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Deafness is defined as impairment of hearing, regardless of its severity. It is a major community health problem requiring a high index of suspicion for diagnosis, esp. in children. Deafness may be conductive, sensorineural (SND) or a combination of both (mixed).
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Deafness occurs at all ages but more common in the elderly—50% >80 yrs—that could be helped by a hearing aid.
The threshold of normal hearing is from 0 to 20 dB, about the loudness of a soft whisper. 60 dB is the level of normal conversation or a sewing machine.
Degrees of hearing impairment:
– mild = loss of 20–40 dB (soft spoken voice is 20 dB)
– moderate = loss of 40–60 dB (normal spoken voice is 40 dB)
– severe = loss of 70–90 dB (loud spoken voice)
– profound = loss of over 90 dB (shout is 90–120 dB)
People who have worked in high noise levels (>85 dB) are more than twice as likely to be deaf.
There is a related incidence of tinnitus with deafness.
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Red flags that warrant referral
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Deafness in childhood is relatively common and often goes unrecognised. A mother who believes that her child may be deaf is rarely wrong in this suspicion.
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Screening The aim of screening should be to recognise every deaf child by the age of 8–10 mths—before the vital time for learning speech is wasted. Optimal screening times:
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No child is too young for audiological assessment. Informal office tests are inadequate to exclude hearing loss. Neonates and infants can be tested using automated brain-stem response (AABR) or Transient Evoked Otoacoustic Emissions (TEOAE).
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A progressive disease of bone surrounding the inner ear
Develops in the 20s and 30s
Family history (autosomal dominant)
Female preponderance
Affects the footplate of the stapes
Conductive hearing loss
SND may be present
Impedance audiometry shows characteristic features of conductive loss with a mild sensorineural loss
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Referral to ENT consultant
Stapedectomy (approx. 90% effective)
Hearing aid (less effective alternative)
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