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