what are the causes of secretory otitis media and secretory otitis media
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The main causes of secretory otitis media are mechanical obstruction and functional ventilation dysfunction
The etiology is not completely clear. At present, it is believed that it is mainly related to eustachian tube dysfunction, infection and immune response.
1. Eustachian tube dysfunction is generally considered as the basic cause of this disease.
(1) Mechanical obstruction: such as adenoid hypertrophy, hypertrophic rhinitis, nasopharyngeal tumor or lymphoid tissue hyperplasia in children, long-term nasopharyngeal tamponade, etc.
(2) Dysfunction: muscle contraction of Eustachian tube opening and closing is weak; Eustachian tube cartilage has poor elasticity. When the tympanum is in a negative pressure state, the wall of Eustachian tube cartilage is prone to collapse, which is one of the anatomical and physiological bases for the high incidence of secretory otitis media in children. Cleft palate patients are prone to this disease because their muscles have no midline attachment point and lose their contraction function.
2. Infection in the past, secretory otitis media was considered aseptic inflammation. In recent years, it has been found that about 1/2-1/3 of the patients with positive bacterial culture in middle ear effusion, among which the main pathogenic bacteria are Haemophilus influenzae and Streptococcus pneumoniae. The results of bacteriological and histological examination and clinical signs indicate that secretory otitis media may be a mild or low toxic bacterial infection of the middle ear. Bacterial product endotoxin may play a role in the pathogenesis, especially in the process of chronic lesions.
3. Immune response the immune system of children is not fully developed, which may be one of the reasons for the high incidence of secretory otitis media in children. The presence of inflammatory mediators such as prostaglandins in middle ear effusion, specific antibodies and immune complexes of bacteria, complement system and lysosomal enzymes have also been detected in middle ear effusion, suggesting that chronic secretory otitis media may be a pathological process mediated by anti-infection immunity. The damage of soluble immune complex to middle ear mucosa (type III allergy) may be one of the pathogenic causes of chronic secretory otitis media.
When Eustachian tube dysfunction occurs, external control cannot enter the middle ear, and the original gas in the middle ear is gradually absorbed by mucosa, resulting in relative negative pressure in the cavity, which causes venous dilation and congestion in the middle ear mucosa, enhances the permeability of blood vessel wall, and leaks in the tympanic cavity. If the negative pressure can not be lifted, a series of pathological changes may occur in the middle ear mucosa, mainly showing epithelial thickening, epithelial cell metaplasia, low pseudostratified columnar epithelium in the front of tympanum becoming thickened ciliated epithelium, monolayer flat epithelium in the back of tympanum becoming pseudostratified columnar epithelium, and goblet cells increasing; Hypersecretion, formation of pathological glands under the epithelium, round cell infiltration around the lamina propria blood vessels, mainly lymphocytes and plasma cells. During the recovery period of the disease, the glands gradually degenerated, the secretions decreased, and the mucosa gradually returned to normal.
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