The middle ear is like a tiny cave in the skull lined with mucous membrane. It is normally filled with air. About the size of a pea, it contains three small bones and their attached muscles, nerves and blood vessels. The middle ear is separated from the outer ear by the eardrum. It links to the throat through a narrow channel called the eustachian (u-stay-shun) tube. This tube allows pressure in the middle ear to change to match air pressure outside the eardrum. When inside and outside pressures are in balance, the eardrum flutters with sound, allowing normal hearing.
Although not part of the middle ear, the eustachian tube plays a role in middle ear infections. It has two functions – controlling pressure and helping to drain normal fluids from the middle ear to the throat. With each swallow, the eustachian tube opens, allowing the air pressure inside the middle ear and outside the eardrum to balance. In infants and young children, the eustachian tube is short and horizontal. It becomes longer and steeper in later childhood.
The eardrum and middle ear work together in normal hearing. They pass sound from the external environment to the inner ear. When sound waves strike a flexible eardrum, the eardrum vibrates. Three tiny bones in the middle ear are attached to the eardrum. They pick up vibrations and pass them along to the inner ear. There, the vibrations become electrical signals sent along nerve pathways to the brain.
When a virus or bacteria settles in the middle ear and eustachian tube, it can cause an infection called otitis media. In young children, the eustachian tube is shorter and more horizontal than in adults. Bacteria have an easier time travelling from the nose or throat up the tube. Once in the middle ear they multiply, irritating delicate tissues lining the tube and ear.
Fluids and pus then appear, making the eustachian tube lining swell enough to block the tube. Once the tube is blocked, pus and mucus are trapped behind the eardrum. If pressure builds behind the eardrum, the thin membrane may bulge. This is often very painful. With too much pressure, the eardrum can break or rupture so that pus drains out of the ear.
As the acute infection passes, the eustachian tube opens and begins to work normally again. Fluid from the middle ear drains through the open tube and normal hearing returns. If the tube remains blocked and the eardrum does not break, fluid can remain in the middle ear. This fluid is called an effusion. After the acute infection passes, any fluid remaining in the middle ear thickens. It becomes sticky, taking up less space. Pressure drops in the middle ear. Inward suction stiffens the eardrum, affecting hearing.
Since the stages of otitis media cause different symptoms and problems, otitis media is classified according to how long the infection has lasted:
Otitis media is especially common in children six to 15 months of age. Children who have an early onset of ear infections are at high risk for recurrent or chronic otitis media. Those who are breastfed are less likely to develop ear infections.
Environmental factors may put a child at more risk of ear infections. Exposure to second-hand smoke may increase the incidence of chronic otitis media. Kids in daycare centres have higher rates of ear and other respiratory infections. Genetic factors are likely a risk too.
Middle ear infection is associated with a wide range of symptoms, including:
Although young children may not be able to express discomfort, their behaviour gives clues. They may pull or tug at the ear and appear unwell and irritable. They may lack energy and appetite, and have sleep or feeding changes.
A physical exam helps your doctor determine the specific type of ear problem. The exam also helps identify other respiratory illnesses such as strep throat, nasal blockage, bronchitis or pneumonia. The doctor will look inside the ears using an instrument called an otoscope. With this instrument, the eardrum can be checked for colour, mobility and fluid in the middle ear.
Two other tests may help in learning more about the ear. An audiogram can measure how much hearing is lost. In this test, tones are sounded at various pitches. A tympanogram measures pressure in the middle ear to check how well the eustachian tube is functioning.
No laboratory tests are specific to the diagnosis of otitis media. To help confirm diagnosis in a child who often has ear infections, blood tests can check for naturally occurring antibodies that help fight infection or measure the complete blood count.
The approach to treatment of ear infection has become controversial. The concern is that ear infections may be diagnosed too often or overtreated too quickly with antibiotics, leading to antibiotic resistance. Some experts recommend waiting two or three days after symptoms begin before starting antibiotics in children over two years of age. As long as parents follow up with the family doctor, this approach is acceptable. At least 30 per cent of ear infections are not caused by bacteria, and many cases resolve without treatment. Ibuprophen or acetominaphen can relieve pain and fever. If antibiotics are prescribed, the drug choice will be based on drug effectiveness, cost, the child’s history, age and possible allergy.
The surgical procedure for relieving recurrent ear infection by inserting ventilation tubes.
Some children with recurrent ear infections or chronic effusions benefit from surgery. Surgery is done by an ear, nose and throat (ENT) specialist, called an otolaryngologist. The specialist works with the aid of an operating microscope. Once the child has received a general anesthetic, a slit is made in the eardrum. Fluid is removed through the slit with special instruments. A plastic tube may then be inserted into the slit in the eardrum. This procedure is called myringotomy with insertion of ventilating tubes. The aim of the ventilation tubes is to provide the drainage for the middle ear usually performed by the eustachian tubes. Tubes remain in place for six to 12 months. During this time, the child can still get ear infections but they should be fewer in number and more easily treated with antibiotics.
Your child should feel much better after two days of treatment. If fever and pain remain, go back to your doctor. The medication may need to be changed. Your child should be checked again after treatment is completed. The doctor will look for any eardrum or hearing changes.
In many cases, middle ear fluid or effusion outlasts the infection by two to three weeks. If the effusion does not disappear within that time, the doctor may check regularly for several months. Even chronic fluid may go away with time if no new infection occurs.
Some children with recurrent ear infections or chronic effusions benefit from surgery. Surgery is done by an ear, nose and throat (ENT) specialist, called an otolaryngologist.
The specialist will use an operating microscope. Once the child has received a general anesthetic, a slit is made in the eardrum. Fluid is removed with special instruments. A plastic tube may then be inserted into the slit. This procedure is called myringotomy with insertion of ventilating tubes. The ventilation tubes are meant to drain the middle ear in the same way that eustachian tubes do.
Tubes remain in place for six to 12 months. During this time, the child can still get ear infections but they should be fewer in number and more easily treated with antibiotics.
Treatment for otitis media in children over age two has changed considerably in the last decade. Your family physician is now less likely to recommend the use of antibiotics. However, earaches can be very painful for children, which is upsetting. If in doubt, talk to your family physician, especially if your child is under the age of two.