Deafness

Deafness is such hearing disorder at which the person cannot hear in general, or degree of a hearing impairment is so strong that perception of sounds of the speech becomes impossible.

Hearing physiology

The acoustic organ consists of the sound carrying out and sound perceiving parts. Each its component in the course of evolution is adapted for the best performance of the tasks. For example, the shape of an auricle of the person allows to catch better sounds, and acoustical pass improves quality of carrying out a sound.

In a structure of the acoustic analyzer it is possible to allocate:

• Outside ear (auricle, outside acoustical pass);
• Middle ear (tympanic membrane, acoustical stones, drum cavity);
• Inner ear (snail, semicircular channels, кортиев body);
• Receptors;
• Conduction paths;
• Cortical department in a brain.

Sounds which we hear are mechanical oscillations of airspace. They cause fluctuations of a tympanic membrane in an inner ear which resonates them with own frequency. Further transfer of fluctuations is carried out by means of acoustical stones (a hammer, an anvil and a stirrup) and liquid (endolymph) in a labyrinth of an inner ear. The hairs of a kortiyev of body which are in this liquid (in fact they are sensory cells) turn oscillatory mechanical waves into acoustical nervous impulse which further on nerve fibrils is transferred in a brain.

Deafness reasons

Now it is authentically known that reasons of deafness there can be a set.

Hearing disorder can arise from constant noise at work (a so-called, noise injury), after the postponed otitis (an ear inflammation), meningitis (an inflammation of a meninx) or toxic influence on an acoustical nerve of antibiotics from group of aminoglycosides. Scarlet fever, respiratory viral and some other infectious diseases can become the reason of deafness. The injury of a temporal bone can cause disturbance of a structure of an acoustic organ or integrity of an acoustical nerve and, as a result of it is deafness.

Types of deafness

Completely hearing is absent quite seldom. Much situations when residual audibility remains meet more often, and the person is capable to distinguish very loud speech or some of its frequencies. These states are called relative deafness. Accurately it is difficult to differentiate definitions of relative deafness and deafness, and it depends on a research method.

If the person lost hearing still before learned to speak, then he can remain a deaf-mute.

By origin allocate the following types of deafness:

• Hereditary (passes from father to son, it is connected with chromosomal disturbances);
• Inborn (appeared at an adverse effect on a fruit during its pre-natal development or at the time of delivery);
• Acquired (as a result of age changes of an acoustic organ, diseases, injuries, toxic influence of some medicines, etc.).

In the place of damage of the acoustic analyzer allocate neurosensory and conductive deafness. Neurosensory deafness arises if formation of acoustical impulses, their carrying out or perception in a brain is broken. Disturbances of functions of the carrying-out device of the acoustic analyzer (are the reason of deafness of conductive type at ear injuries, an otosclerosis, etc.).

Deafness is also classified by extent of decrease in hearing.

Inborn deafness

The hearing organogeny at an embryo begins with the 5th week of the pre-natal period. On the 20th week of pregnancy future child already has an inner ear, on maturity degree comparable with the adult. Since the same time the kid in a maternal womb begins to distinguish sounds of different intensity and frequency.

Inborn deafness develops because of pathological influence of some factors on a fruit and damages of components of the acoustic analyzer. Extent of decrease in hearing as a result can widely vary – from full deafness (occurs at 0,25% of newborns) before its insignificant decrease.

Among the reasons of inborn deafness most often note infections (generally viral, for example, measles, a rubella, flu), toxic influence of medicines which are accepted by mother during pregnancy (streptocides, aminoglikozidny antibiotics and others). In emergence of a number of cases of inborn deafness toxic influence of alcohol is scientifically proved.

Detection of deafness

The doctor-audiologist deals with problems of a hearing disorder though at first patients most likely will ask for the help the otolaryngologist.

Deafness can develop suddenly or gradually, is quite imperceptible for the person. Complaints to deafness demand carrying out additional methods of inspection. Modern techniques and the exact equipment allow to estimate objectively degree of deafness and the remains of hearing.

Hearing disorder has to be revealed as soon as possible after the birth because the level of development of the child and extent of his adaptation, and also a possibility of recovery of the hearing aid depends on it.

Already in the neonatality period in many maternity hospitals the screening research is conducted by special audiometers of acoustical function of all children. Audioscreening is carried out before an extract from maternity hospital by specially trained employee. It is bystry, painless and absolutely safe method of detection of inborn deafness. At adults carrying out perhaps audiometriya the speech.

Treatment of deafness

Hearing to a large extent influences quality of human life therefore at incomplete deafness its correction using the hearing aids strengthening sounds is possible. It is so-called electro-acoustic correction.

Medicamentous methods of treatment of deafness are ineffective, the plastics or endoprosthesis replacement most often is required.

Recently in treatment of deafness hearing aid using the special electrodes implanted in an inner ear (cochlear implantation) is used. Intensively the surgery of an inner ear develops at the microscopic level (a tympanoplasty, a stapedoplasty, etc.).

Corrections give in most often conductive types of deafness.