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The hearing mechanism involves a mechanical (conductive) component and a
nerve (sensorineural) component. Although problems in either component can
produce hearing loss, the treatments are quite different and an accurate
diagnosis is important.
Conductive Hearing Loss
Conductive hearing loss occurs when the sound does not reach the hearing
nerve. Blockage in the ear canal, lesions of the tympanic membrane
(eardrum) or problems with the ossicles (hearing bones) can all produce
conductive hearing loss.
Ear Canal Disorders
- Wax (cerumen) impaction
- Congenital narrowing or absence
- Infections or narrowing (swimmer's ear)
Eardrum (tympanic membrane) and Middle Ear Disorders:
- Inflammation (myringitis)
- Holes (perforations)
- Infection (Otitis media)
- Fluid (effusion)
Ossicles (hearing bones) Disorders
- Congenital (since birth) abnormalities
- Erosion (dissolved) by infection
- Fixation (lack of vibration) by abnormal bone such as Otosclerosis
Nerve (Sensorineural) Hearing Loss
Nerve (Sensorineural) Hearing Loss occurs when the nerve endings (hair cells)
in the inner ear (cochlea), the main auditory (hearing) nerve, or the brain
connections do not function properly to carry the electrical sound signals to
the brain.
Disorders causing nerve hearing loss
- Congenital (birth) deformities of the nerve
- Noise damage
- Ototoxic (drug effect)
- Infections
- Auto-immune (body inflammation)
- Trauma (fractures)
- Age (presbycusis)
- Tumors (acoustic tumors)
- Meniere's Disease (inner ear fluid disorders)
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