Ears

18 May

Ears
The ear is the organ of hearing and balance. It has three main parts: the outer ear, the middle ear, and the inner ear. Sound waves enter the outer ear and proceed to the middle ear, where they cause the eardrum to vibrate. The vibrations move through three tiny bones—the malleus (hammer), incus (anvil), and stapes (stirrup)—in the middle ear and proceed into the inner ear, where they are changed into nerve impulses. These nerve impulses are transmitted by way of the vestibulocochlear nerve to the brain, where they are perceived as sound.

Hearing loss can interfere with your ability to communicate and can compro- mise your safety. Other ear disorders can cause unpleasant symptoms such as ringing in the ears (tinnitus), dizziness, and loss of balance. Tiny, fluid-filled structures in the inner ear help you keep your balance.

Hearing Loss

Aging and excessive exposure to loud noise are the most common causes of hearing loss. Other factors—such as viral or bacterial infections, an inherited disorder, or a benign tumor in the ear—also can produce hearing loss. One in 10 people in the United States has a hearing loss severe enough to affect his or her ability to hear normal speech. After age 50, most people have some degree of hearing loss. The changes occur very gradually and usually go unnoticed until a family member or friend mentions the person’s hearing problems. Among older people, a third of those between ages 65 and 74 and half of those over age 85 have hearing loss.

There are two main types of hearing loss: conductive hearing loss and sen- sorineural hearing loss. Conductive hearing loss occurs when something, such as a buildup of earwax or an abnormality in the eardrum, prevents sound waves from being transmitted to the inner ear. This type of hearing loss can sometimes be corrected with medication or surgery. Sensorineural hearing loss refers to hearing problems that occur because of damage to the inner ear or the auditory nerve. Such damage can occur as a result of the aging process or because of exposure to loud noise. A hearing aid (see page 399) is most helpful for this type of hearing loss.

Exposure to loud noises—either a one-time exposure or repeated exposure over time—damages both the sensory hair cells of the inner ear and the auditory nerve. The longer you are exposed to loud noise and the closer you are to its source, the more damage it can cause.

The loudness of sound or noise is measured in units called decibels. A ticking watch is about 20 decibels, normal conversation is about 60 decibels, and city traffic noise is about 80 decibels. Sounds at 80 decibels or less are considered safe. Sounds between 90 and 100 decibels, such as a rock concert or a jet engine, may damage your hearing. Sounds that are between 120 and 140 decibels are usually painful and even a brief exposure can cause permanent hearing loss. Examples of things that can produce sounds over 120 decibels include motorcy- cles, snowmobiles, jackhammers, firecrackers, woodworking tools, and firearms.

Exposure to loud noise can occur in the workplace, in recreational settings, and at home. Some people are more sensitive to noise than others. In general, however, noise is loud enough to affect your hearing if you have to shout over it to be heard or if the noise causes pain or ringing in your ears. Temporary hearing loss that lasts for a few hours after exposure to loud noise is a sign of damage to your hearing.

For some people with hearing loss, sounds may gradually become distorted or muffled. They may experience problems having a conversation, listening to music, or even hearing a ringing doorbell or telephone. Participating in daily activities may become more difficult and less enjoyable because the person cannot hear properly and feels left out. He or she also may hear a hissing or a ringing in the ears (tinnitus; see page 401). Hearing loss also may have psycho- logical effects. The person may become a source of annoyance or frustration and be ridiculed or ignored by family and friends. He or she might become depressed or withdraw from others to avoid embarrassment.

Although noise damage to the inner ear is irreversible, there are steps you can take to prevent noise-induced hearing loss. The most important thing you can do to protect your hearing is to avoid loud noise whenever possible. It is a good idea, for example, to keep the volume low on your personal stereo. If other peo- ple can hear music coming from your headphones, the sound is probably loud enough to cause permanent damage to your hearing.

If you are exposed to loud noise in the workplace, be sure to wear appropriate ear protection. Using specially designed earmuffs is the most effective way to protect your hearing on the job. These earmuffs, which resemble stereo head- phones, block out almost all sound. Usually they are worn by people who work around noisy equipment or under extremely noisy conditions, such as construc- tion workers or airport baggage handlers.

Another effective form of ear protection (although less effective than ear- muffs) is earplugs made of foam rubber, plastic, or wax. Earplugs are inserted into the outer ear canal and must fit snugly to provide optimal protection. They should be replaced promptly if they become soiled or worn, because they will quickly lose their effectiveness. Ordinary cotton balls cannot adequately protect your hearing. You can purchase earplugs in a variety of styles, shapes, and sizes at your local pharmacy.

If your workplace is very noisy, it is extremely important that you have your hearing checked regularly. If your employer does not have your hearing checked regularly, see your doctor, who will perform hearing tests (see “Diagnostic Pro- cedures,” page 404) to check for hearing loss. If hearing loss is detected early, you can take steps to prevent further damage to your ears. If noise levels at work seem too high, talk to your employer or your union representative. You may also contact your local health department or the local office of the Occupational Safety and Health Administration (OSHA) to report the problem.

If you think you may have hearing loss, see your doctor. He or she will per- form audiometry (see page 404) using an instrument called a screening audio- meter to test your hearing. This instrument produces a range of sound tones at various frequencies and volumes that are typically heard during speech. The doc- tor will ask you to raise your finger each time you hear a tone. The results of this test will determine whether your hearing loss is serious enough for your doctor to refer you to an audiologist, a health professional trained in evaluating hearing loss and fitting hearing aids (see below), or an otolaryngologist, a physician who specializes in treating disorders of the ear, nose, and throat.

Do You Have Hearing Loss?
H
earing loss is common, especially among older people. You may have some degree of hearing loss if any of the following apply to you:

•   You have difficulty hearing over the telephone.

•   You have difficulty following a conversation when two or more people are talking at the same time.

•   Friends and family complain that you turn the TV up too loud.

•   People often ask if you can hear them.

•   You strain to understand conversations.

•   You have difficulty hearing over background noise.

•   You think that other people are mumbling when they speak.

•   You have difficulty hearing someone who is whispering.

•   You have difficulty hearing women or children talking.

If you have any of these problems, talk to your doctor. He or she can perform a simple hearing test to determine whether you have hearing loss and may refer you to an oto- laryngologist or an audiologist for additional testing.

Hearing Aids

A hearing aid is a small, battery-powered device that fits in or over your ear and amplifies sounds. Although a hearing aid can be fitted to only one ear, hearing aids are usually placed in both ears to provide the best overall hearing. Amplifi- cation of sound in both ears allows the person to hear speech more clearly and helps him or her to distinguish where sounds are coming from, especially in noisy surroundings.

Although many models of hearing aids are available, most can be placed into one of the following categories. Behind-the-ear hearing aids fit over the ear and are connected to a custom-made earpiece. In-the-ear hearing aids sit inside the outer ear and the outer part of the ear canal. In-the-canal hearing aids are small, unobtrusive devices that fit inside the ear canal. The smallest and least visible devices are completely-in-the-canal hearing aids, which fit more deeply inside the ear canal. In-the-canal hearing aids and completely-in-the-canal hearing aids are the most cosmetically appealing because they provide powerful assistance to hearing without being visible. Many hearing aids also come with telephone pickup switches that provide special assistance while you are on the phone or listening to a public sound system. The type of hearing aid that is right for you

depends on your degree of hearing loss, the size and shape of your ear and ear canal, your lifestyle, and your budget.

Custom-made hearing aids vary in price, depending on style and special fea- tures. Prices typically range from $500 for a standard hearing aid up to $2,500 for hearing aids that are fully computerized and programmable. However, price should not be your only consideration when choosing a hearing aid. You should also consider factors such as comfort, appearance, durability, reliability, and the service agreement.

Before choosing a hearing aid, you should have a thorough hearing evaluation (see “Diagnostic Procedures,” page 404) performed by an otolaryngologist or an audiologist. You can purchase the hearing aid directly from the doctor or the audiologist or from an independent, licensed hearing aid distributor. A wax impression of your ear will be made so that the laboratory can create a hearing aid that fits your ear exactly. No matter where you purchase your hearing aid, however, it is essential to have it custom-fitted to your ear for best results. It is important to note that hearing aids purchased through mail order usually cannot be custom-fitted.

When you receive your hearing aid, you will be tested to determine how well you can hear and understand speech while wearing the device. You will also learn how to care for your hearing aid, how to insert and remove it, how to change the batteries, and how to use your hearing aid correctly. You will need to have your hearing aid tested and adjusted regularly to ensure that it is working properly. Once you begin wearing your hearing aid, give yourself time to adjust. You should begin by wearing the device first in quiet surroundings and gradually work up to noisier situations. Although a hearing aid cannot cure your hearing loss, it can allow you to hear sounds and voices more clearly so that you can communicate better and more easily participate in your usual activities.

Surgery to Correct Hearing Loss

Almost all people with hearing loss can benefit from using a hearing aid. Others, however, may need surgery to improve their hearing. Here are some surgical procedures that are performed to treat hearing loss:

•  Myringoplasty. This procedure is used to repair a perforated eardrum (a hole in the eardrum) with a tissue graft (a transplantation of healthy tissue from one part of the body to another). The tissue is usually taken from another part of the ear, or from an area near the ear. The procedure is often performed using local anesthesia and causes a minimal amount of pain. The person may need to stay overnight in the hospital and will need to rest at home for about a week after surgery. In most cases, recovery is complete in about 6 weeks.

•  Tympanoplasty and stapedectomy. These procedures are used to repair a per- forated eardrum or to replace damaged bones in the middle ear. Damaged bones may be repaired, or they may be replaced with artificial implants, trans-

planted bones supplied by a donor, or bones constructed from cartilage. The procedure is performed using either local or general anesthesia and may cause mild pain for a few days. The person may not need to stay overnight in the hospital but will need to rest at home for about 7 to 10 days after surgery. In most cases, recovery is complete in about 2 months.

•  Cochlear implant. This procedure involves implantation of an electronic device to treat severe sensorineural hearing loss (see page 397) that has caused total or near-total deafness. The implant changes sound waves into electronic impulses that are carried along the auditory nerve to the hearing center in the brain, enabling the person to distinguish different kinds of sounds and often to understand speech. The device has both internal and external components. The internal component (a special signal processor and elec- trodes) is surgically implanted into the ear while the person is under general anesthesia. The person usually needs to stay in the hospital for a couple of days. The ear will heal in about 4 to 6 weeks, after which the physician will fit the person with the external components (a microphone, a transmitting coil, a speech processor, and connecting wires). The person will then work with an audiologist to adjust the settings on the implant for the best hearing level and to learn how to use the device properly.

Tinnitus

Tinnitus is the medical term for ringing or other sounds in the ears that occur when there is no external source of these sounds. It is a very common condition, affecting an estimated 35 million people in the United States each year. It is esti- mated that 1 to 5 percent of these people have tinnitus so severe that it affects their ability to lead a normal life. Symptoms include ringing, hissing, buzzing, or whistling in one or both ears. The symptoms may be constant or come and go, the pitch can vary from high to low, and the sound can pulsate in time with the heartbeat. One type of tinnitus causes clicking or crackling sounds. These annoy- ing sounds can be a major source of distraction and irritation, affecting per- formance at work and other daily activities. Tinnitus can make it difficult for the person to fall asleep.

Tinnitus is caused by hearing loss or by spasms (involuntary muscle contrac- tions) in the muscles of the neck or jaw. The hearing loss, which may not be noticeable, may result from a variety of diseases and conditions, including stiff- ening of the bones in the middle ear, allergies, high blood pressure, diabetes, a tumor, a thyroid condition, or head or neck injury. Certain medications—such as anti-inflammatory drugs, antidepressants, aspirin, or antibiotics—can trigger tinnitus. However, most cases of tinnitus result from damage to the sensory hair cells and the microscopic endings of the auditory nerve, which are in the inner ear. This damage is common in older people. In younger people the damage

usually results from continual exposure to loud noise. Hearing loss typically accompanies tinnitus, but one often becomes apparent before the other.

If you hear ringing in your ears or other unusual or unwanted sounds, see your doctor. He or she will probably refer you to an otolaryngologist, who will first administer a hearing test. Additional tests, such as a computed tomography (CT) scanning or magnetic resonance imaging (MRI), a test for balance, and blood tests, may be performed to determine the cause of your tinnitus. Possible causes may include infection, obstruction, or Ménière’s disease (see below). If the tin- nitus is caused by an infection, your doctor will probably prescribe antibiotics. If there is an obstruction, such as a buildup of earwax or dirt, your doctor will remove it. In many cases, however, a cause cannot be identified.

There are a number of steps you can take to reduce the severity of your tinni- tus, depending on its cause. The most important thing you can do is to avoid loud noises. Some people also find that relaxation exercises (see page 119) help to relax their muscles, improve circulation, and reduce the ringing in their ears. If your tinnitus is caused by high blood pressure or poor circulation, you should have your blood pressure checked regularly and work with your doctor to control it. Reduce your intake of stimulants such as coffee, tea, colas, and tobacco prod- ucts. Exercise regularly to promote good circulation.

Some doctors recommend using a technique called masking to relieve the effects of tinnitus. Because the condition is more noticeable in quiet surround- ings, you can try to mask the unwanted sounds in your ears by listening to a competing sound, such as a radio or television, an air conditioner, a ticking clock, or radio static. Tapes that play “white noise” can also distract you from the annoying sounds of tinnitus. Your doctor may recommend a tinnitus masker, which is worn like a hearing aid and gives off a more pleasant sound that masks the tinnitus. A hearing aid sometimes helps mask tinnitus, even if your hearing seems adequate. Before trying any of these techniques, however, talk to your doctor about which methods are best for you. Most people will learn to tolerate their tinnitus. Some people benefit by joining a support group where they can share experiences and information with other people who have tinnitus. Others may find that counseling helps them to cope with the condition. Ask your doctor for a referral.

Ménière’s Disease

Ménière’s disease is an abnormality in the inner ear that causes a number of symptoms—dizziness, tinnitus (see page 401), hearing loss that comes and goes, and pressure in the affected ear. The symptoms of Ménière’s disease appear suddenly and can occur daily or as seldom as once a year. The dizziness can lead to nausea, vomiting, and sweating and can become so severe that the person has to lie down. Ménière’s disease usually affects only one ear and is a somewhat common cause of hearing loss. At first the person’s hearing returns to normal

between episodes, but over time the hearing worsens. Ménière’s disease affects about 3 million to 5 million people in the United States, with about 100,000 new cases diagnosed each year. The cause of the disease is unknown.

A part of the inner ear known as the labyrinth is necessary for hearing and balance. The labyrinth contains a fluid called endolymph. When you move your head, the fluid moves within the labyrinth, causing nerves in the labyrinth to send signals to the brain about the movement of your body. Symptoms of Ménière’s disease occur when excess fluid builds up in the labyrinth.

To diagnose Ménière’s disease, a doctor first takes a medical history and per- forms a thorough physical examination. The doctor is usually able to diagnose the condition on the basis of the person’s symptoms. Hearing tests (see “Diag- nostic Procedures,” next page) and balance tests help to confirm the diagnosis and rule out other possible causes of the symptoms. The most common hearing test used to diagnose Ménière’s disease is audiometry, in which a person’s ability to hear sounds of varying frequencies and volumes is evaluated.

To assess the person’s balance, the doctor may perform a test that includes flooding the person’s ears with water. This produces rapid eye movements that help the doctor evaluate balance. Because a brain tumor can produce symptoms similar to those of Ménière’s disease, the person may need to have a scan of the brain to rule out a possible tumor.

There is no cure for Ménière’s disease, but certain treatments can help manage the symptoms. Some doctors recommend dietary changes. Eliminating salt (sodium), caffeine, and alcohol relieves the frequency and intensity of episodes in some people. Stopping the use of tobacco (see page 107) and reducing stress (see page 118) also may lessen the severity of symptoms. Your doctor may pre- scribe diuretics to help your body eliminate excess fluid, thereby decreasing the severity and frequency of episodes. Medications that control allergies also can be helpful. The dizziness typically stops after 10 to 20 years, but the hearing loss will persist.

Three types of surgery have been developed to correct the disorder, but their effectiveness has been difficult to establish. Another important factor to consider is that all surgery on the ear carries a risk of hearing loss. The most commonly performed surgical treatment for Ménière’s disease is insertion of a shunt (a tiny tube) into the inner ear to drain excess fluid. In another type of surgery, called vestibular neurectomy, the nerve responsible for balance is cut so it can no longer send distorted messages to the brain. Because this nerve lies close to the nerves that are responsible for hearing and facial muscle control, this type of surgery carries a risk of loss of hearing or facial movement. Older people often have difficulty recovering from this type of surgery. During a third type of surgery called a labyrinthectomy, the surgeon removes the membrane inside the labyrinth to eliminate the dizziness caused by Ménière’s disease. This procedure is irreversible and produces a total loss of hearing in the affected ear. People

considering this type of surgery need to know that their other ear may someday also be affected by Ménière’s disease, which means that total deafness is a pos- sibility in the future. In rare cases, labyrinthectomy and vestibular neurectomy may cause permanent balance problems, especially in older people.

Diagnostic Procedures

The following procedures are used to test for hearing loss and to diagnose or rule out certain possible underlying causes of hearing loss:

•  Audiometry. This is the most commonly used hearing test. The first part meas- ures how well you can hear sounds conducted through the air and indicates the condition of your overall hearing. The test is usually administered in a sound- proof room using a machine called an audiometer. Through headphones, you listen to a series of sound tones that range from high to low, one tone at a time. Each tone begins at an easily audible sound level. You indicate with a pre- arranged signal when you hear the tone. The sound level decreases gradually until you are no longer able to hear the tone; this point is your hearing thresh- old for that frequency. The second part of the test measures how well you can hear sounds conducted through your head and indicates whether your hearing loss is conductive or sensorineural (see page 397). The procedure is the same as for the first part of the test, but this time you wear special vibrating head- phones. Next you are tested for words to establish the lowest threshold at which you can hear two-syllable words (called your speech-reception thresh- old) and to determine the percentage of one-syllable words you can repeat back correctly (called speech discrimination).Your hearing thresholds for all parts of the test are recorded on a graph called an audiogram.

•  Impedance audiometry. This hearing test measures how well your eardrums reflect sound waves. During the test, a probe that is covered with soundproof material is placed into your outer ear canal, sealing off the entrance to both sound and outside air pressure. The probe then transmits a continuous sound as air is pumped into the ear canal through the probe at various pressure lev- els (from low to high), and a microphone in the probe measures reflected sound waves. These reflections are recorded on a graph called a tym- panogram. This test is used to detect fluid in the middle ear, a perforated eardrum, and disorders of the three tiny sound-conducting bones (the malleus or hammer, the incus or anvil, and the stapes or stirrup) of the middle ear.

•  Auditory evoked response testing (also called auditory brain stem response testing). This computerized hearing test is used to measure the electrical activ- ity of the vestibulocochlear nerve by determining how long it takes nerve impulses traveling along the nerve to reach the brain stem. During the test, electrodes are placed on your scalp to analyze your brain’s response to sound

stimulation produced by an audiometer. This test is sometimes used to rule out an acoustic neuroma (a noncancerous tumor in the ear canal).

•  Electrocochleography. This hearing test measures the electrical activity of the sensory hair cells in the inner ear in response to sound waves. During the test, the eardrum is anesthetized and a very fine needle is passed through the eardrum until it is very near the sensory hair cells. Sound tones of varying frequency (low to high) and loudness are then transmitted into the ear through headphones, while the needle detects the electrical activity of the sensory hair cells. The electrical activity is recorded on a graph called an electro- cochleogram. This test is sometimes used to diagnose Ménière’s disease (see page 402).

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