Description

Infection of the mastoid air cells characterized clinically by protrusion of the pinna and erythema/tenderness over the mastoid process; can range from an asymptomatic illness to a severe life-threatening disease. Acute mastoiditis is defined as the presence of symptoms for <1 month. Masked mastoiditis is a persistent middle ear and mastoid infection with bony destruction.

Epidemiology

• Most patients are between 6 and 24 months old.
• It is unusual to see mastoiditis in young infants because of incomplete pneumatization of the mastoid air cells.

Risk Factors

• Age <2 years of age
• Acute otitis media
• Recurrent otitis media

General Prevention

• Appropriate treatment of otitis media and timely follow-up to identify treatment failures
• Avoid factors that predispose to otitis media, including caretaker smoking and bottlefeeding.
• Pneumococcal vaccination may help decrease the occurrence of otitis media.
• Delayed antibiotic treatment for antecedent otitis media does not increase the risk of more severe mastoiditis.

Pathophysiology

• The mastoid process is the posterior portion of the temporal bone and consists of interconnecting air cells that drain superiorly into the middle ear. Because these mastoid air cells connect with the middle ear, all cases of acute otitis media 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 but spreads to the mastoid.
• Acute mastoiditis can progress to a coalescent phase after the bony air cells are destroyed and may then progress to subperiosteal abscess or to chronic mastoiditis.

Etiology

• Acute mastoiditis is generally caused by an extension of the inflammation and infection of acute otitis media into the mastoid air cells. However, 20–50% of patients may present without evidence of preceding otitis media.
• The bacteria isolated from middle ear drainage or from the mastoid are usually Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus. Many patients’ cultures are sterile which may be related to antibiotic use prior to retrieval of fluid.
  • S. pneumoniae is the most frequently isolated cause of mastoiditis. Isolates highly resistant to penicillin has decreased since the introduction of the 13-valent pneumococcal vaccine.
  • Pseudomonas infection should be suspected if the child has been on antibiotics recently or has a history of recurrent otitis media.
• Chronic mastoiditis is usually caused by S. aureus, anaerobic bacteria, enteric bacteria, Pseudomonas aeruginosa, or multiple-organism infection.
• 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.
• Cholesteatomas may contribute to the development of mastoiditis by impeding mastoid drainage or erosion of underlying bone.