Otosclerosis is a disease that causes progressive hearing loss and affects the bone of middle and inner ear. It is often surgically reversible. Otosclerosis causes abnormal bone to deposit around the stapes and sometimes cochlea. As this bony deposit accumulates, it restricts the normal movement of the third bone of hearing (the stapes “stay-peas”). This bony fixation impairs the normal conduction of sound energy to the inner ear to cause a hearing loss. This conductive hearing loss may be corrected with an operation (stapedectomy) to reverse the hearing loss. Excessive otosclerotic bone around the inner ear (cochlea) may also cause sensorineural (inner ear) hearing loss, which is not surgically reversible. To understand otosclerosis and stapes surgery, it is necessary to understand the structure and function of the ear.
The Normal Ear and Hearing
The ear consists of three parts: the external ear, the middle ear and the inner ear. Each part performs an important function and may be affected by different conditions. The external ear collects sound, the middle ear mechanism transforms the sound and the inner ear receives and transmits the sound to the brain. Sound travels across airwaves to the outer ear and then through the ear canal to the eardrum, which moves back and forth very rapidly. This vibration is then passed through the three hearing bones. The three bones (hammer or malleus, anvil or incus and stirrup or stapes) act as a transformer, changing air (sound) vibrations into inner ear fluid waves. This wave like movement of the inner ear fluids activates special hair cells and nerve endings to create electrical signals that go to the brain. The hearing centers in the brain then receive the electrical signal from the hearing nerve and we detect sound. The inner ear, hearing nerve, and brain code this sound energy allowing us to hear sounds and clearly understand speech.
Otosclerosis disease process
Otosclerosis is a disease of the middle and inner ear that causes hearing loss that worsens over time. Unlike hearing loss of the inner ear, hearing loss from otosclerosis in the middle ear is surgically reversible.
The term “otosclerosis” comes from the Greek words for “ear” (oto) and “hard” (sclero). In otosclerosis, the stapes middle bone becomes fixed by abnormal bone preventing its normal movement. In the early stages of otosclerosis disease, bone around the stapes softens or breaks down by chemical enzymes. Later, these areas of bone destruction are replaced by new hard bone (otosclerosis).
Continued otosclerotic disease of the inner ear can sometimes damage inner ear function which cannot be reversed. Rarely does otosclerosis cause complete hearing loss.
Complete understanding of what causes otosclerosis is not known yet. There are some interesting observations about otosclerosis, which only affects humans. The bony capsule of the inner ear normally does not undergo the continuous breakdown and repair process seen in the other bones in the human body. This allows the normal bony capsule containing the inner ear to become the hardest bone in the human body. Otosclerosis can be caused by a genetic condition.
Types of Hearing Loss
The external ear and middle ear collect and conduct sound to the inner ear which transforms it to electrical signals and transmits it to the brain. Conductive hearing loss (CHL) results when there are problems of the external or middle ear that prevent sound wave transmission to the inner ear. Causes include blockage of the external ear canal by wax or growths, tympanic membrane perforations, middle ear fluid, damage to the hearing bones, growths in the ME, and infection. Sensorineural hearing loss (SNHL) results when there is a problem in the inner ear or auditory nerve. Common causes include aging, noise, inherited conditions, and toxins. When there is difficulty in both the middle and the inner ear a mixed or combined impairment exists. Mixed impairments are common in Otosclerosis.
Hearing Impairment from Otosclerosis
When otosclerosis spreads to the inner ear a sensorineural 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.
Usually otosclerosis spreads to the stapes or stirrup bone, the final link in the middle ear transformer chain. The stapes rests in a small depression in contact with the inner ear fluids. Anything that interferes with its motion results in a conductive hearing impairment. This type of impairment is called stapedial otosclerosis and is usually correctable by surgery. The amount of hearing loss due to involvement of the stapes varies with the amount of disease and is detected using hearing tests or audiograms.
What are the symptoms of otosclerosis?
The most common symptom is a slowly progressive hearing loss that presents from age 20 to 45 years. It can appear at a younger age, but this is uncommon. Otosclerosis can occur in both ears 80% of the time. The hearing loss may not be equal in each ear. The severity of the hearing loss is variable. Total deafness is rare with otosclerosis. Ringing in the ear or rushing ear noises, known as tinnitus, occurs in about 75% of patients with otosclerosis. Balance problems occasionally are present in patients with otosclerosis.
How do I know if I have otosclerosis?
The hearing test, exam and patient history usually indicate the cause of conductive hearing loss. Frequently, the audiogram has certain features typical for otosclerosis. A CT scan of the ear may demonstrate changes seen with otosclerosis. CT scans are not routinely ordered for the diagnosis of otosclerosis. If your history and examination indicate that there may be other causes of your conductive hearing loss, then a CT scan may be utilized. While the hearing tests are very helpful, otosclerosis is definitively diagnosed at the time of surgical examination of the middle ear. If otosclerosis is confirmed at this time, the surgeon will perform a stapes surgery to fix the hearing loss. If another cause of hearing loss is found an attempt at repair will usually be performed.
How is otosclerosis treated?
Conductive hearing loss is treated with surgery or amplification with a hearing aid. Amplification is very successful because the inner ear (nerve) function is usually normal. Sometimes the abnormal bone metabolism may also affect the sensorineural (nerve) function in the cochlear, which can reduce hearing.
The stapes operation
Stapes surgery is done through the ear canal under local or general anesthesia. At times an incision may be made behind the ear to remove a tissue graft or provide extra room to work. The procedure is called stapedectomy when part or all of the stapes is removed and stapedotomy when a small hole is placed into the stapes footplate. Using high power magnification incisions are made around the eardrum membrane which allows it to be opened and folded forward. This allows examination of the middle ear and confirmation of the cause of hearing loss. If the stapes is diseased it is partially or completely removed. The stapes may be removed with instruments, a drill, or a laser. A prosthesis (synthetic hearing bone) is inserted to replace it and then checked to ensure good mobility. The eardrum is then replaced in its normal position.
The stapes prosthesis allows sound vibrations to bypass the diseased area and be delivered to the inner ear. The hearing improvement is usually permanent.
In properly selected cases, the conductive hearing loss is significantly reduced or eliminated in vast majority of the operative cases. Rarely, surgery will result in no change and in about 1% cases may cause severe hearing loss, which would not be helped with a hearing aid. Dizziness may occur following stapedectomy but is usually mild and temporary. Tinnitus may be reduced or eliminated but results vary considerably. If there is a mixed hearing loss, that is a combined hearing loss from conductive (stapes fixation) and sensorineural (inner ear) deficit, successful surgery will resolve only the conductive component. A hearing aid still may be required for the sensorineural hearing loss if it is symptomatic.
- The surgery takes about 1-2 hours. After surgery you will recover in the hospital for a few hours then you will be released home. Antibiotics and pain medications for mild pain are prescribed.
- Patients are advised not to fly, scuba dive, weight lift, and do heavy exertion for 2 weeks after surgery.
- Most patients return to work in three or four days.
- The operated ear canal should be kept dry for 10 days following surgery. Packing is placed into the ear canal to hold the eardrum in position. Sometimes this packing dissolves and sometimes it needs to be removed.
- You should change the outer ear cotton as needed if there is drainage from the ear canal. This drainage usually stops in one or two days.
- During shower or bathing, a cotton plug with Vaseline may be placed in the outer part of the ear to protect it from water.
- You may wash your hair 48 hours after discharge or use dry shampoo earlier.
- Patients will be seen in the office one to two weeks after surgery for a wound check and packing removal.
- Some hearing improvement is usually experienced at this point, but it continues to improve with more healing. The hearing is tested with an audiogram six to eight weeks after surgery. It may continue to improve over another four to six months.
If you have otosclerosis in both ears, the second ear can be operated on six to twelve months after operating on the first ear. Usually the poorer hearing ear is operated on first.
Complications associated with stapedectomy surgery
Complications are very uncommon when experienced otological surgeons perform this surgery.
- Hearing loss can occur due to infection, scar tissue, inflammatory reaction of unknown cause, displaced or improperly sized prosthesis, or unknown cause. Stapes surgery can cause a temporary dip in the hearing, which is why we wait six weeks to get the first hearing test after surgery. Hearing loss occurs about three to five percent of the surgeries. Total irreversible hearing loss is very rare: about one percent of the surgeries. Distorted, squeaky, or fluctuating hearing may be due to a loose prosthesis or inner ear fluid leak, which usually can be corrected with revision surgery.
- Tinnitus (ear noises) is uncommon complication from this surgery unless there is sensorineural hearing loss. Preoperative tinnitus is less following stapedectomy in about half the cases.
- Dizziness may be due that the inner ear fluid bathes the balance nerve endings in the inner ear. The surgery may cause an irritative response in the nerves of balance. Dizziness may present with quick head turns or getting up quickly during the first few days after surgery. Rarely it can take several weeks for this dizziness associated with quick turns to go away. Vertigo (spinning) is very uncommon. Prolonged dizziness may be due to inner ear fluid leaks, overly long prosthesis, and other causes, some of which may be surgically corrected. Please note that stapedectomy surgery often reduces preoperative dizziness from otosclerosis.
- Taste disturbances happen in about 10-15% of cases and are usually temporary. It happens when the one of the taste nerves (chorda tympani), which runs through the middle ear, is moved to the side to permit completion of the operation. Sometimes there is a metallic or salty taste after this nerve moved to the side of the operative field. In some instances, the nerve is cut. There are multiple nerves in the mouth and throat to compensate for this cut nerve. Over several months the taste disturbance usually resolves.
- Facial paralysis is a very rare occurrence, associated with stapedectomy. It can be delayed, occurring several days after surgery, or less frequently, right after the surgery. Patients with delayed weakness have an excellent recovery.
- Prosthesis problems occur infrequently and can include poor position, erosion of the connections, or migration. It can be delayed occurring many years after surgery or less frequently, right after the surgery. If the problem causes significant hearing loss a revision surgery is usually recommended.
Nonsurgical treatment of otosclerosis
Sensorineural hearing loss in otosclerosis is thought be the end result of abnormal cycle of softening then hardening of the bone surrounding the inner ear: a process called otospongiosis. Some believe that this softening of bone may be moderated by dietary supplement with mineral fluoride and calcium. The benefit of fluoride is unclear. There is considerable controversy concerning the success of this medical therapy in affecting the course and symptoms of otospongiosis/otosclerosis. Generally these medications have minimal side effects but the benefits of these therapies are uncertain. Bisphosphonates used for osteoporosis may have some role in regulate bone metabolism in the medical management of otospongiosis but there is limited scientific information.
- You have a minor degree of stapedial otosclerosis. As such we do not advise surgery at this time.
- You have unilateral (one ear) otosclerosis. If the stapes operation is successful you will have improved hearing from the involved side, will have less difficulty in determining the direction of sound, and should hear better in difficult listening situations.
- You have good hearing nerve function and are a very suitable candidate for the stapes operation.
- Your hearing nerve has deteriorated to some extent. If the stapes operation is successful, you should be able to hear in many situations without an aid, but may need an aid for distant hearing.
- Your hearing nerve has deteriorated considerably. If the stapes operation is successful, you will gain more benefit from the use of a hearing aid.