Mastoiditis is an inflammation within the mastoid bone, which is the bone immediately behind the ear. Mastoiditis is usually caused by an infection.

What is going on in the body?

Inflammation that starts in the mastoid itself is quite rare. Mastoiditis is almost always caused by an infection in the middle ear, which is behind the eardrum. Because the mastoid is close to the middle ear, it is easy for middle ear infections, such as acute otitis media, to spread to the mastoid. Chronic or long-lasting mastoiditis lasts for more than 3 months. Acute or shorter-lasting mastoiditis lasts less than 3 weeks.

What are the causes and risks of the disease?

The main cause of acute mastoiditis is untreated or incompletely treated middle ear infection, or acute otitis media. The main cause of chronic mastoiditis is a perforated eardrum combined with a long-lasting infection in the middle ear, known as chronic otitis media. Benign ear growths, particularly cysts known as cholesteatomas, are also frequent causes.