Otosclerosis

What is Otosclerosis?

Otosclerosis is a condition where abnormal bone growth happens in the middle and inner parts of the ear. It was first discovered by Antonio Maria Valsalva in 1735 and studied further by Adam Politzer in 1839. In this condition, the properly organized and dense bone around the inner ear is replaced by messy, loose bone. This new bone later hardens and causes the bone structure in the ear (the stapes footplate) to become stuck.

This condition mainly leads to a type of hearing loss called conductive hearing loss, and it generally doesn’t affect the eardrum’s appearance. However, in some cases, a red flush might come up on the cochlea (an organ in the inner ear) if the eardrum is transparent enough. This is called the Schwartze sign. In instances where the loose bone affects the cochlea, it can result in a different kind of hearing loss, called sensorineural hearing loss. The tricky part about otosclerosis is that it often doesn’t show noticeable signs in an ear exam and yet can cause significant hearing troubles. This is why ear specialists often say, “The doctor sees nothing, and the patient hears nothing.”

What Causes Otosclerosis?

Otosclerosis, a condition that affects your ears and your hearing, happens for reasons that doctors still don’t fully understand. Different theories have been proposed:

Genetic

Some specific locations on your DNA, which is like a blue-print of your body, have been linked to otosclerosis. Also, certain abnormalities in bone metabolism, like osteogenesis imperfecta, and certain genes connected with bone remodeling could potentially cause otosclerosis. This includes genes like type I collagen (COL1A1), TGF-beta 1 (BMP2 and BMP4), angiotensin II (AGT M235T and ACE I/D), as well as factors related to autoimmune reactions, human leucocyte antigen, inflammation control molecules, parathyroid hormone and related receptors, and oxidative stress.

Hereditary

In more than half of people who have otosclerosis, the condition also exists in their family history. These people also tend to show symptoms earlier. Genetic studies suggest that otosclerosis usually passes on in families in a way where a certain characteristic may not show itself even though the person carries the gene for it.

Sex

Otosclerosis is twice as common in women as compared to men, suggesting that sex hormones might play a role. Interestingly, women seem to suffer less hearing loss than men who have the same degree of otosclerosis because female hormones give elasticity to ligaments.

Ethnicity

Otosclerosis is more common in people of European or Indian descent and is seen less frequently in people of African descent.

Pregnancy

Being pregnant seems to make hearing loss in otosclerosis worse, but the specific connection between pregnancy and otosclerosis isn’t clear.

Viral Infections

It has been theorized that infection with the measles virus might play a role in causing otosclerosis. In fact, traces of the virus has been found in the tiny bone in your ear that helps in hearing in 59%-100% of patients. Also, getting a measles vaccine seems to lower the chances of getting otosclerosis.

Other Causes

In addition to these factors, menopause, trauma, and major surgery have also been reported as either causing or worsening otosclerosis.

Risk Factors and Frequency for Otosclerosis

Otosclerosis, a condition that can impact hearing, is found in different rates across various populations. For instance, its clinical presence is detected in around 0.04% to 1% of White individuals. However, signs of this disease can be found in about 10% of the same group when examined under a microscope. In comparison, in Black individuals, this microscopic presence is at 1%, and it is about 5% in the Asian population.

Otosclerosis typically starts affecting people in their early adulthood. Interestingly, it affects more women than men at a ratio of 2:1. Its symptoms start showing up during the third and fourth decades of a person’s life, but generally doesn’t cause hearing loss until after the fourth decade.

• Otosclerosis is observed in 0.04% to 1% of White individuals clinically.
• Microscopic evidence of this disease can be detected in up to 10% of White individuals.
• In Black individuals, histological or microscopic otosclerosis is present in 1% of cases.
• In the Asian group, this microscopic presence is at around 5%.
• Otosclerosis appears during early adulthood, more often in women than men by a ratio of 2:1.
• The symptoms usually become apparent in the third and fourth decades of life but typically don’t cause hearing loss until after the fourth decade.
• Otosclerosis is responsible for 5% to 9% of all cases of hearing loss and 18% to 22% of conductive hearing loss cases.

Signs and Symptoms of Otosclerosis

Otosclerosis is a condition related to the ear. The most common issue that people with otosclerosis face is hearing loss. However, they may also deal with tinnitus (ringing in the ears) and vertigo (a sensation of feeling off balance). Usually, the condition affects both ears and gets worse over time. More often than not, hearing loss begins in one ear before gradually impacting the other.

The first noticeable signs of otosclerosis are often difficulties hearing low-frequency sounds like whispers. Some patients may find it surprisingly easy to hear conversations in noisy environments, a condition known as “paracusis Willisii.” Although this specific symptom isn’t only associated with otosclerosis, it does point towards conductive hearing loss. As otosclerosis progresses, tinnitus might get worse, and balance issues may also appear, similar to those seen in Ménière disease.

During a physical exam, patients with otosclerosis might speak with a quiet and monotonous voice. A visual examination of the ear (otoscopy) might not show anything unusual. However, in cases of active otosclerosis, a reddening of the cochlea promontory, or inner ear (known as Schwartze sign), might be visible through the eardrum. Keep in mind, this is not common and is only seen in about 10% of cases.

• Hearing loss (usually starting in one ear then affecting the other)
• Tinnitus (ringing in the ears)
• Vertigo (feeling of being off balance)
• Difficulty hearing low-frequency sounds like whispers
• Ability to hear conversations in noisy environments (“paracusis Willisii”)
• Possible decline in balance as the disease progresses
• Speaking in low volume and monotone during a physical exam
• Possible reddening of the inner ear visible through the eardrum (active otosclerosis)

Testing for Otosclerosis

In order to diagnose hearing loss due to a condition known as otosclerosis, doctors could use a technique known as the Weber test. This test involves using a tool called a tuning fork, which vibrates at a frequency of 512 Hz. The sound from the fork will generally seem louder in one ear than the other if there is hearing damage present. This test can indicate whether there is loss of hearing in one ear or both.

Other tests such as the Rinne test can reveal if sound carried through the bones of your ear (bone conduction) is louder than sound conducted through the air. If bone conduction is found to be better, this can indicate a conductive hearing loss of more than 30 dB, which is usually the point at which doctors consider surgically treating the issue.

Another approach for diagnosing otosclerosis is called pure tone audiometry. In this test, the doctor will observe the patient’s ability to hear different frequencies of sound. Often, patients with otosclerosis have difficulty hearing low frequencies, although other parts of their hearing (like bone conduction) remain normal. Sometimes, a decline in hearing at 2,000 Hz – known as a “Carhart notch” – is observed, and this usually disappears after an operation called a stapedectomy.

Moreover, a type of hearing loss called “mixed hearing loss” can also occur in otosclerosis, especially in advanced cases. Here, the patient has difficulty hearing high-frequency sounds due to damage to the cochlear endosteum, a part of the inner ear.

For early diagnosis of otosclerosis, the tympanometry and speech discrimination tests are also employed. These involve measuring the movement of the eardrum and the patient’s ability to distinguish speech sounds, respectively. In severe cases, however, these tests show reduced eardrum and middle ear bone chain flexibility and sensitivity to sound.

A noncontrast, high-resolution computed tomography (CT) scan of your temporal bones (the bones on the sides of your skull around your ears) is deemed the most accurate test for diagnosing otosclerosis. In many cases, this test can find abnormal bone growth in areas of the ear. It can also determine the extent of thickening of certain parts of the middle ear, which is useful for planning surgery if needed.

In some patients, the CT scan shows a “halo sign,” suggesting the otosclerosis has spread to the cochlea, a part of the ear involved in converting sound vibrations into nerve impulses. Depending on the findings of the CT, doctors use a grading system to determine the severity of otosclerosis and plan the appropriate treatment accordingly.

Treatment Options for Otosclerosis

Otosclerosis is a disease that cannot be cured, but its progression can be slowed down or stopped via medical treatment. Doctors often prescribe sodium fluoride for slowing down the disease’s progression, though this medication’s effectiveness is a matter of debate. Bisphosphonates, another type of medication, have been used with seeming success. These medications such as risendronate, zolendronate, or the older etidronate, help prevent bone loss. They need to be avoided in pregnancy. However, many specialists believe the newer medications are more effective and carry fewer side effects compared to older ones. Supplements such as vitamin D and bioflavonoids have been suggested to improve hearing in some cases, but their effectiveness varies from person to person.

For some patients, hearing aids that are worn in both ears could also provide some relief, and these can be used by themselves or in combination with other treatments.

In terms of surgical solutions, there are procedures such as stapedotomy or stapedectomy that can be selected as possible treatments along with the insertion of a prosthesis. These surgical remedies involve either drilling a hole in the center part of one of the tiny bones in the ear (stapes) or removing it completely, and then placing the prosthesis, i.e., an artificial device that replaces this bone. A natural tissue graft is typically used to protect the oval window, a membrane-covered opening that leads from the middle ear to the inner ear.

The surgical approach typically results in positive outcomes irrespective of the chosen method, assuming the patient was an appropriate candidate for surgery. If the patient has otosclerosis in both ears, the ear with worse hearing is usually operated on first. Be assured that both ears are not operated on at the same time, for safety considerations. Sometimes a repeat surgery may be required if hearing doesn’t improve after the initial surgery. In some instances, a hearing aid may still be required even after surgery.

Common risks and complications from surgery can include facial paralysis (if a nerve is injured in the ear) or a change in taste (if another nerve is injured during surgery). There can also be complications such as displacement of the prosthesis, formation of an inflammatory reaction that may lead to more hearing loss, and balance issues if the prosthesis inserted is too long and irritates an inner ear structure. To prevent problems with balance, many surgeons prefer to operate with the patient awake under local anesthesia.

What else can Otosclerosis be?

Otosclerosis is a condition that can lead to hearing loss. However, there are other conditions which can also result in hearing loss and might, therefore, be confused with otosclerosis. These include:

• Otitis media with effusion, which is inflammation of the middle ear accompanied by fluid
• Chronic suppurative otitis media, a long-term ear infection that results in a discharge
• Congenital stapes fixation, a birth defect involving the small bones in the ear
• Ménière disease, an inner ear disorder causing dizziness and hearing loss
• Tympanosclerosis, a condition that causes hardening of the tissue in the eardrum and middle ear
• Fixation of the head of the malleus, a problem with one of the tiny bones in the ear
• Ossicular discontinuity, a disruption in the chain of small bones in the ear
• Superior semicircular canal dehiscence, a condition causing balance and hearing problems

What to expect with Otosclerosis

Approximately 90% of people who have surgery for otosclerosis — a condition that can cause hearing loss — find that their hearing considerably improves. However, there are a few instances where the operation may not help. In rare cases, people’s hearing might even get worse after the procedure.

Sometimes, there’s a chance that the hearing loss may come back. This can happen if the artificial device that was inserted during the surgery moves from its initial position. The device might also become attached to the bone near the oval window or stapes footplate – parts of the inner ear.

If another surgery is necessary to correct these issues, the results might not be as good as they were after the first surgery.

Possible Complications When Diagnosed with Otosclerosis

Untreated otosclerosis, or abnormal bone growth in the ear, can slowly lead to moderately severe hearing loss. However, severe hearing loss is rare and usually indicates further damage in the inner ear. Meanwhile, surgical treatment for otosclerosis might sometimes result in total hearing loss in the operated ear due to surgical mistakes or a type of scar tissue called a reparative granuloma that can form after surgery. However, these are rare events. Surgery can also possibly lead to other complications such as facial nerve damage, dizziness, changes in taste, and ringing in the ears. The surgical implant itself can sometimes cause issues, including tissue death and damage to a bone in the ear called the incus, dislocation of the implant, and formation of the above-mentioned reparative granuloma.

Common Side Effects:

• Moderate to severe hearing loss from untreated otosclerosis
• Rare instances of complete hearing loss due to surgery
• Likely formation of reparative granuloma (a type of scar tissue) after surgery
• Possible facial nerve damage from surgery
• Potential dizziness following surgery
• Chances of changes in taste due to surgery
• Possible ringing in the ears (tinnitus) after surgery
• Risk of tissue death from surgical implants
• Potential damage to the incus (a bone in the ear) from the surgical implant
• Possible dislocation of surgical implant

Preventing Otosclerosis

If you have family members who have dealt with otosclerosis, a condition that can cause hearing loss, it’s a good idea to have your hearing checked regularly. This way, any issues can be spotted early and treated before they get worse. One potential treatment is taking sodium fluoride, a supplement that can help protect your hearing.

If you’re pregnant and you notice that your hearing is getting worse, it’s important to get your hearing tested. If otosclerosis is the cause, you might want to start taking sodium fluoride. This can help slow down or stop the disease from progressing and causing further hearing loss.