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Deafness

Deafness, partial or total impairment of the sense of hearing. Hearing loss is of 2 basic types. In conductive deafness, the eardrum cannot make the bones of the inner ear vibrate. The nerve endings deep inside the ear are not stimulated, and the brain receives no message. This may be caused by blockage of the ear canal by wax or a foreign body; infections and perforation of the eardrum are other causes. This form of deafness can usually be corrected by surgery, antibiotics, hearing aids, or other techniques. Nerve (perceptive) deafness, on the other hand, stems from damage to the hearing nerve itself, which prevents the nerve from transmitting to the brain the message it receives from the vibrating eardrum and bones. The most common cause is atherosclerosis of the blood vessels supplying the nerve or injury due to excessive noise. This form of deafness is often permanent.

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21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Davis, Henry Gassaway to Diamond