Significant hearing loss has been reported in approximately 50% of people with osteogenesis imperfecta (OI). While not everyone who has OI develops hearing loss, the incidence is much higher than in the general population. Sometimes visible deformities in the ossicles and inner ear can lead to hearing loss. Sometimes the cause of the loss is not visible. Environmental factors can contribute to hearing loss in a person with OI in the same way as for anyone else. These include loud noises, head injuries and infection. Hearing loss can start at any time but among people who have OI the loss often starts at an earlier age and the likelihood increases with age. Hearing loss can be treated with hearing aids and/or surgery depending on the type and severity of the loss.
How Does Hearing Work?
Our ability to hear depends on two factors—the mechanical translation of the sound waves into movement within the middle ear and then translation of that motion into a nerve transmission to the brain. In the first part, the sound waves make the tympanic membrane vibrate. That movement is transmitted through three small bones in the middle ear to the fluid in the inner ear. The movement of the fluid makes small hair cells move and that movement alters the signal along the hair cell nerve to the brain.
Types of Hearing Loss
There are two main types of hearing loss: conductive and sensorineural. Both types of hearing loss can occur with all types of OI. Hearing loss type can vary within a family just as much as between unrelated people. Sensorineural hearing loss tends to be more frequent as a person ages. Conductive loss generally occurs around age 20 or 30, but there are many exceptions. OI related hearing loss can occur at any age, including childhood.
Conductive Hearing Loss: Usually results from a physical problem in the external or middle ear. It may occur as a result of ear infection, blockage of the middle ear, or from fixation or fracture of the stapes, one of three tiny bones in the middle ear that transmits the movement of the eardrum through the middle ear to the fluid in the inner ear.
Sensorineural Hearing Loss: This type of hearing loss occurs when the inner ear is not transmitting the nerve signals normally to the brain.
In addition, hearing losses are classified according to the degree of severity:
Hearing losses are also classified according to the sound frequency that can not be heard:
- low, high, all frequencies.
Some of the early signs of hearing loss are:
- Difficulty understanding certain words or parts of words.
- Frequently asking others to repeat themselves.
- Difficulty understanding others on the telephone.
- Turning up the sound on the television or radio to a level that is too loud for others in the room.
- Difficulty hearing in noisy surroundings.
As it progresses, hearing loss can interfere with communication, performance at work or school, social activities, and personal relationships. Left untreated, hearing loss may even result in isolation and depression.
It is recommended that children with OI have a formal evaluation of hearing before they start school. Testing should begin at age 3-4 and be repeated every 3 years. Any child with OI who demonstrates articulation problems, speech delays, recurrent ear infections, or whose parents suspect a hearing loss should have a formal audiologic assessment regardless of age. If borderline hearing is discovered, then yearly testing with a certified audiologist is recommended
Adults with borderline hearing should have yearly testing and follow up appointments similar to the schedule for children. Adults experiencing tinnitus (ringing in the ear) or symptoms of hearing loss should also have an audiologic assessment that includes a hearing test with air and bone conduction and speech reception threshold. This type of test can determine if the hearing loss is conductive or sensorineural. Adults who have an identified hearing loss should continue to see their audiologist or ENT on a regularly scheduled basis and whenever they feel their hearing has changed.
Hearing Loss in Childhood
Treatment of hearing loss in children is the same regardless of the cause. If it occurs early in life, speech therapy usually is necessary. Amplification - hearing aids and FM devices - are used when levels of loss are below the normal hearing range. Preferential seating up front in the classroom is always a good move. If sound muffling can be done (carpeting, acoustic tiles) to soften the overall background noise in the classroom, understanding is easier. Teachers can wear a microphone that sends sound directly to the hearing device the child is wearing. Because of the Americans with Disabilities Act, accommodations for your child's hearing loss must be made if the school receives federal funds. Although most schools readily accommodate special needs, sometimes an advocate is necessary.
Exposure to loud noises can lead to sensorineural hearing loss by damaging the hair cells (sound sensing cells) in the inner ear. The loudness and duration of the noise are the important factors determining damage, not the source of the noise. Power tools, chain saws, and loud music are but a few of the noises that can damage our hearing. Use of protection when working around loud noise or avoidance of the loud noise exposure can prevent this problem. Many different kinds of ear plugs and ear muffs are available
to block out sound. The devices carry a rating of effectiveness on their packaging that tells how much sound is blocked out. When one must be around loud noise, preventive measures can help avoid permanent loss. Another important way to protect hearing is to keep the volume turned down whenever using a device that has personal headphones.
While hearing aids can’t “cure” hearing loss or duplicate natural hearing, they provide amplification that can help all age groups. When hearing loss is identified, hearing aids are usually tried first because, unlike surgery, they carry little risk. Hearing aids come in a wide variety of shapes, sizes and ability to amplify. No single model has been identified as appropriate for all people who have OI. The organizations listed at the end of this fact sheet offer literature to help people learn about hearing aids and become educated consumers. The severity and range of the hearing loss influences which type of aids are best suited to your needs. Thoroughly discuss the styles of hearing aids and the features that suit your needs with your audiologist or ENT specialist.
Some individuals benefit from binaural aids (one in each ear) that provide a stereo effect. Aids equipped with a “T-Switch” make it easier to connect with other assistive listening devices. People who have sensitive skin or contact allergies may want to get information about non-allergenic earmolds. Getting a good fit and understanding how a particular model hearing aid is designed to work will help the individual get maximum benefit. For example, when a hearing aid is turned up too loud, it can give feedback, or the high-pitched squeal that some people complain about. If feedback is a problem, then the individual may need a different kind of hearing aid, or a better fitting mold. It takes time and patience to adjust to a hearing aid. Therefore it is important to work with a reputable dealer who can provide the necessary follow-up care.
It is good practice to use a provider who is a licensed audiologist and also dispenses hearing aids. When choosing a hearing aid dealer, ask questions about the warranty and the service that will be offered after purchase. Unless your physician has prescribed a particular model, whenever possible, consumers are encouraged to work with a dealer who offers more than one brand.
Surgical procedures such as stapedectomy or cochlear implant help some people with OI related hearing loss that is severe, conductive and progressively getting worse. In a stapedectomy, the fixed footplate of the stapes is replaced by a prosthesis, a copy of the bone, that allows the normal transmission of the bone movements to the inner ear. Using a laser to do the surgery improves accuracy and visibility during the surgery. Success of the surgery is highly dependent on the surgeon’s experience and on the person’s ear anatomy. The procedure itself takes less than an hour and the patient may be discharged from the hospital in less than 24 hours. Complications from stapedectomy surgery can include dizziness, change in taste to part of the tongue and worsening of the hearing loss rather than an improvement. Initially successful stapedectomies can fail for a number of reasons. There may be more problems in the ear than just with the stapes, the attachment of the prosthesis to the adjacent small bone called the incus may be faulty, the incus may be too thin to hold the prosthesis long term, or damage can occur to the inner ear leading to nerve loss or malfunction.
A cochlear implant is an electronic device that can provide partial restoration of hearing that was lost because the very first part of the nerve transmission pathway is defective. A portion of the device is implanted behind the ear and electrodes are threaded into the cochlea inside the ear. This is an option for someone who has a sensorineural hearing loss. This surgery has successfully been performed on people with OI. Having a cochlear implant is significant ear surgery that may require a brief hospitalization. Complications can include dizziness and facial nerve injury.
Since OI bone is not as solid or dense as bone in other people, the electrical signals from the device seem to travel a little more easily through the bone. This means that the facial nerve, which runs near the inner ear, may be stimulated from the implant. Stimulation of the facial nerve can be corrected by turning off some of the electrodes. Hearing with a cochlear implant is variable. It requires a period of training and adjustment after the surgery. Hearing does not return to “normal,” but many people adapt well and can even return to talking on the telephone.
A number of important issues need to be assessed, discussed, and clarified before any person with OI can be considered a “good candidate” for surgery. These include anesthesia, cardiac and respiratory issues. As a general rule, patients should seek treatment centers where the otologists (physicians who specialize in ear disorders) have considerable experience with stapes and/or cochlear implant surgery.
Don’t Be Afraid to Seek Help
There are many devices available on the market to help people cope with hearing loss. These can include special doorbells, telephones, smoke alarms that light up and alarm clocks that vibrate. Since hearing loss is an issue for the general population, a number of local and national organizations provide information and have services available to those with hearing loss.
American Association of Retired Persons