DESCRIPTION

Mastoiditis is an infection of the mastoid air cells, which are part of the temporal bone and are contiguous with the middle ear cavity. It is most often a sequela of acute otitis media (AOM). If untreated, it can lead to life-threatening complications, including intracranial infections.

• Acute mastoiditis is defined as the presence of symptoms for <1 month.
• Chronic mastoiditis is defined as the presence of symptoms for >1 month, usually with chronic ear drainage and hearing loss.
• Subacute (or masked) mastoiditis is an insidious infection of the mastoid without classic signs or symptoms, usually after a course of antibiotics for AOM.

EPIDEMIOLOGY

• Most patients are <24 months old.
• Incidence varies in the literature, from ~1 to 6/100,000 children per year.
• Although some reports suggest that mastoiditis is on the rise, larger population-based studies demonstrate a stable incidence.

ETIOLOGY

• Bacterial causes of acute mastoiditis closely mirror those of AOM: Streptococcus pneumoniae (most common), Streptococcus pyogenes, and Staphylococcus aureus.
  • S. pneumoniae isolates that are highly resistant to penicillin have decreased since the introduction of the 13-valent pneumococcal vaccine.
  • Many cultures are sterile, which may be due to antecedent antibiotic use.
• Chronic mastoiditis is usually caused by S. aureus, anaerobic bacteria, enteric bacteria, Pseudomonas aeruginosa, or multiple-organism infection.
• Pseudomonal infection should be suspected if the child has been on antibiotics recently or has a history of recurrent otitis media.
• Fusobacterium necrophorum should be considered in younger children and those with complications such as osteomyelitis, bacteremia, and Lemierre syndrome.
• Unusual agents of chronic mastoiditis include Mycobacterium tuberculosis, nontuberculous mycobacteria, Nocardia asteroides, and Histoplasma capsulatum.

RISK FACTORS

• Age <2 years of age
• Recent or current AOM (>50% of patients have evidence of a preceding otitis media.)

GENERAL PREVENTION

• Appropriate treatment of otitis media and timely follow-up are necessary to identify treatment failures.
• Avoid factors that predispose to otitis media, including passive smoke exposure and bottlefeeding while lying flat.
• Pneumococcal vaccination may help decrease the occurrence of otitis media.

PATHOPHYSIOLOGY

• The mastoid process is the posterior portion of the temporal bone and consists of interconnecting air cells that drain into the middle ear. Because these mastoid air cells connect with the middle ear, all cases of AOM are associated with some mastoid inflammation.
• Acute mastoiditis develops when the accumulation of purulent exudate in the middle ear does not drain through the eustachian tube or through a perforated tympanic membrane and instead spreads to the mastoid.
• Cholesteatomas may contribute to the development of mastoiditis by impeding mastoid drainage or erosion of underlying bone.