How Otosclerosis Could Cause Hearing Loss
Published: September 8, 2021
Updated: July 22, 2022
Otosclerosis is the abnormal growth of bone in the middle ear. Approximately 2.5-10% of adults develop otosclerosis in the middle ear. It can occur in both men and women however, it has been more prevalent in women.
What is otosclerosis?
This happens through the remodeling of the bone in the middle ear. Bone remodeling is a process in which the bone replaces the old tissue with new bone tissue. Otosclerosis occurs when abnormal remodeling happens to the bones in the middle ear. Otosclerosis comes from the word oto, which means ear, and sclerosis, which means hardening of the body tissue.
The middle ear contains 3 small bones called the malleus, incus, and stapes. It usually affects the stapes bone in the middle ear. The stapes bone is attached to the incus and oval window in the inner ear.
What causes otosclerosis?
Otosclerosis affects approximately 3 million Americans. Otosclerosis is usually genetic and runs in families. Approximately 60% of otosclerosis cases have been linked to a genetic cause. The gene can be passed on from one generation to the next. It is estimated that about half of those who have otosclerosis have the gene for it; however, not everyone who carries the gene will have otosclerosis. Other medical conditions can increase the risk of developing otosclerosis. For example, research has shown a decline in otosclerosis among people vaccinated against measles, stress fractures to the bony tissue around the inner ear, and autoimmunity disorders. Researchers also think that the imbalance of certain immune-system cells, such as cytokines responsible for bone remodeling, can cause abnormal remodeling that occurs in otosclerosis.
How does otosclerosis cause hearing loss?
In otosclerosis, an accumulation of abnormal growth of bone occurs on the stapes. This causes the movement of the stapes to reduce partially or entirely. Complete or partial fixation of the stapes affects sound from traveling to the inner ear, thus causing hearing loss. The less movement of the bone, the worse the hearing loss. In an ear without an auditory/hearing problem, the ear (auricle) helps direct sound waves into the ear canal (external auditory canal). Sound waves travel through the ear canal and cause the eardrum (tympanic membrane) to vibrate. The vibrations cause the three small bones called the ossicles (malleus, incus, and stapes) behind the eardrum to vibrate, and those vibrations move to the inner ear. The fluid in the cochlear (organ of hearing) moves due to the vibrations which cause the hair cells on the cochlear to move. The vibrations change into electrical energy and move to the brain, where it is recognized as sound. Otosclerosis usually causes a conductive hearing loss; however, it can affect the inner ear. Conductive hearing loss is hearing loss that occurs in the outer and/or middle ear. Conductive hearing loss causes problems with the transmission of sound to the inner ear.
What are the symptoms of otosclerosis?
- The main symptom is hearing loss. Hearing loss can occur in both ears. About 10% -15% of people have it in only one ear.
- Problems hearing low-pitched sounds, e.g., bass drum, thunder.
- Experiencing tinnitus which is a ringing, buzzing, or hissing sound in the ear.
How is otosclerosis treated?
If you experience any of those symptoms, visit your hearing health provider. They will conduct audiological assessments. The audiological evaluations can determine if the bones in the middle ear are not moving correctly. Based on the results, you may be referred to an Ears Nose, and Throat (ENT) specialist. Many symptoms associated with otosclerosis are related to other ear-related conditions; therefore, it is important to be examined by an ENT (ears, nose, and throat) doctor.
Treatment options include the following:
- Hearing aids: Hearing aids will increase the sound volume, making it louder an individual hear. Depending on the severity or degree of the hearing loss, hearing aids can be beneficial. However, otosclerosis is a progressive disorder. If the hearing loss continues to worsen, then hearing aids might not provide sufficient amplification, and surgery might be considered. Bone conduction hearing devices or a bone-anchored hearing aid may help hear better in otosclerosis cases. Bone conduction hearing devices are used when the problem lies in the outer or middle ear, and when conventional hearing aids cannot provide sufficient amplification. It transfers sound by bone vibration directly to the cochlear. Hearing aids and bone conduction hearing devices help the common symptom, which is hearing loss. It does not treat the underlying condition, which is otosclerosis.
- Surgery: Stapedectomy is a procedure that involves removing part or all of the fixed stapes and replacing it with a prosthetic device. The prosthetic device allows the bones in the middle ear to move properly, allowing better transmission of sound to the inner ear.
- Cochlear implants: Severe forms of otosclerosis can cause severe to profound sensorineural hearing loss. Sensorineural hearing loss occurs in the inner ear. Studies have shown that cochlear implantation in far advanced otosclerosis cases provided good auditory results. Your ENT and hearing health provider will be able to explain which treatment option will be best for you.
- Supplements: Sodium fluoride or bisphosphonate supplements have been reported to slow down the progression of otosclerosis; however, there is insufficient research to show that this definitely helps to limit the progression.
The exact cause of otosclerosis is still unclear however, there are risk factors associated with this condition that one can be aware of. There are also many treatment options available, therefore an assessment with your hearing health provider will provide the clarity you need. Each option has its benefits as well as its limitations, therefore the more you are armed with information, the better your decision-making on treatment options. Depending on your condition, the severity, and your personal needs, an ENT and hearing health provider will advise you.
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