Otosclerosis is a condition of the middle ear and mainly affects the tiny stapes bone. It causes gradual hearing loss. The term otosclerosis is derived from the Greek words for “hard” (scler-o) and “ear” (oto). It describes a condition of abnormal growth in the tiny bones of the middle ear, which leads to a fixation of the stapes bone. The stapes bone must move freely for the ear to work properly and hear well.
The ear is divided into three parts – the outer (external) ear, the middle ear, and the inner ear. The middle ear behind the eardrum is filled with air. Air comes from the back of the nose up a thin channel called the Eustachian tube. In the middle ear there are three tiny bones (ossicles) – the malleus, incus and stapes (also known as the hammer, anvil and stirrup). The inner ear includes the cochlea and semicircular canals.Sound waves come into the outer (external) ear and hit the eardrum. The sound waves cause the eardrum to vibrate. The sound vibrations pass from the eardrum to the middle ear bones. The bones then transmit the vibrations to the cochlea in the inner ear. The cochlea converts the vibrations to sound signals which are sent down a nerve from the ear to the brain, allowing us to hear.
Otosclerosis is a condition that mainly affects the stapes, one of the tiny bony ossicles in the middle ear. What happens in otosclerosis is that abnormal bone material grows around the stapes.The abnormal bone reduces the movement of the stapes, which reduces the amount of sound that is transferred to the cochlea. The growth of the abnormal bone is very gradual. The hearing loss is known as conductive hearing loss. It usually first develops between the ages of 15 and 35 but sometimes develops in younger children. Women are affected twice as often as men. Pregnancy is not a cause but may make the condition worse, so symptoms are commonly first noticed during pregnancy.
You will need to be seen by an ear, nose and throat specialist to diagnose otosclerosis. Hearing tests will show a specific pattern of hearing loss in otosclerosis. The specialist may also use a small device that is placed in your ear, called a tympanometer. This can help them look at the movement of the bones within your ear. In otosclerosis, the stapes will move less. This test is very quick and does not cause any pain. If the hearing loss is mild, the otolaryngologist may suggest continued observation and a hearing aid to amplify the sound reaching the ear drum. Sodium fluoride has been found to slow the progression of the disease and may also be prescribed. In most cases of otosclerosis, a surgical procedure called stapedectomy is the most effective method of restoring or improving hearing.