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James W. Lucarini, MD FACS

The middle ear is an air space behind the ear drum that houses the three ear bones-the "hammer" or malleus, the "anvil" or incus, and the "stirrup" or stapes (see figure 1). When sound travels down the ear canal it vibrates the eardrum and sets in motion the connected middle ear bones. Finally, the bones transmit the sounds into the nerve endings of the inner ear or cochlea, where the signals of sound are sent to the brain. The brain then interprets between sounds as diverse as the chirping of birds, the blast of a firecracker, or the communication of human speech.

Figure 1 The anatomy of the human ear

Infections of the middle ear are quite common in children and account for more visits to pediatricians than any other cause. Today middle ear infections are diagnosed two to three times more commonly than 25 years ago. Subsequently, the use of antibiotics and other treatments has increased substantially. This may be in part due to an increased awareness of the condition by practitioners. However, changing lifestyle changes, such as the increased reliance on day care, may actually be increasing the frequency of the problem. Middle ear infections happen most often between six and eighteen months of age. Children who have had few problems with such infections by age three are unlikely to encounter future episodes.

Children with frequent infections early in life pose two problems. First, there are the repeated illnesses and possible complications from the infections themselves. Back and forth visits to the pediatrician, fevers, awakenings in the middle of the night, and a constantly irritable child can put physical and emotional strain on the entire family. Unusual but potential complications include infection of the mastoid space behind the ear, infections around the brain, and infections causing permanent inner ear hearing loss and dizziness. Second, some relatively mild but prolonged ear infections can produce enough temporary hearing loss to affect development of speech and language. In many ways this second condition can lead to even more profound, long-term educational problems for the affected children. Detection, treatment and prevention of middle ear infections are the cornerstones of proper care and avoidance of such consequences.

Causes and Risks

Bacteria and viruses can lead to infection in the middle ear space. The organisms get into the space through a tube that links the middle ear to the back of the nose (see figure 2). Problems with the angle, shape, and size of this so-called "Eustachian tube" are thought to lead to repeated infections. We know that heredity plays a role in determining how the Eustachian tube works early in life. Many children with frequent infections have siblings with similar problems. As the Eustachian tube grows and matures, it develops a sharper downward angle and a larger opening. This helps mucus that builds up during colds to drain into the nose. Changes in air pressure are also more easily adjusted and oxygen can enter the middle ear. These changes affect how well bacteria can grow since the organisms thrive on the "sugar" of middle ear mucus and the lower oxygen levels.

Certain races have increased tendencies toward ear infections, which goes along with the hereditary or genetic nature of the problem. Native American Indians and Eskimos are particularly prone and often suffer the complications of longstanding middle ear inflammation.

Other factors include breastfeeding, which seems to offer some protection against infection, possibly by transferring immune proteins that help the infant fight bacteria. Bottle-feeding while lying down in a crib may increase infections by encouraging bacteria to back up into the Eustachian tube. Children living in households where there are smokers or woodstoves have higher rates of infection. Cleft palate children, who have a gap in the roof of the mouth, have more middle ear infections because of missing muscles that open the Eustachian tube. The tube can also malfunction because of allergies and colds that cause swelling of the nasal mucous membranes and because of overgrowth of the adenoids, nearby tissues that help fight infection.

Figure 2 The nasal cavity houses the opening to the Eustachian tube, which connects to the middle ear and the mastoid spaces.

Daycare is possibly the factor most responsible for the increase in ear infections in the last 25 years. A child's exposure to a large number of other children early in life typically leads to more frequent colds and flu's that often lead to middle ear inflammation.

How Infections Occur

Ear infections often begin during colds or flu's, when viruses cause inflammation and swelling of the nasal and Eustachian tube passages. The tube has trouble opening, which leads to a lack of oxygen flowing into the middle ear. This also prevents mucus from leaving the middle ear. Bacteria from the nose virtually feast on the "sugar-laden" mucus and they thrive at low oxygen levels. This results in inflammatory cells entering the middle ear to defend against the organisms. The resulting inflammation causes fever, pain, and build up of pus (bacteria and inflammatory cells). Additionally, there is temporary hearing loss from the pus restricting movement of the eardrum. Since the pus cannot escape through the Eustachian tube, it puts intense pressure on the eardrum, occasionally leading to rupture of the drum with drainage of pus out through the ear canal. This is often alarming, but is actually an excellent way for the body to release the pus and help heal the infection. Occasionally doctors will help this process along by recommending a "myringotomy," during which a small nick is made in the eardrum to allow the pus to escape. Physicians refer to this type of infection as "acute otitis media."

Although half of all ear infections get better on their own, antibiotics should be used for 7 to 10 days to insure recovery, speed improvement and prevent complications. The antibiotics have no effect on viruses, but are aimed at destroying the most common bacteria that cause infections (Pneumococcus, Hemophilus Influenzae, and Mycoplasma pneumoniae). Some common antibiotics used are Amoxicillin and Bactrim. For difficult or resistant infections, "broad spectrum" antibiotics such as Augmentin, Ceftin and Suprax are used to cover heartier bacteria.

As the infection improves, the fever, pain and ill feeling resolve. The pus becomes transformed into a liquid or fluid that may be thick or watery. This continues to cause hearing loss and can remain for up to several weeks. Occasionally the fluid will remain indefinitely and needs to be treated more aggressively. Physicians refer to the fluid as "effusion."

Another type of middle ear infection is subtler and occurs without pain or fever. Commonly a cold leads to Eustachian tube blockage and build up of fluid in the middle ear, but there are few bacteria and only limited inflammation. Often hearing loss from the fluid is the only symptom. However, in very young children the hearing loss may not be apparent since they are not yet speaking. Occasionally parents notice their children's lack of response to softer sounds and turn to their doctors for help. This type of chronic ear problem is referred to by physicians as "otitis media with effusion."

Antibiotic Resistance

Over the last 25 years the vast use of antibiotics has lead to a problem referred to as "resistance." Bacteria have learned how to alter their attacks in ways that they overcome the actions of antibiotics. As they have "evolved" over the years, some of the common antibiotics like Amoxicillin have failed to be effective in up to 30% of infections. Parents mistakenly think this is due to their child's "immunity" towards the antibiotic. In fact this is not an effect on the child's immune system, but a tendency for the bacteria themselves to "resist" the effects of the antibiotics. Resistance is more common in parts of the country where antibiotics are used most frequently. Therefore, it is critical that these medicines only be used for short courses (7 to 10 days) and only when bacterial infections are suspected. Giving antibiotics to prevent infections in the winter or during colds (so called "prophylaxis") is probably no longer warranted in the face of this problem of resistance.

Overcoming resistant bacteria involves using "broad spectrum" antibiotics that outsmart these organisms. In some cases increasing the dosage or strength of common antibiotics such as Amoxicillin is necessary to break the resistance. More importantly, avoiding the use of antibiotics for colds or for prolonged periods of time will go far to reduce this problem.

Tympanostomy Tubes

Children who have three to four ear infections over a six-month period or who have fluid in the middle ear that does not go away after three months despite antibiotics need further treatment. There is no proof that decongestants or antihistamines have any impact in treating or preventing ear infections. As mentioned, occasionally draining the middle ear by nicking the eardrum, so-called "myringotomy,"can relieve persistent pain and fever and prevent complications. Tympanostomy tubes are a common way to prevent infections and keep middle ear fluid away. After the eardrum is nicked and any fluid is vacuumed from the middle ear, a small plastic tube is placed into the opening. The flange on the tube keeps it in place for about a year. The tube maintains an opening in the eardrum, so that air and oxygen pressures are maintained and any fluid is allowed to drain. The tympanostomy tube behaves as a substitute for the poorly functioning Eustachian tube until it develops and works normally.

Figure 3 A tympanostomy tube is placed in the eardrum.

Tympanostomy tube placement or "myringotomy and tubes" is the most common procedure performed in this country. The child is briefly given "laughing gas" while the tubes are placed. The child is usually back to normal within an hour or two and the procedure has very few risks. Tubes not only prevent the illnesses associated with ear infections and their possible complications in the vast majority of patients, but can also prevent prolonged periods of middle ear fluid build-up that causes hearing loss and possible speech and language problems.

Other Treatments

Occasionally older children continue to have recurrent ear infections, despite the chances that the Eustachian tube has matured. This can be due to an enlarged adenoid. The adenoid is a mound of inflammatory tissue that helps fight infection at the back of the nose. It can become quite enlarged in some children, causing blockage of the Eustachian tube openings and harboring bacteria that can easily climb up the Eustachian tube. Removal of the adenoid is recommended in these cases as an adjunct to placement of tympanostomy tubes.

More recently, an office procedure employing a laser to create a small opening in the eardrum (laser-assisted tympanostomy) has been suggested as an alternative to tympanostomy tubes for some patients. The procedure does not require anesthesia at the hospital or surgicenter, which is an advantage. The laser opening is made in such a way that the hole remains for at least several weeks. For children who only require a temporary opening in the eardrum, this may be an alternative to tympanostomy tubes.

Speech Development

A child's speech and language development goes through two phases early in life. In the first two to three years of life there is a predominantly "receptive" period. During this time speech centers are developing in the brain as nerve connections and networks are forming. Adequate hearing, especially hearing for speech sounds, is critical for these pathways to develop properly. The first two to three years of life represent a "window" of time during which these speech centers form. If hearing is diminished for long periods the speech areas form abnormally. Even if hearing is adequate beyond this two to three year "window", the child's speech may "catch up" slowly or incompletely. This can lead to substantial delay and limitation of educational development even with speech and language therapy.

The second phase of speech and language is "expressive," during which the child begins to make speech sounds and use words. This may begin as early as one year of age. However, use of words in phrases and sentences usually becomes more obvious after age two years. Therefore, problems with hearing that interfere with speech development may not be detected until after the critical window of the receptive language phase. Children with chronic middle ear fluid additionally may not suffer pain, fever or obvious illness, giving little warning that this type of ear problem is even occurring. This more "silent" form of chronic middle ear infection can therefore have far-reaching consequences, affecting the intellectual, academic, social, and even financial potential of the child.

Solutions

Prevention of hearing loss and language delay is clearly critical. Many states now test hearing at birth as a screen. However, ear infections causing middle ear fluid tend to occur after birth. Therefore, both parents and physicians need to maintain vigilance over possible hearing loss from ear infections. Subtle changes in the way a child reacts to softer sounds should alert the parent to a possible problem of persistent middle ear fluid that requires medical intervention. The child who is prone to episodes of ear infections with fever, pain and illness usually presents less of a dilemma because of all the warning signs and subsequent frequent visits to the doctor. Physicians need to follow children with detected middle ear fluid to ascertain that the problem resolves within a few weeks and does not keep returning. When the fluid is persistent or recurrent in the absence of signs of infection (fever, pain, and illness), referral to an ear, nose and throat specialist (otolaryngologist) should be made. The specialist can determine the degree of hearing loss by performing a hearing test. Pressure tests of the eardrum or "tympanograms" can be easily administered to confirm the presence of fluid, which is typically apparent during the routine ear examination as well. Children can then be treated with tympanostomy tube placement to prevent long-term problems with speech and language development.

Conclusion

Middle ear infections are common and usually temporary in childhood. Because they often interfere with hearing for prolonged periods of time, they can impact the development of speech and language. The potential impact of this on the individual and society is enormous. Therefore, treatment and prevention of childhood ear infections is important not only to deal with the illness, but also to avoid intellectual developmental delay and deterioration.