OTOSCLEROSIS AND HEARING LOSS (Etiology, Diagnostic Evaluation, Treatment and Management
Otosclerosis is a term derived from oto, meaning ‘of the ear’ and sclerosis, meaning ‘abnormal hardening of body tissue’. The condition is caused by abnormal bone remodeling in the middle ear. Bone remodeling is a lifelong process in which bone tissue renews itself by replacing old tissue with new characterized by abnormal remodeling of ear bone that disrupts the ability of sound to travel from the middle ear to the inner ear.
TYPES OF HEARING IMPAIRMENT
The external ear and the middle ear conduct sound, the inner ear receives it. If there is some difficulty in the external or middle ear, a conductive hearing impairment occurs. If the trouble lies in the inner ear, a sensorineural or nerve hearing impairment is the result. When there is difficulty in both the middle and the inner ears a mixed or combined impairment exists mixed impairments are common in 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 may be permanent. On occasions the otosclerosis may spread to the balance canals and may cause episodes of unsteadiness.
Usually otosclerosis spreads to the stapes or stirrup, the final link in the middle ear transformer chain. The stapes rests in the small groove, the oval window, in intimate 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 most commonly affected portion of the bone around the inner ear (otic capsule) is the anterior oval window. It can also involve the round window niche, the internal auditory canal, and occasionally ossicles other than the stapes. Otosclerosis is thought to begin with otospongiosis, which is a localized softening of the normally vary hard bone of the otic capsule. There appear to be three stages of otosclerosis – resorptive osteoclastic stages with signs of inflammation, followed by an osteoblastic stage involving immature bone, followed by mature bone formation.
- Tympanometry can show stiffening of the ossicular chain
- Acoustic reflexes are very useful in otosclerosis, as they show a characteristic ‘inversion’ pattern
- The temporal bone CT scan is both nonspecific and insensitive
TREATMENT OF OTOSCLEROSIS
There are four treatment options:
- Doing Nothing is a Reasonable Option
Otosclerosis does not have to be treated, as there are no medications that have been shown to work, and it will progress or not independent of any treatment. It is advisable to have a formal hearing test repeated once a year.
- Hearing Aids
Hearing aids are effective for conductive hearing loss and certainly are less risky than having ear surgery. Hearing aid technology has undergone tremendous advances since the invention of surgical treatment for otosclerosis. Bone-anchored hearing aids (BAHA), can be especially convenient.
- Medical Treatment
Fluoride therapy is no longer a recommended primary treatment for otosclerosis, because of its effect on other bones including the possibility of increasing the risk of hip fractures. After two years of fluoride treatment, the dose of fluoride is reduced from three times a day to once a day. Once the otospongiosis phase of otosclerosis is over and there is a clear-cut otosclerosis documentated by conductive hearing loss, fluoride may be stopped. The treatment is continued after surgery.
Bisphosphonates can also be recommended in some cases.
Avoidance of estrogens or use of estrogen blockers might be helpful in an individual with otosclerosis as otosclerosis frequently worsens during pregnancy, suggesting hormonal modulation. Similarly, hormone supplements in menopause might be adverse to hearing in persons with otosclerosis.
- Surgical Treatment
For conductive hearing loss, stapedectomy can be done, which produces excellent hearing results, and which remain good for many years after the surgery. This procedure may allow avoidance of hearing aids. It, however, does not help the sensory component of the hearing loss and at best, may close the ‘air-bone’ gap.
The stapes operation (stapedectomy) is recommended for patients with otosclerosis who are candidates for surgery. This operation is usually performed under local anesthesia and requires but a short period of hospitalization and convalescence. Over 90 percent of these operations are successful in restoring the hearing permanently.
Stapedectomy or stapedotomy is performed through the ear canal under local or general anesthesia. A small incision may be made behind the ear to remove muscle or fat tissue for use in the operation.
COMPLICATIONS OF SURGERY
- Hearing loss
- Tinnitus: most patients with otosclerosis notice tinnitus (head noise) to some degree. The amount of tinnitus is not necessarily related to the degree or type of hearing impairment. Following successful stapedectomy, tinnitus is often decreased in proportion to the hearing improvement, but occasionally may be worse.
- Dizziness: it is normal for a few hours following a stapedectomy and may result in nausea and vomiting. Some unsteadiness is common during the first few postoperative days and dizziness on sudden head motion may persist for several weeks
- Taste Disturbance and Mouth Dryness: they are not uncommon for a few weeks following surgery
- Eardrum Perforation: a perforation in the eardrum membrane is an unusual complication of the surgery. If healing does not occur, surgical repair (myringoplasty) may be required.
- Weakness of the Face: A very rare complication of stapedectomy is temporary weakness of the face. This may occur as the result of an abnormality or swelling of the facial nerve.
Successful communication requires the efforts of all people involved in a conversation. Even when the person with hearing loss utilizes hearing aids and active listening strategies, it is crucial that others involved in the communication process consistently use good communication strategies, including the following:
- Face the hearing-impaired person directly, on the same level and in good light whenever possible. Position yourself so that the light is shining on the speaker’s face, not in the eyes of the listener
- Do not talk from another room. Not being able see each other when talking is a common reason people have difficulty understanding what is being said
- Speak clearly, slowly, distinctly, but naturally, without shouting or exaggerating mouth movements. Shouting distorts the sound of speech and may make speech reading more difficult
- Say the person’s name before beginning a conversation. This gives the listener a chance to focus attention and reduces the chance of missing words at the beginning of the conversation
- Avoid talking too rapidly or using sentences that are too complex. Slowdown a little, pause between sentences or phrases, and wait to make sure you have been understood before going on.
- Keep your hands away from your face while talking. If you are eating, chewing, smoking, etc. while talking, your speech will be more difficult to understand. Beards and moustaches can also interfere with the ability of the hearing impaired to speech read
- If the hearing-impaired listener hears better in one ear than the other, try to make a point of remembering which ear is better so that you will know where to position yourself
- Be aware of possible distortion of sounds for the hearing-impaired person. They may hear your voice, but still may have difficulty understanding some words
- Most hearing-impaired people have greater difficulty understanding speech when there is background noise. Try to minimize extraneous noise when talking
- Some people with hearing loss are very sensitive to loud sounds. This reduced tolerance for loud sounds is not uncommon. Avoid situations where there will be loud sounds when possible
- If the hearing-impaired person has difficulty understanding a particular phrase or word, try to find a different way of saying the same thing, rather than repeating the original words over and over.
- Acquaint the listener with the general topic of the conversation. Avoid sudden changes of topic. If the subject is changed, tell the hearing impaired person what you are talking about now. In a group setting, repeat questions or key facts before continuing with the discussion
- If you are giving specific information-such as time, place or phone numbers-to someone who is hearing-impaired, make them repeat the specifics back to you. Many numbers and words sound alike.
- Whenever possible, provide pertinent information in writing, such as directions, schedules, work assignments, etc.
- Recognize that everyone, especially the hard-of-hearing, has a harder time hearing and understanding when ill or tired.
- Pay attention to the listener. A puzzled look may indicate misunderstanding. Tactfully ask the hearing-impaired person if he/she understood you, or ask leading questions so you know your message got across
- Take turns speaking and avoid interrupting other speakers
- Enroll in aural rehabilitation classes with your hearing-impaired spouse or friend