Sensorineural (sensorineural) hearing loss: causes and pathogenesis

Hearing disorders can be acquired and congenital.

[1]

Acquired causes of sensorineural hearing loss

In the emergence of acquired neurosensory hearing loss, numerous clinical observations and scientific studies have proved the role:

• infectious diseases (influenza and SARS, infectious parotitis, syphilis, etc.);
• cardiovascular disorders (hypertension, vertebral-basilar dyskirculation, cerebral atherosclerosis);
• stressful situations;
• ototoxic effects of industrial and household substances, a number of medications (antibiotics of the aminoglycoid series, some antimalarial and diuretics, salicylates, etc.);
• injuries (mechanical and acoustic, barotrauma).

Infectious nature accounts for about 30% of neurosensory deafness and deafness. In the first place are viral infections - influenza, mumps, measles, rubella, herpes, followed by epidemic cerebrospinal meningitis, syphilis, scarlet fever and typhus. The pathology of the organ of hearing in infectious diseases is localized mainly in the receptor of the inner ear or the spiral node of the cochlea.

Vascular-rheological disorders can also lead to deafness development. Changes in vascular tone due to direct or reflex stimulation of the sympathetic nerve endings of large arteries (internal carotid, vertebral), as well as impaired blood circulation in the vertebrobasilar pool lead to a blood circulation disorder in the arterial labyrinth system, the formation of thrombi, hemorrhages in the zodo- and perilymphatic spaces.

One of the most important causes of neurosensory hearing loss is still intoxication, they occupy 10-15% in the structure of the causes of neurosensory hearing loss. Among them, the first place is occupied by ototoxic drugs: antibiotics of the aminoglycoside series (kanamycin, neomycin, monomycin, gentamicin, amikacin, streptomycin) cytostatics (cyclophosphamide, cisplatin, etc.) antiarrhythmic drugs; tricyclic antidepressants; diuretics (furosemide, etc.). Under the influence of ototoxic antibiotics, pathological changes occur in the receptor apparatus of the cochlea, the vessels.

In some cases, the cause of hearing loss is trauma. Mechanical trauma can lead to fracture of the base of the skull with a crack in the pyramid of the temporal bone, often accompanied by damage to the auditory root of the VIII cranial nerve. Possible causes - barotrauma (average pressure yxe above 400 mm Hg), fracture of the base of the stapes with the formation of perilymphatic fistula. Acoustic and vibration injuries at the level of the maximum permissible parameters lead to the destruction of receptors in the cochlea. The combination of both factors gives an unfavorable effect in 25 wounds more often than exposure to noise and vibration alone. High-frequency impulse noise of high intensity causes, as a rule, irreversible sensorineural hearing loss.

The decrease in hearing, which is due to physiological aging, has received the name Presbyacusis. Usually age-related changes in hearing, if they do not combine with hearing loss of another origin, are symmetrical in relation to both ears. Presbyacusis is a multifaceted and versatile process that captures all levels of the auditory system, conditioned by the biological processes of aging and under the influence of the social environment. To date, different authors identify several types of presbybicus in the topic of hearing damage; sensory, metabolic, presbyacusis as a consequence of defeat of auditory neurons, cochlear, cortical.

Among other causes of neurosensory hearing loss, neuroma VIII of the cranial nerve, Paget's disease, sickle-cell anemia, hypoparathyroidism, allergy, local and general exposure to radioactive substances should be noted. A significant role is played by the meteorological factor: a connection is observed between the suddenly occurring sensorineural hearing loss and the weather condition, between the variations in the spectrum of atmospheric electromagnetic waves, the passage of cyclones in the form of a warm low-pressure front, and the frequency of pathology development. It was found that acute sensorineural hearing loss often occurs in the second month of each season (January, April, July, October).

[2], [3], [4], [5], [6], [7]

Congenital causes of sensorineural hearing loss

Among congenital neurosensory hearing impairments, hereditary causes and pathology in labor are distinguished. Under the pathology in childbirth, as a rule, hypoxia of the fetus, leading to CNS and hearing damage, is implied. Heritable causes are diverse. Nonsindromal hearing damage is not associated with either visible anomalies of the external ear, nor with other diseases, but they can be associated with anomalies of the middle and / or inner ear. Syndromic hearing damage is associated with congenital malformations of the ear or other organs. More than 400 genetic syndromes, including hearing loss, are described. Syndromic hearing damage accounts for up to 30% of pre-speech deafness, but their contribution to all cases of deafness is relatively small, since the frequency of post-auditory hearing loss is significantly higher. Syndromal hearing loss is presented according to the types of inheritance. Below are the most common types.

Autosomal-dominant hearing syndrome

The syndrome of Waardenburg is the most common form of autosomal dominant hearing loss syndrome. It includes sensorineural hearing loss of various degrees and pigment abnormalities of the skin, hair (white strand), and the eye (iris heterochromia). Branhyotorenal syndrome includes conductive, sensorineural or mixed hearing loss in combination with bronchial cystic clefts or fistulas, congenital malformations of the external ear, including preauricular points and renal anomalies. The syndrome of the Stickler is a simtomocomplex of progressive sensorineural hearing loss, cleft palate and spondyloepiphysic dysplasia with outcome and osteoarthritis. Neurofibromatosis type II (NF2) is associated with a rare, potentially curable type of deafness. Marker NF2 is a hearing loss secondary to bilateral vestibular neuroma.

[8], [9], [10], [11], [12], [13], [14], [15]

Autosomal recessive syndrome hearing damage

Usher syndrome is the most common form of autosomal recessive syndrome hearing loss. Includes damage in two primary sensory systems.

People suffering from this disease are born with neurosensory hearing loss, then pigment retinitis develops. Pendred's syndrome is characterized by congenital severe neurosensory hearing loss and euthyroid goiter. Jervell and Lange-Nielsen syndrome includes congenital deafness and lengthening of the Q-T-interval on the ECG, Biotinidase deficiency is caused by a deficiency of biotin, a water-soluble B-complex of vitamin. Because mammals can not synthesize biotin, they must receive it from food sources and an endogenous cycle of free biotin. If this deficiency is not recognized and is not corrected by the daily addition of biotin to the food, the affected people develop neurological signs and sensorineural hearing loss. Disease of Refsum includes severe progressive sensorineural hearing loss and retinitis pigmentosa caused by impaired metabolism of phytic acid.

[16], [17], [18], [19], [20]

X-linked syndrome hearing damage

Alport syndrome includes progressive neurosensory hearing loss of varying severity, progressive glomerulonephritis leading to the terminal stage of kidney disease, and various manifestations on the part of the organ of vision.

Pathogenesis of sensorineural (sensorineural) hearing loss

With the development of acquired sensorineural hearing loss, a number of consecutive stages are distinguished: ischemia, circulatory disorders, death (due to intoxication) of sensory cells of the inner ear and nerve elements of the conducting path of the auditory analyzer. Congenital genetic disorders are the cause of congenital neurosensory hearing loss.