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Hearing Disorders

Hearing disorders

Definition

Hearing disorders range from a temporary, partial loss of hearing to the permanent loss of hearing known as deafness.

Description

The variety of hearing disorders includes a loss or decrease in the ability to discern certain frequencies of sound, a ringing or other noise that is unrelated to any actual external sound, damage due to physical trauma or infection, and genetically determined structural malformation.

Demographics

Hearing disorders occur worldwide in all races. The hearing loss that occurs with age is very common, affecting an estimated 30% of Americans over 60 years of age and 50% of those older than 75.

Tinnitus, a ringing or noisy sensation in the ears, is quite common with an estimated 20% of people affected worldwide. In the United States alone, some 36 million people experience tinnitus.

For hearing loss caused by otosclerosis, middle-aged Caucasian women are more prone than others, perhaps as a consequence of hormonal changes. In otosclerosis, abnormal bone development occurs in the middle ear, resulting in progressive hearing loss. Sudden hearing loss happens more often to people ages 3060 for unknown reasons.

Causes and symptoms

Presbycusis

Presbycusis (or sensorineural hearing loss) is the loss of hearing that occurs with age. The condition results from the long-term assault on the ear structures, particularly on the inner ear, from a lifetime of noise, ear infections, or growths on bones of the outer or middle ear. The inner ear is where the vibrational sound waves are converted to electrical signals, courtesy of thousands of tiny hairs that are in a fluid-enclosed space called the cochlea. The hairs are connected to nerve cells, which send the electrical signals to the brain.

Most age-related hearing loss is due to damage to the cochlea. The tiny hairs can bend or even break, and the attached nerve cells can degenerate. The resulting less-efficient transmission of the electrical signal, particularly of higher-pitched tones, causes hearing loss.

Symptoms of presbycusis typically include increased difficulty in making out sounds of a certain volume or tone, especially when background sounds are present.

Conductive hearing loss

In conductive hearing loss, sound is not transmitted efficiently through the outer and middle ears. These regions house the eardrum, ear canal, and the trio of tiny bones (ossicles) in the middle ear that transmits sound energy to the inner ear. The hearing loss can be due to malformation of structures like the canal or the ossicles, dense buildup of ear wax, or fluid in the ear due to colds, allergies, or infections like otitis media. Symptoms include a decreased ability to detect fainter sounds and a general lowering of the sound level that can be detected.

Otitis media

Otitis media is an inflammation in the middle ear that is usually accompanied by fluid buildup. The condition may be transient in some children, but persistent in others to the point of requiring surgical correction. In developed countries, otitis media is second to the common cold as the most common health problem in preschool-aged children. Hearing loss occurs because of the fluid accumulation and the resulting suppression of sound waves moving to the inner ear.

Central auditory processing disorders

Central auditory processing disorders result in hearing loss when the areas of the brain involved in hearing are damaged. Sources of damage include disease, injury, and tumor growth. Consistent with the variety of causes, the symptoms of the disorders include the inability to hear certain sounds, inability to tell one sound from another, and the inability to recognize a pattern such as speech in sounds.

Congenital hearing loss

Congenital hearing loss is present from birth and is caused by a genetic defect or disturbance during fetal development. Genetic factors cause more than half of all such disorders. Depending on the nature of the genetic defect, the occurrence of the hearing loss may be common or rare. For example, if both parents have a genetically determined hearing deficiency, the chance of passing the trait to their children is high. In other cases, people who have normal hearing carry a second, defective copy of a crucial gene. The chance of passing on the hearing loss is 25%.

Hearing loss at birth can also be caused by pre-birth infections such as measles, cytomegalovirus, or herpes simplex virus.

Otosclerosis

The abnormal growth of the bone of the middle ear prevents the ossicles, particularly the last of the trio of bones (the stapes), from properly transmitting sound waves to the inner ear in otosclerosis. The cause(s) of otosclerosis are not clear, although observations that the disorder spans family generations make a genetic source likely.

The diminished hearing that occurs is not sudden. Rather, the change is gradual and is usually recognized when the person becomes aware that she or he can no longer hear a low-pitched sound such as a whisper.

Other genetically based hearing losses

Usher syndrome affects both the ears and eyes. The defective genes that are at the heart of the malady are passed from parents to children. Depending on the nature of the syndrome, children can be born with moderate to severe hearing loss, or can be totally deaf. Others begin life essentially normal, with hearing loss progressively worsening to deafness by the teenage years.

Waardenburg syndrome affects both the ears and the color of the skin, eyes, or hair. Eyes can be different colors and hair can have a patch of white or become prematurely gray. Hearing can range from normal to severely impaired. At least four genes can produce the syndrome when they undergo mutation.

Ménière's disease

Ménière's disease is a change in the volume of the inner ear that produces swelling, pressure, pain , intermittent hearing loss, dizziness , and tinnitus. Swelling may be so pronounced that membranes like the eardrum can rupture. As well, some people report that their voice sounds louder than normal. The disease may be caused by a viral or bacterial infection.

Tinnitus

Tinnitus is a ringing noise or other sound that occurs in the absence of an external source of sound. For some, tinnitus is an infrequent occurrence. Others are very inconvenienced by near-constant tinnitus. The noises experienced in tinnitus range in description and include electronic noise, hissing steam, chirping crickets, bells, breaking glass, buzzing, and even the noise of a chainsaw. The noises can be constant or may rise and fall in volume with head motion or with the planting of feet during running.

Tinnitus has various known triggers. Foods such as red wine, cheese, and chocolate have been implicated. Over-the-counter drugs such as ibuprofen and extra-strength aspirin, and prescribed drugs, including oral contraceptives and aminoglycoside antibiotics, can cause tinnitus. Drug-related tinnitus disappears when the dosage is reduced or the drug stopped. The growth of certain tumors can cause tinnitus.

The aging of the inner ear is also a factor in tinnitus. As nerve cells deteriorate and the many hairs in the cochlea that transmit sound waves to the nerves become damaged and broken with time, the signaling of sound impulses to the brain becomes faulty. Nerves may fire when there has been no stimulus. The brain interprets the signal as actual noise.

Sudden deafness or sudden sensorineural hearing loss

This rapid decrease or complete loss of hearing can occur within minutes or over the course of several days. The hearing loss typically affects one ear and often resolves with time. Sudden deafness is much more serious and should be treated as a medical emergency requiring immediate medical attention. Causes are unclear and may involve an infection, head injury, reaction to a drug, problems with circulation, and other disorders such as multiple sclerosis .

Deafness

The complete loss of hearing can be due to genetically determined developmental difficulties, a trauma such as a loud noise, physical damage to structures in the ear, nerves, or relevant areas of the brain, and infection during pregnancy (such as rubella). In a great many cases, deafness is permanent. Childhood deafness typically becomes apparent when a child appears inattentive and fails to meet language milestones.

Diagnosis

Presbycusis is usually first detected by a family physician. Diagnosis is subsequently made by a hearing specialist or an audiologist, and involves a hearing test in which sounds of differing frequencies and gradually decreasing volume are sent to one ear at a time.

Tinnitus is self-evident, as the ringing or other sensation is impossible to ignore. In contrast, otitis media can be difficult to diagnose, as it is often not accompanied by pain or a fever. Fluid in the ear can be a sign of otitis media. Also, changes in children's behavior such as playing the television louder, misunderstanding directions, and pulling at the ears can all be indicators of otitis media.

Imaging of the inside of the ear using the technique of magnetic resonance imaging (MRI) can be useful in diagnosing Ménière's disease. Usher syndrome is diagnosed by the simultaneous appearance of ear and eye problems.

Treatment team

The varied treatment can involve the family physician and more specialized doctors, including audiologists and otolaryngologists (specialists in ear, nose, and throat disorders). As well, speech-language pathologists can be involved in the treatment of hearing loss-related speech disorders in children.

Treatment

Treatment for presbycusis can be as simple as keeping the ear canals free from sound-muffling wax buildup. Another fairly common treatment for older people is the use of a hearing aid, which amplifies sound and directs the sound into the ear canal. About 20% of those with age-related hearing loss can benefit from an aid. More severe presbycusis can be treated using a cochlear implant. The device actually compensates for the nonworking parts of the inner ear. Conductive hearing loss can usually be fully corrected by medication or surgery. Similarly, when tinnitus is caused by overmedication, the condition is alleviated by modifying or eliminating the dosage of the drug.

Ménière's disease and Usher syndrome cannot be cured, however, the symptoms can be greatly relieved by release of the buildup of pressure in the inner ear and the use of hearing aids or implants, respectively. Coping strategies and increased knowledge of the conditions can then help a person lead an essentially normal life.

Otosclerosis that is more pronounced can be treated by a surgical procedure called a stapedectomy, in which the damaged portion of the middle ear, the stapes, one of the three bones of the middle ear, is bypassed by an implanted device that routes sound to the inner ear. Milder otosclerosis may be lessened by the use of a hearing aid.

Recovery and rehabilitation

Some conditions that can be addressed by surgery or the use of a hearing aid or an implant have varying levels of recovery. Other conditions involving permanent deafness cannot be cured.

Clinical trials

As of April 2004, at least eight clinical trials were active in the United States. Most focus on deafness, in particular the determination of the genetic factors that contribute to or cause deafness. Updated information on these studies can be found at the National Institutes of Health Web site for clinical trials at <http://www.clinicaltrials.gov>.

Prognosis

Age-related hearing loss can be partially or almost completely compensated for by a change in lifestyle and the development of coping skills (listening to the radio at higher volume, different conversational behavior in crowds, use of hearing aids or implants). Otitis media can cause delayed speech development, if undiagnosed, because of the child's impaired ability to hear. Sudden hearing loss usually resolves on its own within a few days to several weeks. However, in about 15% of cases, the condition worsens with time.

Special concerns

The various surgeries that can be performed all carry some risk, and the quality of sound that is provided by cochlear implants varies greatly among recipients.

Additionally, tinnitus can be caused by the buildup of cholesterol in arteries around the ear, high blood pressure, and by malformed arteries or veins. Tinnitus, therefore, may be an indication of a more serious health problem.

Resources

BOOKS

Dugan, Marcia B. Living with Hearing Loss. Baltimore: Gallaudet Press, 2003.

Schwartz, Sue. Choices in Deafness: A Parents'Guide to Communication Options. Bethesda, MD: Woodbine House, 2003.

PERIODICALS

DeJonckere, P. H., and G. G. de Surgeres. "Acute Tinnitus and Permanent Audiovestibular Damage after Hepatitis B Vaccination." International Tinnitus Journal (July 2001): 5961.

Waddell, A., and R. Canter. "Tinnitus." American Family Physician (February 2004): 591592.

OTHER

"Hearing Loss." MayoClinic.com. April 8, 2004 (May 30, 2004). <http://www.mayoclinic.com/invoke.cfm?id=DS00172>.

"Tinnitus." MayoClinic.com. April 8, 2004 (May 30, 2004). <http://www.mayoclinic.com/invoke.cfm?id=DS00365>.

ORGANIZATIONS

American Academy of Audiology. 8300 Greensboro Drive, Suite 750, McLean, VA 22102. (703) 790-8466 or (800) 222-2336; Fax: (703) 790-8631. [email protected] <http://www.audiology.org>.

American Speech-Language-Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (301) 638-8255 or (800) 638-8255; Fax: (301) 571-0457. [email protected] <http://www.asha.org>.

American Tinnitus Association. PO Box 5, Portland, OR 97207-0005. (503) 248-9985 or (800) 634-8978; Fax: (503) 248-0024. [email protected] <http://www.ata.org>.

Deafness Research Foundation. 1050 17th Street NW, Suite 701, Washington, DC 20036. (202) 289-5850. <http://www.drf.org>.

National Center on Deafness. 18111 Nordhoff Street, Northridge, CA 91330-8267. (818) 677-2145; Fax: (818) 677-7693. [email protected] <http://ncod.csun.edu>.

National Institute on Deafness and Other Communication Disorders, National Institutes of Health. 31 Center Drive, MSC 2320, Bethesda, MD 20892-2320. (301) 496-7243 or (800) 241-1044; Fax: (301) 402-0018. [email protected] <http://www.nidcd.nih.gov>.

Brian Douglas Hoyle, PhD

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Hearing Loss

Hearing loss

Definition

Hearing loss is any degree of impairment of the ability to apprehend sound.

Description

Sound can be measured accurately. The term decibel (dB) is a measure of loudness and refers to a unit for expressing the relative intensity of sound on a scale from zero, for a nearly imperceptible sound, to 130, which is the level at which sound causes pain in the average person. A drop of more than 10 dB in the level of sound a person can hear is significant.

Sound travels as waves through a medium like air or water. These waves are collected by the external ear and cause the tympanic membrane (eardrum) to vibrate. The chain of ossicles (tiny bones) connected to the eardrumthe incus, malleus, and stapescarries the vibration to the oval window (an opening to the inner ear), increasing its amplitude 20 times on the way. There, the energy causes a standing wave in the watery liquid (endolymph) inside the organ of Corti. (A standing wave is one that does not move.) The frequency of the sound determines the configuration of the standing wave. Many thousands of tiny nerve fibers detect the highs and lows of the standing wave and transmit their findings to the brain, which interprets the signals as sound.

To summarize, sound energy passes through the air of the external ear, the bones of the middle ear, and the liquid of the inner ear. It is then translated into nerve impulses, sent to the brain through nerves, and understood there as sound. It follows that there are five steps in the hearing process:

  • air conduction through the external ear to the eardrum
  • bone conduction through the middle ear to the inner ear
  • water conduction to the organ of Corti
  • nerve conduction into the brain
  • interpretation by the brain

Hearing can be interrupted in a variety of ways at each of the five steps.

The external ear canal can be blocked with ear wax, foreign objects, infection, and tumors. Overgrowth of the bone can also narrow the passageway, making blockage and infection more likely. This condition can occur when the ear canal has been flushed with cold water repeatedly for years, as is the case with surfers, for whom the condition called "surfer's ear" is named.

The eardrum is so thin a physician can see through it into the middle ear. It can be ruptured by sharp objects, pressure from an infection in the middle ear, or even a firm cuffing or slapping of the ear. The eardrum is also susceptible to pressure changes during scuba diving.

Several conditions can diminish the mobility of the small bones (ossicles) in the middle ear. Otitis media, an infection in the middle ear, occurs when fluid cannot escape into the throat because the eustachian tube is blocked. The fluid (pus or mucus) that accumulates prevents the ossicles from moving as efficiently as they normally do, thus dampening the sound waves. In a disease called otosclerosis, spongy tissue grows around the bones

DECIBEL RATINGS AND HAZARDOUS LEVELS OF NOISE
Decibel Level Example Of Sounds
Above 110 decibels, hearing may become painful
Above 120 decibels is considered deafening
Above 135 decibels, hearing will become extremely painful and hearing loss may result if exposure is prolonged
Above 180 decibels, hearing loss is almost certain with any exposure
30 Soft whisper
35 Noise may prevent the listener from falling asleep
40 Quiet office noise level
50 Quiet conversation
60 Average television volume, sewing machine, lively conversation
70 Busy traffic, noisy restaurant
80 Heavy city traffic, factory noise, alarm clock
90 Cocktail party, lawn mower
100 Pneumatic drill
120 Sandblasting, thunder
140 Jet airplane
180 Rocket launching pad

of the inner ear. This growth sometimes binds the stapes in the oval window, which interferes with its normal vibration and causes deafness. All the conditions mentioned so farthose that occur in the external and middle earare causes of what is known as conductive hearing loss.

The second category, sensory hearing loss, refers to damage to the organ of Corti and the acoustic nerve. Prolonged exposure to loud noise is the leading cause of sensory hearing loss. A million people have this condition, many identified during the military draft and rejected as being unfit for duty. The cause is often believed to be prolonged exposure to rock music. Occupational noise exposure is the other leading cause of noise-induced hearing loss (NIHL) and is ample reason for wearing ear protection on the job.

More unusual, but often undetected, is low-frequency hearing loss. Scientists discovered in 2001 that people with a particular gene mutation gradually lose their abilities to hear low-frequency sounds. Since those people with this type of hearing loss can still distinguish speech, they often remain unaware of the low-frequency changes in their hearing. The scientists believe that the same gene mutations might make some people more susceptible to high-frequency hearing loss, but further study is needed.

One-third of people older than 65 have presbycusis, which is sensory hearing loss due to aging . Both NIHL and presbycusis are primarily loss of the ability to hear high-frequency sounds. In speech, consonants generally have a higher frequency than vowels. Yet in most languages, consonants provide us the clues needed for determining what a person is saying. So these people hear plenty of noise, they just cannot easily make out what it means. They have particular trouble differentiating speech from background noise.

Brain infections such as meningitis , drugs such as the aminoglycoside antibiotics (streptomycin, gentamycin, kanamycin, tobramycin), and Meniere's disease can also cause permanent sensory hearing loss. Meniere's disease combines attacks of hearing loss with attacks of vertigo. The symptoms may occur together or separately. High doses of salicylates such as aspirin and quinine can cause a temporary high-frequency loss, and prolonged high doses can lead to permanent deafness. There is also a hereditary form of sensory deafness and a congenital form most often caused by rubella (German measles ).

Sudden hearing loss of at least 30 dB in less than three days is most commonly caused by cochleitis, a mysterious viral infection.

The final category of hearing loss is neural hearing loss. Permanent neural hearing loss most often results from damage to the acoustic nerve and the parts of the brain that control hearing. Strokes, multiple sclerosis , and acoustic neuromas are all possible causes of neural hearing loss.

Hearing can also be diminished by tinnitus , which is characterized by extra sounds generated by the ear. These sounds are referred to as tinnitus, and can be ringing, blowing, clicking, or anything else that no one but the patient hears. Tinnitus may be caused by loud noises, medication, allergies , or medical conditionsfrom the same kinds of disorders that can cause diminished hearing.

Diagnosis

Many common causes of hearing loss can be detected through an examination of the ears and nose combined with simple hearing tests performed in the physician's office. An audiogram (a test of hearing at a range of sound frequencies) often concludes the evaluation. These simple tests often produce a diagnosis. If the defect is in the brain or the acoustic nerve, further neurological testing and imaging will be required.

The audiogram has many uses in diagnosing hearing deficits. The pattern of hearing loss across the audible frequencies gives clues to the cause. Several alterations in the testing procedure can give additional information. For example, speech is perceived differently than pure tones. Adequate perception of sound combined with inability to recognize words points to a brain problem rather than a sensory or conductive deficit. Loudness perception is distorted by disease in certain areas but not in others. Acoustic neuromas often distort the perception of loudness.

Treatment

Conductive hearing loss can be treated with alternative therapies that are specific to the particular condition.

Nutritional therapy

The following dietary changes may help improve certain hearing impairment conditions:

  • Alleviate accumulated wax in the ear by taking oral supplements with essential fatty acids such as flax oil and omega-3 oil.
  • Identify and avoid potential allergenic foods. Children who are allergic to foods have an increased risk of getting chronic ear infections.
  • Take nutritional supplements. B-complex vitamins and iron supplements may be helpful in preventing protein deficiency and anemia . These conditions depress immune function and increase the risk of chronic ear infections. Children suffering from frequent ear infections may need supplementation with strong antioxidants such as vitamins A and C, zinc , and bioflavonoids . High-potency multivitamin and mineral supplements should contain most of these helpful nutrients as well as other essential vitamins and minerals.

Herbal therapy

There are several effective herbal treatments for hearing impairments. They include:

  • Ginkgo biloba. Ginkgo may be effective in patients with hearing loss who often complain of ringing in the ears.
  • Natural antibiotics such as echinacea and goldenseal can help prevent or treat ear infections.
  • Certain Chinese herbal combinations can help alleviate tinnitus, ear infections, and chronic sinus infections that can lead to hearing loss.

Homeopathy

Homeopathic therapies may help patients who have sensory hearing loss. An experienced homeopathic physician will prescribe specific remedies based on knowledge of the underlying cause.

Acupuncture

Acupuncture may be able to improve hearing in some patients with sensory-neural deafness. It may be used to improve the circulation of fluids in the head that lead to chronic congestion and noises.

Other therapies

Other therapies that may help improve hearing in some patients include Ayurvedic medicine, craniosacral therapy , and auditory integration training .

Allopathic treatment

Conductive hearing loss can almost always be restored to some degree, if not completely.

  • Matter in the ear canal can easily be removed, with a dramatic improvement in hearing.
  • Surfer's ear gradually regresses if the patient avoids cold water or uses a special ear plug. In advanced cases, surgeons can grind away the excess bone.
  • A middle-ear infection involving fluid is also simple to treat. If medications do not work, fluid may be surgically drained through the eardrum, which heals completely after treatment.
  • Traumatically damaged eardrums can be repaired with a tiny skin graft.
  • Otosclerosis may be surgically repaired through an operating microscope. In this intricate procedure, tiny artificial parts are substituted for the original ossicles.

Now available for complete conductive hearing loss are bone conduction hearing aids and even devices that can be surgically implanted in the cochlea.

Sensory and neural hearing loss, on the other hand, cannot readily be cured. Fortunately such hearing loss is rarely complete, and hearing aids can fill the deficit. In-the-ear hearing aids can boost the volume of sound by up to 70 dB. (Normal speech is about 60 dB.) Federal law now requires that aids be dispensed only by prescription.

Tinnitus can sometimes be relieved by adding white noise (such as the sound of wind or waves crashing on the shore) to the environment.

Decreased hearing is such a common problem that there are legions of organizations to provide assistance. Special language training, both in lip reading and signing, is available in most regions of the United States, as well as special schools and camps for children.

KEY TERMS

Meniere's disease
The combination of vertigo and decreased hearing caused by abnormalities in the inner ear.

Prevention

Prompt treatment and attentive follow-up of middle ear infections in children will prevent this cause of conductive hearing loss. Sensory hearing loss as a complication of epidemic disease has been greatly reduced by control of infectious childhood diseases, such as measles. Laws that require protection from loud noise in the workplace have substantially reduced incidences of noise-induced hearing loss. Surfers, cold-water fishermen, and other people who are regularly exposed to frigid water should use the right kind of ear plugs.

Resources

BOOKS

Alberti, R. W. "Occupational Hearing Loss." Disorders of the Nose, Throat, Ear, Head, and Neck, edited by John Jacob Ballenger. Philadelphia: Lea & Febiger, 1991.

Bennett, J. Claude, and Fred Plum, eds. Cecil Textbook of Medicine. Philadelphia: W. B. Saunders, 1996.

"Hearing and Ear Disorders." In Alternative Medicine: The Definitive Guide, compiled by The Burton Goldberg Group. Tiburon, Calif.: Future Medicine Publishing, 1999.

Tierney, Lawrence M., M.D., et al., eds. Current Medical Diagnosis and Treatment. Stamford, CT: Appleton & Lange, 1998.

PERIODICALS

Nadol, J. B. "Hearing Loss." New England Journal of Medicine 329 (1993): 1092102.

"Scientist Identify Gene Linked to Low-Frequency Hearing Loss." Genomics and Genetics Weekly (December 14, 2001): 6.

Sodipo, Joseph O., and Phillip A. Okeowo. "Therapeutic Acupuncture for Sensory-Neural Deafness." Am J Chin Med 8, no. 4 (1980): 385390.

ORGANIZATIONS

Alexander Graham Bell Association for the Deaf. 3417 Volta Place NW, Washington, DC 20007-2778. (202) 337-5220. http:/www.agbell.org.

National Association of the Deaf. 814 Thayer Ave., Silver Spring, MD 20910-4500. (301) 587-1788. http://www.nad.org.

National Institute on Deafness and Other Communication Disorders, National Institutes of Health. 31 Center Dr., Bethesda, MD 20892. (301) 496-7243. Fax: (301) 402-0018. http://www.nih.gov/nidcd.

Self Help for Hard of Hearing People, Inc. 7910 Woodmont Avenue, Suite 1200, Bethesda, MD 20814. (301) 657-2248. http://www.shhh.org.

OTHER

DeafSource: An Internet Guide to Resources for Helping Professionals Working with Deaf and Hard of Hearing Individuals. http://home.earthlink.net/~drblood.

Mai Tran

Teresa G. Odle

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Hearing Loss

Hearing Loss

Definition

Hearing loss is any degree of impairment of the ability to apprehend sound.

Description

Sound can be measured accurately. The term decibel (dB) refers to an amount of energy moving sound from its source to our ears or to a microphone. A drop of more than 10 dB in the level of sound a person can hear is significant.

Sound travels through a medium like air or water as waves of compression and rarefaction. These waves are collected by the external ear and cause the tympanic membrane (ear drum) to vibrate. The chain of ossicles connected to the ear drumthe incus, malleus, and stapescarries the vibration to the oval window, increasing its amplitude 20 times on the way. There the energy causes a standing wave in the watery liquid (endolymph) inside the Organ of Corti. (A standing wave is one that does not move. A vibrating cup of coffee will demonstrate standing waves.) The configuration of the standing wave is determined by the frequency of the sound. Many thousands of tiny nerve fibers detect the highs and lows of the standing wave and transmit their findings to the brain, which interprets the signals as sound.

To summarize, sound energy passes through the air of the external ear, the bones of the middle ear and the liquid of the inner ear. It is then translated into nerve impulses, sent to the brain through nerves and understood there as sound. It follows that there are five steps in the hearing process:

  • air conduction through the external ear to the ear drum
  • bone conduction through the middle ear to the inner ear
  • water conduction to the Organ of Corti
  • nerve conduction into the brain
  • interpretation by the brain.
Decibel Ratings And Hazardous Levels Of Noise
Decibel Level Example Of Sounds
Above 110 decibels, hearing may become painful Above 120 decibels is considered deafening Above 135 decibels, hearing will become extremely painful and hearing loss may result if exposure is prolonged Above 180 decibels, hearing loss is almost certain with any exposure
30 Soft whisper
35 Noise may prevent the listener from falling asleep
40 Quiet office noise level
50 Quiet conversation
60 Average television volume, sewing machine, lively conversation
70 Busy traffic, noisy restaurant
80 Heavy city traffic, factory noise, alarm clock
90 Cocktail party, lawn mower
100 Pneumatic drill
120 Sandblasting, thunder
140 Jet airplane
180 Rocket launching pad

Hearing can be interrupted in several ways at each of the five steps.

The external ear canal can be blocked with ear wax, foreign objects, infection, and tumors. Overgrowth of the bone, a condition that occurs when the ear canal has been flushed with cold water repeatedly for years, can also narrow the passageway, making blockage and infection more likely. This condition occurs often in Northern Californian surfers and is therefore called "surfer's ear."

The ear drum is so thin a physician can see through it into the middle ear. Sharp objects, pressure from an infection in the middle ear, even a firm cuffing or slapping of the ear, can rupture it. It is also susceptible to pressure changes during scuba diving.

Several conditions can diminish the mobility of the ossicles (small bones) in the middle ear. Otitis media (an infection in the middle ear) occurs when fluid cannot escape into the throat because of blockage of the eustachian tube. The fluid that accumulates, whether it be pus or just mucus and dampens the motion of the ossicles. A disease called otosclerosis can bind the stapes in the oval window and thereby cause deafness.

All the conditions mentioned so far, those that occur in the external and middle ear, are causes of conductive hearing loss. The second category, sensory hearing loss, refers to damage to the Organ of Corti and the acoustic nerve. Prolonged exposure to loud noise is the leading cause of sensory hearing loss. A million people have this condition, many identified during the military draft and rejected as being unfit for duty. The cause is often believed to be prolonged exposure to rock music. Occupational noise exposure is the other leading cause of noise induced hearing loss (NIHL) and is ample reason for wearing ear protection on the job. A third of people over 65 have presbycusissensory hearing loss due to aging. Both NIHL and presbycusis are primarily high frequency losses. In most languages, it is the high frequency sounds that define speech, so these people hear plenty of noise, they just cannot easily make out what it means. They have particular trouble selecting out speech from background noise. Brain infections like meningitis, drugs such as the aminoglycoside antibiotics (streptomycin, gentamycin, kanamycin, tobramycin), and Meniere's disease also cause permanent sensory hearing loss. Meniere's disease combines attacks of hearing loss with attacks of vertigo. The symptoms may occur together or separately. High doses of salicylates like aspirin and quinine can cause a temporary high-frequency loss. Prolonged high doses can lead to permanent deafness. There is an hereditary form of sensory deafness and a congenital form most often caused by rubella (German measles ).

Sudden hearing lossat least 30dB in less than three daysis most commonly caused by cochleitis, a mysterious viral infection.

The final category of hearing loss is neural. Damage to the acoustic nerve and the parts of the brain that perform hearing are the most likely to produce permanent hearing loss. Strokes, multiple sclerosis, and acoustic neuromas are all possible causes of neural hearing loss.

Hearing can also be diminished by extra sounds generated by the ear, most of them from the same kinds of disorders that cause diminished hearing. These sounds are referred to as tinnitus and can be ringing, blowing, clicking, or anything else that no one but the patient hears.

Diagnosis

An examination of the ears and nose combined with simple hearing tests done in the physician's office can detect many common causes of hearing loss. An audiogram often concludes the evaluation, since these simple means often produce a diagnosis. If the defect is in the brain or the acoustic nerve, further neurological testing and imaging will be required.

The audiogram has many uses in diagnosing hearing deficits. The pattern of hearing loss across the audible frequencies gives clues to the cause. Several alterations in the testing procedure can give additional information. For example, speech is perceived differently than pure tones. Adequate perception of sound combined with inability to recognize words points to a brain problem rather than a sensory or conductive deficit. Loudness perception is distorted by disease in certain areas but not in others. Acoustic neuromas often distort the perception of loudness.

Treatment

Conductive hearing loss can almost always be restored to some degree, if not completely.

  • matter in the ear canal can be easily removed with a dramatic improvement in hearing.
  • surfer's ear gradually regresses if cold water is avoided or a special ear plug is used. In advanced cases, surgeons can grind away the excess bone.
  • middle ear infection with fluid is also simple to treat. If medications do not work, surgical drainage of the ear is accomplished through the ear drum, which heals completely after treatment.
  • traumatically damaged ear drums can be repaired with a tiny skin graft.
  • surgical repair of otosclerosis through an operating microscope is one of the most intricate of procedures, substituting tiny artificial parts for the original ossicles.

Sensory and neural hearing loss, on the other hand, cannot readily be cured. Fortunately it is not often complete, so that hearing aids can fill the deficit.

In-the-ear hearing aids can boost the volume of sound by up to 70 dB. (Normal speech is about 60 dB.) Federal law now requires that they be dispensed only upon a physician's prescription. For complete conduction hearing loss there are now available bone conduction hearing aids and even devices that can be surgically implanted in the cochlea.

Tinnitus can sometimes be relieved by adding white noise (like the sound of wind or waves crashing on the shore) to the environment.

Decreased hearing is such a common problem that there are legions of organizations to provide assistance. Special language training, both in lip reading and signing, special schools and special camps for children are all available in most regions of the United States.

Alternative treatment

Conductive hearing loss can be treated with alternative therapies that are specific to the particular condition. Sensory hearing loss may be helped by homeopathic therapies. Oral supplementation with essential fatty acids such as flax oil and omega 3 oil can help alleviate the accumulation of wax in the ear.

KEY TERMS

Decibel A unit of the intensity of sound, a measure of loudness.

Meniere's disease The combination of vertigo and decreased hearing caused by abnormalities in the inner ear.

Multiple sclerosis A progressive disease of brain and nerve tissue.

Otosclerosis A disease that scars and limits the motion of the small conducting bones in the middle ear.

Stroke Sudden loss of blood supply to part of the brain.

Prevention

Prompt treatment and attentive follow-up of middle ear infections in children will prevent this cause of conductive hearing loss. Control of infectious childhood diseases such as measles has greatly reduced sensory hearing loss as a complication of epidemic diseases. Laws that require protection from loud noise in the workplace have achieved substantial reduction in noise induced hearing loss. Surfers should use the right kind of ear plugs.

Resources

ORGANIZATIONS

Alexander Graham Bell Association for the Deaf. 3417 Volta Place NW, Washington, DC 20007. (202) 337-5220. http://www.agbell.org.

Auditory-Verbal International. 2121 Eisenhower Ave., Suite 402, Alexandria, VA 22314. (703) 739-1049. [email protected] http://www.auditory-verbal.org/contact.htm.

Better Hearing Institute. 515 King Street, Suite 420, Alexandria, VA 22314. (703) 684-3391.

Central Institute for the Deaf. Washington University. St. Louis, Missouri. http://cidmac.wustl.edu.

League for the Hard of Hearing. 71 West 23rd St., New York, New York 10010-4162. (212) 741-7650. http://www.lhh.org.

National Association of the Deaf. 814 Thayer Ave., Silver Spring, MD, 20910. (301) 587-1788. http://nad.policy.net.

Self Help for Hard of Hearing People, Inc. 7800 Wisconsin Ave., Bethesda, MD 20814. (301) 657-2248. http://www.shhh.org.

The Sight & Hearing Association (SHA). http://www.sightandhearing.org.

World Recreation Association of the Deaf (WRAD). http://www.wrad.org.

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Hearing Disorders

HEARING DISORDERS

Hearing impairment occurs in all age groups. In children hearing loss can be genetic or acquired as a result of infection either during fetal development or during childhood. It is estimated that up to 1 child in every 1,000 live births suffers from hearing loss. The prevalence of hearing loss in children grows to 1.5 to 2 cases per 1,000 children by the age of six. Overall, 50 percent of childhood hearing loss can be traced to genetic factors. This includes congenital conditions such as Down syndrome. Parents with familial deafness pass an increased risk of deafness to their children. Infections during pregnancy (e.g., German measles or cytomegalovirus) can cause congenital deafness. Only 6 percent of children with hearing impairment are profoundly impaired, while the majority retain some hearing ability. Children without a profound hearing loss still have difficulty with speech development and later learning.

In adults, the greatest hearing losses are due to presbycusis and noise-induced hearing loss. Presbycisus of "old hearing" affects men more than women and is estimated to affect up to 80 percent of persons over 65 years of age. Presbycusis may also be linked to noise exposure. Noise exposure is a preventable cause of hearing loss. It is also among the most commonly identified disabilities in industrialized nations. In 1996 the National Institute for Occupational Safety and Health estimated that 30 million people work with noise levels above the level of 85 decibels and 17 percent of production workers suffer some hearing loss. Hearing loss is also associated with a family history of hearing loss, a history of smoking, and presence of hypertension, diabetes, and elevated cholesterol.

The human hearing mechanism is complex. Sound waves enter the ear canal and set up movement of the eardrum, also called the tympanic membrane. The eardrum is connected to the hearing organ, or cochlea, by small bones called ossicles. The cochlea is filled with fluid and it rests in the fluid-filled inner ear. One of the ossicles is anchored to the eardrum; another to an opening in the cochlea called the oval window. The movement of the eardrum sets up movement in the bones, which in turn moves the oval window. This sets up waves in the fluid of the cochlea. Thousands of tiny hair cells that line part of the cochlea are stimulated by these waves, which are then translated to nerve impulses that travel to the brain where they are deciphered by the hearing center of the brain and perceived as sound.

Problems with hearing can be caused from problems all along the hearing pathway. Physicians generally divide hearing loss into two major types: "conductive" and "sensorineural" (sensory). Conductive losses are those involving the transmission of sound waves from the environment to the cochlea. Sensory losses involve the cochlea and its nerve cells, as well as the eighth cranial nerve, called the auditory nerve, which carries nerve impulses to the brain. Some physicians also include a third type of hearing impairment, called central, in which the brain is unable to decipher the information from the hearing complex because of stroke or brain damage.

CONDUCTIVE HEARING LOSS

The most common cause of conductive hearing loss is cerumen, or earwax, impaction. It is often caused by attempts at cleaning the ears with cotton swabs. Putting a swab in the ear usually pushes wax further back in the canal causing buildup over time and leading to impaction. Some patients genetically make more or harder earwax that predisposes them to impactions. Children are notorious for introducing foreign objects into their ears. These objects most often must be removed under controlled circumstances to avoid damage to the inner ear. Water can lodge behind wax buildups causing irritating noises and a sense of fullness in the ears. People who use hearing aids may also experience wax buildup, possibly because the introduction of the hearing aid affects the natural mechanism by which earwax flows from the inner ear. Irrigation and solutions are used to soften the wax so that it can be rinsed out. A physician may also use a removal scoop. Prevention includes avoidance of cotton tipped swabs and maintenance use of solutions to soften earwax.

Another cause of hearing loss is disruption or dislocation of the bones of the inner ear. This occurs when a foreign object, such as a cotton swab or pencil, is put in the ear. This can cause perforation of the eardrum and dislocation of the bones, requiring surgery. Conductive hearing loss is also caused by common cold and other upper respiratory infections, including infections of the fluid of the inner ear.

The eustachian tube drains the inner ear into the back of the throat, but when swollen because of infection of the upper respiratory tract, the fluid builds up in the inner ear. This decreases the ability of the eardrum to move and decreases hearing. The effect is usually transient and hearing is restored when the infection resolves. In young children, however, repetitive ear infections can cause speech delay because children depend on acute hearing in order to mimic language sounds.

Cholesteatoma is a buildup of skin cells around the bones of the ear preventing their movement. It usually occurs as a complication of chronic middle-ear infections and is corrected by surgery, but it must be caught early in order to avoid destruction of the ossicles by the built up material. Otosclerosis is a slowly progressive hearing loss that is more common in women than in men. It is caused by a change in the bones of the ear and is treatable with surgery if recognized early. Other causes of conductive hearing loss are rigidity of the eardrum from scarring caused by old ear infections, eardrum perforations, and barotrauma (pressure trauma) in divers and air travelers.

SENSORY HEARING LOSS

Generally, sensory hearing loss is less amenable to surgery and treatment, and is better dealt with through prevention. The most common cause of sensory loss is presbycusishearing loss associated with aging. Treatment consists of hearing aids, or "amplification."

Noise-associated hearing loss is usually preventable. Noise damage may be part of the hearing loss associated with aging. Earplugs and hearing protection in the workplace helps to prevent some hearing loss, but loud music, concerts, sporting events, and power tools and machinery used in the home also adds to the damage. Hearing protection should be used in all of these cases.

Other causes of sensory hearing loss include multiple sclerosis, tumors of the nerves, congenital deafness associated with infection, or genetic abnormalities and toxins. A tumor on the auditory nerve, known as acoustic neuroma, may be surgically removed, but depending on the position and size of the tumor, hearing may not improve. Toxic effects of drugs such as aspirin, certain antibiotics, and some cancer treatments can lead to hearing loss, and can be avoided by careful monitoring of the dosage. Sudden sensory hearing loss has many causes including viral illness, diabetes, and Meniere's syndrome.

Karen L. Hall

(see also: Hearing Protection; Occupational Safety and Health )

Bibliography

Beers, M. H., and Berkow, R., eds. (1999). The Merck Manual of Diagnosis and Therapy, 17th edition. Whitehouse Station, NJ: Merck and Company.

Nelson, W. E., ed. (1996). Textbook of Pediatrics. Philadelphia, PA: W. B. Saunders Company.

Taylor, R. B. (1998). Family Medicine Principles and Practice. New York: Springer-Verlag.

Turkington, C., and Sussman, A. (2000). Living with Hearing Loss. New York: Checkmark Books.

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Hearing Loss

HEARING LOSS

DEFINITION


Hearing loss is any reduction in a person's ability to detect sound.

DESCRIPTION


Hearing is a complex process that consists of many steps. It begins when sound waves strike the outside of the ear. Sound waves are vibrations that occur in air. When sound waves hit the ear, they cause tissue in the ear to start vibrating.

The ear consists of three major sections: the external ear, the middle ear, and the inner ear. The external ear acts like a small sound-collecting tube. Sound waves enter the ear and pass down a narrow canal called the auditory canal. At the end of the canal, the sound waves strike a thin membrane called the tympanic (pronounced tim-PA-nik) membrane, or ear drum. They cause the tympanic membrane to begin vibrating.

Hearing Loss: Words to Know

Audiometer:
An instrument for testing a person's hearing.
Auditory canal:
A tube that leads from the outside of the ear to the tympanic membrane.
Auditory nerve:
A bunch of nerve fibers that carries sound from the inner ear to the brain.
Conductive hearing loss:
Hearing loss that occurs in the external or middle ear.
Eustachian tube:
A passageway that connects the middle ear with the back of the throat.
Ossicles:
A set of tiny bones in the middle ear responsible for transmitting sound vibrations from the outer ear to the inner ear.
Otosclerosis:
A disorder in which the bones of the middle ear become joined to each other.
Sensory hearing loss:
Hearing loss that occurs in the inner ear, auditory nerve, or brain.
Tympanic membrane:
A thin piece of tissue between the external ear and the middle ear.

Just beyond the tympanic membrane is the middle ear. The middle ear contains three bones called ossicles (pronounced AH-sih-kulls). Vibration of the tympanic membrane is passed along to the ossicles. They too begin to vibrate.

The ossicles are connected to the inner ear. The inner ear is filled with a clear, watery fluid. As the ossicles vibrate, they create another wave inside the watery fluid in the inner ear. This wave is similar to a water wave on a lake or the ocean.

In the last stage of hearing, the water wave in the inner ear collides with the auditory nerve. The auditory nerve picks up these vibrations and transmits them to the brain. The brain "reads" these vibrations as a sound.

Hearing loss can occur at any stage of this process. For example, sound waves may be blocked as they try to pass down the auditory canal. Or they may not be able to pass through the ossicles in the middle ear. Or they may not be transmitted through the liquid of the middle ear or along the auditory nerve. Finally, the brain may lose its ability to make sense out of the vibrations it receives from the auditory nerve.

Hearing loss is usually defined as being either conductive or sensory hearing loss. Conductive hearing loss is caused by damage to the external or middle ear. Sound vibrations are unable to pass down the auditory canal, across the tympanic membrane, and through the ossicles. Sensory hearing loss occurs in the inner ear and the auditory nerve. Sound waves may reach the inner ear, but they are not transmitted successfully to the brain.

CAUSES AND SYMPTOMS


Some possible causes and symptoms of hearing loss at each of the above stages are as follows:

  • External ear. The auditory canal may become blocked with ear wax, foreign objects, infection, or a tumor. A tumor is a mass of cells that forms a lump somewhere in the body. This blockage prevents all or some of a group of sound waves from passing down the auditory canal.
  • Middle ear. The tympanic membrane and ossicles can be damaged by injury or infection. A sharp object inserted into the ear can break the membrane. A blow to the head may damage the membrane or the ossicles. High water pressure caused by a deep-sea dive can also damage the middle ear. Infection of the middle ear may be caused when fluids from the throat pass down the Eustachian (pronounced you-STAY-shee-un) tube into the middle ear. The Eustachian tube connects the middle ear with the back of the throat. A disease called otosclerosis (pronounced oh-toe-skle-RO-suss) can cause the ossicles to bind to each other. When that happens, they are not able to vibrate properly.
  • Inner ear. The primary cause of sensory hearing loss is exposure to loud noise. By some estimates, more than one million people have hearing problems for this reason. Exposure to loud noise may be caused by listening to loud music or working at a job where loud sounds are produced. Sensory hearing loss also occurs as a natural part of aging. About a third of the people over the age of sixty-five have partial or complete hearing loss. Infections of the inner ear and brain can also cause hearing loss. Certain drugs, including some common antibiotics, may damage the inner ear or auditory nerve. Finally, damage to the brain, such as stroke (see stroke entry) or multiple sclerosis (see multiple sclerosis entry), can cause hearing loss.

DIAGNOSIS


Hearing loss can often be diagnosed with a physical examination. A doctor may look directly into a patient's ears to see if any blockage is present, such as an infection or tumor. Another test involves the use of a tuning fork. A tuning fork is a metallic instrument that vibrates when struck. The tuning fork is placed next to the ear or placed against the patient's head. The vibrations it produces result in a musical tone. The patient's responses can help the doctor determine the patient's range of hearing.

Another important tool in the diagnosis of hearing problems is the audiometer (pronounced aw-dee-AH-meh-tur). An audiometer is a device that produces very pure tones of differing pitch and volume (loudness). A patient is provided with earphones connected to the audiometer. He or she is then asked to indicate the level at which various sounds can be heard. The data provided by this test may diagnose the type and severity of a patient's hearing loss. Many other tests are available to diagnose hearing disorders within the inner ear, the auditory nerve, and the brain itself.

TREATMENT


Conductive hearing loss can almost always be restored to some degree, if not completely. Some effective treatments include the following:

  • Matter blocking the auditory canal can usually be removed easily.
  • Middle ear infections can be treated with antibiotics. If necessary, the middle ear can be drained through the tympanic membrane. The tympanic membrane normally heals quickly after this surgery.
  • Damaged tympanic membranes can usually be repaired with a small skin graft.
  • Otosclerosis can be repaired surgically. Artificial parts can be substituted for the original ossicles.

Sensory hearing loss presents more serious problems. It often cannot be cured. Fortunately, hearing aids can help restore some of the hearing loss. Hearing aids can be dispensed only with a physician's prescription. They can make hearing at least ten times better.

Hearing problems are common. A number of organizations have been formed to help people with hearing loss. Special language training is available for children with reduced hearing. They may learn both lip reading and sign language.

PROGNOSIS


The prognosis for hearing loss varies widely. The likelihood of improvement depends on the type of hearing problem. Most conductive hearing losses can be cured. Normal hearing can be restored by relatively simple procedures. Sensory hearing loss is more difficult to treat. It can seldom be cured or repaired. Hearing aids can often provide people with near-normal hearing, however.

PREVENTION


Many types of hearing loss can be prevented. Infections of the throat and upper respiratory (breathing) tract should be monitored carefully. These infections can spread to the ears. If the ears do become infected, they should be treated as quickly as possible.

Noise reduction can prevent a large number of hearing problems. People who work in noisy environments, for example, should always wear protective headgear. People who enjoy loud music should use some restraint in listening to their favorite performers. This step alone can prevent thousands of cases of hearing loss each year.

FOR MORE INFORMATION


Books

Carmen, Richard, ed. Consumer Handbook on Hearing Loss and Hearing Aids: A Bridge to Healing. Sedona, AZ: Auricle Ink Publishers, 1999.

Pope, Anne. Hear: Solutions, Skills and Sources For People With Hearing Loss. London, New York: DK Publishing, 1997.

Turkington, Carol A. The Hearing Loss Sourcebook: A Complete Guide to Coping With Hearing Loss and Where to Get Help. New York: Plume, 1997.

Wayner, Donna S. Hear What You've Been Missing: How to Cope With Hearing Loss: Questions, Answers, Options. New York: John Wiley & Sons, 1998.

Organizations

Alexander Graham Bell Association for the Deaf. 3417 Volta Place, NW, Washington, DC 20007-2778. (202) 3375220. http://www.agbell.org.

The League for the Hard of Hearing. 71 West 23rd St., New York, NY 10010-4162. (212) 7417650. http://www.lhh.org.

Self Help for Hard of Hearing People, Inc. 79 Woodmon Ave., Suite 120C, Bethesda, MD 20814. (301) 675-2248. http://www.shhh.org.

Web sites

Vessel, B., "Deaf Source." [Online] http://home.earthlink.net/~drblood (accessed April 26, 1998).

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Hearing Loss

Hearing Loss

Definition

Hearing loss is any degree of impairment of the ability to comprehend sound.

Description

Sound can be accurately measured. The term decibel (dB) refers to an amount of energy moving sound from its source to the ears of one or more listeners or to a microphone. A decrease of more than 10 dB in the level of sound a person can hear is significant.

Sound travels through a medium, such as air or water, as waves of compression and rarefaction. These waves are collected by the external ear and cause the tympanic membrane (ear drum) to vibrate. The chain of ossicles connected to the ear drum—the incus, malleus, and stapes—carries the vibrations to the oval window, increasing their amplitude 20 times along the way. There, the energy creates a standing wave in the watery liquid (endolymph) inside the organ of Corti. (A standing wave is one that does not move. A vibrating cup of coffee will demonstrate standing waves.) The shape of the standing wave is determined by the frequency of the sound. Many thousands of tiny nerve fibers detect the highs and lows of the standing wave. Motions in the nerve endings are converted into electrical impulses. These are transmitted to the brain via a nerve. Specialized areas of the brain interpret the signals as sound.

To summarize, sound energy passes through the air of the external ear, the bones of the middle ear, and the liquid of the inner ear. It is then translated into nerve impulses, sent to the brain through the acoustic nerve, and understood there as sound. It follows that there are five steps in the hearing process:

  • air conduction through the external ear to the ear drum
  • bone conduction through the middle ear to the inner ear
  • water conduction inside the organ of Corti
Decibel ratings and hazardous levels of noise
Decibel level Example of sounds
Above 110 decibels, hearing may become painful
Above 120 decibels is considered deafening
Above 135 decibels, hearing will become extremely painful and hearing loss may result if exposure is prolonged
Above 180 decibels, hearing loss is almost certain with any exposure
Source: FDA Consumer, Gale Encyclopedia of Psychology, 1996.
30Soft whisper
35Noise may prevent the listener from falling asleep
40Quiet office noise level
50Quiet conversation
60Average television volume, sewing machine, lively conversation
70Busy traffic, noisy restaurant
80Heavy city traffic, factory noise, alarm clock
90Cocktail party, lawn mower
100Pneumatic drill
120Sandblasting, thunder
140Jet airplane
180Rocket launching pad
  • nerve conduction into the brain
  • interpretation by the brain

Causes and symptoms

Hearing can be interrupted in several ways at each of the five steps noted above.

The external ear canal can be blocked with ear wax (cerumen), foreign objects, infection, and tumors. Overgrowth of the bone, a condition that occurs when the ear canal has been flushed with cold water repeatedly for years, can also narrow the passageway, making blockage and infection more likely. This condition occurs often among northern Californian surfers and is aptly called "surfer's ear."

The ear drum is so thin that a physician can see through it, into the middle ear. Sharp objects, pressure from an infection in the middle ear, or even a firm cuffing or slapping of the ear, can rupture the ear drum. The eardrum is also susceptible to pressure changes, such as those that occur when one is scuba diving.

Several conditions can diminish the mobility of the ossicles (small bones) in the middle ear. Otitis media (an infection in the middle ear) occurs when fluid cannot escape into the throat because of blockage of the eustachian tube. The fluid that accumulates, whether it is pus or mucus, dampens the motions of the ossicles. A disease called otosclerosis can bind the stapes in the oval window and cause deafness.

All of the problems and conditions that occur in the external and middle ear are causes of conductive hearing loss. The second category, sensory hearing loss, refers to damage to the organ of Corti, or the acoustic nerve. Prolonged exposure to loud noise is the leading cause of sensory hearing loss. More than a million people have been identified as having this condition. The cause is often believed to be prolonged exposure to loud music. Occupational noise exposure is the other leading cause of noise induced hearing loss (NIHL) and is an ample reason for wearing ear protection on the job. Jobs in construction and loud offices may contribute to ear damage, as may noises of recreation, such as loud music or the engine of a motorcycle. Both types of noises may lead to loss of hairs in one's inner ear. Thousands of these tiny hairs are attached to nerve cells in the cochlea (a snailshaped structure in the inner ear). These tiny hairs aid the conversion of sound vibrations into electrical signals, which are then transmitted to the brain. When hairs become broken or bent, the transmission of the electric signals is not as good, and sound may become muffled. Words may become difficult to distinguish against background noises.

One-third of people over 65 have presbycusis (gradual loss of hearing that occurs as one ages) and one-half of those older than age 75 have a hearing impairment. Both NIHL and presbycusis are primarily high frequency losses. The human speech frequencies are in relatively low ranges. People with presbycusis hear noise but cannot easily make sense of it. They have particular trouble distinguishing speech from background noise. Brain infections, such as meningitis, drugs such as the aminoglycoside antibiotics (e.g., streptomycin, kanamycin, tobramycin), and Meénière's disease may also cause permanent sensory hearing loss. Meénière's disease combines attacks of hearing loss with attacks of vertigo. The symptoms may occur together or separately. High doses of salicylates, like aspirin and quinine, can cause a temporary high-frequency loss. Prolonged high doses can lead to permanent deafness. There is an hereditary form of sensory deafness and a congenital form most often caused by rubella (German measles).

Sudden hearing loss—at least 30dB in less than three days—is most commonly caused by cochleitis, an inflammation of the cochlea. The source of this process is thought to be viral, but as of 2001, no causative virus has been identified.

The final category of hearing loss is neural. Damage to the acoustic nerve and the parts of the brain that integrate and interpret sounds are the most likely to produce permanent hearing loss. Strokes, multiple sclerosis, and acoustic neuromas are all possible causes of neural hearing loss.

Hearing can also be diminished by extra sounds generated by the ear, most of them from the same kinds of disorders that cause hearing loss. These sounds are referred to as tinnitus and can be ringing, blowing, clicking, or anything else that no one but the affected person hears.

Diagnosis

An examination of the ears and nose, combined with simple hearing tests that can be conducted in a physician's office, detect many common causes of hearing loss. Analysis of an audiogram often concludes the evaluation, since these simple imaging often enables a diagnosis. If the defect is in the brain or the acoustic nerve, further neurologic testing and imaging will be required.

An audiogram has many uses in diagnosing hearing deficits. The pattern of hearing loss across the audible frequencies gives clues to the cause. Several alterations in the testing procedure can give additional information. For example, speech is perceived differently than pure tones. Adequate perception of sound, combined with inability to recognize words, indicates a brain problem rather than a sensory or conductive deficit. Loudness perception is distorted by disease in certain areas of the brain, but not in others. Acoustic neuromas often distort the perception of loudness.

Treatment

Conductive hearing loss can almost always be restored to some degree, if not completely.

  • Matter in the ear canal can be easily removed. This results in a dramatic improvement in hearing. In cases of earwax blockage, wax may be removed by the physician, who may loosen it and drain the ear, scoop it out, or use a suction device to removed softened wax.
  • Surfer's ear gradually regresses if cold water is avoided or a special ear plug is used. In advanced cases, excess bone can be ground away by surgeons.
  • Middle ear infection with fluid is also relatively easy to treat. If medications do not work, surgical drainage of the ear is accomplished through the ear drum, which heals completely after treatment.
  • Traumatically damaged ear drums can be repaired with a tiny skin graft.
  • Surgical repair of otosclerosis through an operating microscope is one of the most intricate procedures available, and substitutes tiny, artificial parts for the original ossicles.

Sensory and neural hearing loss, on the other hand, cannot readily be cured. Fortunately, the loss is not often complete, so that hearing aids can fill the deficit.

In-the-ear hearing aids can boost the volume of sound by up to 70 dB. (Normal speech is about 60 dB.) Federal law now requires that they be dispensed only with a physician's prescription. For complete conduction hearing loss, there are now bone conduction hearing aids available, as well as devices that can be surgically implanted in the cochlea.

Tinnitus can sometimes be relieved by adding white noise (like the sound of wind or waves crashing on the shore) to the environment.

Decreased hearing is such a common problem that there are many organizations that provide assistance. Special language training, both in lip reading and signing, and special schools and camps for hearing-impaired children are all available in most regions of the United States.

Conductive hearing loss can be treated with alternative therapies that are specific to the particular condition. Sensory hearing loss may be helped by homeopathic therapies. Oral supplementation with essential fatty acids such as flax oil and omega-3 oil can help alleviate the accumulation of wax in the ear.

Prognosis

The prognosis for conductive hearing loss is quite good. Since there is no cure for sensory or neural hearing loss, the prognosis is poor.

Health care team roles

Hearing examinations are usually conducted by physicians. Audiologists are trained to evaluate hearing. Speech language specialists are trained to provide treatment and rehabilitation for persons with impaired hearing.

Prevention

Prompt treatment and attentive follow-up of middle ear infections in children will prevent this cause of conductive hearing loss. Control of infectious childhood diseases, such as measles, has greatly reduced sensory hearing loss as a complication of epidemic diseases. Laws that require protection from loud noise in the workplace have achieved substantial reduction in noise induced hearing loss. Wearing specially designed earmuffs that resemble earphones may be of use where the noise is still too loud. Surfers should use the right kind of ear plugs.

One should have his or her hearing tested on a regular basis if a noisy environment cannot be avoided. Early detection will enable one to take steps to prevent further hearing loss. Avoiding exposure to loud noise and using hearing protection are the best ways to prevent hearing loss and slow the onset of presbycusis.

KEY TERMS

Compression— Narrower than average distances between wave peaks.

Decibel— A unit of the intensity of sound, a measure of loudness.

Meniere's disease— The combination of vertigo and decreased hearing caused by abnormalities in the inner ear.

Multiple sclerosis— A progressive disease of brain and nerve tissue.

Otosclerosis— A disease that scars and limits the motion of the small conducting bones in the middle ear.

Rarefaction— Wider than average distances between wave peaks.

Stroke— A sudden loss of blood supply to part of the brain.

Resources

BOOKS

Axelsson, Alf, Hans M. Borchgrevnik, and Roger P. Hamernick. Scientific Basis of Noise-Induced Hearing Loss. New York: Thieme Medical Pub, 1996.

Myers, David G. A Quiet World: Living With Hearing Loss. New Haven, CT: Yale University Press, 2000.

Pappas, Dennis G. Diagnosis and Treatment of Hearing Impairment in Children. Albany, NY: Delmar Publishers, 1998.

Roland, Peter S., Bradley F. Marple, and William I. Myerhoff. Hearing Loss. New York: Thieme Medical Pub, 1997.

Turkington, Carol, and Allen E. Sussman. The Encyclopedia of Deafness and Hearing Disorders, 2nd ed. New York: Facts on File, Inc., 2000.

PERIODICALS

Hager, L. "The many faces of hearing loss prevention. Occupational Health and Safety 70 (2001): 80-82, 93.

"High-tech help for hearing loss." Johns Hopkins Medical Letter on Health After 50 13 (2001): 3.

Todd, N.W. and T.M. Jarmuz. "The newborn with hearing loss." Journal of the Medical Association of Georgia 90 (2001): 32-36.

ORGANIZATIONS

American Academy of Audiology. 8300 Greensboro Dr., Suite 750, McLean, VA 22102. (800) 222-2336 or (703) 790-8466, Fax: (703) 790-8631. 〈http://www.audiology.org,〉 [email protected]

American Academy of Otolaryngology, Head and Neck Surgery. One Prince Street, Alexandria, VA 22314-3357. (703) 836-4444. 〈http://www.entnet.org/〉. [email protected]

American Speech-Language Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (800) 638-8255. 〈http://www.asha.org〉. [email protected]

Center on Deafness. 1490 Lafayette, Suite 408, Denver, CO 80203. (303) 839-8022. Fax: (303) 839-8027. 〈http://www.centerondeafness.org/services.html〉. [email protected]

National Institute on Deafness and Other Communication Disorders. National Institutes of Health, 31 Center Drive, MSC 2320, Bethesda, MD 20892-2320. 〈http://www.nidcd.nih.gov〉.

Rochester Institute of Technology. 90 Lomb Memorial Dr. Rochester, NY 14623. (716) 475-2562. 〈http://wally.rit.edu/internet/subject/deafness.html〉. [email protected]

OTHER

American Academy of Audiology Web Search. 〈http://www.searchwave.com/search〉.

Baylor College of Medicine. 〈http://www.bcm.tmc.edu/oto/studs/innear.html〉.

MayoClinic Web Search. 〈http://www.mayoclinic.com/home?id=5.1.1.8.21〉.

National Academy of Science. 〈http://www4.nas.edu/beyond/beyonddiscovery.nsf/web/cochlear11?OpenDocument〉.

National Council on Aging: 〈http://www.ncoa.org/news/archives/hearing_loss.htm〉.

National Institute for Occupational Safety and Health. 〈http://www.cdc.gov/niosh/noise.html〉.

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Hearing Loss

Hearing loss

Definition

Hearing loss is partial or full loss of hearing in one or both ears. There are three different types of hearing loss: conductive, sensorineural, and mixed hearing loss. Presbycusis, or age-related hearing loss, is the most common type of hearing loss.

The ear consists of three key areas: the outer ear, middle ear, and inner ear. The three different types of hearing loss affect one or more areas of the ear:

  • Conductive Hearing Loss: Occurs when sound cannot pass through the outer or middle ear to reach the inner ear. This is sometimes caused by a
    Percentage of people in the United States age 65 and over who reported having any trouble hearing, by sex, age, and poverty status 2006
    Sex Age and poverty status Any trouble hearing
    source:> National Health Interview Survey, National Center for
    Health Statistics, Centers for Disease Control and Prevention,
    U.S. Department of Health and Human Services
    (Illustration by GGS Information Services. Cengage Learning,
    Gale)
    Both sexes65–7431.9%
     75–8446.3%
     85 and over61.8%
     Below poverty36.6%
     Above poverty42.1%
    Men65–7440.8%
     75–8454.6%
     85 and over66.3%
    Women65–7424.3%
     75–8440.3%
     85 and over59.8%

    buildup of earwax, an infection, deformity of the middle or outer ear, or a foreign object. Doctors can generally treat conductive hearing loss surgically or medically if treatment is sought in a timely manner.
  • Sensorineural Hearing Loss: Occurs when there is damage or degeneration of the nerves in the inner ear, which reduces the ability to understand what is being said. Presbycusis is the most common type of sensorineural hearing loss. However, environmental factors, such as loud noise, head or ear injury, medications, disease, tumor, or infection may also cause sensorineural hearing loss. Hearing aids are often prescribed for this type of hearing loss.
  • Mixed Hearing Loss: A combination of conductive and sensorineural hearing loss. Treatment options vary.

Description

Hearing loss is common among seniors, but the development and extent of it occurs at different points in every senior's life. Many seniors are quick to admit they have hearing loss, but many do not admit to dealing with its consequences, including hearing common warning sounds, such as car horns or fire alarms. This effect can prove dangerous.

While many still do not admit to the consequences of hearing loss, a different attitude about hearing loss is developing among seniors in the late 2000s than in past generations. Celebrity seniors such as Bill Clinton and Paul Newman have been treated for hearing loss and freely admit to wearing hearing aids . It is hoped that because hearing loss is a mainstream topic, many seniors will choose to be diagnosed properly and receive treatment so they can continue to participate in an active lifestyle.

Demographics

Presbycusis, or age-related hearing loss, is the third most common condition among seniors 65 or older, according to Ann Carter. Carter was quoted in a 2007 issue of Senior Health Advisor as saying: “By age 65, 1 in 3 persons has some hearing loss. By age 75, it's nearly 1 person in 2.”

If hearing loss in seniors goes undiagnosed or misdiagnosed, it may cause difficulty communicating, depression, anxiety , and social isolation . These problems can take a toll on the senior, the family, and/or the caregiver .

It is estimated that men are more susceptible than women to developing hearing loss due to environmental factors since they are more likely to have worked around and/or had prolonged exposure to loud power tools or instruments or devices that exceed 80 decibels.

Additionally, the National Academy on an Aging Society indicates that the majority of hearing loss is “highly associated with aging” and occurs in people 65 and older, second only to those ages 45 to 64. Caucasians make up 91% of the general population that has hearing loss, while 6% are black, and 3% are other.

While many seniors with hearing loss could benefit from the use of a hearing aid, many do not or will not use one. There are a few factors accounting for this pattern:

  • Hearing aids can be expensive and not all insurance plans cover them. They can sometimes be as high as $2,500 for one ear.
  • The learning curve for operating one may be too high. Many hearing aids are digital and require the owner to program them. Some seniors may feel uncomfortable with or overwhelmed by the technology or the process.
  • A senior may not be fully educated about the benefits of wearing a hearing aid or of the great advances that have led to excellent sound quality in many models.

Prevention

Loud noise is an environmental factor that can oftentimes be prevented, possibly reducing future hearing loss. Loud noise at a hazardous level that may contribute to or cause hearing loss is any “noise above 80–90 decibels on average over an 8-hour workday,” according to the American Hearing Aid Association (AAHA). Furthermore, AAHA states, “firearms, music, airplanes, lawnmowers, power tools and many appliances are louder than 80 decibels and potentially hazardous to hearing with prolonged exposure.”

QUESTIONS TO ASK YOUR DOCTOR

  • How significant is the hearing loss?
  • Is it conductive, sensorineural, or mixed?
  • What is causing the loss?
  • How will you treat it?
  • Do I need to see an otologist, otolaryngologist, or ear, nose, and throat (ENT) doctor?
  • Do I need a hearing aid?
  • What will a hearing aid cost?
  • Will insurance cover it?
  • Will you or a specialist fit me for or recommend a hearing aid?
  • Will you assist me in making adjustments to my hearing aid, if needed?
  • Will my hearing improve with treatment? If so, by how much?

In addition to preventing prolonged exposure to loud noise, studies were being conducted in the 2000s to determine whether folic acid can actually slowdown the process of hearing loss. A study conducted in the Netherlands between 2000 and 2004 asked half of its participating men and women who did not currently consume folic acid to take 800 micrograms once a day for three years. After three years, those who had consumed folic acid had less lowfrequency hearing loss, though the high frequency hearing loss showed no change. While the study's results were positive, the slowing of the low frequency hearing loss was minor—less than a decibel. That has left scientists wondering if a little folic acid is good would a larger amount be better. As of 2008 the answer was unknown; more studies were needed in the United States where folic acid is already part of the daily diet of seniors because manufacturers are required to enrich flour and other items with folic acid.

Symptoms

There are several signs that may indicate hearing loss:

  • Ringing or buzzing in ear (called tinnitus)
  • Difficulty hearing or understanding words in a crowded or noisy room; increased ability to hear words in a quiet room
  • Voices and noise sounds muffled
  • Difficulty hearing or differentiating certain consonants when pronounced, such as -s and -th.
  • Lack of desire to attend social settings
  • Frustration or depression

When to seek medical attention

Each senior affected by hearing loss is affected at a different level. Hearing loss may occur gradually or have a rapid onset, depending on the cause. And not every symptom is so obvious to imply that hearing loss is the issue—or the only issue.

If seniors exhibit symptoms of hearing loss or notice a change in their ability to hear, they should seek a physician's opinion immediately. According to the American Hearing Aid Association, 16% of doctors routinely check for hearing loss. Therefore, a senior's (or caregiver's) due diligence for seeking treatment for hearing loss is imperative.

Treatment

The extent of the hearing loss dictates treatment options. Depending on the type and extent of hearing loss, doctors may prescribe medication to treat an ear infection, refer the patient to a doctor who specializes in conditions and diseases of the ear, recommend the patient wear a hearing aid, or perform surgery.

Once the condition has been established, it is important for seniors to do the following in order to have the most successful treatment:

  • Seek the support of a physician for hearing loss and any emotional distress due to the condition
  • Understand the cause and condition of their hearing loss
  • Know their options in treatment, including cost for and coverage of hearing aids or surgeries
  • Seek the support of friends and family members by revealing the condition of hearing loss
  • Speak to their physician if they are unhappy with their hearing aid, if applicable, or if their condition changes

Prognosis

Hearing loss can be managed but not always cured. The cause for the hearing loss and the extent of the damage generally dictate the outcome.

KEY TERMS

Audiologist —A specialist who evaluates and rehabilitates patients who suffer from hearing loss.

Conductive hearing loss —Occurs when sound cannot pass through the outer or middle ear to reach the inner ear.

Decibels —A measurement of the intensity of sound perceptible ranging from zero to 130.

Hearing aid —An electronic and/or digital device worn in the ear to amplify sound.

Mixed hearing loss —A combination of conductive and sensorineural hearing loss.

Presbycusis —Age-related hearing loss usually caused from degeneration in the ear.

Sensorineural hearing loss —Occurs when there is damage or degeneration of the nerves in the inner ear which reduces the ability to understand what is being said. Generally caused by exposure to loud noise, head or ear injury, medications, disease, tumor(s), or infection.

Tinnitus —A condition in which a person may hear ringing or buzzing in one or both ears when there is no exterior ringing or buzzing present.

Caregiver concerns

Hearing loss may be so gradual that seniors do not recognize their condition. Caregivers realize it is crucial to a senior's mental and physical safety and wellbeing to understand and notice the signs of hearing loss so that a doctor may treat the senior.

Signs of hearing loss:

  • Inability to recognize warning sounds, such as fire alarms, car horns, or sirens
  • Appearing depressed or despondent
  • Straining to hear someone over the phone or in person
  • Asking people to repeat themselves
  • Difficulty differentiating certain consonants when pronounced, such as -s and -th
  • Misunderstanding words
  • Asking people not to mumble
  • Complaining they hear ringing or muffled sound when none is present
  • Speaking unnecessarily loud.
  • Listening to the television or radio at a high volume
  • Withdrawing from social settings
  • Experiencing dizziness when they wake, stand, or change head positions

Resources

PERIODICALS

Carter, Ann. “Hearing Loss.” Senior Health Advisor 2 (May 31, 2007): 1–2.

Durga, Jane, Petra Verhoef, Lucien J. C. Anteunis, Evert Schouten, and Frans J. Kok. “Effects of Folic Acid Supplementation on Hearing in Older Adults.” Annals of Internal Medicine 146 (January 2, 2007): 1–9.

OTHER

Badash, Michelle. “Hearing loss.” Mayoclinic.com. November 2007 [cited March 28, 2008]. http://www.mayoclinic.com/print/hearing-loss/DS00172/DSECTION=all&METHOD=print;.

“Hearing Loss.” umm.edu. November 8, 2005 [cited March 28, 2008]. http://www.umm.edu/ency/article/003044.htm.

Heppner, Cheryl. “Seniors and Cochlear Implants: Results and Other Considerations—1.” Northern Virginia Resource Center for Deaf and Hard of Hearing Persons (NVRC). 2006 [cited March 28, 2008]. http://www.hearinglossweb.com/res/hlorg/shhh/cn/2006/srci1.htm.

Public Health Agency of Canada. “Hearing Loss Info-sheet for Seniors.” Aging and Seniors. March 7, 2006 [cited March 28, 2008]. http://www.phac-aspc.gc.ca/seniorsaines/pubs/info_sheets/hearing_loss/index.htm.

“Understanding the 3 Basic Types of Hearing Loss.” disabled-world.com. January 16, 2006 [cited March 28, 2008]. http://www.disabled-world.com/artman/publish/hearing_loss.shtml.

ORGANIZATIONS

American Academy of Audiology, 11730 Plaza America Drive, Suite 300, Reston, VA, 20190, (703) 790-8466, (800) 222-2336, http://www.audiology.org.

American Academy of Otolaryngology—Head and Neck Surgery, One Prince Street, Alexandria, VA, 22314 3357, (703) 836-4444, http://www.entnet.org/.

American Hearing Aid Associates, 1380 Wilmington Pike, West Chester, PA, 19382, (800) 984-3272, (610) 455-3018, http://www.ahaanet.com.

American Speech-Language Hearing Association, 2200 Research Blvd., Rockville, MD, 20850-3289, (800) 638 8255, [email protected], http://www.asha.org.

National Academy on an Aging Society, 1220 L St. NW, Suite 901, Washington, DC, 20005, (202) 408-3375, (202) 842-1150, [email protected], http://www.agingsociety.org/agingsociety/index.html.

National Council on Aging, 1901 L St. NW, 4th Floor, Washington, DC, 20036, (202) 479-1200, http://www.ncoa.org.

Lauren Long Stinson

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"Hearing Loss." The Gale Encyclopedia of Senior Health: A Guide for Seniors and Their Caregivers. . Retrieved November 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/caregiving/encyclopedias-almanacs-transcripts-and-maps/hearing-loss

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Hearing Loss

Hearing loss

Definition

Hearing loss is any degree of impairment of the ability to comprehend sound.

Description

Sound can be accurately measured. The term decibel (dB) refers to an amount of energy moving sound from its source to the ears of one or more listeners or to a microphone. A decrease of more than 10 dB in the level of sound a person can hear is significant.

Sound travels through a medium, such as air or water, as waves of compression and rarefaction. These waves are collected by the external ear and cause the tympanic membrane (ear drum) to vibrate. The chain of ossicles connected to the ear drum—the incus, malleus, and stapes—carries the vibrations to the oval window, increasing their amplitude 20 times along the way. There, the energy creates a standing wave in the watery liquid (endolymph) inside the organ of Corti. (A standing wave is one that does not move. A vibrating cup of coffee will demonstrate standing waves.) The shape of the standing wave is determined by the frequency of the sound. Many thousands of tiny nerve fibers detect the highs and lows of the standing wave. Motions in the nerve endings are converted into electrical impulses. These are transmitted to the brain via a nerve. Specialized areas of the brain interpret the signals as sound.

To summarize, sound energy passes through the air of the external ear, the bones of the middle ear, and the liquid of the inner ear. It is then translated into nerve impulses, sent to the brain through the acoustic nerve, and understood there as sound. It follows that there are five steps in the hearing process:

  • air conduction through the external ear to the ear drum
  • bone conduction through the middle ear to the inner ear
  • water conduction inside the organ of Corti
  • nerve conduction into the brain
  • interpretation by the brain

Causes and symptoms

Hearing can be interrupted in several ways at each of the five steps noted above.

The external ear canal can be blocked with ear wax (cerumen), foreign objects, infection , and tumors. Overgrowth of the bone, a condition that occurs when the ear canal has been flushed with cold water repeatedly for years, can also narrow the passageway, making blockage and infection more likely. This condition occurs often among northern Californian surfers and is aptly called "surfer's ear."

The ear drum is so thin that a physician can see through it, into the middle ear. Sharp objects, pressure from an infection in the middle ear, or even a firm cuffing or slapping of the ear, can rupture the ear drum. The eardrum is also susceptible to pressure changes, such as those that occur when one is scuba diving.

Several conditions can diminish the mobility of the ossicles (small bones) in the middle ear. Otitis media (an infection in the middle ear) occurs when fluid cannot escape into the throat because of blockage of the eustachian tube. The fluid that accumulates, whether it is pus or mucus, dampens the motions of the ossicles. A disease called otosclerosis can bind the stapes in the oval window, thereby cause deafness.

All of the problems and conditions that occur in the external and middle ear are causes of conductive hearing loss. The second category, sensory hearing loss, refers to damage to the organ of Corti, or the acoustic nerve. Prolonged exposure to loud noise is the leading cause of sensory hearing loss. More than a million people have been identified as having this condition. The cause is often believed to be prolonged exposure to loud music. Occupational noise exposure is the other leading cause of noise induced hearing loss (NIHL) and is an ample reason for wearing ear protection on the job. Jobs in construction and loud offices may contribute to ear damage, as may noises of recreation, such as loud music or the engine of a motorcycle. Both types of noises may lead to loss of hairs in one's inner ear. Thousands of these tiny hairs are attached to nerve cells in the cochlea (a snail-shaped structure in the inner ear). These tiny hairs aid the conversion of sound vibrations into electrical signals, which are then transmitted to the brain. When hairs become broken or bent, the transmission of the electric signals isn't as good, and sound may become muffled. Words may become difficult to distinguish against background noises.

One-third of people over 65 have presbycusis (gradual loss of hearing that occurs as one ages) and one-half of those older than age 75 have a hearing impairment. Both NIHL and presbycusis are primarily high frequency losses. The human speech frequencies are in relatively low ranges. People with presbycusis hear noise but cannot easily make sense of it. They have particular trouble distinguishing speech from background noise. Brain infections, such as meningitis , drugs such as the amino-glycoside antibiotics (e.g., streptomycin, kanamycin, tobramycin), and Menière's disease may also cause permanent sensory hearing loss. Menière's disease combines attacks of hearing loss with attacks of vertigo. The symptoms may occur together or separately. High doses of salicylates, like aspirin and quinine, can cause a temporary high-frequency loss. Prolonged high doses can lead to permanent deafness. There is an hereditary form of sensory deafness and a congenital form most often caused by rubella (German measles).

DECIBEL RATINGS AND HAZARDOUS LEVELS OF NOISE
Decibel Level Example Of Sounds
Above 110 decibels, hearing may become painful
Above 120 decibels is considered deafening
Above 135 decibels, hearing will become extremely painful and hearing loss may result if exposure is prolonged
Above 180 decibels, hearing loss is almost certain with any exposure
30Soft whisper
35Noise may prevent the listener from falling asleep
40Quiet office noise level
50Quiet conversation
60Average television volume, sewing machine, lively conversation
70Busy traffic, noisy restaurant
80Heavy city traffic, factory noise, alarm clock
90Cocktail party, lawn mower
100Pneumatic drill
120Sandblasting, thunder
140Jet airplane
180Rocket launching pad

Sudden hearing loss—at least 30dB in less than three days—is most commonly caused by cochleitis, an inflammation of the cochlea. The source of this process is thought to be viral, but as of 2001, no causative virus has been identified.

The final category of hearing loss is neural. Damage to the acoustic nerve and the parts of the brain that integrate and interpret sounds are the most likely to produce permanent hearing loss. Strokes, multiple sclerosis , and acoustic neuromas are all possible causes of neural hearing loss.

Hearing can also be diminished by extra sounds generated by the ear, most of them from the same kinds of disorders that cause hearing loss. These sounds are referred to as tinnitus and can be ringing, blowing, clicking, or anything else that no one but the affected person hears.

Diagnosis

An examination of the ears and nose, combined with simple hearing tests that can be conducted in a physician's office, detect many common causes of hearing loss. Analysis of an audiogram often concludes the evaluation, since these simple imaging often enables a diagnosis. If the defect is in the brain or the acoustic nerve, further neurologic testing and imaging will be required.

An audiogram has many uses in diagnosing hearing deficits. The pattern of hearing loss across the audible frequencies gives clues to the cause. Several alterations in the testing procedure can give additional information. For example, speech is perceived differently than pure tones. Adequate perception of sound, combined with inability to recognize words, indicates a brain problem rather than a sensory or conductive deficit. Loudness perception is distorted by disease in certain areas of the brain, but not in others. Acoustic neuromas often distort the perception of loudness.

Treatment

Conductive hearing loss can almost always be restored to some degree, if not completely.

  • Matter in the ear canal can be easily removed. This results in a dramatic improvement in hearing. In cases of earwax blockage, wax may be removed by the physician, who may loosen it and drain the ear, scoop it out, or use a suction device to removed softened wax.
  • Surfer's ear gradually regresses if cold water is avoided or a special ear plug is used. In advanced cases, excess bone can be ground away by surgeons.
  • Middle ear infection with fluid is also relatively easy to treat. If medications do not work, surgical drainage of the ear is accomplished through the ear drum, which heals completely after treatment.
  • Traumatically damaged ear drums can be repaired with a tiny skin graft.
  • Surgical repair of otosclerosis through an operating microscope is one of the most intricate procedures available, and substitutes tiny, artificial parts for the original ossicles.

Sensory and neural hearing loss, on the other hand, cannot readily be cured. Fortunately, the loss is not often complete, so that hearing aids can fill the deficit.

In-the-ear hearing aids can boost the volume of sound by up to 70 dB. (Normal speech is about 60 dB.) Federal law now requires that they be dispensed only with a physician's prescription. For complete conduction hearing loss, there are now bone conduction hearing aids available, as well as devices that can be surgically implanted in the cochlea.

Tinnitus can sometimes be relieved by adding white noise (like the sound of wind or waves crashing on the shore) to the environment.

Decreased hearing is such a common problem that there are many organizations that provide assistance. Special language training, both in lip reading and signing, and special schools and camps for hearing-impaired children are all available in most regions of the United States.

Conductive hearing loss can be treated with alternative therapies that are specific to the particular condition. Sensory hearing loss may be helped by homeopathic therapies. Oral supplementation with essential fatty acids such as flax oil and omega-3 oil can help alleviate the accumulation of wax in the ear.

Prognosis

The prognosis for conductive hearing loss is quite good. Since there is no cure for sensory or neural hearing loss, the prognosis is poor.

Health care team roles

Hearing examinations are usually conducted by physicians. Audiologists are trained to evaluate hearing. Speech language specialists are trained to provide treatment and rehabilitation for persons with impaired hearing.

Prevention

Prompt treatment and attentive follow-up of middle ear infections in children will prevent this cause of conductive hearing loss. Control of infectious childhood diseases, such as measles, has greatly reduced sensory hearing loss as a complication of epidemic diseases. Laws that require protection from loud noise in the workplace have achieved substantial reduction in noise induced hearing loss. Wearing specially designed earmuffs that resemble earphones may be of use where the noise is still too loud. Surfers should use the right kind of ear plugs.

One should have his or her hearing tested on a regular basis if a noisy environment cannot be avoided. Early detection will enable one to take steps to prevent further hearing loss. Avoiding exposure to loud noise and using hearing protection are the best ways to prevent hearing loss and slow the onset of presbycusis.


KEY TERMS


Compression —Narrower than average distances between wave peaks.

Decibel —A unit of the intensity of sound, a measure of loudness.

Meniere's disease —The combination of vertigo and decreased hearing caused by abnormalities in the inner ear.

Multiple sclerosis —A progressive disease of brain and nerve tissue.

Otosclerosis —A disease that scars and limits the motion of the small conducting bones in the middle ear.

Rarefaction —Wider than average distances between wave peaks.

Stroke —A sudden loss of blood supply to part of the brain.


Resources

BOOKS

Axelsson, Alf, Hans M. Borchgrevnik, and Roger P. Hamernick. Scientific Basis of Noise-Induced Hearing Loss. New York: Thieme Medical Pub, 1996.

Myers, David G. A Quiet World: Living With Hearing Loss. New Haven, CT: Yale University Press, 2000.

Pappas, Dennis G. Diagnosis and Treatment of Hearing Impairment in Children. Albany, NY: Delmar Publishers, 1998.

Roland, Peter S., Bradley F. Marple, and William I. Myerhoff. Hearing Loss. New York: Thieme Medical Pub, 1997.

Turkington, Carol, and Allen E. Sussman. The Encyclopedia of Deafness and Hearing Disorders, 2nd ed. New York: Facts on File, Inc., 2000.

PERIODICALS

Anonymous. "High-tech Help for Hearing Loss." Johns Hopkins Medical Letter on Health After 50 13 (2001): 3.

Hager L. "The Many Faces of Hearing Loss Prevention. Occupational Health and Safety 70 (2001): 80-82, 93.

Todd, N. W., and T. M. Jarmuz. "The Newborn with Hearing Loss." Journal of the Medical Association of Georgia 90(2001): 32-36.

ORGANIZATIONS

American Academy of Audiology. 8300 Greensboro Dr., Suite 750, McLean, Virginia 22102. (800) 222-2336. (703) 790-8466. Fax: (703) 790-8631. <http://www.audiology.org>. [email protected]

American Academy of Otolaryngology, Head and Neck Surgery. One Prince Street, Alexandria, VA 22314-3357.(703) 836-4444. <http://www.entnet.org/.> [email protected]

American Speech-Language Hearing Association. 10801 Rockville Pike, Rockville, MD 20852. (800) 638-8255. <http://www.asha.org>. [email protected]

Center on Deafness. 1490 Lafayette, Suite 408, Denver, CO 80203. (303) 839-8022. Fax: (303) 839-8027. <http://www.centerondeafness.org/services.html>. [email protected]

National Institute on Deafness and Other Communication Disorders, National Institutes of Health. 31 Center Drive, MSC 2320, Bethesda, MD 20892-2320. <http://www.nidcd.nih.gov>.

OTHER

American Academy of Audiology Web Search. <http://www.searchwave.com/search>.

Baylor College of Medicine. <http://www.bcm.tmc.edu/oto/studs/innear.html>.

MayoClinic. <http://www.mayoclinic.com/home?id=5.1.1.8.21>.

National Academy of Science. <http://www4.nas.edu/beyond/beyonddiscovery.nsf/web/cochlear11?OpenDocument>.

National Council on Aging. <http://www.ncoa.org/news/archives/hearing_loss.htm>.

National Institute for Occupational Safety and Health. <http://www.cdc.gov/niosh/noise.html>.

Rochester Institute of Technology. 90 Lomb Memorial Dr. Rochester, NY 14623. 716-475-2562. <http://wally.rit.edu/internet/subject/deafness.html>. [email protected]

L. Fleming Fallon Jr., M.D, Ph.D, Dr.PH

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