Middle-ear infection

Anatomy or system affected: Auditory system, ears

Also known as: Acute otitis, otitis media

Definition

An infection of the middle ear occurs when the middle ear, which is located behind the eardrum, becomes infected and inflamed.

Causes

A middle-ear infection is caused by bacteria such as Streptococcus pneumoniae (most common), Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and S. pyogenes (less common). Viruses that cause middle-ear infections include those associated with the common cold.

Risk Factors

The factors that increase the chance of developing a middle-ear infection include a recent viral infection (such as a cold); recent sinusitis; day care attendance; medical conditions that cause abnormalities of the eustachian tubes, such as cleft palate; Down syndrome; history of allergies (environmental allergies and food allergies); gastroesophageal reflux disease (GERD); and exposure to secondhand smoke from cigarettes, cooking, and burning wood. Also at higher risk are infants and toddlers, infants whose mothers drank alcohol while pregnant, and infants who are formula-fed. Middle-ear infections are most common in the winter months.

Infants and toddlers. Three-quarters of children will experience an ear infection before their third birthday, and nearly one-half of these children will have three or more infections by age three years. Although adults can get ear infections, children between the ages of six months and six years are the most prone to ear infections. The risk of ear infections is higher in children because their immune systems have had less exposure to common viruses. Virus infections are, most likely, the direct or indirect cause of most middle-ear infections. Moreover, children’s shorter eustachian tubes (the small channels that let air pass from the nose into the middle ear) make it easier for bacteria to gain access to the middle ear. Larger adenoids in some children also contribute to the development of ear infections. Boys are probably more likely to get otitis, especially chronic otitis media, than are girls.

Day care attendance. Children in day care or in nursery schools are more likely to get ear infections because they are exposed to more upper respiratory infections that can subsequently infect the middle ear. While day care is a necessary fact of life for many children, it is also one of the strongest risk factors for ear infection.

Exposure to cigarette smoke. Children who live with adults who smoke cigarettes are more likely to develop ear infections.

Poverty. While ear infections are common in persons from all levels of income, they tend to be more frequent and more prolonged in poor children, who often lack adequate health care.

Breast-feeding. Infants who are breast-fed, especially for four to six months or longer, have fewer and shorter ear infections than do bottle-fed infants.

Other infections. Children are more likely to get an ear infection if they have a cold, sore throat, or eye infection. Although ear infections are not themselves contagious, colds, sore throats, and other respiratory infections are readily passed from person to person.

Allergies and asthma. People with allergies or asthma are more likely to develop ear infections. The reasons for this increased risk remain incompletely understood.

Immune suppression. Children with immune disorders, including acquired immunodeficiency syndrome (AIDS), and those receiving immunosuppressive therapy are more likely to develop ear infections because their bodies fight bacteria and viruses less effectively. The occurrence of an ear infection, or even multiple ear infections, is not itself an indication of AIDS or another immune disorder.

Congenital conditions. Medical conditions that cause abnormalities of the eustachian tubes, such as cleft palate, increase the risk of developing ear infections.

Drinking from a bottle while lying down. Children who drink from a bottle while lying on their backs are more likely to develop ear infections, possibly because fluid is allowed to accumulate in the eustachian tubes.

Pacifier use. Children who use pacifiers continually may be at greater risk for developing ear infections than children who use them less frequently or not at all.

Family history. A strong family history of ear infections, especially in older brothers or sisters, also increases risk.

Symptoms

Ear infections frequently develop during or shortly after another infection, such as a cold or sore throat. Symptoms include ear pain (children who can talk may say that their ear hurts, while babies may tug or rub at the ear or face or become irritable); drainage from the ear, which may appear as blood, clear fluid, pus, or dry crust on the outer portion of the ear after sleeping; hearing loss, which resolves with appropriate treatment; fever; irritability; decreased appetite or difficulty feeding; disturbed sleep; difficulty with balance, frequent falling, or sensations of dizziness; nausea, vomiting, or diarrhea; malaise (a feeling of general illness); chills; and inattentiveness.

Some children with ear infection, particularly chronic otitis, have no symptoms. Their condition may be discovered on examination for some other problem.

Screening and Diagnosis

When there is ear pain or drainage from the ear, then infection is likely present. If a child is too young to report pain, the doctor or nurse practitioner must rely solely on looking into the child’s ear with a special lighted instrument (an otoscope). A small tube and bulb (insufflator) may be attached to the otoscope so that a light puff of air can be blown into the ear. This helps the health care provider see if the eardrum is moving normally. When infection is present the eardrum is often stiffened by the presence of fluid behind it and does not move. The eardrum may also be red and bulge outward because the fluid behind it is under pressure. A red, bulging drum that does not move with an air puff is a good sign that acute otitis is present.

It is often difficult to see the eardrum in young children, and ear wax frequently makes getting a good view of the drum difficult. Even in the absence of wax, the accurate diagnosis of middle-ear infection using an otoscope is not easy. Most studies suggest that even experienced doctors may overdiagnose acute ear infections, especially if an air puff insufflator is not used. Doctors may have a particularly difficult time distinguishing between children with chronic otitis (who frequently do not need antibiotics) and those with acute otitis (for whom antibiotics are often helpful). The use of a microscope to examine the ear may also help.

Other tests may also be performed, especially if the parent or child has had repeated ear infections. Tests may include the following:

Tympanocentesis. A needle is used to withdraw fluid or pus from the middle ear under local or general anesthesia. This fluid can then be cultured to determine if bacteria are present in the fluid. Once the bacteria are cultured, the lab can determine what drugs are best for treatment. However, the fluid does not always have bacteria.

Tympanometry. A soft plug is inserted into the opening of the ear canal. The plug contains a speaker, a microphone, and a device that is able to alter the air pressure in the ear canal. This allows several different measures of the middle ear and eardrum and provides important information about the condition of the ear, but it is not a hearing test.

Hearing test. A hearing test may be ordered for persons with repeated ear infections or with signs of hearing impairment, such as speaking in a louder voice, sitting closer to a television, or turning up the volume of a television or stereo.

Treatment and Therapy

Treatments include antibiotics that are commonly used to treat ear infections. These include amoxicillin (Amoxil, Polymox) and clavulanate (Augmentin). Other medications are cephalosporins (cefprozil, cefdinir, cefpodoxime, and ceftriaxone) and sulfa drugs (such as Septra, Bactrim, and Pediazole).

Because bacteria develop a resistance to antibiotics, doctors may take a “wait and see” approach before writing a prescription. In some cases, the doctor may prescribe an antibiotic for children and ask the parent to administer the medication if the pain or fever lasts for a certain number of days. This approach has been effective. Some ear infections are caused by a virus and thus cannot be treated with antibiotics. Most middle-ear infections (including bacterial infections) tend to improve on their own in two to three days.

Over-the-counter pain relievers, which can help reduce pain, fever, and irritability, include acetaminophen, ibuprofen, and aspirin. Aspirin is not recommended for children or teens with a current or recent viral infection because of the risk of Reye’s syndrome. One should consult the doctor about medicines that are safe for children. Decongestants and antihistamines are not recommended to treat an ear infection.

In children, ear drops that have a local anaesthetic (such as ametocaine, benzocaine, or lidocaine) can help decrease pain, especially when the drops are used with oral pain relievers. If there is a chance that the eardrum has ruptured, one should avoid using ear drops. Another treatment option is myringotomy, surgery to open the eardrum. A tiny cut is made in the eardrum to drain fluid and pus.

Prevention and Outcomes

To reduce the chance of getting an ear infection, one should avoid exposure to smoke and should breast-feed for the first six months or so of an infant’s life and should try to avoid giving the infant a pacifier. If the infant is bottle-fed, his or her head should be propped up as much as possible. One should not leave a bottle in the crib with the infant.

Other preventive measures include getting tested for allergies, treating conditions such as GERD, practicing good hygiene, and ensuring children’s vaccinations are up to date. The pneumococcal vaccine and the flu vaccine can prevent middle-ear infections. If the child has a history of ear infections, one should consult the doctor about long-term antibiotic use. Another option for the child is the use of tympanostomy tubes, which help equalize pressure behind the eardrum. Large adenoids can interfere with the eustachian tubes. The child’s doctor should be consulted about having the adenoids removed.

Key Terms: Middle-Ear Infections

• Cholesteatoma: A tumor-like mass of cells that usually results from chronic middle-ear infection.
• Eardrum: The membrane separating the outer ear canal from the middle ear that changes sound waves into movements of the ossicles; also called the tympanic membrane.
• Eustachian tube: The tube connecting the middle ear to the back of the throat; air exchange through this tube equalizes air pressure in the middle ear with outside air pressure.
• Labyrinth: A structure consisting of three fluid-filled, semicircular canals at right angles to one another in the inner ear; they monitor the position and movement of the head.
• Middle ear: The air-filled cavity in which vibrations are transmitted from the eardrum to the inner ear via the ossicles.
• Ossicles: Three small bones in the middle ear that transmit vibrations from the eardrum to the fluid of the inner ear.
• Otoscope: An instrument for viewing the ear canal and the eardrum.
• Tympanic membrane: Another term for the eardrum.

Bibliography

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