Conductive Hearing Loss
Conductive hearing loss is due to any condition that interferes with the transmission of sound through the external ear and middle ear to the inner ear. If it is in the middle ear, the damage may involve the footplate of the stapes (bottom of the stirrup bone), as in otosclerosis, or the mobility of the drum and ossicle caused by fluid. Conductive hearing losses are generally correctable. In cases of conductive hearing loss, sound waves are not transmitted effectively to the inner ear because of some interference in the external canal, the eardrum, the ossicular chain, the middle-ear cavity, the oval window and round window, or the eustachian tube. For example, damage to either the middle ear, which transmits sound energy efficiently, or the eustachian tube, which maintains equal air pressure between the middle ear cavity and the external canal, could result in a mechanical defect in sound transmission. In pure conductive hearing loss, there is no damage to the inner ear or the neural pathway.
Patients diagnosed as having conductive hearing loss receive a much better prognosis than those with sensorineural loss because modern techniques make it possible to cure or at least improve the vast majority of cases in which the damage occurs with the outer or middle ear. Even if they are not improved medically or surgically, these patients stand to benefit greatly from a hearing aid, because what they need most is amplification. They are not bothered by distortion and other hearing abnormalities that may occur in sensorineural loss.