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Hearing Loss
Essentials of Diagnosis
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Three main types of hearing loss: conductive, sensory, and neural.
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Most commonly due to cerumen impaction or transient auditory tube dysfunction associated with upper respiratory tract infection.
Classification & Epidemiology
Conductive Hearing Loss
Conductive hearing loss results from dysfunction of the external or middle ear. There are four mechanisms, each resulting in impairment of the passage of sound vibrations to the inner ear: (1) obstruction (eg, cerumen impaction), (2) mass loading (eg, middle ear effusion), (3) stiffness effect (eg, otosclerosis), and (4) discontinuity (eg, ossicular disruption). Conductive losses in adults are most commonly due to cerumen impaction or transient auditory tube dysfunction associated with upper respiratory tract infection. Persistent conductive losses usually result from chronic ear infection, trauma, or otosclerosis. Conductive hearing loss is generally correctable with medical or surgical therapy—or in some cases both
Sensory Hearing Loss
Sensory hearing loss results from deterioration of the cochlea, usually due to loss of hair cells from the organ of Corti. Sensorineural losses in adults are common. A gradually progressive, predominantly high-frequency loss with advancing age (presbyacusis) is typical. Other than aging effects, common causes of sensorineural loss include excessive noise exposure, head trauma, and systemic diseases such as diabetes mellitus. Sensory hearing loss is not correctable with medical or surgical therapy but often may be prevented or stabilized.
Neural Hearing Loss
Neural hearing loss occurs with lesions involving the eighth nerve, auditory nuclei, ascending tracts, or auditory cortex. It is the least common clinically recognized cause of hearing loss. Causes include acoustic neuroma, multiple sclerosis, and cerebrovascular disease.
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