Otitis Media: Anatomy, Pathophysiology, Risk Factors, Types of OM, Symptoms and Treatment, Animation

(USMLE topics) Middle ear infection: anatomy, pathophysiology, risk factors, types of OM, symptoms and treatment.

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Otitis media is inflammation or infection of the middle ear. The middle ear is the cavity between the tympanic membrane - the eardrum, and the oval window of the inner ear. Its function is to amplify sound vibrations of the eardrum and transmit them to the inner ear. The middle ear is linked to the upper throat by the auditory tube, or eustachian tube. The tube helps equalizing air pressures between the middle ear and the outside atmosphere. It also drains mucus secretion from the middle ear into the throat.
The eustachian tube is usually closed, opening only when the person is yawning, swallowing, or chewing. When atmospheric pressure changes rapidly, causing a sudden feeling of fullness in the ear, such as during airplane travel, these activities can be done on purpose to open the tube, allowing air passage to equalize the pressure.
Otitis media develops when the eustachian tube is blocked, commonly as a result of upper respiratory tract infections or allergies. Mucus builds up in the middle ear, creating an environment for bacteria or viruses to grow.
Otitis media can occur at any age, but it is most common in small children, whose Eustachian tube is narrower and more horizontal. The tube opening mechanism in children is also less efficient due to the angle between the tube and the muscle acting on it. Children also have larger adenoids - the pads of lymphoid tissue located near the opening of Eustachian tubes. Adenoid swelling may block the tube’s opening.
Other risk factors include exposure to smoking, male gender, family history, pacifier use, bottle feeding, and attending a daycare center.
There are several types of otitis media:
Acute otitis media is an infection that develops suddenly. Fluid and pus accumulate inside the ear. The tympanic membrane appears red and bulging. Patients typically experience fever and ear pain. In some cases, the eardrum may rupture and the ear may drain.
Chronic suppurative otitis media is an infection that doesn't go away, or occurs repeatedly. Tympanic membrane perforation and ear drainage are common features. Hearing is usually impaired.
Otitis media with effusion is when fluid continues to accumulate in the middle ear even after the initial infection subsides. Patients may experience a feeling of fullness and impaired hearing, but there are no signs of infection. When fluid remains for an extended period of time, or returns repeatedly, the condition is known as chronic otitis media with effusion.
The primary complication of ear infections is eardrum rupture, which heals spontaneously in most cases, without the need for surgical repair. Untreated recurrent or chronic infections may lead to hearing loss, speech and language development delay, and rarely, infection spread to surrounding tissues, including the brain.
Treatment of acute otitis media includes pain medications and possibly antibiotics. Because the majority of ear infections resolve without antibiotic treatment, children with mild symptoms are usually observed for 48 hours before antibiotics are prescribed.
For cases with prolonged effusion, a tiny tube may be placed in the eardrum to help drain the fluid. The tube usually falls out on its own after some time as the incision closes.