All about hearing impairment

Hearing impairment - loss of the ability to distinguish between whispering speech and sounds with low amplitude. Permanent hearing loss is referred to as hearing loss, and the severity ranges from mild to very severe. If the auditory analyzer is unable to perceive sounds with a frequency of less than 90 dB, complete deafness is diagnosed, which can be eliminated by surgery or by installing a hearing aid.

The degree of hearing loss is determined in the course of audiometric studies, the essence of which is to determine the threshold of sensitivity of the auditory receptors. In the absence of pathologies, a person perceives speech and sounds at frequencies from 0 to 25 dB. If the sound-sensing system detects sound signals in the range of 25 dB or more, hearing loss is diagnosed.

Types of hearing impairment

Persistent hearing impairment, the causes and classification of pathological changes are determined during an audiometric examination of a patient complaining of the development of auditory dysfunction in one or both ears. The type of hearing loss depends on which department the pathological processes are located in. According to the physiological and anatomical features of the structure of the auditory analyzer, there are two main sections:

1. sound-conducting - provides the transmission of a sound signal from the outside to the receptor system through the main sections of the middle and outer ear;
2. sound-perceiving - transforms the energy of ambient sounds into nerve impulses, which is due to the modulation of physical oscillations of waves in the main parts of the ear cochlea, subcortical centers and nerve cells.

In the context of this classification, the development of auditory dysfunction may be due to:

• violations in the sound-conducting department;
• violations in the sound-perceiving department;
• combined disorders in both departments.

To determine the type of hearing loss, specialists conduct subjective audiometric studies, during which they determine the level of audibility of bone and air-conducted signals. Thus, it is possible to establish in which of the departments of the auditory analyzer disorders occur, due to which the type of hearing loss and the subsequent principles of treatment are determined.

Classification

Partial auditory dysfunction is determined by the inability of the auditory analyzer perceive and process sound signals of low frequency and amplitude. The modern classification of hearing impairments indicates which pathologies in the auditory system provoked the development of hearing loss:

• conductive - appear due to blocking of the sound signal at the level of the sound-receiving section of the auditory analyzer and are characterized by the formation of physical barriers in the form of granulations, transudate, ear plugs, etc.;
• neural - the inability of specific parts of the brain to process nerve impulses coming from the auditory analyzer; with the development of auditory dyssynchrony, electrical impulses can be misinterpreted, which is the cause of audiological hallucinations;
• sensory - appear when hair cells die, which leads to the impossibility of processing sound signals in the ear labyrinth;
• sensorineural - due to the occurrence of disorders at the level of hair cells and the processing of electrical impulses in the corresponding parts of the brain;
• combined - a mixed type of hearing loss, characterized by a combination of sensorineural and conductive disorders.

With the development of sensorineural pathologies, it is almost impossible to restore the ability to hear sounds in the range of up to 25 dB.

Causes of auditory dysfunction

What are the main causes of hearing impairment? Hearing dysfunction can be congenital or acquired. Its development is due to a number of exogenous and endogenous factors leading to the emergence of pathologies at the level of sound-perceiving and sound-conducting departments in the auditory analyzer.

Experts include the following among the main causes of congenital hearing impairment:

• hereditary predisposition;
• non-hereditary genetic characteristics;
• abnormally low birth weight;
• transfer of jaundice in the neonatal period;
• asphyxia at birth and difficult childbirth;
• the use of ototoxic drugs by the expectant mother.

It is possible to eliminate auditory dysfunction only in the case of a normal structure of the main parts of the auditory analyzer in a newborn.

Most often, auditory dysfunction is observed in older patients and is due to the following reasons:

• infectious lesion of the nasopharynx;
• chronic inflammation in the ears;
• abuse of cytostatics and antibiotics;
• serious trauma to the base of the skull;
• age-related degeneration of sensory cells;
• exposure to strong noise;
• regular listening to audio devices with headphones.

Most often, auditory dysfunction develops against the background of irrational and untimely treatment of meningitis, rubella, influenza and measles.

Degrees of hearing loss

Hearing impairment is the inability to perceive sound signals with a frequency of up to 25 dB. However, the degree of development of hearing loss depends on what frequency oscillations are perceived and processed by the main parts of the hearing organ. In this regard, an international classification of hearing impairment arose, which describes 4 degrees of development of auditory dysfunction:

• 1 degree (weak) - the ability to perceive sound vibrations with a frequency above 25-40 dB;
• 2nd degree (medium) - the ability to perceive sound vibrations of average intensity with a frequency of more than 41-55 dB;
• Grade 3 (severe) - the ability to perceive sound vibrations of high intensity with a frequency of 56-70 dB;
• Grade 4 (very severe) - the ability to perceive sound vibrations of very high intensity with a frequency of more than 71-90 dB.

Important! With a noticeable hearing loss, you need to be examined by a specialist. If the death of hair cells is not stopped in time, it will not be possible to restore auditory function even after surgical treatment.

If the patient has difficulty in perceiving sound signals over 90dB, he is diagnosed with deafness. Hearing can be partially restored only after undergoing a course of medical and surgical treatment.

Genetic disorders

Conventionally, the main hearing impairments of a genetic nature are divided into two categories: syndromic and isolated (non-syndromic). Syndromic disorders occur mainly in conjunction with the influence of exogenous factors, such as infectious ENT diseases. In medical practice, it is customary to distinguish between several main syndromes of auditory dysfunction:

• Usher's syndrome - the simultaneous development of visual and auditory dysfunction;
• Jervell's syndrome - the development of hearing loss against the background of cardiac arrhythmia with the occurrence of a long QT interval;
• Waardenburg's syndrome - the appearance of malfunctions in the auditory analyzer, associated with increased pigmentation;
• Pendred's syndrome - persistent hearing loss against the background of thyroid hyperplasia.

It should be noted that the types of hearing impairment largely depend on which gene was damaged in the course of mutational changes. According to experts, more than 100 genes are known today, damage to which inevitably leads to permanent hearing loss. In about a third of cases, genetic auditory dysfunction is due to mutations in the 35delG or GJB2 gene.

Diagnostics

At the slightest hearing loss, experts recommend being examined by an otolaryngologist. Timely elimination of the reasons for the development of hearing loss contributes to the complete or partial restoration of hearing without the use of hearing aids and cochlear implants. To determine the degree of hearing loss and the sensitivity threshold of hair cells, the patient must undergo the following types of examination:

1. tuning forks;
2. tonal audiogram;
3. otoneurological analysis;
4. registration of auditory potentials;
5. impedance measurement;
6. computed tomography;
7. Doppler ultrasound.

After accurately determining the form of hearing impairment, the specialist will prescribe pharmacological or physiotherapeutic treatment using drugs that improve the blood supply to the tissues in the hearing organ, eliminate inflammation and accelerate regeneration processes. At the stage of irreversible morphological changes in soft and bone tissues, surgical intervention may be required, involving the replacement of deformed auditory ossicles, implantation of a cochlear implant, etc.

Reason for contacting an ENT doctor

The reason for the development of persistent hearing loss, which is difficult to respond to pharmacological treatment, is the delay in seeking help from a specialist. You can not postpone a visit to the otolaryngologist if you find the following symptoms:

• noise in ears;
• a sensation of fluid overflow in the ear;
• recurrent ear pain;
• painful sensations on palpation;
• fuzzy perception of whispered speech.

The presence of auditory dysfunction is evidenced by constant requests to repeat the phrases just said by the interlocutors or insufficiently clear recognition of the voice on the phone when talking on the street. If these symptoms occur, it is advisable to undergo an audiometric examination by a specialist.