Otosclerosis

What happens in otosclerosis

Sound travels through the ear canal to the eardrum, then through three tiny bones in the middle ear, the malleus, incus and stapes, to the inner ear (cochlea). The stapes footplate sits in a small window and works like a piston.

In otosclerosis, the hard bone surrounding the inner ear is replaced by spongy, abnormal bone that later hardens. When this happens around the stapes, it becomes fixed and cannot move freely, so less sound reaches the inner ear. This is a conductive hearing loss. If the process spreads to the cochlea, it can also damage nerve hearing (sensorineural hearing loss), resulting in mixed hearing loss.

Causes and risk factors

The exact cause is unknown, but contributing factors include:

• Genetics: about half of people have a family history; it can be inherited in an autosomal dominant pattern with variable expression.
• Sex: about twice as common in women.
• Hormones: pregnancy can accelerate hearing loss in some women.
• Measles virus: some studies link otosclerosis to past measles infection, and rates appear lower since measles vaccination.
• Ancestry: more common in people of European descent.

Symptoms

• gradual hearing loss, usually first in one ear, later both in most people
• difficulty hearing low-pitched sounds and whispers
• paracusis of Willis: hearing speech better in noisy environments, because others speak louder
• hearing your own voice and chewing sounds more loudly
• tinnitus: ringing, buzzing or roaring
• occasional dizziness or balance problems, less common

The ear canal and eardrum usually look normal. Rarely, a pinkish tinge behind the eardrum (Schwartze sign) is seen in active disease.

Diagnosis

An ENT specialist or audiologist will:

• Examine the ears to rule out ear wax, fluid or infection.
• Use tuning forks: in conductive hearing loss, sound is heard better through bone than air (Rinne test) and lateralizes to the affected ear (Weber test).
• Perform an audiogram: shows a gap between air and bone conduction, often with a dip in bone hearing around 2,000 Hz (Carhart notch).
• Do tympanometry: usually normal; acoustic reflexes are typically absent.
• Order a CT scan of the temporal bone in some cases, to confirm the diagnosis or plan surgery.

Other causes of conductive hearing loss, such as chronic otitis media, cholesteatoma or a disrupted ossicle, are ruled out.

Treatment

Monitoring

Mild hearing loss may simply be monitored with periodic audiograms.

Hearing aids

Hearing aids work well for conductive hearing loss and avoid surgical risks. They are a good option at any stage, and for people who prefer not to have surgery.

Stapes surgery

Stapedotomy (a small hole in the stapes footplate) or stapedectomy (removing part of the stapes) replaces the fixed bone's function with a tiny prosthesis, so sound can again reach the inner ear.

• done through the ear canal, usually under local or general anesthesia, often as day surgery
• significant hearing improvement in over 90% of people
• usually the worse ear is operated on first; the second ear may be done later
• avoid air travel, heavy lifting and nose blowing for a short time afterward, as advised

Risks are low but include dizziness for a few days, taste changes on one side of the tongue, tinnitus and, rarely (about 1%), permanent loss of hearing in the operated ear.

Medicines

Sodium fluoride has been used to try to slow progression, particularly when the inner ear is affected, but evidence is limited and it is not routine in the US.

Cochlear implants

For advanced otosclerosis with severe sensorineural loss, cochlear implants can restore access to sound.

Outlook

Otosclerosis is progressive but not life-threatening. With hearing aids or surgery, most people maintain good hearing. Inner ear involvement may progress slowly over years.

Frequently asked questions

What are the first symptoms of otosclerosis?

The first symptom is usually gradual hearing loss in one ear, especially for low-pitched sounds and whispers, often with tinnitus. Some people notice they hear better in noisy places, which is typical of conductive hearing loss.

Is otosclerosis hereditary?

Often, yes. About half of people with otosclerosis have a family history. It can be passed down in families, though not everyone who inherits the tendency develops hearing loss.

Can otosclerosis be cured?

Stapes surgery effectively restores hearing in more than 90% of people, though the underlying bone condition remains. Hearing aids are an effective non-surgical alternative. Inner ear involvement cannot be reversed.

Does pregnancy make otosclerosis worse?

In some women, hearing loss from otosclerosis worsens during pregnancy, probably due to hormonal changes. Not everyone is affected. Women with otosclerosis who notice hearing changes during pregnancy should have a hearing test.