Mastoiditis is an inflammatory process of the mastoid air cells in the temporal bone.
Because the mastoid is contiguous to the middle ear cleft and an extension of it, virtually all children or adults with acute otitis media (AOM) and most individuals with chronic middle ear inflammatory disease have mastoiditis. In most cases, symptoms involving the middle ear (eg, fever, pain, conductive hearing loss) predominate, and the disease in the mastoid is not considered a separate entity.
In some patients, the infection spreads beyond the mucosa of the middle ear cleft, and osteitis in the mastoid air-cell system or periosteitis of the mastoid process develops, either directly by means of bone erosion through the cortex or indirectly via the emissary vein of the mastoid. These patients are considered to have acute mastoiditis (also called acute surgical mastoiditis [ASM]), which is an intratemporal complication of otitis media.
Mastoiditis can be acute, subacute or chronic.
Acute mastoiditis is divided into acute mastoiditis with periosteitis (incipient mastoiditis), characterized by purulence in the mastoid cavities; and coalescent mastoiditis (acute mastoid osteitis), characterized by effacement of the bony septae between the mastoid air cells. This can lead to abscess formation cavity and the dissection of pus into surrounding areas.
Subacute mastoiditis (masked mastoiditis) is persistent and low-grade ear and mastoid infection that causes bony septae destruction.
Chronic mastoiditis is a prolonged mastoid air cell suppurative infection lasting months to years. Chronic mastoiditis most commonly is associated with chronic suppurative otitis media (CSOM) and, in particular, with cholesteatoma formation.