Article by Jennifer Lee, Senior Clinical Audiologist at Hearing Partners
Otosclerosis is a condition that affects the tiny bones in the middle ear and/or the cochlea, leading to progressive hearing loss. While it is not life-threatening, it can significantly impact daily communication and quality of life.
In this article, we will explain what otosclerosis is, outline its common causes and symptoms, and discuss how it is diagnosed and treated. We will also cover some frequently asked questions relating to otosclerosis.
Table of Contents
Otosclerosis is a condition where irregular bone growth or abnormal bone remodelling develops in the middle ear, and in some cases, the inner ear. This irregular bone formation interferes with the way sound vibrations are transmitted through the ear, making it difficult for sounds to reach the hearing nerve.
Otosclerosis most often occurs in the form of stapes calcification, which is when the stapes bone in the middle ear becomes stuck in place.
Normally, the stapes vibrates to transmit sound waves into the inner ear. When it is unable to move, sound cannot travel effectively into the inner ear, leading to conductive hearing loss. It is also possible to have cochlear otosclerosis, where spongy bone develops within the cochlear, thereby damaging the inner ear structures and causing sensorineural hearing loss.
The degree of hearing loss can range from mild to severe, although total deafness is rare, and usually both ears are affected, with one ear more affected than the other.
The exact cause of otosclerosis is still not fully understood. However, several contributing factors may play a role:
Certain factors may increase the likelihood of developing otosclerosis. While not everyone with these risk factors will develop the condition, they may make it more likely:
Otosclerosis often develops slowly, and symptoms may not be noticeable right away. Common signs and symptoms include:
Diagnosing otosclerosis requires a thorough evaluation by an Ear, Nose and Throat (ENT) specialist, otologist, or audiologist.
Your clinician will begin by asking about the onset and progression of your hearing loss. They will also explore possible contributing factors to the hearing loss, such as:
The clinician will perform a visual examination of your ears using an otoscope. This allows them to check for other possible causes of hearing loss, such as:
Otosclerosis itself cannot be directly seen through an otoscope, but this step is important to rule out alternative conditions.
A series of hearing tests will be carried out to determine the type and degree of hearing loss. These may include:
Image caption: Otosclerosis audiogram, with the Carhart notch at 2kHz
If otosclerosis is suspected, your doctor may request a CT (computed tomography) scan of the temporal bone. This imaging test provides a detailed view of the middle and inner ear structures, helping to confirm the presence of abnormal bone growth and assess how extensive it is.
The diagnosis of otosclerosis is made based on a combination of your medical history, hearing test results, and imaging findings. Confirming the condition is important, as it guides the most suitable treatment plan, which may involve hearing aids, surgery, or ongoing monitoring.
Management for otosclerosis focuses on improving hearing by bypassing or compensating for the abnormal bone growth. The choice of treatment depends on the location of the irregular bone, the severity of hearing loss, and your overall ear health.
A stapedectomy is a surgical procedure to replace the affected stapes bone. During the operation, an ENT surgeon removes the affected stapes and puts a prosthesis in its place, which allows sound waves to travel more freely into the inner ear.
If both ears are affected by otosclerosis, surgery is usually performed on one ear at a time, with at least six months of healing before the second procedure. While stapedectomy can restore significant hearing, some hearing loss may remain, and in rare cases, hearing may worsen after surgery. Stapedectomy is also unable to prevent or stop any future development of otosclerosis.
Hearing devices are often the first-line management for the hearing loss caused by otosclerosis or for the residual hearing loss post-stapedectomy. They work by amplifying surrounding sounds so that you can hear more clearly. Both conventional hearing aids and bone-anchored hearing devices can provide relief to the conductive hearing loss in individuals with otosclerosis.
An audiologist can adjust and customise the settings to match your specific hearing profile, ensuring effectiveness and comfort for your daily listening needs. While hearing devices improve hearing ability, they do not stop the progression of otosclerosis.
Cochlear implants may be considered for individuals with severe hearing loss due to cochlear otosclerosis. These implants bypass the damaged inner ear structures and directly stimulate the auditory nerve, sending sound signals to the brain. Even in advanced cases, cochlear implants can help restore functional hearing and improve communication.
The progression of cochlear otosclerosis has to be monitored closely to keep the option of cochlear implant viable. If the cochlea is severely or fully ossified, the insertion of the implant would be challenging or deemed impossible.
Otosclerosis usually progresses slowly over several years. It often begins with hearing loss in one ear and may gradually affect the other ear over time. In rare cases, the condition can advance more quickly and cause more noticeable hearing changes in a short time.
As abnormal bone growth develops around the stapes footplate, the stapes becomes fixed in place. This fixation can lead to the characteristic Carhart notch on an audiogram during pure tone audiometry.
The Carhart notch is most prominent around the 2000 Hz frequency and is caused by reduced movement of the ossicles in bone conduction, especially the stapes, rather than true inner ear damage. After successful stapes surgery, this notch often disappears.
Otosclerosis cannot be prevented. The condition is largely influenced by genetic factors rather than lifestyle or environmental causes. Unlike hearing loss caused by loud noise exposure, there are currently no proven measures to prevent otosclerosis.
If left untreated, otosclerosis can worsen over time. In some cases, the condition may progress to the inner ear, leading to cochlear otosclerosis, which causes more significant hearing loss and impacts overall hearing function. When the cochlea is fully ossified, albeit rare, hearing aids and cochlear implants would not be of any help.
It is important to consult a healthcare provider or hearing care professional for recommendations on whether to monitor the condition or consider management options such as hearing aids or surgery.
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