conductive hearing loss

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hearing loss

partial or complete loss of the sense of hearing; called also deafness. The number of hearing impaired individuals has steadily increased over the past few decades. While improved detection and reporting of impaired hearing can account for some of this increase, other contributing factors include an aging population and increased noise levels in the environment.
Types of Hearing Loss. There are three broad categories of hearing loss: conductive, sensorineural, and central. Conductive hearing loss is associated with impaired transmission of sound waves through the external ear canal to the bones of the middle ear. A blockage of the external ear or dysfunction of the middle ear will produce conductive loss of hearing. Examples of common causes of conductive hearing loss are obstruction of the ear canal by cerumen or a foreign object, perforated eardrum, otitis media, otosclerosis, and congenital malformations of the outer or middle ear.

Sensorineural hearing loss is associated with some pathological change in structures within the inner ear or in the acoustic nerve. Normally, sound waves received by the external and middle ear are conveyed to the fluid in the cochlea of the inner ear. On the surface of its basilar membrane lies the organ of Corti, which contains mechanically sensitive cells. These minute structures act as end-organs that generate nerve impulses in response to sound vibrations. Thus the mechanical energy of sound vibrations is transformed into electrical energy that stimulates the nerve fibers of the acoustic (eighth cranial) nerve. The impulses are then transmitted to the brain, where the cerebral cortex decodes or interprets the sound. A sensorineural hearing loss results when there is dysfunction in either the perception or the interpretation of sound waves. Common causes of sensorineural hearing loss include hereditary disease, aging (presbycusis), noise damage, viral childhood infections, skull fractures and intracranial tumors, ototoxic drugs, and Rh incompatibility during fetal life.

Central hearing loss occurs when there is a pathologic condition above the junction of the acoustic nerve and the brainstem. Brain tumors, vascular changes that suddenly deprive the structures of the inner ear of their blood supply, stroke syndrome, and erythroblastosis fetalis are examples of pathologic conditions that can produce central hearing loss.
Preventing Hearing Loss. Not all cases of hearing loss can be prevented, but there are measures that are known to be effective in curtailing the incidence and severity of many types of hearing loss. For example, excessive environmental noise is a major contributing factor that is avoidable or at least manageable. Permanent damage to hearing can result when the structures of the inner ear and nerve cells are repeatedly bombarded with loud sound waves which reduce their blood supply. The cells thus lost are replaced by scar tissue that cannot transmit sound waves and impulses. If one's occupation requires continued exposure to loud noises, ear protection devices should be worn to mitigate the harmful effect.

Excessive noise in one's environment often can be greatly reduced by lowering the volume on radios and other music appliances, especially those with headphones. Authorities recommend that one should avoid continual exposure to music amplified to more than 104 to 111 decibels. It is believed that the loss of hearing associated with aging may not be an inevitable outcome of growing older, but rather a lasting effect of living in an increasingly noisy environment.

Efforts to reduce the risk of atherosclerosis can help prevent hearing loss by lowering the possibility of atherosclerotic plaque in the blood vessels supplying the delicate structures of the inner ear, and also by minimizing the risk of stroke.

There are some drugs that are particularly toxic to the ear. Examples are aspirin, which can produce tinnitus and temporary deafness; the antibiotics erythromycin, kanamycin, neomycin, and streptomycin; the nonsteroidal antiinflammatory drugsfenoprofen and indomethacin; the diureticfurosemide (Lasix); and several drugs used in the chemotherapeutic treatment of malignancies. Any person taking a prescribed medication should be alert for hearing-related problems while taking the drug and report such problems as soon as they appear.

Prompt attention to and successful treatment of ear infections is another means by which hearing loss can be prevented. Symptoms such as ringing in the ears, a feeling of pressure in the ear, or increasing hearing difficulty call for medical consultation.

Great progress has been made in the treatment of conditions that once almost always resulted in impaired hearing. One example is the use of antibiotics to manage ear infections. Another is the development of microsurgery, which enables the surgeon to operate freely in the crowded inner chambers of the ear. Two such surgical procedures are stapedectomy and tympanoplasty. In a stapedectomy to correct otosclerosis the diseased stapes or stirrup is removed and replaced by a prosthesis that allows the chain of sound transmission to function again. Tympanoplasty is useful in correcting some types of conductive hearing loss. If chronic ear infection or injury has destroyed one or more of the ossicles, they can be rebuilt or replaced surgically.
Detecting Hearing Loss. In the infant and very young child hearing loss is evidenced by a lack of response to the sounds in the immediate environment. As the infant matures and begins to approach the age at which talking should begin, there may be either a failure to talk at all by age two or scarcely intelligible speech after age three.

Emotional and behavioral disorders can be signs of hearing loss in children and adults. The frustration they feel in trying to cope with their disability can be manifested by irritability, hyperactivity, hostility, and withdrawal. Other signs include speaking in either a very loud or very soft voice; habitually saying “What?” and failing to follow instructions; facial expressions indicating difficulty in understanding what is being said; and inappropriate responses to questions asked or statements made during a conversation.

Among the tests used to evaluate hearing are tuning fork tests such as the weber test and the rinne test. A tympanogram provides information about the movement of the eardrum. Evaluation of hearing acuity by audiometry uses a special machine for testing sound perception.
Rehabilitation. For those cases of hearing loss that cannot be corrected, some form of rehabilitation is prescribed to make the best of whatever hearing remains and to improve the person's quality of life and socialization. The hearing aid is helpful for persons with certain kinds of hearing loss. It should be selected with the help of an audiologist or an otologist because different types of hearing loss require different types of hearing aids. Careful training in the proper use of the hearing aid is also necessary to assure that the person wearing it will achieve maximum benefit.

An important tool in rehabilitation of the profoundly hearing impaired is training in signing and lip reading. For lip reading, the patient is taught to use visual clues, such as facial expression and body movements, as well as movements of the lips and tongue.

A third component of rehabilitation of the hearing impaired is speech therapy. Profoundly deaf persons cannot hear their own voices, and those who have never heard spoken language have difficulty learning to speak coherently. Those who have lost their hearing over a period of time often suffer a gradual deterioration in their speech so that communication becomes increasingly awkward.
Patient Care. Communicating with the partially hearing impaired person can be enhanced by following a few simple rules. Speak slightly more loudly than normal but do not shout, as this can distort your speech and will not make your message any clearer. Speak slowly and distinctly. Get the person's attention before speaking. The best distance for speaking to a hearing-impaired person is 1 to 2 meters (3 to 6 feet). Face the person to whom you are speaking and place yourself at eye level so that other visual clues can be seen. Never speak directly into the person's ear. This can distort the message and hide all visual clues. Be aware of nonverbal communication; facial expressions, gestures, and lip and body movements all give clues to the meaning of the message you are trying to send. Use short, simple sentences. If the person does not appear to understand or responds inappropriately, rephrase your statement. Give the person time to respond to what you have asked or stated.
Sources of Help for Those with Hearing Loss. Among the resources available to hearing impaired persons and their families are universities and medical centers with departments of speech and hearing that provide lip-reading classes, rehabilitation, and hearing aid clinics. The national institute on deafness and other communication disorders (NIDCD), a part of the National Institutes of Health, has a clearinghouse for information on hearing, balance, language, and related issues. Their mailing address is NIDCD Information Clearinghouse, 1 Communication Ave., Bethesda, MD 20892, and their web site is They can be reached by telephone at (voice) 1-800-241-1044 or (TDD/TTY) 1-800-241-1055. Other societies and organizations devoted to helping the hearing impaired include The Better Hearing Institute, 515 King Street, Suite 420, Alexandria VA 22314, which operates a toll-free “Hearing Helpline” at 1-800-327-9355; and The Alexander Graham Bell Association for the Deaf, 3417 Volta Pl. NW, Washington, DC 20007. Web site is a worldwide hearing information web site.
central hearing loss central deafness.
conductive hearing loss that due to a defect of the sound-conducting apparatus, i.e., of the external auditory canal or middle ear. See hearing loss.
functional hearing loss hearing loss that lacks any organic lesion; called also hysterical deafness and nonorganic hearing loss.
mixed hearing loss hearing loss that is both conductive and sensorineural in nature.
nonorganic hearing loss functional hearing loss.
ototoxic hearing loss deafness caused by ingestion of toxic substances or medications that affect the eighth cranial nerve.
paradoxic hearing loss that in which the hearing is better during loud noise.
sensorineural hearing loss that due to a defect in the inner ear or the acoustic nerve. See hearing loss.
transmission hearing loss conductive hearing loss.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

conductive hearing loss

Conductive hearing impairment ENT Hearing loss due to a defect in the outer ear–eg a block of the external ear canal or middle ear–ossicles or eardrum, in the face of a normal auditory nerve
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

con·duc·tive hear·ing loss

(kŏn-dŭk'tiv hēr'ing laws)
Hearing loss caused by an obstruction or lesion in the outer ear, middle ear, or both.
See also: air-bone gap
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Conductive hearing loss

A type of medically treatable hearing loss in which the inner ear is usually normal, but there are specific problems in the middle or outer ears that prevent sound from getting to the inner ear in a normal way.
Mentioned in: Stapedectomy, Tinnitus
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

con·duc·tive hear·ing loss

(kŏn-dŭk'tiv hēr'ing laws)
Hearing loss caused by an obstruction in the outer ear, middle ear, or both.
Medical Dictionary for the Dental Professions © Farlex 2012