Mastoiditis is a serious bone infection that begins in the mastoid bone behind the ear, often resulting from untreated middle ear infections. Early diagnosis and treatment are crucial to prevent complications such as hearing loss, abscess formation, or spread of infection to nearby structures.
Mastoiditis is an infection of part of the bone behind your ear — the mastoid or “mastoid process” of the temporal bone. In most cases, it stems from a middle ear infection (otitis media). The middle ear shares tissue with the mastoids, making it possible for the infection to spread, causing inflammation and possibly damage to the bone. Because children are more prone to ear infections, it’s more common for them to develop mastoiditis.
To understand mastoiditis, it helps to also understand where the mastoid bone is located and a bit about the anatomy of the ear.
Your skull is made up of multiple bones held together by fibrous tissue. Mastoids (or mastoid processes) are part of the skull’s temporal bone, which surrounds the middle ear. The mastoids are cone-shaped projections at the bottom of the temporal bone — you can easily feel them where they curve behind your ears.
Mastoids are not solid bones. They have a structure similar to honeycomb, with pockets of air called “mastoid air cells.” As mentioned above, there is tissue that lines both the middle ear and the mastoids — specifically the mastoid air cells.1 With that connection in mind, it’s easy to understand how infection can spread from the middle ear to the mastoids. While middle ear infections can spread to the mastoids, not every ear infection will result in mastoiditis. With prompt medical treatment, middle ear infections can be cured before they spread.
There are two types of mastoiditis, and the main difference is how long each lasts.
Mastoiditis can happen on either the left or right side of your head; the location doesn’t change anything about how it’s treated. It can happen on one side at a time, but can also be bilateral, meaning it occurs on both sides at the same time. However, bilateral mastoiditis is relatively rare, and in adults, is mostly found in people with diabetes or compromised immune systems.2
Mastoiditis symptoms usually show up after a middle ear infection, typically within a few days or a week. If you have a middle ear infection, it’s important to get that treated by a medical professional, but it’s still a good idea to keep an eye out for signs of the early stages of mastoiditis, which include:
The most common cause of mastoiditis is a middle ear infection, particularly one that goes untreated for too long or is completely untreated. These infections can be either viral or bacterial — a doctor will need to make the specific diagnosis to treat it appropriately.
While it’s far less common, mastoiditis without ear infection is possible. It can potentially be caused by cholesteatoma, which is an abnormal growth of skin in the middle ear. That extra skin can prevent proper drainage of fluids from the middle ear and lead to mastoiditis.
Mastoiditis diagnosis is usually done through an examination. Your physician will talk to you about your symptoms, do a physical exam and look in your ears. Other tests and scans will help give your doctor information about the spread or complications of the infection. Ear cultures (testing fluid extracted from the ear) are sometimes used to help find out the exact bacteria that’s causing the infection. This helps your physician understand which medications can be used to treat it.
In cases of mastoiditis, radiology is especially useful because it gives physicians a visual of what’s happening behind the eardrum. A couple of types of scans might be used:
● CT scan: “Computerized axial tomography,” better known as a CT or CAT scan, is a type of complex X-ray that shows bones, soft tissues and blood vessels. For mastoiditis, CT scans of the ear and/or the head are usually the first choice.
● MRI : “Magnetic resonance imaging” uses radio waves and powerful magnets to create detailed images of soft tissues. In the case of mastoiditis, MRI can help show the spread of fluid. It’s also an option that avoids exposing patients to radiation, but it takes much longer than a CT scan.
Mastoiditis treatments start with medicines to help knock out the infection. If there are complications, or in the case of chronic mastoiditis, additional treatment might be necessary.
Drug therapy used in the treatment of mastoiditis includes a variety of antibiotics, depending on the exact nature of the infection. Doctors may move quickly to get you started on antibiotics and make adjustments once results from an ear culture identify the specific bacteria causing the problem.
For treating mastoiditis, medical procedures might be relatively minor or more intensive, depending on how severe the infection is and how much it has spread.
An otolaryngologist, also known as an ENT, who specializes in ear, nose and throat conditions, should treat mastoiditis. An ENT surgeon would perform a mastoidectomy.
If you see signs of a middle ear infection, it’s important to go to a healthcare professional quickly. Getting it treated quickly can prevent mastoiditis from developing. However, if you have been treated for a middle ear infection and still develop symptoms of mastoiditis, you should be seen again as soon as possible, as the complications can be serious.
1 Sahi D, Callender KD. Mastoiditis. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560877/.
2 Samantha Honner, Raphael M. Kudela, Ethan Handler. Bilateral Mastoiditis from Red Tide Exposure. The Journal of Emergency Medicine,Volume 43, Issue 4, 2012, Pages 663-666. ISSN 0736-4679. https://doi.org/10.1016/j.jemermed.2010.06.007.
