Conductive hearing loss is a common type of hearing impairment that can occur for a number of reasons. Typically, it develops due to problems with the transmission of sound to the inner ear. Abnormalities in the ear canal, tympanic membrane, and middle ear are common causes of this condition. The diagnosis of conductive hearing loss relies on a physical examination and audiometric tests. Treatment of this condition varies depending on the reason that the hearing loss developed.
In general, conductive hearing loss occurs when sound cannot properly be transmitted from the external environment into the inner ear. To understand what different processes can cause this type of hearing loss, it helps to understand the basics of how humans hear. Sound travels through the ear canal, a region known as the external ear, and causes vibrations of the tympanic membrane. The vibrations are then transmitted through tiny bones called the malleus, incus, and stapes of the middle ear. Movements of the stapes result in changes in the pressure of the inner ear, which contains the cochlea, a structure that translates the pressure changes into signals sent to the brain.
As a result, any problems or abnormalities of the outer and middle ear can cause conductive hearing loss. Something as simple as having a buildup of earwax can cause this type of hearing loss because it decreases the transmission of sound to the inner ear and therefore to the brain. Another common cause is otosclerosis, a disease in which the tiny bones of the middle ear become rigid and unable to transmit vibrations. Other causes can include perforation of the tympanic membrane and fluid buildup in the middle ear.
The diagnosis of conductive hearing loss can be made using a number of different techniques. When a patient complains of hearing loss or is found to have evidence of it on a screening test, the patient will be asked about how long he or she has been having the symptoms, and if there are any other associated problems. A thorough physical exam is then performed, paying special attention to the appearance of the external ears and the ear canals. There are a couple of special examinations a doctor can perform immediately using a tuning fork, which can help narrow down the possible types of hearing loss present. In most cases, patients are then referred to a specialist to have audiometry tests performed, which provide a wealth of information regarding what sounds patients can hear; in most cases, the audiometry results can confirm a diagnosis of conductive hearing loss.
The treatment of conductive hearing loss varies depending on the cause of the hearing impairment. Certain conditions are easy to treat, such as wax buildup. Ear infections causing fluid buildup in the middle ear can be treated with antibiotic medications. Otosclerosis is a somewhat harder to treat, but patients are often helped either by a hearing aid or by a surgery to remove the stapes bone.