What Treatments are Available?
For many hearing disorders, there is no actual available cure. However, there are assistive devices and some promising new treatments that allow patients to manage their hearing disorders. While regeneration of inner ear hair cells is presently not possible, as medicine advances, it seems very likely that a method will be found to regrow inner ear hair cells in the future.
Hearing aids are electrical devices that assist in optimizing perception of speech or other sounds. Most hearing aids are designed for hearing impaired individuals, of which there are approximately 37 million in the United States (Schiller et al 2012). A basic hearing aid consists of a microphone, amplifier, volume control, battery and receiver. A straightforward approach is simply to amplify sound coming in. This approach often fails due to a limited range of usable volumes (it might be either too loud or too soft). More recent designs use compression circuitry to represent the full range of sounds within the range tolerated by the wearer. Digital hearing aids and programmable hearing aids offer more flexibility in the processing. It is often desirable to have a hearing aid behave differently in a busy room than when speaking one-on-one. This is possible with a programmable aid.
Who Needs a Hearing Aid?
In essence, you need a hearing aid if you have hearing problems and the cost/benefit ratio of a particular aid is reasonable. An “ideal” hearing aid candidate is someone with a mild or moderate bilateral hearing loss, who has experienced a noticeable communication handicap. Many individuals who have good hearing on one side can adjust reasonably well to any degree of hearing loss on the other side, and for this reason, most people that get hearing aids have bilateral decreases in hearing.
Hearing aids are not indicated for an ear with minor hearing loss, and are also not very useful in an ear with profound hearing loss. In other words, hearing aids are usually most appreciated in people with mild to moderate hearing loss on both sides. Sometimes an “assistive device” can be used — this is a small personal amplifier. Amplifiers are also available for telephones and TVs. The telephone company may supply you with one for your telephone at little or no charge. You should be able to find many vendors by using “Google” to search for “assistive devices for hearing”. Some low-end assistive devices sell for as little as $50.
What Tests are Necessary Before Selecting a Hearing Aid?
An audiometric evaluation should be performed to determine the type of hearing loss (sensorineural, conductive or central), the degree, and the frequency slope. The evaluation should also be able to predict the amount of benefit that an aid will provide, in terms of speech comprehension.
In selecting a hearing aid, a special appointment called a “fitting” is usually needed. The fitting maps out how much amplification is needed, the uncomfortable loudness level, (ULC) (which is the maximum tolerable loudness) and the most comfortable listening level (MCL). The dynamic range is defined as ULC minus MCL. Fitting also involves selection of the style of hearing aid, and usually selection or fabrication of an ear-mold. Recently, the process has gotten a little easier as off-the-shelf aids (for example, the Songbird) seem to provide as good results as the more arduous process. Social service agencies are often involved with hearing aid dispensing.
An otologic evaluation should also be performed to determine whether medical or surgical treatment is possible (for example, ear wax removal). Medical clearance is advisable before purchasing a hearing aid.
Types of Hearing Aids
There are many types of hearing aids available in the market. Selecting a hearing aid depends on the specific hearing loss, the cosmetic appearance, and the amount one wishes to spend. Hearing aids can be categorized by technology and by style (size and appearance). The different technologies are available in the different styles.
- Analog (now nearly obsolete). There are several circuits.
- Simple programmable. (now nearly obsolete).
- Complex programmable.
- 4. Digital. Flexible but expensive. Most commonly prescribed.
- Implantable aids. Somewhat better performance can be obtained by implanting the hearing aid.
New advances that may be beneficial include intra-aural silicone directional microphones that allow the wearer to better understand sounds from multiple directions (Bentler 2005, Miles & Hoy 2006, Miles et al 2009, Ricketts 2005)and bone anchored hearing aids (BAHA). BAHA percutaneously transmit sound through the skull and may be more effective than traditional aids in some patients with conductive hearing loss (Hol et al 2005) and single-sided deafness (Christensen et al 2010, Linstrom et al 2009). Interest is growing for bilateral BAHA implantation for bilateral conductive hearing losses, although the efficacy of two devices is still in question (Janssen et al 2012). An implantable ossicular stimulator has proven effective in clinical trials (Jenkins et al 2007, Jenkins et al 2004).
Styles of Hearing Aids
- Assistive listening devices. A large variety of devices are available at much lower cost than hearing aids. Some of these are free. Telephone companies provide free amplifiers and ringers if patients present a physician or audiologist release. Hotels provide telephone amplifiers in 10 percent of rooms. Examples are devices that flash lights when the telephone rings, vibration devices when the doorbell sounds, flashing smoke alarms, television amplifiers, etc.
- Behind the ear (BTE). Cheapest, easiest to adjust, less feedback than other devices. Fairly visible. Most powerful. Fewest number of problems with wax or infections.
- In the ear (ITE). Low visibility; harder to put in and adjust.
- In the canal (ITC). Very low visibility. Clearer than Assistive listening devices and BTE. Lower power. Patients with tremor or poor eyesight are not good candidates.
- Completely in the canal (CIC). Cannot be seen. Requires tight fit. Hard to adjust and remove. Clearer than assistive listening devices and BTE. Patients with tremor or poor eyesight are not good candidates.