Stapedectomy for Otosclerosis

Gradually, the new bone matures and becomes hard, in a process called sclerosis. In otosclerosis, the consistency of the sound-conducting bones of the ear changes from hard, mineralized bone to spongy, immature bone tissue. The troble is that the lack of vibration prevents the sound from being conducted to the inner, leading to a conductive hearing loss.

Ear anatomy

Normally, the ear conducting system is divided into three parts, the outer ear, the middle ear and the inner ear. The outer ear collects the sound via the ear drum that vibrates. These vibrations are transmitted to the inner ear by three small bones:

• the malleus (hammer),
• the incus (anvil),
• the stapes (stirrup)

These are the three smallest bones in our body. They work by increasing the sound pressure and transmitting the sound to the inner ear. In the inner ear, the vibrations stimulate the hair cells which transform the vibrations into electrical impulses that are carried by the hearing nerve to the brain.

Pathophysiology of otosclerosis

If there are any problems in the outer or middle ear, a conductive hearing impairment occurs. There are different impairments depending on the localization of the damage.

• If the trouble is in the inner ear, it will lead to some nerve hearing impairment
• When there is difficulty in both the middle and inner ear, it leads to the mixed impairment. The mixed impairments are very common in otosclerosis but the conductive component predominates in most cases.

Why is this stapes bone so important?

It is the stapes which connects to the inner ear in a bony gap called the oval window. The biggest problem is that, when we talk about otosclerosis, the formation of new bone around the oval window stops the stapes from moving which normally leads to complete deafness.

Incidence of the condition

When this condition is present, both ears are usually involved. Several studies have proven that the condition occurs in men and women with almost equal frequency and that it usually begins in the teens or early twenties. Less than 1% of the population is affected by this condition. Although otosclerosis tends to run in families, it does so irregularly; parents with otosclerosis do not necessarily transmit it to their offspring. Some studies have shown that about 10 percent to as high as 18 percent of all caucasian women and 7-9 percent of all caucasian men between the ages of 30 and 50,  have histological signs of otosclerosis. Less than 10 percent of these people will actually seek help for hearing loss.

Types of hearing impairment from otosclerosis:

Generally, there are two types of otosclerosis and they are:

Cochlear Otosclerosis
During this process, otosclerosis can spread to the inner ear and a sensory-neural hearing impairment may result due to interference with the nerve function. This nerve impairment is called cochlear otosclerosis and once it develops it is permanent and there is no cure for it.  
Stapedial Otosclerosis
In some cases, otosclerosis can spread to the stapes or stirrup bone, the final link in the middle ear transformer chain which leads to the conductive hearing impairment. This type of impairment is called Stapedial otosclerosis and is usually correctable by surgery. 

Possible causes of otosclerosis

Heredity
Many experts believe that only heredity can be the cause. Otosclerosis runs in families in many cases, but the truth is that genetic cause is not clear. It is very possible that there are a number of different genetic types of otosclerosis but there is still no clear distinction between them. The most common theory has been that there is a dominant gene that can cause otosclerosis.
It is difficult to find the underlying cause of otosclerosis, since it may not be the same in everyone.

Gender
It some studies, it is proven that women are more likely to develop otosclerosis than men.

Pregnancy
It is proven that susceptible women may develop otosclerosis during pregnancy.

Race
Caucasians tend to be the most commonly affected race.

Osteogenesis imperfecta
It is a genetic disorder is characterized by abnormally brittle bones

Non-fluoridated water
Some evidence suggests that drinking non-fluoridated water may increase the risk of otosclerosis in susceptible people.

Unknown causes
Some people develop otosclerosis even though they don't have any of the known risk factors.

Symptoms of otosclerosis

Deafness is the main symptom and is usually present in both ears. Most patients notice the deafness before the age of 50. Noises in the ear (tinnitus) are present in most cases. Several patients have also noticed:

• slight unsteadiness
• pain
• discharge from the ears
• hearing may improve in noisy conditions
• dizziness

Diagnosis of otosclerosis

Diagnosis of otosclerosis is based on a combination of the:

• patient's family history
• the patient's symptoms
• the results of hearing tests

Every doctor should first determine whether the patient's hearing loss is conductive or sensory-neural. The two tests that are commonly used to distinguish conductive hearing loss from sensory-neural are:

1. Rinne's test
2. Weber's test

A computed tomography (CT) scan or x ray study of the head may also be done to determine whether the patient's hearing loss is conductive or sensorineural.

Treatment of otosclerosis - Stapedectomy

The best possible treatment of otosclerosis is Stapedectomy. Stapedectomy is a surgical treatment for otosclerosis in which the immobilized stapes is removed, and a tiny platinum or stainless steel prosthesis is inserted in the middle ear to replace it. It is a very good and effective procedure. The fact is that the artificial stainless steel prosthesis is less than 1/8 of an inch long. The more extensive damage may require removal of the entire stapes footplate, while a small focus of disease allows for removal of less tissue. In Stapedectomy, the ear drum is turned forward and the fixed stapes is removed. After this, tissue is placed over the opening to the inner ear and a prosthesis is inserted and attached to the anvil.

Stapedectomy effectiveness

This operation has been performed for years now and the fact is that it is extremely effective and usually restores normal hearing in patients with conductive hearing loss. Patients can usually return to work in about a week.! Procedure is usually performed on an outpatient basis. Either local or general anesthesia may be used, depending on the comfort of the surgeon and the patient.  A small tissue graft, usually taken from a vein in the patient’s hand, is taken and used to seal the oval window after the prosthesis is inserted.

Possible complications of Stapedectomy
 
Hearing loss
It is clear that each manipulation of the stapes produces a reaction in the inner ear which can sometimes lead to giddiness and possibly hearing loss. However, in 90% of cases the results of stapedectomy are very good. In a small percentage of cases there may be severe or total loss of hearing in the ear which was operated on.
It is important to know that this may occur immediately after the surgery or be delayed for several years.
No improvement
In about 10% of cases the hearing is only slightly improved or there is no improvement.
Damage of the facial nerve
Since the facial nerve which supplies the muscles of the face runs through the middle ear, it occasionally gets damaged, producing a lop-sided weakness of the face.
Impaired sense of taste
Nerve called the chorda tympani supplies the sense of taste and it can often get damaged. This results in a temporary metallic taste which does not usually cause any significant problems.
Other complications
Giddiness with loss of hearing and tinnitus may occur after the surgery due to either a leakage of fluid around the artificial stapes, infections of the middle ear or some other conditions.

After operation tips

The evening after the operation, a patient should lie quietly on the un-operated ear. The surgery usually takes two to three hours. If all goes well, you can go home when you are fully awake and deemed ready for discharge by your doctor. Be sure to bring someone to drive you home.
It is not recommended to:

• Blow your nose
• Lie flat on the bed
• Remove any packing from your ear

Other tips:

• Do not get water in the ear
• No strenuous exercise
• Do not remove any packing
• Notify your doctor of fever greater than 100 degrees F, excessive pain, excessive drainage, or drainage that has an odor.

Alternative to surgery

In some cases, surgery is not possible and a hearing aid may be used instead. People who should not have stapedectomy include those who experience frequent changes in barometric pressure (pilots and divers), elderly patients with a baseline imbalance, people whose vocations demand excellent balance, and anyone with known Meniere’s disease (stapedectomy often causes permanent profound hearing loss in patients with Meniere’s disease). If a person has a perforated tympanic membrane due to middle ear infection, the infection must be cleared and the membrane healed before stapedectomy. Patients with sensorineural hearing loss or mixed hearing loss may not improve after stapedectomy, and are not likely to benefit from surgery.