conduction deafness


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Related to conduction deafness: nerve deafness, tone deafness, sensorineural deafness, transmission deafness

deafness

 [def´nes]
hearing loss; lack or loss of all or a major part of the sense of hearing. For types, see under hearing loss.
Alexander's deafness congenital deafness due to cochlear aplasia involving chiefly the organ of Corti and adjacent ganglion cells of the basal coil of the cochlea; high-frequency hearing loss results.
central deafness that due to causes in the auditory pathways or in the brain; see hearing loss.
conduction deafness (conductive deafness) conductive hearing loss.
functional deafness functional hearing loss.
hysterical deafness functional hearing loss.
pagetoid deafness that occurring in osteitis deformans of the bones of the skull (paget's disease).
sensorineural deafness
1. that due to a defect in the inner ear or the acoustic nerve. See hearing loss.
word deafness auditory aphasia.

conduction deafness

deafness

(def'nes)
Complete or partial loss of the ability to hear. The deficit may be temporary or permanent. More than 20 million Americans have hearing impairment; most of them are over 65 although about 5% are children. Hereditary forms of hearing impairment affect about 1 newborn out of 2000. In this population hearing deficits may impair language acquisition and speech. Acquired hearing loss affects the lives of nearly half of all people over 80, in whom it may be a prominent cause of social isolation or depression. Synonym: hearing loss

Etiology

Hearing impairment has multiple causes. Congenital deafness occurs during pregnancy or delivery and in such syndromes as neurofibromatosis or Usher syndrome. Toxic deafness may result from exposure to such agents as salicylates, diuretics, or aminoglycoside antibiotics, or infections of the central nervous system (meningococcal meningitis, syphilis) or of the eighth cranial nerve. Many viruses may contribute to loss of hearing, as may prolonged or repetitive exposures to environmental noise. Otosclerosis is an example of bilateral conductive hearing loss due to progressive ossification of the annular ligaments of the ear. Presbycusis is an otologic effect of aging resulting from the loss of hair cells in the organ of Corti and leading to progressive, symmetrical, bilateral sensorineural hearing loss, esp. of high-frequency tones. Sudden hearing loss may result from ear trauma, fistulae, stroke, drug exposures, cancer, multiple sclerosis, vasculitis, or Ménière disease. Not infrequently, adult patients with unilateral conductive hearing loss have a cerumen impaction.

Diagnosis

Simple bedside tests (such as assessing a patient's ability to hear a whispered phrase or the sound of rasping fingers) may suggest hearing impairment. Tuning fork tests that compare air and bone conduction of sound help clinicians identify whether hearing loss is due to conductive or sensorineural causes. Audiometry provides definitive diagnosis.

Treatment

The degree of hearing loss is calculated according to an American Medical Association formula: For every decibel that the pure tone average exceeds 25 dB, hearing impairment equals 1.5%. Therapy depends on the underlying condition. Cerumen impaction, for example, responds to irrigation of the external auditory canal, while otosclerosis may respond to the intra-aural (surgical) placement of prostheses or laser surgery. Other forms of therapy include the use of hearing amplifiers or cochlear implants or education in lip reading or sign language.

Patient care

Patients can prevent damage to hearing from excessively loud noises by wearing sound-muffling ear plugs or muffs when exposed to loud noise from any source, esp. industrial noise, and by recognizing that loud music can be as detrimental to hearing as the noise of a jackhammer. After exposure to noise levels above 90 dB for several hours, overnight rest will usually restore normal hearing, but not in those who experience repeated exposure. Patients should avoid cleaning inside the ears or putting sharp objects in them. Many antibiotics and chemotherapeutic drugs are ototoxic and hearing should be evaluated continually when such drugs are used.

When interacting with a person with a hearing deficit, the health care professional should make his or her presence known to the patient by sight by raising or waving of the arm (as even gentle touch may startle the person) before beginning to speak. If possible, background noise should be decreased. The health care professional's face should be well lit to make the lips and facial expression easy to see. He or she should face the patient directly or direct the voice toward the side preferred by the patient. To facilitate lip reading, short words and simple sentences should be used. Clear and distinct enunciation and speaking slowly in a low tone are helpful. Exaggerated mouthing of words or loud tones and shouting should be avoided. Placing a stethoscope in the patient's ears and speaking into the bell helps to limit extraneous sounds and to direct words into the patient's ears. If the patient is literate, sign language or finger spelling may be used to communicate. Written information should be presented clearly and in large letters, esp. if the patient has poor visual acuity.

Any child in whom hearing loss is suspected or who fails a language screening examination should be referred to an audiologist or otolaryngologist for further evaluation and therapy and, as necessary, to a speech therapist for language evaluation and therapy.

Health care professionals can help prevent hearing loss in their patients and communities by teaching about and assessing for signs of hearing impairment in anyone receiving ototoxic drugs; stressing the dangers of excessive noise exposure; explaining to pregnant women the danger to the fetus from exposure to drugs, chemicals, and infections, esp. rubella; and encouraging the use of protective devices in noisy environments and during occupational or recreational exposure to noise.

acoustic trauma deafness

Impaired hearing due to repeated exposure to loud noise.

acquired deafness

Loss of hearing that is not present at birth but develops later in life.

bass deafness

Inability to hear low-frequency tones.

central deafness

Deafness resulting from lesions of the auditory tracts of the brain or the auditory centers of the cerebral cortex.

cerebral deafness

Cortical deafness.

conduction deafness

Conductive hearing loss.

cortical deafness

Deafness caused by a lesion of the auditory cortex of the brain rather than by a problem in the auditory nerve or the ear.
Synonym: cerebral deafness

hereditary deafness

Hearing loss passed down through generations of a family.

high-frequency deafness

Inability to hear high-frequency sounds, e.g., sound frequencies just below 20 kHz.

mitochondrial deafness

Deafness caused by the inheritance of a mutation in mitochondrial DNA. It is transmitted from mother to child.

nerve deafness

Deafness due to a lesion of the auditory nerve or central neural pathways.

nonsyndromic deafness

Any form of hereditary hearing impairment caused by one of many genetic mutations, e.g., in somatic, mitochondrial, or X-linked genes.

occupational deafness

Deafness caused by working in places where noise levels are quite high. Persons working in such an environment should wear protective devices.

ototoxic deafness

Hearing loss due to the toxic effect of certain chemicals or medicines on the eighth cranial nerve.

CAUTION!

Commonly used drugs that may damage hearing include aminoglycoside antibiotics, aspirin, cis-platinum, erythromycin, loop diuretics, and vancomycin.

partial deafness

Deafness in which the ability to hear low-frequency sounds is preserved but high-frequencies are inaudible.

perceptive deafness

Deafness resulting from lesions involving sensory receptors of the cochlea or fibers of the acoustic nerve, or a combination of these.

postlingual deafness

Hearing impairment that develops after a patient has learned language.

prelingual deafness

Hearing impairment that is present in infancy and childhood, before language skills are acquired.

profound deafness

A level of hearing loss in which a person cannot hear a sound unless it is at least 90 decibels loud (about as loud as a lawnmower or a nearby motorcycle).

psychic deafness

A condition in which auditory sensations are perceived but not comprehended.

pure word deafness

Word deafness.

rhinogenic deafness

Deafness that is caused by chronic nasal or pharyngeal inflammation, with chronic otitis.

sensorineural deafness

Deafness due to defective function of the cochlea or acoustic nerve.

sex-linked deafness

A form of sensorineural deafness, found only in males, and carried as a recessive trait on the X chromosome.

sudden deafness

Deafness that occurs after an acute insult to the ear, e.g., after exposure to a toxin or medication (as from too high a dose of aminoglycosides), after a viral infection that damages the inner ear, or after blasts or head trauma.

tone deafness

The inability to detect differences in musical sounds.
Synonym: asonia

tune deafness

The inability to detect differences in musical pitch or to appreciate differences in melodies.

word deafness

A form of aphasia in which sounds and words are heard but linguistic comprehension is absent.
Synonym: auditory agnosia; auditory amnesia; auditory aphasia; pure word deafness