Otitis Media - Epidemiology

Epidemiology

Otitis media is very common in childhood, with the average toddler having two to three episodes a year, almost always accompanied by a viral upper respiratory infection (URI), mostly the common cold. The rhinoviruses (nose viruses) that cause the common cold infect the eustachian tube that goes from the back of the nose to the middle ear, causing swelling and compromise of pressure equalization, which is one of the normal functions of the tube. The other main function is the lateral drainage of fluids from tissues on either side of the skull. It has to be remembered that the eustachian tube is only the width of three to four hairs in places along its length. It also changes its anatomical and physiological appearance during the early growth period of the child. In the newborn the tube is horizontal making it more difficult to drain naturally, and the surface of the tube is 100% cartilage, with a lining of lymphatic tissue which is an extension of the adenoidal tissue from the back of the nose. As the early years pass by, the superior (upper) part of the tube ossifies to bone but the lower remains the same. The angle of the tubes changes and descends to roughly a 45 degree angle increasing the downward flow of fluids. Individuals with Down syndrome (DS) anatomically have more severe curves to their tubes, hence DS children tend to have more grommet operations than other children. In general, the more severe and prolonged the compromise of eustachian tube function, the more severe the consequences are to the middle ear and its delicate structures. If a person is born with poor eustachian tube function, this greatly increases the likelihood of more frequent and severe episodes of otitis media. Progression to chronic otitis media is much more common in this group of people, who often have a family history of middle ear pathology.