How do we hear?The ear consists of three major parts:
the outer ear, the middle ear and the inner ear. The outer ear includes the pinna (the visible part of the ear) and the ear canal. The outer ear extends to the tympanic membrane (eardrum), which separates the outer ear from the middle ear. The middle ear is an air-filled space located behind the eardrum. It contains 3 tiny bones, the malleus, incus and stapes, which transmit sound from the middle ear to the inner ear. The middle ear is connected to the back of the nose and upper throat by the Eustachian tube. This tube ventilates the ear and equalizes the air pressure in the middle ear to the outside air pressure. The inner ear contains the hearing (cochlea) and balance (labyrinth) organs. The auditory nerve connects the cochlea to the brain.
In a healthy ear, sound waves striking the eardrum send vibrations through the 3 tiny bones in the middle ear. Movement of these bones transmits sound waves across the middle ear to the cochlea of the inner ear. In the cochlea, sound is transformed into nerve impulses that travel to the brain. In this manner, sound is perceived.
What is Otitis Media?Otitis Media is an
infection or inflammation of the middle ear that usually follows a buildup of fluid in the middle ear space. This condition occurs when the Eustachian tube becomes inflamed following a cold, sinus or throat infection, allergic reaction, or is blocked by enlarged adenoid tissue. Fluid accumulating in the middle ear cannot drain properly and may become infected. Bacteria are the primary causes of otitis media and are detected in 70% of cases. The most common microorganisms detected are Haemophilus influenzae and Streptococcus pneumoniae. Less common bacteria involved are Moraxella catarrhalis and Streptococcus pyogenes. Viruses are not usually a direct cause of otitis media, but play a major role by causing inflammation in the nasal passages and impairing defense systems, such as cilia, in the ear. Respiratory syncytial virus (RSV), Influenza virus and Rhinovirus are the prime suspects. Although this condition occurs most often in children one to three years of age, older children and adults may develop it as well.
Why is Otitis Media so common in children?There are various reasons why children are more likely to suffer from Otitis Media than adults. First, young children have more trouble fighting infections because their immune systems are still developing.
Another reason is related to a child's Eustachian tube, which is shorter and more horizontal than in adults. This contributes to Otitis Media in the following ways. The Eustachian tube usually opens regularly to ventilate or replenish the air in the middle ear and to equalize its air pressure to that of the environment. However, a blocked Eustachian tube, either due to swelling of its lining or plugged with mucus, cannot open properly to ventilate the middle ear. This in turn impedes the drainage of fluid from the middle ear tissue, which collects in the middle ear. Also, the angle of the Eustachian tube in children makes it easier for bacteria from the nose and throat to enter the middle ear.
Enlarged adenoids represent another factor that makes children more susceptible to Otitis Media. Adenoids are positioned in the back of the upper part of the throat near the Eustachian tubes. When enlarged, they can interfere with the Eustachian tube opening. In addition, adenoids may themselves get infected, thereby spreading infection into the Eustachian tubes.
What are the risk factors for developing Otitis Media?The greatest risk factor for Otitis Media is Eustachian Tube blockage due to an upper respiratory illness such as common cold, flu, throat or sinus infection.
Additional risk factors include:
Age: Infants and young children are more prone as discussed earlier. Also, the younger a child is at the time of the first ear infection, the greater the chance he or she will have repeated infections.
Enlarged Adenoids: Contribute to ear infections as discussed earlier.
Bottle-feeding: Babies, who are bottle-fed, especially while they are lying down, are more susceptible to ear infections than breast-fed babies. Also, breast milk provides immunity
Colds & Allergies: Often lead to ear infections by causing swelling of the Eustachian tube.
Cigarette smoke: Children inhaling tobacco smoke have a higher risk of developing health problems, including ear infections.
Socioeconomic Status: Children from low socioeconomic groups have a higher incidence than those living in wealthier communities.
Gender: Boys are more apt to have infections than girls.