Any problem which blocks transmission of sound through the ear canal and/or the middle ear will cause a conductive type of hearing loss. Therefore, abnormalities of the ear canal, tympanic membrane, ossicular chain (little bones in the middle ear) or middle ear space will cause this type of hearing loss.
The most common cause of conductive hearing loss is fluid in the middle ear space. The presence of fluid instead of air in the middle ear reduces efficient transmission of sound into the inner ear. Fluid can persist in the middle ear after birth, as the middle ear may not immediately fill with air. Later in infancy and childhood, fluid in the middle ear occurs most commonly as secondary to an ear infection. Once the fluid is gone, the child's hearing typically returns to normal. Another acquired, reversible cause of hearing loss is wax or a foreign body that completely blocks the ear canal.
Conductive loss can also develop because of abnormalities of the eardrum or the little bones in the middle ear. For example, a large hole in the eardrum can cause conductive hearing loss. Holes in the drum can be repaired by a surgical procedure called tympanoplasty. If the hole was the only cause of hearing loss, surgical closure should improve hearing.
Abnormalities of the little bones can occur due to chronic middle ear and mastoid infection, or can occur due to cholesteatoma. A small number of children are born with middle ear bones that did not develop normally. Their ossicles do not vibrate normally in response to sound, and these children have a conductive hearing loss in the affected ear. Some children are born with a condition known as aural atresia. In these children, the ear canal, tympanic membrane and ossicular chain do not fully develop in one or both ears.
In the majority of cases, conductive hearing loss can be corrected surgically. Conductive hearing loss can also be managed in many cases by use of hearing aids. A new implant system for children and adults who have conductive hearing loss is the bone-anchored hearing device.