This editorial illustration was created for a September 2013 cover of American Family Physician. The image summarizes Otitis Media, infection of the middle ear. Although several subtypes of otitis media are distinguished, the term is often used synonymously with acute otitis media. It is very common in childhood. An integral symptom of acute otitis media is ear pain; other possible symptoms include fever, and irritability (in infants). Since an acute otitis media is usually precipitated by an upper respiratory tract infection, there often are accompanying symptoms like cough and nasal discharge.
The common cause of all forms of otitis media is blockage of the Eustachian tube. This is usually due to swelling of the mucous membranes in the nasopharynx, which in turn can be caused by a viral upper respiratory infection or by allergies. Because of the blockage of the Eustachian tube, the air volume in the middle ear is trapped and parts of it are slowly absorbed by the surrounding tissues, leading to a mild vacuum in the middle ear. Eventually the vacuum can reach a point where fluid from the surrounding tissues is sucked in to the middle ear’s cavity (also called tympanic cavity), causing middle ear effusion. This is seen as a progression from a Type A tympanogram to a Type C to a Type B tympanogram.
By reflux or suction of material from the nasopharynx into the normally sterile middle ear space, the fluid may then become infected – usually with bacteria. In rare cases, however, the virus that caused the initial upper respiratory tract infection can itself be identified as the pathogen causing the infection in the middle ear.
Acute otitis media (AOM) is usually developing on the basis of a (viral) upper respiratory infection with blockage of the Eustachian tube and effusion in the middle ear, when the fluid in the middle ear gets additionally infected with bacteria. The most common bacteria found in this case are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.
As its typical symptoms overlap with other conditions, clinical history alone is not sufficient to predict whether acute otitis media is present; it has to be complemented by visualization of the tympanic membrane.
To confirm the diagnosis, middle ear effusion and inflammation of the eardrum have to be identified; signs of these are fullness, bulging, cloudiness and redness of the eardrum. Viral otitis may also result in blisters on the external side of the tympanic membrane, which is called bullous myringitis (myringa being Latin for “eardrum”). However, sometimes even examination of the eardrum may not be able to confirm the diagnosis, especially if the canal is small and there is wax in the ear that obscures a clear view of the eardrum. Also, an upset child’s crying can cause the eardrum to look inflamed due to distension of the small blood vessels on it, mimicking the redness associated with otitis media.