What is the most common cause of mastoiditis?

Mastoiditis is primarily a complication of ear infections, particularly chronic otitis media. This condition arises when bacteria from the middle ear penetrate the mastoid air cells located in the mastoid part of the temporal bone, leading to inflammation and infection of the mastoid process.

Chronic otitis media, which involves persistent inflammation or infection of the middle ear, is a direct pathway that allows pathogens to migrate to the mastoid region. As the infection in the middle ear persists, it can cause the surrounding bony structure, such as the mastoid, to become infected, resulting in mastoiditis.

Other conditions listed, such as chronic sinusitis, acute otitis externa, and nasal infections, are less commonly associated with mastoiditis. While they may lead to upper respiratory or ear issues, they do not directly cause the mastoid infection as frequently as chronic otitis media does. Thus, recognizing chronic otitis media as the most common precipitating factor for mastoiditis is crucial in understanding the underlying mechanisms of these infections.