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Otosclerosis: causes and pathogenesis
Last reviewed: 23.04.2024
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Causes of otosclerosis
The cause of otosclerosis is not established. Among the numerous theories of the onset of the disease, the effect of inflammation and infection is distinguished.
Recent studies have identified a provoking role for measles virus in patients with a genetic predisposition to otosclerosis. Elevated IgG peaks, specific for measles virus antigens, were observed in perilymph patients. These antigens are also isolated immunohistochemical methods from the active otosclerotic focus, but the actual value of the virus in the development of the disease is not established.
There is a hereditary theory of otosclerosis. His gene is not exactly defined, in some studies the place of his search is limited to chromosome 15q25-26, in others the appearance of the disease is associated with the state of the gene COL1A1, responsible for the synthesis of collagen. Participation in the onset of otosclerosis of autoimmune processes was confirmed, but their significance was not finally determined.
Pathogenesis of otosclerosis
Histologically, the otosclerotic focus is a region of newly formed bone with an irregular structure with numerous vascular spaces. Areas of high activity are more common in otosclerosis foci in young patients. Activation of otosclerotic processes occurs under the influence of various endogenous and exogenous factors, including surgical trauma of the "immature" focus. With age, the number of active foci decreases. The centers of otosclerosis can be single and multiple, limited and diffuse, as a rule, symmetrical. They are found in a capsule of cochlea in 35%, semicircular canals in 15%, in the area of the cochlea in 40% of cases of "histological" otosclerosis. Massive lesion of the base of the stapes, detectable intraoperatively, occurs in 10-40% of patients, Often the foci are located in the window area of the vestibule. Localization otoskleroticheskogo focus on the edge of the window vestibule with the involvement of the ring-shaped ligament and the legs of the stapes leads to ankylosis of the latter and the development of conductive hearing loss (conductive form of otosclerosis). The formation of an otosclerotic focus in the staircase of the labyrinth leads to the development of hearing loss with a neurosensory component (cochlear or mixed otosclerosis).
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