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Deafness: Ears
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Deafness is the complete loss of the ability to hear from one or both ears. Deafness may be inherited, or caused by complications at birth, certain infectious diseases, such as meningitis, use of ototoxic drugs, and exposure to excessive noise. Around half of all deafness and hearing impairment can be prevented.
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Deafness in childhood can either be nerve deafness which involves the auditory or hearing nerve in the brain itself, or it can be a form of conduction deafness. This occurs when there is interference with the transmission of sound waves from the outer ear through to the inner ear before the auditory nerve carries sound on into the brain.
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The Second International Symposium on Cognition, Education, and Deafness in 1989 broadened and deepened the scope of investigation initiated at the first conference held five years earlier. Advances in Cognition, Education, and Deafness provides the results in a single integrated volume. The 39 scholars from 14 nations who attended offered consistent progress from the first symposium and new areas of research, especially in the study of applications in education and the new field of neuro-anatomical dimensions of cognition and deafness.
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Deafness varies greatly among those with hearing impairments. For example, some individuals only lack hearing in one ear. Others are unable to distinguish tone. Most individuals... are able to hear or communicate with others in some manner, usually either through sign language or lip reading.
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Dogs with acquired deafness are born with the capability of developing and maintaining normal hearing, but hearing is lost as the animal ages. Acquired deafness is not common to any one breed, but rather, is seen in individuals of all breeds. It is usually the result of damage to the ear components such as the eardrum, middle or inner ear structures, and nerves. Diseases such as canine distemper is a common cause of ear damage. Trauma to the ear areas of the head may result in hearing impairment. Various drugs including the Aminoglycoside antibiotics can be toxic to the ear structures and cause deafness.
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The two main types of hearing loss are sensorineural (nerve deafness which involves impairment of the auditory nerve) and conductive deafness (usually a dysfunction of a part of the ear mechanism). Hearing loss is measured by decibels, and according to the decibel count the loss may be mild, moderate, or profound. The 21 million plus people in the United States who have this disability differ considerably. A person may be born with a hearing loss or may become hard of hearing due to an accident or illness. If the age of onset occurs before the acquisition of language and the development of speech, the individual may have language-based deficiencies such as poor syntax and vocabulary, and difficulty understanding abstract concepts.
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