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OTOSCLEROSIS | A common cause of hearing loss

Written by by Randa Mansour-Shousher, AuD, CCC-A. Posted in August

Otosclerosis is the abnormal growth of bone in the middle ear that can cause hearing loss. According to the American Academy of Otolaryngology, the term otosclerosis is derived from the Greek words for “hard” (scler-o) and “ear” (oto). The abnormal bone growth occurs around the stapes bone, one of the tiny bones in the middle ear. It’s important for the stapes bone to move freely for the ear to work properly and hear well.

 

The cause of otosclerosis is unfortunately still unknown, but evidence indicates that it is genetically passed through the family. Otosclerosis is sponge-like, which prevents the bone from vibrating as it should in response to sound waves. These sound waves are vital as they travel from the outer ear, through the middle ear, and beyond to the inner ear for the brain to hear.

Otosclerosis is one of the most common causes of hearing loss, and its symptoms progress slowly. This condition usually starts in the early 20s but may be recognized later in life. It is more prevalent in women, with the risk increasing during pregnancy. It may affect one or both ears with Caucasians being at higher risk. Nearly 60% of cases have a genetic link. According to research, a person who has one parent with otosclerosis has a 25% chance of developing the disorder; if both parents have it, the likelihood jumps to 50%.

Otosclerosis can be caused by another medical condition, and an examination by an otolaryngologist (ear, nose and throat physician) is crucial to eliminate other potential causes. A hearing examination to determine the type of hearing loss is also crucial. The typical form is what is called a conductive hearing loss. This occurs when the sound cannot be transferred to the inner ear because of the growth of the abnormal bone. The diagnosis is made and a treatment plan is prescribed after the completion of a comprehensive hearing examination. If the hearing loss is mild, it will most likely be closely monitored. Hearing aids may be suggested if it is bothersome to the patient. The otolaryngologist may prescribe sodium fluoride, which has been shown to slow down the disease.

The majority of the time, otoscleorsis will worsen. If the otosclerosis is severe, a surgical procedure called a stapedectomy may be performed. This is usually an outpatient procedure performed through the ear canal. During this process, part of the stapes bone is removed and replaced with a device to allow the ossicular chain in the middle ear to resume its action of stimulating fluid in the inner ear and improving the hearing. The surgery may restore some of the hearing, but, over time, it may worsen, eventually leading to the necessity of hearing aids.

The complicated architecture of the inner ear makes it difficult for scientists to study this part of the body. Because researchers can’t remove and analyze a sample of the ear from someone who has otosclerosis, they use ear bone samples from cadavers.

To encourage more research on otosclerosis, The National Institute of Deafness and Other Communication Disorders (NIDCD) supports national temporal bone collections such as the Otopathology Research Collaboration Network at the Massachusetts Eye and Ear Infirmary. This effort coordinates the collection and sharing of temporal bone tissue among laboratories. It also encourages scientists to combine modern biology, imaging, and computer technologies with information from patient history and pathology reports to look for new clues and solutions to ear disorders caused by bone abnormalities.

The NIDCD also funds genetic studies and bone-remodeling research to better understand the causes of otosclerosis as well as to investigate potential new treatments. NIDCD-supported researchers are currently testing—in animals—the effectiveness of an implantable device that can deliver a bone-growth-inhibiting drug directly into the inner ear to correct the bone abnormalities that cause otosclerosis. If the results are promising, testing will later be done in people.

We’ve encountered and treated many patients with otosclerosis. If you’re suffering with its symptoms, feel free to reach out to us.❦

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