Hearing Loss
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Introduction
Hearing loss is a raised hearing threshold, measured as decibels, relative to the normal population. It becomes a problem when communication by speech is affected. This level is commonly defined as a hearing level loss of 16 dB at frequencies of 500, 1000, and 2000 Hz.
Deafness is defined when the above three frequencies are lost at or above 82 dB.
Ten percent of the population is hard of hearing or deaf. It is detectable (by audiology) in greater than 1/3 of people over 65, and is associated with significant physical, functional, and mental health consequences.
The speech banana is between 250-4000 Hz.
People don't enjoy conversations and can become intimidated in many settings.
It shrinks one's world.
Conductive hearing loss
is caused by problems with the outer and inner ear. Otoscopy is often abnormal, and problems are often amenable to surgery. These are usually aidable.
Causes:
- canal atresia/stenosis
- canal obstruction (wax and bodies)
- otitis externa
- otitis media with effusion (OME) - glue ear
- very common amongst children
- one-sided OME in adults is worrisome, suggesting potential naso-pharyngeal CA
- acute suppurative otitis media (ASOM)
- chronic suppurative otitis media - once eardrum
- atelectasis - collapsed eardrum
- attic retraction and cholesteatoma - retracted eardum and osteolytic erosion of the underlying bone
- otosclerosis
- autosomal dominant
- onset younger than 30 years
- accelerated during pregnancy
- quite commonly bilateral
Diagnosis
- history
- otoscopy
- tuning fork tests (Rinne, Weber)
- audiogram (air bone gap)
- tympanometry (p
- CT
- surgical exploration (tympanotomy)
Sensorineural hearing loss
Sensorineural hearing loss is caused by problems with the inner ear, the cochlear nerve through to auditory nuclei. It is most commonly caused by damage to hair cells. Often the higher frequency is lost.
Progressive bilateral SNHL is the commonest impairment in the adult population
causes:
- age
- trauma
- noise
- pressure
- drugs
- ciprodex drops is ok
- gentamycin is bad news
- topical therapy
- aminoglycosides
- chemotherapies (cisplatin, adriamycin)
Assymetrical sensorineural
- unknown in 85%
- vestibular syndromes (Meniere's)
- acoustic neuroma (ie from Neurofbromatosis type II)
- congenital and infections
- noise
- head injury
- drugs
Diagnosis
- history for risk factors
- tuning fork tests
- pure tone audiometry
- speech audiogram
- assess diasability and aid as appropriate
The Case of...
Differential Diagnosis
History and Physical Exam
- history
- physical exam
History
Diagnosing Hearing Loss
Rinne - base of tuning fork on mastoid until it is no longer heard, then placed beside ear
Weber - base of tuning fork is placed on on forehead
Conductive hearing loss |
Sensorimotor hearing loss |
|
noisy environment helps |
noisy environment makes it more difficult |
|
onset |
childhood/young |
middle/old age |
visible abnormality with eardrum |
no visible abnormality |
|
Webber test |
lateralizes to damaged ear |
lateralizes to good ear |
Rinne |
BC > AC |
BC < AC |
Physical Exam
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Diagnostic Imaging
Management
As with most conditions, prevention is the best medicine. Counsel patients about noise control and hearing protection.
Refer patients with hearing loss on screening for complete audiological examination.
Hearing amplification can dramatically improve quality of life
- hearing aids: can be annoying and cause eczema, soggy ear canal
- bone anchored hearing aids
- cochlear implants
- brain stimulation of the auditory nuclei is possible
Pathophysiology
Resources and References
Topic Development
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