INTRODUCTION	Section 2 of 10
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Background: Before the use of antibiotics, acute mastoiditis was the most common complication of acute otitis media (AOM). Antibiotic treatment of AOM has decreased the incidence of acute mastoiditis.

Mastoiditis has been classified into 2 types: classic and latent. Classic mastoiditis is a term used to refer to acute disease following AOM. Latent, or masked mastoiditis, refers to a more chronic disease, which can be subclinical, often secondary to partial treatment of AOM with antibiotics.

Anatomy/development

The mastoid at birth consists of one cell, the antrum, located in the petromastoid part of the temporal bone. The tympanic cavity of the middle ear is connected with the antrum by a small canal. Soon after birth, mastoid air cells develop within the antrum. By age 2 years, small mastoid processes form, giving the mastoid a honeycomb appearance.

Pathophysiology: Mastoiditis develops when middle ear inflammation spreads to the mastoid air cells, resulting in infection and destruction of the mastoid bone.

Complications of mastoiditis occur when inflammation extends through the antrum and into the posterior cranial fossa, the middle cranial fossa, the canal of the facial nerve, the sigmoid and lateral sinuses, and the petrous tip of the temporal bone. Extension of local disease can cause significant morbidity and life-threatening disease.

Frequency:

• In the US: The incidence of mastoiditis from AOM is 0.004%. Prior to the 1980s, the reported incidence was 0.4%.

• Internationally: Incidence in other developed countries is similar to that of the United States. Developing countries and countries that do not treat uncomplicated AOM with antibiotics have a higher incidence of mastoiditis, presumably resulting from untreated otitis media.

  For example, the incidence rate of acute mastoiditis in the Netherlands, with a low antibiotic prescription rate for AOM, is reported as 3.8 cases per 100,000 person-years. In all other countries with very high antibiotic prescription rates, incidence was considerably lower, ranging from 1.2-2 cases per 100,000 person-years.

Mortality/Morbidity: Although mastoiditis is rare, significant morbidity and mortality can arise. Morbidity consists of the following:

• Hearing loss

• Extension of the infectious process beyond the mastoid system, resulting in either intracranial complications or extracranial complications

Sex: Mastoiditis occurs equally in males and females.

Age:

• The incidence of mastoiditis parallels that of otitis media, affecting mostly young children and peaking in those aged 6-13 months.

• Mastoiditis is reported in both healthy and immunocompromised adults and adolescents.

	CLINICAL	Section 3 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

History: Mastoiditis has been classified into 2 types: classic and latent. Classic mastoiditis is a term used to refer to acute disease following AOM. Latent or masked mastoiditis refers to a more chronic disease, which can be subclinical, often secondary to partial treatment of AOM with antibiotics.

• Classic mastoiditis

• Recent or concurrent episode of AOM

• Otalgia and pain behind the ear, sometimes accompanied by a tender mass

• Fever

• Latent and/or masked mastoiditis

• Recurrent or chronic otitis media

• Recurrent pain

• Nonspecific symptoms (most commonly observed in infants)

• Poor feeding

• Irritability

Physical:

• Signs of classic mastoiditis are as follows:

• Bulging erythematous tympanic membrane

• Erythema, tenderness, and edema over the mastoid area

• Postauricular fluctuance

• Protrusion of the auricle

• Signs of latent mastoiditis are as follows:

• May have no external signs of mastoid inflammation

• Infected or normal-appearing tympanic membrane

• Recurrent or persistent fever

• The neurologic examination is usually nonfocal. However, cranial nerve involvement is possible with advanced disease.

• Abducens (VI) nerve palsy

• Pain from involvement of the ophthalmic branch of the trigeminal nerve

• Facial (VII) nerve palsy

Causes: The organisms that cause mastoiditis are those most commonly associated with bacterial otitis media, although mastoid cultures are often sterile after prior antibiotic treatment.

• Streptococcus pneumoniae (22%)

• Haemophilus influenzae (4%): Nontypeable H influenzae is isolated less commonly than is expected from its incidence in AOM.

• Moraxella (Branhamella) catarrhalis

• Streptococcus pyogenes (16%)

• Pseudomonas aeruginosa (4%, although prevalence is as high as 25% in some recent studies): This organism is increasing in incidence, especially internationally. However, the reason why children with recurrent AOM seem to be the most at risk is unclear.

• Gram-negative organisms (other than Pseudomonas): These are found more frequently in chronic mastoiditis, in more virulent infections, and in young infants. This may be due to prolonged antibiotic therapy as well as a different spectrum of organisms causing infection in infants.

• Staphylococcus species (7%)

• Mycobacterium species (rare)

• Aspergillus fumigatus and other fungi (rare)

• Risk factors

• Cholesteatoma is an infected cyst in the middle ear that usually occurs as a complication of chronic otitis media. It is treated surgically.

• Recurrent AOM

• Immunocompromised host