What are ear infections (otitis media) in children?

The ear is the organ of hearing and balance and is organized into external, middle, and internal areas.

Ear Infections (Otitis Media) in Children

Ear infections are often defined by whether they are acute (acute otitis media) or chronic (otitis media with effusion).

Acute Otitis Media (AOM). Acute otitis media (AOM) is an infection in the middle ear that causes an inflammation behind the tympanic membrane.

Otitis Media with Effusion (OME). Otitis media with effusion (OME) occurs when an effusion (fluid) builds up in one or both middle ears. When this is chronic and severe the fluid is very sticky and is commonly called "glue ear.";

What causes middle ear infections (Otitis Media) in Children?

Otitis media (middle ear infection) is most often the result of a combination of factors that increase susceptibility to infections by specific organisms in the middle ear.

Conditions that Predispose a Person to Ear Infections

Problems in the Eustachian Tube. Many bacteria thrive in the passages of the nose and throat. Most are benign and some are even important in preventing harmful bacteria from getting out of control. In addition, the body has a number of defenses that prevent the harmful bacteria from replicating and infecting deeper passages, such as those in the ear.

However, various factors can impair these defenses. Such factors may include, but are not limited to the following:

In general, these or other irritants can produce the following conditions that lead to ear infection:

Genetic Factors. Several studies suggest that multiple genetic factors may play a role in making a child susceptible to otitis media.

For example, genetic susceptibility to certain bacteria may result in development of persistent and recurrent otitis media.

Abnormalities in genes that affect the defense systems (cilia and mucus production) and the anatomy of the skull and passages would also increase the risk for ear infections.

Researchers are hoping that these findings may encourage primary care physicians to closely monitor children who are offspring or siblings of individuals with a history of unusually frequent or severe upper respiratory tract infections.

Infecting Agents

Bacteria. Certain bacteria are the primary causes of acute otitis media (AOM) and are detected in about 60% of cases. The bacteria most commonly causing ear infections are:

Of note, about 15% of these bacteria are now believed to be resistant to the first-choice antibiotics.

Viruses. Studies have reported the presence of viruses in the middle ear fluid in about 40% of children with ear infections. While viruses are not usually a direct cause of otitis media, they may play an important role by causing inflammation in the nasal passages and impairing defense systems, such as cilia, in the ear.

Respiratory syncytial virus (RSV), a common virus responsible for upper and lower respiratory infections, and influenza viruses ("Flu";) are prime suspects in this process.

Rhinovirus, a cause of the common cold, has been found in between 1% and 8% of otitis media cases, and, in one study 74% of patients with rhinovirus caused colds had middle-ear pressure abnormalities.

Causes of Otitis Media with Effusion (OME)

In some cases, otitis media with effusion develops after an acute otitis media attack, although often the direct cause of OME is unknown.

It is not clear, for example, what role bacteria or other infectious agents play. Standard tests do not detect bacteria in 40% to 60% of cultures taken from fluid in OME-affected ears. (In one study, a sophisticated test found genetic evidence of Haemophilus influenza bacteria in about a third of specimens in which no bacteria were detected by standard culture techniques.)

Susceptibility to OME is almost always due to an abnormal or malfunctioning Eustachian tube that causes a negative pressure in the middle ear, which, in turn, allows fluid to leak in through capillaries.

Problems in the Eustachian tube can be due to viral infections, second-hand smoke, injury, or birth defects, such as cleft palate.

Rare genetic conditions, such as Kartagener's syndrome, in which the cilia (hair-like structures) in the ear are immobile and cause fluid build up, can contribute to OME.

Who Gets Ear Infections?

General Risk Factors for Ear Infections

Acute ear infections are the most common reason for childhood visits to the doctor. About 62% of children can expect to have a least one attack of acute otitis media (AOM) in their first year and 80% will have had an infection by age three.

And, the incidence of AOM has been rising over the past decades. One study reported a 44% increase in prevalence between 1981 and 1988, with infants particularly affected.

In American children, otitis media is second in prevalence only to the common cold.

Gender and Age. Boys are more apt to have infections than girls are, and the risk is higher the younger the child:

About 17% of all children under two have recurrent ear infections (i.e., three or more episodes within a six-month period). The earlier a child has a first ear infection the more susceptible he or she is to recurrent episodes. The peak incidence occurs between seven and nine months of age.

As children grow, however, the structures in their ears enlarge and their immune systems become stronger. By 16 months the risk for recurrent infections is rapidly declining. Still, about two thirds of children have had at least one acute ear infection by the time they are three years old.

Half of the cases of otitis media with effusion (OME) appear to develop within the first year of life. In one study, 18% of healthy children between birth and age three had frequent recurrences of OME in one or both ears. (Because OME has fewer symptoms than acute otitis media, however, its prevalence among very young children is unclear.)

After age five, most children have outgrown their susceptibility to any ear infections.

Other General Risk Factors. The following children also have higher risks for ear infections.

Children with a family history of ear infections.

Children from lower socioeconomic groups.

Increased Co-Incidence in Other Airway Infections and Disorders

Increased diagnosis of other disorders and infections of the upper and lower airways, such as asthma, allergies, and sinusitis, have paralleled the rise in ear infections.

For example, the same bacteria are often responsible for both ear infections and sinusitis. In one study, 38% of children with ear infections also had sinusitis, and other studies have reported that nearly half of children with OME have concurrent sinusitis. These studies may have overestimated the extent of clinically important sinus disease, but none the less, the association is significant. Researchers are looking for common risk factors:

Day Care Center Attendance. Although ear infections themselves are not contagious, the respiratory infections that precipitate them can pose a risk for children with close and frequent exposure to other children. Some experts believe, then, that the increase in ear and other infections may be due to the higher attendance of very small children, including infants, in day care centers beginning in the 1970s.

For children who had the condition for a long time, however, neither day care attendance nor any other risk factor, including a history of upper respiratory tract infections or family history of OME, appeared to be relevant.

Attendance in day care centers, then, may explain part, but not all, of the current increase in ear infections and other upper airway disorders.

Increase in Allergies. Some experts believe that the increase in allergies is also partially responsible for the higher number of ear infections, which is unlikely to be related to day care attendance. Studies indicate that 40% to 50% of children over three years old who have chronic otitis media also have allergic rhinitis (hay fever). Allergies are also associated with asthma and sinusitis.

The rise in the rate of otitis media, then, is probably due to a combination of factors that are also responsible for the increase in these other airway problems.

Dr. Newaz G. MD. is a practicing pediatrician in the States.

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