HEARING LOSS/DEAFNESS By: Rabiu Hassan Musa
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HEARING LOSS/DEAFNESS
By:Rabiu Hassan Musa
DEFINITION
The World Health Organization defines
“disabling hearing impairment” in
children under the age of 15 years as an
unaided hearing threshold level in the
better ear of 31 dB HL or more using
pure tone averages at 0.5, 1, 2 and 4
kHz.
On the other hand, Hearing loss exists when
there is diminished sensitivity to the sounds
normally heard. The terms hearing impairment
or hard of hearing are usually reserved for
people who have relative insensitivity to sound
in the speech frequencies. The severity of a
hearing loss is categorized according to the
increase in volume above the usual level
necessary before the listener can detect it.
Deafness is defined as a degree of impairment
such that a person is unable to understand
speech even in the presence of amplification.
In profound deafness, even the loudest sounds
produced by an audiometer (an instrument
used to measure hearing by producing pure
tone sounds through a range of frequencies)
may not be detected. In total deafness, no
sounds at all, regardless of amplification or
method of production, are heard.
SPEECH PERCEPTIONAnother aspect of hearing involves the
perceived clarity of a sound rather than its
amplitude. In humans, that aspect is usually
measured by tests of speech perception. These
tests measure one's ability to understand
speech, not to merely detect sound. There are
very rare types of hearing impairments which
affect speech understanding alone
INCIDENCE AND PREVALENCE Globally hearing loss affects about 10% of the
population to some degree. It caused moderate to severe disability in
124 million people as of 2004 (108 million of whom are in low and middle income countries). Of these 65 million developed the condition during childhood.
The problem of hearing loss is particularly significant in older adults, affecting about 30% to 35% of people between the ages of 65 and 74, and more than 40% of those over age 75.
The prevalence of childhood hearing loss is 1.2 to 1.7 cases per 1000 live births and the prevalence increases up to 6 years of age as a result of meningitis, delayed onset of genetic hearing loss, or delayed diagnosis.
The prevalence is greater still in developing countries because of lack of immunization, exposure to ototoxic drugs, and consanguinity.
Profound hearing loss (hearing loss > 90 dB) has far-reaching, lifelong consequences in children.
RISK FACTORSAging: Exposure to sounds over the years can
damage the cells of your inner ear.Heredity: Genetic makeup may make you more
susceptible to ear damage from sound or deterioration from aging.
Occupational noises: Jobs where loud noise is a regular part of the working environment, such as farming, construction or factory work, can lead to damage inside your ear.
Recreational noises: Exposure to explosive noises, such as from firearms and jet engines, can cause immediate, permanent hearing loss.
Some medications: Drugs, such as the antibiotic gentamicin and certain chemotherapy drugs, can damage the inner ear. Temporary effects on your hearing, ringing in the ear (tinnitus) or hearing loss can occur if you take very high doses of aspirin, other pain relievers, antimalarial drugs or loop diuretics.
Some illnesses: Diseases or illnesses that result in high fever, such as meningitis, may damage the cochlea.
CLASSIFICATION Conductive hearing loss, Sensorineural hearing loss, or Mixed hearing loss.
ETIOLOGICAL FACTORSConductive Hearing Loss External ear conditions Impacted ear wax or foreign body Otitis externa Middle ear conditions Trauma Otitis media Otosclerosis Tumors
Sensorineural Hearing Loss• Aplasias• Abiotrophies• Intrauterine/perinatal damage• Trauma e.g. head injury, middle ear surgery• Sudden (idiopathic) sensoryneural hearing loss• Noise induced hearing loss• Central nervous system infections (e.g., meningitis)• Degenerative conditions• Age related presbyacusis • Vascular conditions• Ototoxic drugs• Acoustic neuroma• Meniere’s disease
Mixed Conductive and Sensorineural Hearing Loss
Middle ear conditions Temporal bone fractures
PATHOPHYSIOLOGY
CATEGORIES OF HEARING LOSSSlight hearing loss : 16 - 25 dBMild hearing loss : 26 - 40 dBModerate hearing loss: 41 - 55 dBSevere hearing loss : 71 - 90 dBProfound : More than 90 dB
(American National Standards Institute)
CLINICAL MANIFESTATIONSMuffling of speech and other soundsDifficulty understanding words, especially against
background noise or in a crowd of peopleTrouble hearing consonantsFrequently asking others to speak more slowly,
clearly and loudlyNeeding to turn up the volume of the television or
radioWithdrawal from conversationsAvoidance of some social settings
DIAGNOSISAir Conduction, Conventional or Standard
AudiometryBone ConductionRinne and Weber testsAudiometryTympanometryAcoustic reflex testingWord RecognitionAcoustic ImmittanceOtoacoustic Emissions (OAEs)Auditory Brainstem Response (ABR)
Medical Management
AntibioticsAnalgesics
MANAGEMENT
Surgical Management
Stapedectomy Tympanoplasty Cochlear implant
Nursing Management
PATIENT’S PROBLEMS Disturbed Sensory Perception: AuditoryImpaired Verbal CommunicationSocial Isolation
REHABILITATION
Audiologic rehabilitation classesLearning good listening strategiesEstablishing guidelines for
communicating with those around you
Assistive Listening, Hearing Enhancement and Alerting Devices
Signaling or Test Display Devices Assistive Listening Devices
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