Mastoid cells are small, air-filled spaces inside the skull bone behind the ear. They are part of a bony structure called the mastoid. They connect to the middle ear and play an important role in ventilation and pressure balance inside the ear.
Structure and location in the skull
Behind the ear there is a bony bump called the mastoid. You can feel it easily by running your finger behind your earlobe. Inside this section of bone sit the mastoid cells. These are not cells in the biological sense. They are many small, connected chambers. Thin walls of bone separate these air-filled spaces from one another. They connect to the middle ear through a passage called the mastoid antrum.
Function of the mastoid cells
Mastoid cells make sure the middle ear stays well ventilated and that pressure inside the ear remains balanced. They act like a kind of air cushion, absorbing pressure changes that can happen when flying, diving, or moving quickly to a different altitude. They also help reduce the overall weight of the skull bone without losing any of its strength.
What does it mean when mastoid cells are mentioned in a report?
The term mastoid cells often appears in doctor's letters, radiology reports, or after an ear examination. In most cases, it simply describes the normal anatomy of the ear. Sometimes the phrase "ventilated mastoid cells" is used, which means the small spaces are filled with air as they should be, a sign that things in the ear are healthy.
If changes are described, such as "opacification" or "obstruction" of the mastoid cells, this can point to inflammation or another problem. In such cases, the connection to the middle ear is often affected, which can happen with a middle ear infection.
Mastoid cells and the middle ear
Mastoid cells are closely connected to the middle ear. Together with the tympanic cavity, they form one shared air-filled system. In healthy people, this system is well ventilated. If inflammation develops in the middle ear, it can spread to the mastoid cells. When this happens, it is called mastoiditis. This condition is rare today because middle ear infections are usually treated early.
How are mastoid cells examined?
Imaging methods are used to assess the mastoid cells, mainly a CT scan or MRI scan of the skull. On these images, the air-filled spaces can be seen clearly. Radiologists then describe whether the mastoid cells are normally ventilated, opacified, or changed in some way. Normal ventilation is a sign of healthy conditions in the ear area.
When changes are found
Not every change in the mastoid cells means there is a disease. During colds, allergies, or after a middle ear infection, temporary changes can occur, for example when the spaces are no longer fully filled with air. A closer look is only needed when further symptoms appear, such as pain, fever, or hearing loss. In many cases, things return to normal on their own once the cause, such as an infection, has cleared up.
Further information about the mastoid
Mastoid cells are an important but usually unremarkable part of the ear. They keep pressure balanced and the middle ear well ventilated. Changes are often temporary and rarely a cause for concern. If you are unsure about a report, it helps to discuss the findings with a medical professional.
