None — Acoustic Neuroma
An acoustic neuroma is a type of benign tumor affecting the eighth cranial nerve, the nerve from the inner ear to the brain responsible for hearing and balance. The tumor is also known as a vestibular schwannoma. It develops when a group of cells, called Schwann cells, overproduce. Normally, these cells insulate and support nerve function. As the tumor grows, it presses against the nerve.
The most common initial signs of an acoustic neuroma are loss of hearing in one ear, tinnitus (ringing in the ear) and dizziness or balance problems. Some people also have a sensation of fullness in the affected ear. Although the tumors are not malignant, they grow slowly and can eventually put pressure on nearby brain structures. Enlarging tumors may also press on the facial nerves, causing facial numbness, weakness or paralysis. Eventually, the tumor can reach the brain stem and cerebellum and become life-threatening.
Acoustic neuromas are relatively rare tumors. According to the American Hearing Research Foundation, about 2,000 to 3,000 new cases are diagnosed annually. In many cases, the initial symptoms are dismissed as normal signs of aging or other medical conditions.
Unilateral Hearing Loss
Unilateral hearing loss is a loss of hearing in one ear (as opposed to bilateral, which affects hearing in both ears). Permanent one-sided hearing loss can be caused by acoustic neuroma treatment or an inner ear virus. However, Michael Murray, M.D., Ear Surgeon in San Jose, CA, says, in most cases, the cause of one-sided hearing loss isn't known.
People with one-sided hearing loss typically have normal hearing in the unaffected ear. But having two ears for hearing is needed to locate the direction of sound and understand clear speech. A person with one-sided hearing loss often has to turn his/her head in the direction of the sound to hear and may have difficulty separating speech from background noise.
Sinking the Teeth into Unilateral Hearing Loss
Traditional hearing aids won't help people with one-sided hearing loss. One option is the Baha™, or bone-anchored hearing aid. However, placement of the Baha requires surgery to implant the device into the bone behind the ear.
Another option under study is called the SoundBite™ Hearing System. Instead of simply increasing the volume of sound (as with traditional hearing aids), the SoundBite system transmits sound vibrations from the nonhearing ear directly to the cochlea in both ears.
There are three main components in the SoundBite system:
1. A Behind the Ear Unit (BTE) contains a tiny microphone worn in the canal of the nonhearing ear. 2. The In the Mouth (ITM) Hearing Device fits over the top of the back molars like a removable retainer. Each ITM is custom-made using dental impressions from the patient. 3. A Power Supply, recharges the batteries in the BTE and the ITM components.
To use the system, the BTE receives the sounds from the nonhearing ear. A digital signal processor picks up and processes the sound while a second microphone cancels out unwanted noise. Next a wireless chip transmits the sound signals to the ITM. Here the signals are converted into sound vibrations. The vibrations are conducted through the teeth, then through the bone to the cochlea (hearing structure in the inner ear) in the other ear.
Murray says studies show the SoundBite system works well for patients with one-sided hearing loss. It provides a more natural, directional sound and better clarity at higher frequency ranges. An important advantage of SoundBite is that is doesn't require any surgery for placement of the components.
Currently the SoundBite system is classified as an investigational device. Researchers are hopeful it will be approved by the FDA soon and available by the end of the year. Cost is expected to be comparable to that of traditional hearing aids.
For information about the SoundBite™ Hearing System, click here.
For information about acoustic neuroma, click here.
For general information on hearing loss or hearing aids:
American Hearing Research Foundation National Institute on Deafness and Other Communication Disorders
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