubella, influenza, treatment with ototoxic drugs;
• pathological births: premature, rapid, protracted with the use of forceps, cesarean section, partial placental abruption, etc.;
• pathology of the early neonatal period: hyperbilirubinemia associated with hemolytic disease of the newborn, prematurity, congenital malformations, etc.;
• in infancy and early childhood, risk factors include: previous sepsis, febrile condition after childbirth, viral infections (rubella, chickenpox, measles, mumps, flu), meningoencephalitis, complications after vaccinations, inflammatory diseases of the ear, traumatic brain injury, treatment with ototoxic drugs, etc.

Maternal history

The maternal anamnesis plays a major role in the initial assessment of the hearing status of a child with suspected hereditary hearing loss. When interviewing the parents of a child under 4 months, it is determined whether the sleeping child is awakened by unexpected loud sounds, whether he flinches or cries: the Moro reflex is typical for this age. It manifests itself in the spreading and bringing together of the arms (the clasping reflex) and the stretching of the legs with strong sound stimulation.

For the approximate detection of hearing impairments, the innate sucking reflex is used, which occurs in a certain rhythm (similar to swallowing). The change in this rhythm when exposed to sound is usually detected by the mother, this indicates that the child has hearing. Of course, all these orientation reflexes are better determined by parents. These reflexes are characterized by rapid extinction, this means that with frequent repetition, the reflex may stop being reproduced; from 4 to 7 months, the child usually makes attempts to turn towards the source of the sound, that is, already determines its localization, at 7 months he differentiates certain sounds, reacts, even if he does not see the source, by 12 months attempts at speech responses (cooing) begin.

Risk factors play an extremely important role in the early diagnosis of hearing loss, and therefore, in the beginning of treatment or deaf education. It should be noted that hearing loss and deafness among newborns is noted on average in 0.3%, and in risk groups it increases almost 5 times.

Method of conditioned reflex reactions

The second group of methods is based on the use of conditioned reflex reactions. To do this, it is necessary to first develop an orienting reaction not only to the sound, but also to another stimulus that reinforces the sound. Thus, if you combine feeding with a loud sound (for example, a bell), then after 10-12 days the sucking reflex will arise only in response to the sound.

There are numerous methods based on this pattern, only the nature of the reinforcement changes. Sometimes, painful stimuli are used as reinforcement, for example, a sound is combined with an injection or a strong air stream directed at the face. Such sound-reinforcing stimuli cause a defensive reaction (quite stable) and are used mainly to identify aggravation in adults, but cannot be used in children for humane reasons. In this regard, modifications of the conditioned reflex method are used in children, based not on a defensive reaction, but on the contrary, on positive emotions and the natural interest of the child. Sometimes, food (candy, nuts) is used as such reinforcement, but this is not harmless, especially with a large number of repetitions, when it is necessary to develop reflexes to different frequencies. This is why this option is more applicable to trained animals in the circus. The main method currently used in the clinic is play audiometry, where the child's natural curiosity is used as reinforcement. In these cases, sound stimulation is combined with the display of pictures, slides, videos, moving toys (for example, a railroad), etc.

Methodology: the child is placed in a sound-proof and isolated chamber. An earphone connected to some sound source (audiometer) is placed on the ear being examined. The doctor and recording equipment are outside the chamber. At the beginning of the examination, high-intensity sounds are played in the ear, the child must hear them in advance, the child's hand is placed on a button, which the mother or assistant presses when the sound signal is given. After several exercises, the child usually learns that the combination of sound and pressing the button leads either to a change of pictures or to the continuation of the video film, in other words, to the continuation of the game - and then presses the button independently when the sound appears.

Gradually, the intensity of the sounds produced decreases. Thus, conditioned reflex reactions make it possible to identify:

• unilateral hearing loss;
• determine the thresholds of perception;
• provide a frequency characteristic of auditory function disorders.

Hearing examination using these methods requires a certain level of intelligence and understanding on the part of the child. Much also depends on the ability to establish contact with parents, the qualifications and skillful approach to the child on the part of the doctor. However, all efforts are justified by the fact that already from the age of three in many cases it is possible to conduct a hearing examination and obtain a full description of the state of his hearing function.

Objective methods of studying auditory function

Objective methods of studying the auditory function include measuring the acoustic impedance, i.e. the resistance provided by the sound-conducting apparatus to the sound wave. Under normal conditions, it is minimal; at frequencies of 800-1000 Hz, almost all sound energy reaches the inner ear without resistance, and the acoustic impedance is zero (tympanogram A). However, in pathologies associated with deterioration of the mobility of the eardrum, auditory ossicles, windows of the labyrinth and other structures, part of the sound energy is reflected. It is considered a criterion for changing the magnitude of acoustic impedance. An impedance meter sensor is hermetically inserted into the external auditory canal, and a sound of constant frequency and intensity, called probing, is fed into the closed cavity.

Three tests are used: tympanometry, static compliance, and acoustic reflex threshold. The first test provides an idea of the mobility of the eardrum and the pressure in the middle ear cavities, the second allows differentiation of the stiffness of the auditory ossicle chain, and the third, based on the contraction of the middle ear muscles, allows differentiation of damage to the sound-conducting apparatus from damage to the sound-perceiving apparatus. The data obtained during acoustic impedancemetry are recorded as different curves on tympanograms.

Acoustic impedancemetry

There are some features that should be taken into account when conducting acoustic impedancemetry in childhood. In children of the first month of life, the study does not present any great difficulties, since it can be carried out during a fairly deep sleep that occurs after the next feeding. The main feature at this age is associated with the frequent absence of the acoustic reflex. Tympanometric curves are recorded quite clearly, although a large spread of the tympanogram amplitude is observed, sometimes they are of a two-peak configuration. The acoustic reflex can be determined from approximately 1.5-3 months. However, it should be taken into account that even in a state of deep sleep, the child makes frequent swallowing movements, and the recording can be distorted by artifacts. This is why studies should be repeated for sufficient reliability. It is also necessary to take into account the possibility of errors in acoustic impedancemetry due to the compliance of the walls of the external auditory canal and changes in the size of the auditory tube during screaming or crying. Of course, anesthesia can be used in these cases, but this leads to an increase in the thresholds of the acoustic reflex. It can be considered that tympanograms become reliable starting from the age of 7 months; they provide a reliable idea of the function of the auditory tube.

In general, acoustic impedancemetry is a valuable method for objectively examining hearing in infants and young children.

The method of recording the potential of the retroauricular muscle also has some advantages: using it, it is possible to do without the use of sedatives and determine hearing loss mainly at low frequencies up to 100 Hz,

The development and introduction into clinical practice of a method for objectively determining auditory evoked potentials using computer audiometry led to a real revolution in the study of hearing in children. Already at the beginning of the 20th century, with the discovery of electroencephalography, it was clear that in response to sound irritation (stimulation), electrical responses (evoked auditory potentials) arise in different parts of the sound analyzer: the cochlea, spiral ganglion, nuclei of the brainstem and the cerebral cortex. However, it was not possible to register them due to the very small amplitude of the response wave, which was less than the amplitude of the constant electrical activity of the brain (beta, alpha, gamma waves).

Only with the introduction of electronic computing technology into medical practice did it become possible to accumulate in the machine's memory individual, insignificant responses to a series of sound stimuli, and then sum them up (total potential). A similar principle is used in objective computer audiometry. Multiple sound stimuli in the form of clicks are fed into the ear, the machine remembers and sums up the responses (if, of course, the child can hear), and then presents the overall result in the form of a curve. Objective computer audiometry allows for hearing testing at any age, even in a fetus from 20 weeks.

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Electrocochleography

To get an idea of the location of the lesion of the sound analyzer, on which hearing loss depends (topical diagnostics), various methods are used. Electrocochleography is used to measure the electrical activity of the cochlea and spiral ganglion. The electrode, with which electrical responses are recorded, is installed in the area of the wall of the external auditory canal or on the eardrum. This is a simple and safe procedure, but the potentials recorded are very weak, since the cochlea is located quite far from the electrode. If necessary, the eardrum is pierced with an electrode and placed directly on the promontory wall of the tympanic cavity near the cochlea, that is, the place of potential generation. In this case, it is much easier to measure them, but such transtympanic ECOG is not widely used in pediatric practice. The presence of spontaneous perforation of the eardrum significantly facilitates the situation. ECOG is a fairly accurate method and gives an idea of the hearing thresholds, helps in the differential diagnosis of conductive and sensorineural hearing loss. Up to 7-8 years of age it is performed under general anesthesia, at an older age - under local anesthesia.

Thus, ECOG gives an opportunity to form an idea of the condition of the hair apparatus of the cochlea and the spiral ganglion. The study of the condition of the deeper sections of the sound analyzer is carried out by determining short-medium and long-latency auditory evoked potentials. The fact is that the response to sound stimulation of each section occurs a little later in time, that is, it has its own more or less long latent period. Naturally, the reaction from the cerebral cortex occurs last and long-latency potentials are precisely their characteristic. These potentials are reproduced in response to sound signals of sufficient duration and even differ in tonality.

The latent period of short-latency - stem potentials lasts from 1.5 to 50 mg/s, cortical from 50 to 300 mg/s. The sound source is sound clicks or short tonal parcels that do not have a tonal coloring, supplied through headphones, a bone vibrator. It is also possible to study using speakers in a free sound field. Active electrodes are placed on the mastoid process, attached to the lobe or fixed at any point on the skull. The study is carried out in a sound-proof and electrically shielded chamber, in children under 3 years old - in a state of drug-induced sleep after the introduction of diazepam (Relanium) or 2% chloral hydrate solution rectally in a dose corresponding to the child's body weight. The study continues on average 30-60 minutes in a lying position.

As a result of the study, a curve is recorded containing up to 7 positive and negative peaks. It is believed that each of them reflects the state of a certain section of the sound analyzer: I - the auditory nerve, II-III - cochlear nuclei, trapezoid body, superior olives, IV-V - lateral loops and superior colliculus, VI-VII internal geniculate body.

Of course, there is a great deal of variability in short-latency auditory evoked potential responses not only in adult hearing studies but also in each age group. The same is true for long-latency auditory evoked potentials - many factors must be taken into account to get an accurate picture of the child's hearing status and the location of the lesion.

Electrophysiological methods for determining auditory function remain the most important, and sometimes the only option for such a study of hearing in neonates, infants and early childhood, and are currently becoming increasingly widespread in medical institutions.

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Acoustic emission

Literally recently, a new method has been introduced into pediatric hearing research practice - registration of delayed evoked acoustic emission of the cochlea. We are talking about extremely weak sound vibrations generated by the cochlea, they can be registered in the external auditory canal using a highly sensitive and low-noise microphone. In essence, this is an "echo" of the sound supplied to the ear. Acoustic emission reflects the functional capacity of the external hair cells of the organ of Corti. The method is very simple and can be used for mass hearing examinations, starting from the 3rd-4th day of a child's life, the study takes several minutes, and the sensitivity is quite high.

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Study of hearing in whispered and spoken language

In older children, starting from 4-5 years old, the same methods are used to examine hearing as in adults. However, even in this case, it is necessary to take into account some of the peculiarities of childhood.

Thus, the examination of hearing in whispered and spoken language is very simple, but it is necessary to follow the exact rules for its implementation in order to obtain a correct judgment about the state of the child's hearing function. Knowledge of this method is especially important for a pediatrician, since it can be carried out independently, and the detection of any hearing loss is already a basis for referral to a specialist. In addition, some features of the psychological nature of children should be taken into account when examining using this method.

First of all, it is very important for the doctor and the child to establish trust, otherwise the child will not answer questions. It is better to make the dialogue a game with the involvement of one of the parents. First, you can address the child and interest him to some extent, for example, with the question: "I wonder if you will hear what I am about to say in a very quiet voice." Usually, children are sincerely happy if they can repeat a word and willingly get involved in the examination process. And, on the contrary, they get upset or withdraw into themselves if they do not hear the words the first time. This is why it is necessary to start examining children from a close distance, and only then increase it. The second ear is usually muffled to prevent overlistening. In adults, everything is simple: a special rattle is used. In children, its use usually causes fear, so muffling is caused by pressing on the tragus and stroking it, it is better for the parents to do this. The words offered for repetition are not arbitrary, since normally, if high phonemes predominate, they are heard better and from a greater distance. From this point of view, it is better to use special tables containing grouped words according to the tonality feature and selected taking into account the interests and intelligence of the child.

The acuity of hearing is determined by the distance from which these words are perceived confidently (high tones up to 20 m in whispered speech, low tones - from 6 m). Words are pronounced thanks to the reserve air (remaining in the lungs after a normal exhalation), to ensure approximately the same sound intensity, many times, until complete repetition.

Hearing examination using whispered and spoken speech with the use of tables composed of words with predominantly low and high tones already gives the doctor some opportunities for differential diagnostics of damage to the sound-conducting and sound-perceiving apparatus. Great opportunities are provided by hearing examination using tuning forks, which is quite accessible to the pediatrician. Tuning forks were invented in the early 18th century as musical instruments. They are sources of pure low or high tone. The classic set of tuning forks makes it possible to examine hearing across the entire audible tone scale from 16 to 20,000 Hz. However, for practical purposes it is quite sufficient to use two tuning forks: low-frequency and high-frequency. A low-frequency tuning fork is used to examine hearing through air (air permeability) and through bone, placing it on the mastoid process (bone conduction). A high-frequency tuning fork is used only to determine hearing through air. This is due to the fact that air conduction is normally twice as long as bone conduction, and high-frequency sounds with low amplitude easily go around the child's head during examination, getting into the other ear (relistening with the second ear). This is why examination of hearing through the bone with a high-frequency tuning fork can give a false positive result. From the age of 4-5, a child understands well what is wanted from him, and usually gives reliable answers. The tuning fork is set in motion by squeezing its branches or by lightly hitting them, the duration of the sound is determined by the data of the tuning fork passport. During the examination, both branches of the tuning fork are placed in the plane of the auricle, to exclude adaptation, it is taken away from time to time and brought back to the ear. A decrease in the duration of perception of a tuning fork with low tones indicates a lesion of sound conduction with high tones - euphony. This is an important conclusion that a doctor can make. However, the use of a tuning fork (T) to perceive it through air and bone significantly expands our capabilities in this regard.

To better understand the complex relationship between air and bone conduction, it is necessary to remember the following: if a child has difficulty hearing sound during air conduction, this may be due to two options. First: if there are diseases that disrupt sound conduction (cerumen plug, perforation of the eardrum, rupture of the auditory ossicle chain, etc.). However, if the sound-conducting apparatus is preserved and conducts sound well, and only the receptor cells are damaged (the second option), the result will be the same: the child will have poor hearing, air conduction is shortened.

Thus, a decrease in air conduction may indicate damage to the sound-conducting or sound-perceiving apparatus.

The situation is different with bone conduction. There are practically no diseases accompanied by a decrease in bone conduction, therefore shortening of bone conduction can only be associated with damage to the sound-perceiving apparatus. Thus, the value of bone conduction is a characteristic of the state of the receptor function. Based on these concepts, it is easy to understand the Rinne experiment, in which air and bone conduction are compared. Normally, a child hears through air approximately twice as well as through bone, for example, through air - 40 sec, and through bone - 20 sec, this is designated as a positive Rinne. Shortening of perception through air (for example, by 30 sec) while maintaining its perception through bone (or even some lengthening) indicates damage to the sound-perceiving apparatus (Rinne becomes negative). Simultaneous shortening of bone and air conduction indicates a disease of the sound-perceiving apparatus (Rinne remains positive). Now the Schwabach experiment is also understandable, in which the bone conduction of a child and a doctor is compared (naturally, if the latter has normal hearing). The "shortened" Schwabach indicates damage to the sound-perceiving apparatus. These experiments are easily accessible for a pediatrician to conduct and can provide fundamentally important information about the state of the child's hearing for the future.

Pure Tone Threshold Audiometry

Tone threshold audiometry is the main method of hearing examination in adults. In childhood, it can be used from about 5 years of age. The purpose of audiometry is to determine thresholds, i.e. the minimum sound intensity that the patient perceives. These studies can be conducted over the entire audible frequency range (usually from 125 to 8000 Hz) and thus, as a result of the subject's responses, obtain a complete quantitative (in dB) and qualitative (in Hz) characteristic of hearing loss for each ear separately. These data are recorded graphically in the form of curves (audiograms). The study is best conducted in a sound-proof chamber or a quiet room using special devices - audiometers. Depending on the goals (practical, research), they can be of varying degrees of complexity. For applied tasks, a study using screening, polyclinic and clinical audiometers is quite sufficient. They are used to determine bone and air conduction.

Of course, it is good when a child placed in a sound-proof chamber (an unfortunate, but unfortunately generally accepted term) behaves calmly. However, this is far from always the case, and is often accompanied by fear. That is why it is better to place him there together with one of the parents or an assistant. The room for hearing testing should have a homely appearance, pictures, toys. Sometimes it is recommended to conduct hearing testing on several children at the same time, this calms them down.

It is better to conduct audiometry in the morning, soon after breakfast; the examination usually begins with determining the hearing in the better-hearing ear. However, in capricious children with severe hearing loss, it is sometimes necessary to examine the worse-hearing ear first. For adults, the determination of the hearing function begins with small subthreshold intensities. It is better for children to initially give an intense tone, and then gradually reduce it to the threshold, so they better understand the task of the examination.

Air conduction thresholds are determined by feeding sound through headphones. When examining bone conduction, a special vibrator is placed on the mastoid process. Accurate determination of bone conduction is complicated by the fact that the sound reaches both labyrinths through the bones of the skull, and some sounds also enter the external auditory canal. With a large difference in hearing, cross-listening with the better hearing ear may occur, and the doctor receives false data. To eliminate this, the better hearing ear is muffled, as if masking it with a specially supplied intense noise. This must be done to exclude serious diagnostic errors that distort the overall picture of the child's hearing. The data obtained during tonal audiometry are recorded on the audiogram using generally accepted symbols: right ear (o-o-o), left ear (x-x-x), air conduction by a solid line, and bone conduction by a dotted line.

In addition to tonal audiometry, if necessary, studies such as suprathreshold, speech and ultrasound audiometry can also be used in childhood.

Tone audiometry determines the weakest sound that a hearing-impaired person begins to hear. If the sound is gradually and further increased, most patients will note the same gradual increase in perception. However, some patients suddenly experience a sharp increase in volume at some level. Thus, when talking to a hearing-impaired person, he often asks for phrases to be repeated, but suddenly, with a slight increase in voice, he says: "You don't need to shout like that, I can hear everything anyway." In other words, these patients experience an accelerated increase in volume, and this phenomenon is called the phenomenon of accelerated increase in volume. This phenomenon occurs in patients with local damage to the hair apparatus of the cochlea. It is of great diagnostic importance, and should be especially taken into account when selecting hearing aids. Modern audiometers are usually equipped to conduct suprathreshold tests.

Speech audiometry

Speech audiometry is an advanced method of research using whispering and spoken language. Its special advantage is the nature of the research. After all, speech perception is one of the main ones for the intellectual development of a child. That is why speech audiometry has found wide application as a prognostic method for the work of a teacher of the deaf, in hearing-improving operations, selection of hearing aids, re-education, etc.

Individual words or phrases are transmitted from a tape recorder via headphones or room-mounted speakers (free sound field). The child repeats the text transmitted to him into the microphone, and the doctor records the responses. The following parameters are usually determined: the threshold of sound detection (in dB), the threshold of initial speech intelligibility (20% of words are normal at an intensity of 25 dB); 100% of words are usually understood at 45 dB. As we have already mentioned, speech tables are recorded on the tape recorder, including some words or phrases selected from acoustically homogeneous sounds.

These tables are not always applicable for examining hearing in hard-of-hearing and deaf children, since the vocabulary of such children is significantly poorer. For them, there is a specially selected dictionary and phrasal material, accessible for understanding by a hard-of-hearing child.

Thus, speech audiometry has the following advantages over conventional research of whispered and spoken speech: the text and diction of the researcher are constant, the volume of the speech can be adjusted, and hearing loss can be determined not in meters, but in decibels.

In some cases, ultrasound audiometry can be used after the age of 6-7. Research by Russian scientists has shown that the ear perceives sound not only in the range of the audible spectrum up to 20,000 Hz, but also much higher, but only through the bone. Preservation of such a reserve of the cochlea, not detected on a regular audiogram, indicates some prospects for hearing aids, as well as hearing-improving operations (otosclerosis). For most children, the upper limit of hearing is not 200 kHz, but only 150 kHz.

Modern electrophysiological methods of hearing examination, similar to ultrasound, are used not only in otolaryngology, but also to a large extent by neurologists, neurosurgeons and other specialists. They play an important role in topical diagnostics of intracranial pathology: in tumors of the brainstem and temporal lobe, brainstem encephalitis, temporal epilepsy, etc.