Encyclopedia of Health and Medicine

hearing loss 29
ductive hearing loss in adults. Compacted CERUMEN
(ear wax) in the auditory canal and OTOSCLEROSIS
(fusion of the auditory ossicles, the tiny bones of
the middle ear) are common causes of treatable
conductive hearing loss. Damage to the areas of
the brain that process hearing, speech, and language
can result in auditory processing disorders
in which, though the structures and mechanical
functions of hearing may remain intact, the person
cannot understand spoken words. Typically
other language impairments, such as the abilities
to read and write, also exist with auditory processing
disorders.
Hearing loss in children, whether congenital or
acquired, has significant developmental consequences.
It is now the standard of care in the
United States to test newborns for hearing in the
first few weeks of life, with regular screening for
hearing difficulties at well child checks and routine
medical examinations through ADOLESCENCE.
The ability to hear forms the basis for understanding
language. Early intervention to correct or
accommodate hearing loss in prelingual children is
essential for appropriate development and communication.
A teacher’s voice in a classroom projects
an intensity of about 70 dB; children with
hearing loss at this level or greater will be unable
to hear in school.
The majority of hearing loss in adults is
acquired. Excessive noise exposure and changes
related to aging (PRESBYCUSIS) are the most common
causes of acquired adult hearing loss. Hearing
loss may also result from health conditions,
such as ACOUSTIC NEUROMA and MÉNIÈRE’S DISEASE,
that interfere with the functions of hearing.
Trauma, such as FRACTURE of the bones in the
face and head or BURNS that damage the external
ear, can cause hearing loss. Various medications,
including certain antibiotics, diuretics, antihypertensives,
high doses of aspirin, and
CHEMOTHERAPY drugs, also can damage or destroy
hearing.
Symptoms and Diagnostic Path
Sudden hearing loss in adults is typically obvious.
Progressive hearing loss is often subtle and noticed
more by others than the person experiencing the
loss. Common indicators of diminishing hearing
ability include
• perception that “everyone” mumbles when
speaking
• unable to hear the telephone or doorbell ring
• volume is past the halfway mark when listening
to television or radio
• easier to hear someone talking when looking
directly at him or her
• restaurants are “too noisy” for conversation
TINNITUS (sensation of roaring or buzzing sound
in one ear or both ears) may be an early sign of
sensorineural hearing loss. Children with undetected
hearing loss may fail to respond when spoken
to or to follow instructions, have difficulty in
school, seem to mumble or slur their words, or be
developmentally delayed especially in language
skills.
Diagnosing hearing loss begins with physical
examination of the outer and middle ears to look
for obvious problems such as compacted cerumen,
inflamed or damaged TYMPANIC MEMBRANE
(eardrum), and structural anomalies. An audiologic
assessment then measures hearing response
to a variety of tests. If questions remain about the
cause of the hearing loss, the doctor may request
COMPUTED TOMOGRAPHY (CT) SCAN or MAGNETIC RESO-
NANCE IMAGING (MRI).
Treatment Options and Outlook
Medical or surgical treatments can restore most
conductive hearing loss. Sensorineural hearing
loss requires interventions such as hearing aids,
which amplify sound, or cochlear implants, which
directly stimulate nerve cells in the inner ear.
Hearing lost as a result of health conditions such
as acoustic neuroma often returns when the neuroma
is removed. Accommodations for profound
hearing loss include training in lip reading and
SIGN LANGUAGE.
Hearing loss, however subtle, can significantly
affect on a person’s ability to function in, and enjoy,
everyday life. Even mild to moderate hearing loss
removes many common sounds from daily experience.
Early intervention and appropriate accommodation
can mitigate to the extent possible much
hearing loss. Hearing aids, though they cannot
restore normal sound quality and hearing, make it
possible to participate in conversation and to hear