What is Otosclerosis?
Otosclerosis is a condition, often genetic in origin, which causes a decline in hearing. The term is a combination of two Greek words: “sclera” for hard and “oto” for ear, and “hard ear” is an accurate description of the underlying problem. This condition is usually caused by the gradual immobilization of one of the three key bones in the ear, the stapes, so that sound is no longer able to be transmitted to the auditory nerves. Otosclerosis may also involve the other bones in the area; the incus, malleus and the otic capsule.
What types of hearing loss are caused by otosclerosis?
Otosclerosis is a hearing condition that develops with age and usually becomes evident between 10-30 years of age. If one of your parents suffers from otosclerosis, there is a 50% chance of inheriting the gene; however, 75% of those with the gene will not develop the condition. If both parents have the gene, the odds rise to 50% that you will develop otosclerosis.
The early phase of the disease is called otospongiosis, which is a form of sensory hearing loss that develops while the bones of the otic capsule begin to be remodeled. Enzyme activity, bone activity near the cochlear capsule and degeneration of the stria vascularis are all part of the genetic mutation process that drives the disease. After several years, usually after the age of 30, otosclerosis will begin to cause conductive hearing loss, as sound waves are impeded or blocked completely as they try to pass through the fused bones in the otic capsule region.
What are the symptoms of Otosclerosis?
- Hearing loss starting around age 10
- Progresses to maximum loss of hearing level at age 30 and plateaus at that point
- Dizziness, poor balance, vertigo experienced in 25% of cases
- Persistent ringing in the ear (tinnitus) for 40%-60% of cases
Who is most likely to get Otosclerosis?
Otosclerosis is typically found in populations of Caucasian and Asian descent, and it is rarely found in African-Americans. Women are twice as likely to develop it as men, especially if there is a history of pregnancy. Some studies strongly correlate measles and the development of otosclerosis for those with a genetic propensity for it. In one interesting clinical study, the data indicated that otosclerosis should be manifesting as a clinical disease in 1% of the US population. Otosclerosis is the most common type of progressive hearing loss in young adults.
How is Otosclerosis diagnosed?
- Due to the genetic link for the disease, family history plays an important role in the assessment by your doctor.
- Hearing tests are important for establishing the presence of progressive hearing loss. The doctor will also be able to determine over time the change from sensory to conductive hearing loss as the patient ages which focuses the diagnosis.
- The use of Tympanometry can pinpoint the hardening or fusing of the otic bones.
How do you treat Otosclerosis?
Non- Surgical Treatments:
- Watchful Waiting
Otosclerosis is unique to each patient and each case will experience different hearing loss levels. While treatment is not required, an annual hearing test is suggested.
In most cases, hearing aids are effective for conductive hearing losses.
- Medical Treatment
There is no definitive proof that fluoride treatments are effective, but uncontrolled studies have shown that the use of fluoride resulted in smaller otosclerotic foci in CT scans during the early phase of the disease. Fluoride treatments are usually stopped when the early otospongiosis phase passes into the otosclerosis phase, which results in conductive hearing loss.
Dr. John Shea invented the stapedectomy operation in 1957, which still continues to produce excellent results for otosclerosis patients today, with a success rate of 90%. ENT&AA surgeons have performed numerous stapedectomies with excellent outcomes over the years. The basic concept of the surgery is to ‘free-up’ the immobilized stapes by removing it, and replacing it with a prosthetic device that can be more mobile and more likely to conduct sound waves and improve conductive hearing. The operation has been shown to improve conductive hearing, reduce tinnitus and has eliminated the need for hearing aids for some patients, or improved the use of amplification aids. For patients whose discrimination scores are lower than 65%, the operation is not advised as there may be a significant sensory component as the cause of the hearing loss. The procedure is usually performed in a surgical center as an outpatient, and most individuals are home on the same day. During this process, one ear is operated on at a time, with the worse ear being the first one selected. Usually, the second ear is operated on after six months have passed.
- Cochlear Implants
Cochlear implants are slightly more difficult to perform in patients with otosclerosis, due to the bone immobilization that is part and parcel of the ankylosing process of otosclerosis. Issues regarding facial nerve stimulation may occur post-operatively in patients with severe otosclerosis. Recent clinical data indicates positive results for cochlear implantation as initial treatments and following stapedectomy.