36 Hearing Aids & Implantable Devices Flashcards
What are the major components of a digital hearing aid and how does each contribute to the function of the device?
What are the major components of a digital hearing aid and how does each contribute to the function of the device?
In a very rough sense, the digital hearing aid has five major components: the microphone, the analog to digital converter, the microchip, the digital to analog converter, and the receiver. The microphone on the outside of the hearing aid picks up sound waves, and they are converted to an electrical signal. This signal is then passed through an analog/digital converter and sent to the microchip, which is essentially a tiny computer chip. The microchip filters the signal into bands and channels and manipulates the sound according to the user’s hearing loss. The manipulated signal is converted back to an analog signal through the digital/analog converter. The analog signal is sent to the receiver where it is converted back to an acoustic signal that the patient hears.
When should a patient be referred to audiology for a hearing aid consult?
When should a patient be referred to audiology for a hearing aid consult?
A hearing aid consult should be recommended for those patients who exhibit hearing loss and report a disruption in communication with others. With improved hearing aid technology available today, hearing aids can enhance the quality of life for almost any patient with hearing loss, regardless of the type, severity or configuration.
Name the most common styles of hearing aids (Figure 36-1).
Name the most common styles of hearing aids.
- Behind-the-ear (BTE) hearing aids
- Receiver-in-the-canal (RIC) hearing aids
- In-the-ear (ITE) hearing aids
- In-the-canal (ITC) hearing aids
- Completely-in-the-canal (CIC) hearing aids
- Invisible-in-the-canal (IIC) hearing aids
- Contralateral routing of sound (CROS) and bilateral CROS (BiCROS) hearing aids
What is acoustic feedback and what causes it?
What is acoustic feedback and what causes it?
Acoustic feedback occurs when the acoustic signal leaks out from the receiver of the hearing aid and is picked up again by the microphone. This sound loop results in an unpleasant, high-pitched squealing sound. Feedback occurs most often in the instance of high-power hearing aids, ITE hearing aids, and hearing aids used in conjunction with a vented earmold or open-fit configuration. Feedback can also be an indication that the patient’s earmolds are not inserted properly, are a poor fit, or the patient has outgrown the molds.
What is loudness recruitment and how is this phenomenon addressed in the hearing aid fitting?
What is loudness recruitment and how is this phenomenon addressed in the hearing aid fitting?
Loudness recruitment, or just “recruitment,” refers to the abnormally rapid growth of loudness with increasing stimulus level, and is a common clinical symptom of sensorineural hearing loss. The theory of recruitment is that as the hair cells in the cochlea become damaged, normal adjacent hair cells are “recruited” to help hear the frequency of the damaged hair cell in addition to their own frequency. This increases the signal from the good hair cell and perceived loudness at the brain rapidly increases causing discomfort. One way to address recruitment in the hearing aid fitting is through the use of wide dynamic range compression (WDRC). WDRC improves the audibility of soft sounds and reduces discomfort of loud sounds by applying more gain to low-level inputs and less gain to high-level inputs.
What advancements in hearing aid technology have we seen in the last decade?
What advancements in hearing aid technology have we seen in the last decade?
Hearing aid technology is now close to completely digital. The most significant advancements lie in signal processing. Improvements are seen in the hearing aid’s ability to make consistent changes to the directionality of the microphones, manipulation of the frequency, compression (non-linear amplification) and gain (amount of amplification applied to the input level), advanced digital noise reduction, digital speech enhancement, and acoustic feedback reduction. All of these features work together to improve the user’s ability to understand speech in any environment. Binaurally integrated hearing systems use wireless connectivity to exchange information between the right and the left hearing aid and adjust the settings based on the user’s listening environment. This technology significantly improves speech comprehension in the presence of background noise.
How can an individual enhance hearing aid use in common and difficult listening situations?
How can an individual enhance hearing aid use in common and difficult listening situations?
Wireless connectivity available in today’s digital hearing aids allows for wireless communication between hearing aids and numerous forms of media devices. Individuals are now able to stream television, music, and phone calls wirelessly to their hearing aids through the use of an intermediary device between the hearing aids and the external source. This allows for a gateway to media connectivity and greater convenience in communication that was once not available to hearing aid users.
What are indications for a bone conduction hearing aid?
What are indications for a bone conduction hearing aid?
- Congenital malformations of the external and/or middle ear (i.e., microtia/atresia)
- Chronically discharging ear (i.e., chronic otitis media or mastoiditis)
- Single-sided deafness
- As an option for patients who cannot wear conventional hearing aids or are dissatisfied with outcomes
What are the most common devices used to treat single-sided deafness (SSD)?
What are the most common devices used to treat single-sided deafness (SSD)?
A common treatment approach to SSD is the fitting of contralateral routing of sound (CROS) or bilateral CROS (BiCROS) amplification. Individuals who use a CROS system have normal or near-normal hearing in the better ear and no useable hearing in the poorer ear. A transmitting device with a microphone is placed on the poorer ear and a receiving instrument is placed on the better ear. Sound picked up by the transmitting device microphone is sent wirelessly to the receiving hearing instrument on the better ear. A BiCROS system is appropriate for those patients who exhibit some hearing loss in the better ear. In addition to the CROS, it has a second microphone located on the receiving hearing instrument that picks up and amplifies sound. Historically, patients using CROS or BiCROS systems have been dissatisfied with sound quality and cosmetic appearance, but advancements in hearing aid technology have improved CROS and BiCROS systems.
A second common treatment option for SSD is bone conduction hearing aids. Bone conduction hearing aids use direct bone conduction to transmit sound vibrations directly to the inner ear through the skull. Bone conduction hearing aids can be worn on a softband, can be percutaneous or transcutaneous, and can even be worn on the teeth.
Recent studies have evaluated the use of cochlear implants as treatment for SSD, although this is not an FDA-approved indication for CI.
What are the challenges associated with percutaneous bone-anchored hearing aids and are nonsurgical bone conduction hearing aid options available?
What are the challenges associated with percutaneous bone-anchored hearing aids and are nonsurgical bone conduction hearing aid options available?
Postoperative complications associated with percutaneous bone-anchored hearing aids range anywhere from 8% to 59%. The two most common postoperative complications include infection or inflammation at the implant site, and failure of the device to osseointegrate. Longevity and health of the device are highly dependent on patient hygiene and at-home care of the implant. Even so, revision surgery is likely over the lifetime of the bone-anchored hearing implant. Other bone conduction hearing aid options include a transcutaneous bone-anchored hearing aid that is held in place via internal and external magnets. In addition, patients also have a nonsurgical bone conduction hearing aid option that transmits sound through the teeth. The device is composed of two parts: a custom-made in-the-mouth (ITM) device and a small BTE device that contains a microphone. Both parts are removable.
What is an implantable hearing aid?
What is an implantable hearing aid?
An implantable hearing aid is designed for those individuals with mild to severe hearing loss who are unable to wear or do not wish to wear a conventional hearing aid. There is currently one FDA-approved fully implantable hearing device on the market. This device consists of three implantable components: the sound processor, a sensor, and a driver. Implantation of the device requires disruption of the ossicular chain, and the device then vibrates the ossicular chain directly.
What are the challenges associated with implantable hearing aids?
What are the challenges associated with implantable hearing aids?
- Capacity and recharging ability of batteries required to power the device
- Adequate middle ear space necessary to house the device. Inadequate space can limit the amount of gain the device can provide, making it challenging to aid more severe degrees of hearing loss.
- Cost is significantly more than conventional hearing aids.
- Insurance coverage
- MRI contraindicated
Describe a cochlear implant and how it works.
Describe a cochlear implant and how it works.
A cochlear implant (CI) is a sophisticated, surgically implanted electronic device that is designed to produce useful hearing to a person with severe to profound sensorineural hearing loss by electrically stimulating the auditory nerve within the inner ear. It has become the standard treatment option for restoring hearing in those individuals with significant loss who no longer benefit from hearing aids. The device consists of internal and external components (Figure 36-2). The internal components consist of the receiver and the electrode array. The receiver is implanted just under the skin behind the ear, and the electrode array is inserted into the cochlea. The external components consist of a speech processor, microphone, and transmitting coil. The microphone picks up sound and sends the information to the speech processor, which digitally encodes the sound. The coded signals are then sent up the cable to the coil, which sends the information across the skin via FM radio frequency to the receiver implanted just under the skin. The receiver, via the electrode array, presents the information to the auditory nerve in the form of tiny electrical pulses, which then travel to the brain where they are perceived as sound.
Describe how the electrical stimulation provided by a CI is perceived as sound to the patient.
Describe how the electrical stimulation provided by a CI is perceived as sound to the patient.
Specific characteristics of speech that are critical to word understanding are selectively coded by the speech processor. The coded signal is sent through the auditory nerve to the brain, where the code is interpreted into useful hearing sensations to enable speech understanding. The quality of the sound varies, but most recipients are able to understand speech without visual cues.
What are the current FDA criteria for cochlear implant candidacy in the adult and pediatric populations?
What are the current FDA criteria for cochlear implant candidacy in the adult and pediatric populations?
- Adults (>18 years)
- Bilateral moderate to profound hearing loss
- Limited benefit from hearing aids as demonstrated by test scores of ≤50% sentence recognition in the ear to be implanted, and ≤60% in the contralateral ear or binaurally aided depending on insurance (≤40% in binaurally aided condition for Medicare)
- All candidates should have realistic expectations regarding the cochlear implant process and outcomes, as well as exhibit a strong desire to be a part of the hearing world. A stable, quality support group available to the patient is strongly desired.
- Children (2–17 years)
- Bilateral severe to profound sensorineural hearing loss
- Limited benefit from hearing aids as demonstrated by binaural amplification trial (at least 6 months) with word recognition scores of less than or equal to 30%
- Infants (12–24 months)
- Bilateral profound sensorineural hearing loss
- No progress in auditory skill development with binaural hearing aids (at least 3 months trial except in cases of meningitis, where the hearing aid trial can be bypassed and implantation can be done under 12 months of age due to the possibility of cochlear ossification) and intervention.
For children and infants, the placement of an educational plan and rehabilitation therapy that emphasizes development of auditory skills is imperative for successful outcomes with CI. High motivation and realistic expectations from family are strongly encouraged.
