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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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