Ear Infection Health Article

Definition

Otitis media is an infection of the middle ear space, which lies behind the eardrum (tympanic membrane). It is characterized by pain, dizziness, and partial loss of hearing.

Description

A little knowledge of the basic anatomy of the middle ear will be helpful for understanding the development of otitis media. The external ear canal is a tube that leads from the outside opening of the ear to a structure called the tympanic membrane. Behind the tympanic membrane is the space called the middle ear. Within the middle ear are three tiny bones called ossicles. These are the malleus, the incus, and the stapes. Their shapes are often described as a hammer, an anvil, and a stirrup. Sound in the form of vibration causes movement in the eardrum, and then in the chain of ossicles. The ossicles transmit the sound to the cochlea within the inner ear, which sends it to the brain for processing.

The nasopharynx is the passageway behind the nose that takes inhaled air into the breathing tubes leading to the lungs. The eustachian tube is a canal that runs between the middle ear and the nasopharynx. One of the functions of the eustachian tube is to keep the air pressure in the middle ear equal to that outside. This equalization of the air pressure allows the eardrum and ossicles to vibrate appropriately, so that hearing is normal.

By age three, almost 85% of all children will have had otitis media at least once. It is the most common pediatric complaint. Babies and children between the ages of six months and six years are most likely to develop otitis media. Children at higher risk for otitis media include boys, children from poor families, those with allergies, Native Americans, Native Alaskans, children born with cleft palate or other defects of the structures of the head and face, and children with Down syndrome. Babies whose first ear infection occurs prior to six months of age are more prone to chronic problems with otitis media. There also appears to be some genetic predisposition towards otitis media, which may be related to the structure and function of the area in and around the middle ear. Exposure to cigarette smoke significantly increases the risk of ear infections, as well as other problems affecting the respiratory system. In addition, children who enter daycare at an early age have more upper respiratory infections (URIs or colds), and thus more cases of otitis media. Although the ear infection itself is not contagious, the URIs that predispose children to them certainly are. The most common times of year for otitis media to strike are winter and early spring, which are the same times that URIs are most common.

Otitis media is an important medical problem, because it often results in fluid accumulation within the middle ear. This is known as otitis media with effusion (OME). The effusion can last for weeks to months. Effusion within the middle ear can cause significant hearing impairment. When such hearing impairment occurs in a young child, it may interfere with the development of normal speech and language processing. A chronic effusion also increases the risk for subsequent infections, as the fluid provides a growth medium for bacteria.

In adults, acute otitis media can lead to such complications as paralysis of the facial nerves. Recovery from these complications may take from two weeks to as long as three months.

Causes & symptoms

The first precondition for the development of acute otitis media is exposure to an organism capable of causing the infection. Otitis media can be caused by either viruses or bacteria. Virus infections account for about 15% of cases. The three most common bacterial pathogens are Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis. As of 2003, about 75% of ear infections caused by S. pneumoniae are reported to be resistant to penicillin.

Otitis media may also be caused by other disease organisms, including Bordetella pertussis, the causative agent of whooping cough, and Pneumocystis carinii, which often causes opportunistic infections in patients with AIDS.

There are other factors that make the development of an ear infection more likely. Because the eustachian tube has a more horizontal orientation and is considerably shorter in early childhood, material from the nasopharynx can easily reach the middle ear. Discharges from the nasopharynx include infection-causing organisms. Children also have a lot of lymph tissue, some of which makes up the adenoids, in the area of the eustachian tube. The adenoids may enlarge with repeated respiratory tract infections, ultimately blocking the eustachian tubes. When the eustachian tube is blocked, the middle ear is more likely to fill with fluid. This fluid increases the risk of infection, and the corresponding risks of hearing loss and delayed speech development.

Recent advances in gene mapping have led to the discovery of genetic factors that increase a child's susceptibility to otitis media. Researchers are hoping to develop molecular diagnostic assays that will help to identify children at risk for severe ear infections.

Most cases of acute otitis media occur during the course of a URI. Symptoms may include cold symptoms, fever, ear pain, irritability, and problems with hearing. Babies may have difficulty feeding. When significant fluid is present within the middle ear, pain can increase depending on position. Lying down may cause an increase in painful pressure within the middle ear, so that babies often fuss if not held upright. Older children sometimes complain of a full sensation in the affected ear. If the fluid build-up behind the eardrum is sufficient, the eardrum may develop a hole (perforate), causing bloody fluid or greenish-yellow pus to drip from the ear. Although the pain may be severe before the eardrum perforates, the pain is usually relieved by the reduction of pressure brought on by a perforation.