Partial or total inability to hear. In conduction deafness, the passage of sound vibrations through the ear is interrupted. The obstacle may be earwax, a ruptured eardrum, or stapes fixation, which prevents the stapes bone from transmitting sound vibrations to the inner ear. In sensorineural deafness, a defect in the sensory cells of the inner ear (e.g., injury by excessive noise) or in the vestibulocochlear or eighth cranial nerves prevents the transmission of sound impulses to the auditory centre in the brain. Some deaf people are helped by hearing aids or cochlear implants; others can learn to communicate with sign language and/or lip reading.
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Table 1. A table comparing sensorineural hearing loss to conductive
|Criteria||Sensorineural hearing loss||Conductive hearing loss|
|Anatomical Site||Inner ear, cranial nerve VIII, or central processing centers||Middle ear (ossicular chain), tympanic membrane, or external ear|
|Weber Test||Sound localizes to normal ear||Sound localizes to affected ear (ear with conductive loss)|
|Rinne Test||Positive Rinne; Air conduction > Bone conduction (both air and bone conduction are decreased equally, but the difference between them is unchanged).||Negative Rinne; Bone Conduction > Air Conduction (Bone/Air Gap)|