HOW TO PREVENT OTITIS MEDIA

The ear is the organ of hearing. The parts of the ear include:

EXTERNAL OR OUTER EAR; consisting of:

• PINNA OR AURICLE - the outside part of the ear.

• EXTERNAL AUDITORY CANAL OR TUBE - the tube that connects the outer ear to the inside or middle ear.

TYMPHANIC MEMBRANE - also called the eardrum. The tympanic membrane divides the external ear from the middle ear.middle ear (tympanic cavity), consisting of:

OSSICLES- three small bones that are connected and transmit the sound waves to the inner ear. The bones are called:

• MALLEUS
• INCUS
• STAPES

EUSTACHIAN TUBE - a canal that links the middle ear with the throat area. The eustachian tube helps to equalize the pressure between the outer ear and the middle ear. Having the same pressure allows for the proper transfer of sound waves. The eustachian tube is lined with mucous, just like the inside of the nose and throat.inner ear, consisting of:

• COCHLEA- contains the nerves for hearing

• VESTIBULE- contains receptors for balance

• SEMICIRCULAR CANALS - contain receptors for balance

Hearing is one of the major senses and like vision is important for distant warning and communication. It can be used to alert, to communicate pleasure and fear. It is a consciousappreciation of vibration perceived as sound. In order to do this, the appropriate signal must reach the higher parts of the brain. The function of the ear is to convert physical vibration into an encoded nervous impulse. It can be thought of as a biological microphone. Like a microphone the ear is stimulated by vibration: in the microphone the vibration is transduced into an electrical signal, in the ear into a nervous impulse which in turn is then processed by the central auditory pathways of the brain. The mechanism to achieve this is complex. This chapter will deal mainly with the ear, first its structure and then its function, for it is the ear that is mainly at risk from hazardous sounds. The ears are paired organs, one on each side of the head with the sense organ itself, which is technically known as the cochlea, deeply buried within the temporal bones. Part of the ear is concerned with conducting sound to the cochlea, the cochlea is concerned with transducing vibration. The transduction is performed by delicate hair cells which, when stimulated, initiate a nervous impulse. Because they are living, they are bathed in body fluid which provides them with energy, nutrients and oxygen. Most sound is transmitted by a vibration of air. Vibration is poorly transmitted at the interface between two media which differ greatly in characteristic impedance (product of density of the medium and speed of sound within it, c), as for example air and water. The ear has evolved a complex mechanism to overcome this impedance mis-match, known as the sound conducting mechanism. The sound conducting mechanism is divided into two parts, an outer and the middle ear, an outer part which catches sound and the middle ear which is an impedance matching device.

THE OUTER EAR:

The outer ear transmits sound to the tympanic membrane. The pinna, that part which protrudes from the side of the skull, made of cartilage covered by skin, collects sound and channels it into the ear canal. The pinna is angled so that it catches sounds that come from in front more than those from behind and so is already helpful in localizing sound. Because of the relative size of the head and the wavelength of audible sound, this effect only applies at higher frequencies. In the middle frequencies the head itself casts a sound shadow and in the lower frequencies phase of arrival of a sound between the ears helps localize a sound. The ear canal is about 4 centimetres long and consists of an outer and inner part. The outer portion is lined with hairy skin containing sweat glands and oily sebaceous glands which together form ear wax. Hairs
grow in the outer part of the ear canal and they and the wax serve as a protective barrier and a disinfectant. Very quickly however, the skin of the ear canal becomes thin and simple and is attached firmly to the bone of the deeper ear canal, a hard cavity which absorbs little sound but directs it to the drum head (eardrum or tympanic membrane) at its base. The outer layer of the drumhead itself is formed of skin in continuity with that of the ear canal."

The pinna and external auditory canal form the outer ear, which is separated
from the middle ear by the tympanic membrane. The middle ear houses three ossicles, the malleus, incus and stapes and is connected to the back of the nose by the Eustachian tube. Together they form the sound conducting mechanism. The inner ear consists of the cochlea which transduces vibration to a nervous impulse and the vestibular labyrinth which houses the organ of balance. (from Hallowell and Silverman, 1970)

In life, skin sheds and is continuously renewing. Ear canal skin grows like a fingernail fromthe depths to the exterior so that the skin is shed into the waxy secretions in the outer part and falls out. This is the reason for not using cotton buds to clean the ear canal because very frequently they merely push the shed skin and wax deep into the canal, impacting it and obstructing hearing. The ear canal has a slight bend where the outer cartilaginous part joins the bony thin skinned inner portion, so that the outer part runs somewhat backwards and the inner part somewhat forwards. This bend is yet another part of the protective mechanism of the ear, stopping foreign objects from reaching the tympanic membrane. However it means that to inspect the tympanic membrane from the outside, one must pull the ear upwards and backwards. The tympanic membrane separates the ear canal from the middle ear and is the first part of the sound transducing mechanism. Shaped somewhat like a loudspeaker cone (which is an ideal shape for transmitting sound between solids and air), it is a simple membrane covered by a very thin layer of skin on the outside, a thin lining membrane of the respiratory epithelium tract on the inner surface and with a stiffening fibrous middle layer. The whole membrane is less than a 1/10th of millimetre thick. It covers a round opening about 1 centimetre in diameter into the middle ear cavity. Although the tympanic membrane is often called the ear drum, technically the whole middle ear space is the ear drum and the tympanic membrane the drum skin.

THE MIDDLE EAR:

The middle ear is an air filled space connected to the back of the nose by a long, thin tube called the Eustachian tube. The middle ear space houses three little bones, the hammer, anvil and stirrup (malleus, incus and stapes) which conduct sound from the tympanic membrane to the inner ear. The outer wall of the middle ear is the tympanic membrane, the inner wall is the cochlea. The upper limit of the middle ear forms the bone beneath the middle lobe of the brain and the floor of the middle ear covers the beginning of the great vein that drains blood from the head, the jugular bulb. At the front end of the middle ear lies the opening of the Eustachian tube and at its posterior end is a passageway to a group of air cells within the temporal bone known as the mastoid air cells. One can think of the middle ear space shaped rather like a frying pan on its side with a handle pointing downwards and forwards (the Eustachian tube) but with a hole in the back wall leading to a piece of spongy bone with many air cells, the mastoid air cells. The middle ear is an extension of the respiratory air spaces of the nose and the sinuses and is lined with respiratory membrane, thick near the Eustachian tube and thin as it passes into the mastoid. It has the ability to secret mucus. The Eustachian tube is bony as it leaves the ear but as it nears the back end of the nose, in the nasopharynx, consists of cartilage and muscle. Contracture of muscle actively opens the tube and allows the air pressure in the middle ear and the nose to
equalize.

How do we hear?

Hearing starts with the outer ear. When a sound is made outside the outer ear, the sound waves, or vibrations, travel down the external auditory canal and strike the eardrum (tympanic membrane). The eardrum vibrates. The vibrations are then passed to three tiny bones in the middle ear called the ossicles. The ossicles amplify the sound and send the sound waves to the inner ear and into the fluid-filled hearing organ (cochlea).

Once the sound waves reach the inner ear, they are converted into electrical impulses which the auditory nerve sends to the brain. The brain then translates these electrical impulses as sound.

What is otitis media?

Otitis media is an infection or inflammation of the middle ear. This inflammation often begins when infections that cause sore throats, colds, or other respiratory or breathing problems spread to the middle ear. These can be viral or bacterial infections. Seventy-five percent of children experience at least one episode of otitis media by their third birthday. Almost half of these children will have three or more ear infections during their first 3 years. Although otitis media is primarily a disease of infants and young children, it can also affect adults.

Are there different types of otitis media?

Yes. There are two main types. The first type is called acute otitis media (AOM). This means that parts of the ear are infected and swollen. It also means that fluid and mucus are trapped inside the ear. AOM can be painful.

The second type is called otitis media with effusion (fluid), or OME. This means fluid and mucus stay trapped in the ear after the infection is over. OME makes it harder for the ear to fight new infections. This fluid can also affect your child's hearing.

How does otitis media happen?

Otitis media usually happens when viruses and/or bacteria get inside the ear and cause an infection. It often happens as a result of another illness, such as a cold. If your child gets sick, it might affect his or her ears.

It is harder for children to fight illness than it is for adults, so children develop ear infections more often. Some researchers believe that other factors, such as being around cigarette smoke, can contribute to ear infections.

Why are more children affected by otitis media than adults?

There are many reasons why children are more likely to suffer from otitis media than adults. First, children have more trouble fighting infections. This is because their immune systems are still developing. Another reason has to do with the child's eustachian tube. The eustachian tube is a small passageway that connects the upper part of the throat to the middle ear. It is shorter and straighter in the child than in the adult. It can contribute to otitis media in several ways.

The eustachian tube is usually closed but opens regularly to ventilate or replenish the air in the middle ear. This tube also equalizes middle ear air pressure in response to air pressure changes in the environment. However, a eustachian tube that is blocked by swelling of its lining or plugged with mucus from a cold or for some other reason cannot open to ventilate the middle ear. The lack of ventilation may allow fluid from the tissue that lines the middle ear to accumulate. If the eustachian tube remains plugged, the fluid cannot drain and begins to collect in the normally air-filled middle ear.

One more factor that makes children more susceptible to otitis media is that adenoids in children are larger than they are in adults. Adenoids are composed largely of cells (lymphocytes) that help fight infections. They are positioned in the back of the upper part of the throat near the eustachian tubes. Enlarged adenoids can, because of their size, interfere with the eustachian tube opening. In addition, adenoids may themselves become infected, and the infection may spread into the eustachian tubes.

Bacteria reach the middle ear through the lining or the passageway of the eustachian tube and can then produce infection, which causes swelling of the lining of the middle ear, blocking of the eustachian tube, and migration of white cells from the bloodstream to help fight the infection. In this process the white cells accumulate, often killing bacteria and dying themselves, leading to the formation of pus, a thick yellowish-white fluid in the middle ear. As the fluid increases, the child may have trouble hearing because the eardrum and middle ear bones are unable to move as freely as they should. As the infection worsens, many children also experience severe ear pain. Too much fluid in the ear can put pressure on the eardrum and eventually tear it.

What are the effects of otitis media?

Otitis media not only causes severe pain but may result in serious complications if it is not treated. An untreated infection can travel from the middle ear to the nearby parts of the head, including the brain. Although the hearing loss caused by otitis media is usually temporary, untreated otitis media may lead to permanent hearing impairment. Persistent fluid in the middle ear and chronic otitis media can reduce a child's hearing at a time that is critical for speech and language development. Children who have early hearing impairment from frequent ear infections are likely to have speech and language disabilities.

How can someone tell if a child has otitis media?

Otitis media is often difficult to detect because most children affected by this disorder do not yet have sufficient speech and language skills to tell someone what is bothering them. Common signs to look for are

• unusual irritability
• difficulty sleeping
• tugging or pulling at one or both ears
• fever
• fluid draining from the ear
• loss of balance
• unresponsiveness to quiet sounds or other signs of hearing difficulty such as sitting too close to the television or being inattentive

Can anything be done to prevent otitis media?

Specific prevention strategies applicable to all infants and children such as immunization against viral respiratory infections or specifically against the bacteria that cause otitis media are not currently available. Nevertheless, it is known that children who are cared for in group settings, as well as children who live with adults who smoke cigarettes, have more ear infections. Therefore, a child who is prone to otitis media should avoid contact with sick playmates and environmental tobacco smoke. Infants who nurse from a bottle while lying down also appear to develop otitis media more frequently. Children who have been breast-fed often have fewer episodes of otitis media. Research has shown that cold and allergy medications such as antihistamines and decongestants are not helpful in preventing ear infections. The best hope for avoiding ear infections is the development of vaccines against the bacteria that most often cause otitis media. Scientists are currently developing vaccines that show promise in preventing otitis media. Additional clinical research must be completed to ensure their effectiveness and safety.

How does a child's physician diagnose otitis media?

The simplest way to detect an active infection in the middle ear is to look in the child's ear with an otoscope, a lightinstrument that allows the physician to examine the outer earand the eardrum. Inflammation of the eardrum indicates aninfection. There are several ways that a physician checks for middle ear fluid. The use of a special type of otoscopecalled a pneumatic otoscope allows the physician to blow a puff of air onto the eardrum to test eardrum movement. (An eardrum with fluid behind it does not move as well as an eardrum with air behind it.)

A useful test of middle ear function is called tympanometry. This test requires insertion of a small soft plug into the opening of the child's ear canal. The plug contains a speaker, a microphone, and a device that is able to change the air pressure in the ear canal, allowing for several measures of the middle ear. The child feels air pressure changes in the ear or hears a few brief tones. While this test provides information on the condition of the middle ear, it does not determine how well the child hears. A physician may suggest a hearing test for a child who has frequent ear infections to determine the extent of hearing loss. The hearing test is usually performed by an audiologist, a person who is specially trained to measure hearing.

How is otitis media treated?

Many physicians recommend the use of an antibiotic (a drug that kills bacteria) when there is an active middle ear infection. If a child is experiencing pain, the physician may also recommend a pain reliever. Following the physician's instructions is very important. Once started, the antibiotic should be taken until it is finished. Most physicians will have the child return for a followup examination to see if the infection has cleared.

Unfortunately, there are many bacteria that can cause otitis media, and some have become resistant to some antibiotics. This happens when antibiotics are given for coughs, colds, flu, or viral infections where antibiotic treatment is not useful. When bacteria become resistant to antibiotics, those treatments are then less effective against infections. This means that several different antibiotics may have to be tried before an ear infection clears. Antibiotics may also produce unwanted side effects such as nausea, diarrhoea, and rashes.

Once the infection clears, fluid may remain in the middle ear for several months. Middle ear fluid that is not infected often disappears after 3 to 6 weeks. Neither antihistamines nor decongestants are recommended as helpful in the treatment of otitis media at any stage in the disease process. Sometimes physicians will treat the child with an antibiotic to hasten the elimination of the fluid. If the fluid persists for more than 3 months and is associated with a loss of hearing, many physicians suggest the insertion of "tubes" in the affected ears. This operation, called a myringotomy, can usually be done on an outpatient basis by a surgeon, who is usually an otolaryngologist (a physician who specializes in the ears, nose, and throat). While the child is asleep under general anaesthesia, the surgeon makes a small opening in the child's eardrum. A small metal or plastic tube is placed into the opening in the eardrum. The tube ventilates the middle ear and helps keep the air pressure in the middle ear equal to the air pressure in the environment. The tube normally stays in the eardrum for 6 to 12 months, after which time it usually comes out spontaneously. If a child has enlarged or infected adenoids, the surgeon may recommend removal of the adenoids at the same time the ear tubes are inserted. Removal of the adenoids has been shown to reduce episodes of otitis media in some children, but not those who are under 4 years of age. Research, however, has shown that removal of a child's tonsils does not reduce occurrences of otitis media. Tonsillotomy and adenoidectomy may be appropriate for reasons other than middle ear fluid.

Hearing should be fully restored once the fluid is removed. Some children may need to have the operation again if the otitis media returns after the tubes come out. While the tubes are in place, water should be kept out of the ears. Many physicians recommend that a child with tubes wear special ear plugs while swimming or bathing so that water does not enter the middle ear.