Hearing Health Guide
Definition
Conductive hearing loss is a reduction in hearing caused by any obstruction or dysfunction in the outer ear canal, eardrum, or the three small bones of the middle ear (ossicles) that prevents sound from being conducted efficiently to the inner ear. Unlike sensorineural hearing loss, many causes of conductive loss are medically treatable.
The most frequent causes include earwax (cerumen) buildup blocking the ear canal, fluid in the middle ear from infection (otitis media) or Eustachian tube dysfunction, a perforated eardrum, and otosclerosis (an abnormal bone growth that stiffens the ossicles).
Less common causes include a foreign object in the ear canal, atresia (a malformed or absent ear canal present from birth), and cholesteatoma (an abnormal skin growth in the middle ear).
On an audiogram, conductive hearing loss is identified by a gap between air conduction thresholds (sound played through headphones) and bone conduction thresholds (sound transmitted directly to the cochlea via a vibrating device placed on the mastoid bone). If bone conduction is normal but air conduction is impaired, the problem lies in the outer or middle ear pathway. That is the conductive mechanism.
Sensorineural loss shows no such gap. Both air and bone conduction thresholds are elevated equally, indicating the problem is in the inner ear or nerve.
Many forms of conductive hearing loss are treatable. Earwax removal, treatment of middle ear infections with antibiotics or pressure equalization tubes, surgical repair of a perforated eardrum (tympanoplasty), and surgery for otosclerosis (stapedectomy) can all restore hearing.
When surgical correction is not possible or appropriate, bone-anchored hearing aids (BAHA) or conventional hearing aids can effectively compensate for conductive loss.
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