Mastoiditis: causes and pathogenesis

Causes of mastoiditis

In secondary mastoiditis, the infection in the cellular structure of the mastoid process predominantly occurs in the otogenic manner with acute or chronic otitis media. In the case of primary mastoiditis, a direct traumatic lesion of the cellular structure of the mastoid process occurs in the case of bumps, bruises, gunshot wounds, exposure to the blast wave, fractures and fissures of the skull bones, including fractures of the skull base, hematogenous metastatic pathogenesis of septicopyemia, from the lymph nodes of the region of the mastoid process to the bone tissue; isolated lesion of the mastoid process in specific infections (tuberculosis, infectious granulomas). The microflora with mastoiditis is quite diverse, but the coccal flora prevails.

Pathogenesis of mastoiditis

The course of mastoiditis depends on the type and virulence of the microflora, the state of immunity, the changes in the ear as a result of previous diseases, the state of the nasal cavity and the nasopharynx. Inadequate drainage of the suppurative focus in the middle ear (with chronic epitymitis due to the high location of the marginal perforation, with an insignificant amount of perforation of the tympanic membrane or its closure by granulation, delayed drainage of the tympanic cavity associated with a delay in spontaneous perforation of the tympanic membrane or paracentesis; airway system of the middle ear due to the closure of the communication between the cells, antrum and the drum cavity inflamed and thickened mucous membrane). In traumatic mastoiditis due to the formation of cracks and fractures, the relationships between the airway cavity system are modified, multiple fractures of the thin bone septa occur, small bone fragments are formed and special conditions are created for the spread of the inflammatory process. Spilled blood with bone damage represents a favorable environment for the development of infection with subsequent melting of bone fragments.

Distinguish the following stages of the development of the inflammatory process in the mastoid process with mastoiditis.

• Exudative. The first 7-10 days of the disease continue, with the inflammation of the mucous (endostal) cover of the cells of the mastoid process - the so-called "internal periostitis of the mastoid process" (according to MF Tsytovich). As a result of mucosal edema, the apertures of the cells close, the cells are disconnected with the mastoid cave, and the communication of the mastoid cave with the tympanic cavity is also disturbed. The cessation of ventilation of the cave and the cells of the mastoid process leads to a thinning of the air with expansion and blood filling of the vessels followed by transudation. The cells of the mastoid process fill the inflammatory serous-purulent or purulent exudate. In this case, a lot of closed empyema is formed in the mastoid process. On the roentgenogram at this stage of inflammation, the septa between the veiled cells are still distinguishable.
• Proliferative-alterative (true mastoiditis). We are usually formed on the 7th-10th day of the disease (children develop much earlier). There is a combination of parallel productive (development of granulations) and destructive (melting of the bone with the formation of lacunae) changes. These changes simultaneously occur not only in the bone walls, but also in the bone marrow spaces and in the vascular canals. The gradual resorption of bone tissue leads to the destruction of bone septa between the cells of the mastoid process: separate disintegrated groups of cells form which, merging, form different sizes of cavity, filled with pus and granulation, or one large cavity.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]