Otosclerosis

Overview

Otosclerosis is a condition in which abnormal bone growth develops within the middle ear around the stapes, the smallest bone in the ear. This abnormal growth interferes with the way sound vibrations travel through the ear. When the stapes is unable to vibrate, sound cannot travel as effectively to the inner ear, causing hearing loss.

About 3 millimeters long—about the thickness of three to four credit cards stacked on top of each other—the stapes transmits sound vibrations from the middle ear to the inner ear by vibrating. Its precise movement is critical for converting sound waves that the inner ear can interpret. Without this rapid motion, even loud sounds can sound faint or muffled. The hearing loss that develops as a result of otosclerosis tends to be gradual, affecting one ear before progressing to the other.

What causes otosclerosis?

While the exact cause of otosclerosis isn’t fully understood, certain factors contribute to the condition:

• Abnormal bone remodeling: The bones in the middle ear undergo a continuous breakdown-and-rebuilding process, but, in the case of otosclerosis, this process becomes dysregulated. As a result, the stapes bone becomes harder or thicker in the wrong spots.
• Genetics: Otosclerosis tends to run in families. This is because certain genetic variations can increase a person’s risk of developing the condition.
• Hormonal influences: In some individuals, hormonal changes or pregnancy can accelerate the progression of otosclerosis.
• Autoimmune factors: Autoimmune processes that influence bone turnover are also thought to play a role in the development of otosclerosis.

Symptoms that may indicate otosclerosis can include:

• Gradual hearing loss: As the most common symptom, hearing loss from otosclerosis often begins with difficulty hearing soft or low-pitched sounds, like whispering. This hearing loss typically starts in one ear before progressing to both ears.  
• Conductive hearing loss: This type of hearing loss causes sounds to feel muffled or less powerful due to the abnormal bone growth that prevents the stapes from moving properly. 
• Sensorineural hearing loss: If the abnormal bone growth extends to the cochlea, the fluid-filled structure in the inner ear, sensorineural hearing loss can occur. This type of hearing loss leads to reduced clarity and difficulty understanding speech. However, it’s less common than conductive hearing loss in people with otosclerosis. 
• Tinnitus: This sounds like ringing, buzzing, humming, or whooshing sounds in the ear, and becomes especially noticeable in quieter environments.
• Paracusis Willisii: This describes a phenomenon in which people perceive sounds more clearly in noisy environments, such as busy restaurants. Paracusis Willisii is often associated with conductive hearing loss.
• A feeling of fullness or pressure in the ear: Similar to having a plugged ear, this sensation can occur even though the ear canal is clear.
• Mild dizziness or balance issues: Some people may experience intermittent dizziness or lightheadedness if their inner ear structures are affected. 

Once the underlying issue is diagnosed and treated, these symptoms often improve or resolve completely. 

Otosclerosis Diagnosis

Diagnosing otosclerosis typically involves a physical examination, a detailed medical history, and hearing-focused tests that reveal the patterns of hearing loss. Imaging is used only in specific instances. 

These diagnostic tools are used by healthcare providers who specialize in hearing, such as an otolaryngologist—commonly referred to as an ENT (ear, nose, and throat) doctor—a neuro-otologist who specializes in neurological diseases of the ear, or an audiologist skilled in identifying and measuring hearing disorders. 

The following exams, tests, and imaging studies can be used in the process of diagnosing otosclerosis: 

• Physical examination and medical history: Your healthcare provider will ask about your hearing loss, personal medical history, family medical history, tinnitus, balance changes, and whether your symptoms have worsened during periods of hormonal changes, like pregnancy. Next, they’ll perform a physical exam with an otoscope, a device used to examine the ear. 
• Hearing test: To measure the degree and type of hearing loss, an audiogram is done to illustrate how well you can hear different pitches and volumes. During an audiogram, you’ll listen to tones through headphones. At the same time, the audiologist records the softest sounds you can detect at each pitch. The result is a simple visual map of your hearing ability that identifies the type and degree of hearing loss. 
• Tympanometry: This diagnostic tool measures how well the eardrum and middle-ear system move in response to pressure changes. If you have otosclerosis, the results may show reduced mobility due to the stiffening of the stapes. However, this test can appear normal in people with otosclerosis.
• Acoustic reflex testing: This test evaluates the reflex that stiffens your middle-ear muscles in response to loud sounds. In otosclerosis, this reflex is often absent because the stapes is unable to move normally. 
• Computed Tomography (CT) scan: A high-resolution CT scan is only ordered when the diagnosis is uncertain, your hearing loss pattern is unusual, or more detailed anatomical information is required. 

Once you’ve been diagnosed with otosclerosis, there are multiple options available to help address your hearing loss.

Surgical Treatments 

Surgical treatments for otosclerosis include: 

• Stapedotomy: As the most common surgical procedure for otosclerosis, a stapedotomy involves creating a small hole in the stapes bone and inserting a tiny prosthesis to restore sound vibrations to the inner ear. Though some symptoms may persist, many people notice substantially improved hearing after they heal, and the benefit is usually long-lasting. 
• Stapedectomy: An older technique, a stapedectomy involves removing part or all of the stapes and replacing it with a prosthesis. This procedure involves a more extensive removal than a stapedotomy, so it’s used less frequently in modern surgeries.
• Revision stapes surgery: If a prior stapes prosthesis loosens, shifts, or becomes less effective over time, a revision surgery can be done, although this is uncommon.
• Cochlear implant: In cases of severe sensorineural hearing loss, a cochlear implant is used when stapes surgery cannot restore functional hearing. A cochlear implant works by directly stimulating the auditory nerve. It captures sound from the environment, converts it into electrical signals, and transmits those signals directly to the hearing nerve, bypassing the damaged parts of the inner ear.

Nonsurgical Treatments 

The following nonsurgical treatments for otosclerosis include:

• Hearing aids: As the leading nonsurgical option, hearing aids are exceptionally effective for treating conductive hearing loss caused by otosclerosis. Hearing aids work by amplifying sound to compensate for reduced transmission through the middle ear, and the effects on sound clarity and volume are immediate. 
• Bone conduction hearing devices: When traditional hearing aids are not well-tolerated or less effective, bone conduction hearing devices can be a suitable alternative. These devices transmit sound through skull vibration, bypassing the stapes, and can be worn externally or implanted.
• Assistive listening devices: Popular hearing loss aids, like amplified phones, TV streamers that send sound directly from the television into your hearing aids, and wireless listening devices, can support communication alongside or in place of traditional hearing aids.
• Watchful waiting with periodic hearing tests: For mild cases of otosclerosis, regular hearing tests and monitoring can be sufficient. Many people can remain stable without intervention for extended periods of time.
• Bisphosphonate therapy: Researchers have studied medications used for osteoporosis for their potential to slow the progression of cochlear otosclerosis. However, due to limited research, this is not an established, routine treatment.

With appropriate treatment—particularly surgery or the use of hearing aids—most people with otosclerosis can regain meaningful hearing function and continue their normal lives. Without treatment, hearing loss from otosclerosis can progress, although it rarely causes complete deafness.