Mastoiditis is an infection affecting the mastoid bone, located directly behind the ear. This condition involves inflammation of the air cells within this bone. While less common today due to widespread antibiotic use, mastoiditis can become serious if left untreated. Prompt treatment is important to prevent the infection from spreading.
Common Bacterial Causes
The majority of mastoiditis cases stem from bacterial infections, typically those that originate in the middle ear. The most frequently identified bacterial culprits include Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Streptococcus pyogenes. Streptococcus pneumoniae is particularly common, often being the most frequently isolated pathogen in acute mastoiditis.
Haemophilus influenzae is another significant bacterium found in mastoiditis, particularly in children, though its incidence has decreased due to vaccination efforts. Moraxella catarrhalis, while a common cause of middle ear infections, is less frequently reported as the sole cause of mastoiditis, suggesting it may lead to milder forms of the disease. Staphylococcus aureus and Streptococcus pyogenes (also known as Group A Streptococcus) are also identified in a notable percentage of mastoiditis cases.
The Path to Mastoiditis
Mastoiditis almost always develops as a complication of an acute middle ear infection, known as otitis media, that has gone untreated or been inadequately treated. The middle ear cavity is directly connected to the mastoid air cells, which are small, honeycomb-like air-filled spaces within the mastoid bone. When an infection takes hold in the middle ear, bacteria can spread into these contiguous mastoid air cells.
As the infection extends into the mastoid, it causes inflammation and the accumulation of fluid and pus within these air cells. The unique porous, honeycomb-like structure of the mastoid bone makes it susceptible to infection. Persistent infection can lead to a process called coalescent mastoiditis, where the bony walls separating the air cells are destroyed, forming larger abscess cavities filled with infected material. This destruction of bone, known as osteitis, can further complicate the condition.
Other Potential Causes
While bacteria are the primary cause of mastoiditis, other factors can rarely contribute to or mimic the condition. In uncommon instances, fungal infections may lead to mastoiditis, particularly in individuals with weakened immune systems. These fungal pathogens are not typical causes for the general population.
Viral infections might also play a rare role, though they are not common direct causes of mastoiditis. Additionally, a condition called cholesteatoma, an abnormal skin growth in the middle ear, can block drainage and contribute to mastoiditis, even without a primary bacterial infection. These non-bacterial causes are significantly less frequent.