Causes of Mastoiditis
Causes of Mastoiditis primarily stem from untreated or poorly managed ear infections, especially otitis media. Mastoiditis is a serious bacterial infection of the mastoid bone behind the ear. The mastoid bone contains air cells that help balance middle ear pressure and drain fluid. When these air cells get infected or filled with fluid, mastoiditis can develop. This often leads to pain and may cause life-threatening complications.
The causes of mastoiditis involve multiple factors, including infection pathways, underlying conditions, anatomical issues, and risky behaviours. Understanding these factors helps doctors diagnose early and plan effective treatment.
Bacterial Middle Ear Infections (Otitis Media)
The most common direct cause of mastoiditis is acute otitis media, a bacterial infection of the middle ear. If untreated, the infection can spread to the mastoid bone through the aditus ad antrum, a small connection between the middle ear and mastoid air cells. This spread causes swelling, inflammation, and bone damage.
Common bacteria causing otitis media and mastoiditis include:
- Streptococcus pneumoniae
- Haemophilus influenzae
- Streptococcus pyogenes (Group A strep)
- Moraxella catarrhalis
- Pseudomonas aeruginosa (chronic cases)
- Staphylococcus aureus, including MRSA (hospital cases)
These bacteria often follow a viral upper respiratory infection. They thrive in fluid behind the eardrum and can move into the mastoid if left untreated.
Inadequate or Delayed Treatment of Ear Infections
Delayed or incomplete treatment of ear infections is another major cause. Some infections resolve with antibiotics, but stopping early or resistance allows bacteria to persist. This can let the infection reach the mastoid.
Limited access to healthcare or underestimating the infection severity increases risk, especially in children.
Chronic Otitis Media
Chronic otitis media, especially with cholesteatoma (skin growth in the middle ear), can also cause mastoiditis. These infections linger for weeks or months, slowly eroding bone. Cholesteatomas damage the mastoid through infection and pressure, making them high-risk factors.
Congenital or Structural Abnormalities
Some people are born with ear canal or Eustachian tube abnormalities, which cause fluid buildup and repeated infections. Children’s shorter, horizontal Eustachian tubes make them more prone to mastoiditis.
Other anatomical contributors include:
- Cleft palate or craniofacial syndromes
- Nasal polyps blocking drainage
- Enlarged adenoids compressing the Eustachian tube
Upper Respiratory Tract Infections
Colds or flu can indirectly cause mastoiditis. URTIs often affect the Eustachian tube, causing poor middle ear ventilation and fluid buildup. This creates a breeding ground for bacteria. Though URTIs don’t directly cause mastoiditis, they can start a chain of events leading to it.
Immunocompromised Conditions
People with weakened immune systems—HIV/AIDS, cancer treatment, diabetes, or long-term steroids—have higher mastoiditis risk. Their bodies may not fight simple ear infections, allowing the infection to spread. Chemotherapy or radiation can damage tissues and drainage, worsening the risk.
Trauma or Surgical Intervention
Ear trauma or previous ear surgery, like tympanostomy tube placement, may lead to mastoiditis. Surgical procedures or injuries can introduce bacteria into the middle ear or mastoid. Even minor trauma, such as aggressive ear cleaning, can allow bacteria to spread. Eardrum perforations create direct bacterial entry points.
Nosocomial (Hospital-Acquired) Infections
Mastoiditis may develop as a hospital-acquired infection in patients already in hospital. ICU stays or ventilator-associated pneumonia may expose patients to bacteria resistant to standard antibiotics, increasing the risk of mastoiditis.
Environmental and Behavioural Factors
Lifestyle and environmental factors can influence mastoiditis risk:
- Exposure to cigarette smoke, especially second-hand in children
- Frequent swimming in non-chlorinated or contaminated water
- Poor hygiene or inserting objects into the ear
Age as a Risk Factor
Children under two are most prone to middle ear infections due to immature immune systems and ear anatomy. Because mastoiditis often follows these infections, age is an indirect risk factor. Adults can develop mastoiditis too, but severity increases with age due to delayed recognition and other health problems.
In summary, the causes of mastoiditis involve many interconnected factors. Untreated or poorly managed ear infections are the main cause, but anatomical differences, immune problems, environmental exposures, and prior ear trauma or surgery also contribute. Early recognition and management of these causes reduce the incidence and severity of mastoiditis.
