Intro to Audiometry 1 (College of Dupage)

Question 1

What is the limitation of hearing aids?

Answer 1

Relies on integrity of hair cells, the more severe the hearing loss, the less effective a hearing aid will be. And amplified sounds can lead to distortion.

Question 2

What are bone-conduction devices?

Answer 2

stimulate the cochlea directly (by bypassing the middle ear). sound is conducted through the base of the skull by oscillating the temporal bone.

Question 3

Middle ear devices drive…

Answer 3

the ossicular chain directly

Question 4

A cochlear implant attempts to…

Answer 4

restore useful hearing to severely hearing-impaired individuals. What it is… it’s a sophisticated implantable device and how it works is that it stimulates the auditory nerve directly by using electrical current.

Question 5

Explain auditory function in pts with significant SNHL.

Answer 5

• Cochlear outer hair cells (which are the sensory receptors for audition) are damaged or significantly reduced in number
• Some surviving auditory nerve fibers within the modiolus
• Damaged hair cells are unable to transmit electrical impulses to the surviving nerve fibers
• Auditory perception severely distorted or not possible

Question 6

In the United States, _____ out of every 1,000 children are born deaf or hard-of-hearing.

Answer 6

3

Question 7

Prior to ______, the primary medical device for profoundly deaf or severely hearing-impaired children and adults was the behind-the-ear (BTE) analog hearing aid.

Answer 7

1975

Question 8

What is the goal of cochlear implants?

Answer 8

Acoustic input -> convert to electrical signal -> interpreted by brain as sound

Send signals via the auditory nerve to the brain (by electrically stimulating the surviving nerve fibers in the cochlea)

Question 9

Sounds are distinguished by what 3 dimensions?

Answer 9

1. Amplitude (intensity)
2. Frequency (spectral)
3. Time (temporal)

Question 10

Cochlear implants must account for what three characteristics in sound coding designs?

Answer 10

1. Frequency conveyed by -> place in the cochlea that is stimulated
2. Amplitude is encoded by -> current level
3. Temporal cues extracted from input and are conveyed by -> stimulation rate and pattern of stimulation

Question 11

What are the primary benefits of CIs?

Answer 11

Increased auditory perception (environmental sounds and speech)
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Question 12

What are the secondary benefits of CIs?

Answer 12

1. enhancement of lipreading skills
2. enhancement of other speech perception skills (ie. discrimination, identification, recognition, and/or comprehension
3. after training and experience with device, many children (and adults) demonstrate improvements in speech production and voice quality

Question 13

What are the possible limitations of CI?

Answer 13

1. Lifelong commitment! Appointments, follow up
2. Everyday considerations and precautions with device use (MRI compatibility, device maintenance- charging batteries, equipment malfunction, etc)
3. Small risk of side effects (surgical and medical)
4. High cost/insurance limitations
5. Very small risk of implant failure (as with any implantable device)
6. Potential loss of residual hearing and remaining natural sound quality
7. Difficulty with identification of music

Question 14

In 1800, who directed electrical current across his own ears by applying two metal probes connected to a 50-volt circuit? Created auditory sensation “like a thick boiling soup”

Answer 14

Alessandro Volta

Question 15

1930 Ernest Wever (Princeton University psychology professor) and Charles Bray (Johns Hopkins otology fellow) discovered the cochlear microphonic. How did they do this?

Answer 15

• Inserted electrode into auditory nerve of a cat
• Sounds made in the test room with the cat were reproduced in electrical recordings in a different room (using a telephone receiver), lead to idea of biological microphonic property
• idea emerged that cochlear hair cells convert sound into an electrical analog signal that mirrors the wave form of the acoustic stimulus

Question 16

Dr. House implants the first two American patients for short-term clinical trials.
Implanted with a gold wire electrode inserted through the round window and brought through the skin. Resulted in local infections of the skin and devices had to be removed patients had sensation of hearing but no speech understanding and loudness discomfort. What year was that?

Answer 16

1961

Question 17

Food and Drug Administration begins to regulate cochlear implants and the NIH began to fund efforts related to cochlear implantation. What year was this?

Answer 17

1980

Question 18

Multichannel cochlear implant was approved by the FDA for use in adults in _______ (approval for children as young as two years came about five years later)

Answer 18

1984

Question 19

Explain Single-channel CI.

Answer 19

Provides direct electrical stimulation to one point of contact in the cochlea using one electrode; all sound frequencies are transmitted as a single signal to the inner ear.

Question 20

What are the benefits of single-channel CIs?

Answer 20

1. Inexpensive to manufacture
2. Do not require much hardware
3. Conveys temporal information fairly adequately
4. Restricts amount of spectral information to below 1000 Hz
5. With single channel devices, patients:
   - were more aware of environmental sounds (such as sirens)
   - Were able to distinguish between a voiced and unvoiced sound
   - Were able to identify prosodic cues (i.e. if sentence is a statement or question)
   - Improved speech lip-reading skills
6. Limited performance! Commonly cited performance measures: ~0-4% monosyllabic word recognition

Question 21

What is a multi-channel device?

Answer 21

• Provides direct electrical stimulation to multiple points of contact in the cochlea using multiple electrodes
• Different electrodes are stimulated depending on stimulus frequency
• Auditory neurons that are in the area of the stimulated electrode are stimulated and then send neural impulses to the brain
• Electrodes near basal end of cochlea—stimulated by high frequencies
• Electrodes near apical end of cochlear—stimulated by low frequencies

Question 22

What is the optimal number of electrodes for best speech understanding?

Answer 22

6-8 electrodes

Question 23

What are the external parts of cochlear implants?

Answer 23

1. microphone: on external processor: picks
   up sound from environment, transduces the sound to
   an electrical signal, sends signal to sound
   processor
2. sound processor: sound goes from pre-amplifier to
   processor, where sound is analyzed and converted to a digital signal
   Signal is then classified in terms of frequency, amplitude, and temporal domains
   Signal is then converted from a digital signal back to an electrical signal
3. transmitter cable: electromagnetic radio frequency (RF) coil: send electromagnetic signal through the skin to the receiver under the skin

Question 24

What are the internal parts of the cochlear implants?

Answer 24

1. Receiver coil: converts electromagnetic signal to digital code/electric pulses, which are then sent to the electrode array
2. Magnet: are located in the center of the external coil and internal coil, adheres the external RF coil to the head and directly over the internal coil
   The RF signal serves as the power supply for the internal stimulator
3. Electrode array: stimulate the auditory nerve directly, which then sends signal to brain where it is perceived as sound

Question 25

What is the purpose of the microphone in the CI?

Answer 25

Picks up sound from the environment and obtains the best audio signal possible.

Question 26

What is the purpose of the speech/sound processor in the CI?

Answer 26

Selects and arranges sounds picked up by the microphone. Convert sound to pattern of electrical stimulation, or creates a set of stimuli for the electrodes.
Powered with batteries. May be body-worn or head-worn.

Question 27

What is the purpose of the transmitter and receiver/simulator in the CI?

Answer 27

Sits over the implant. Transmits signal to internal parts, sent via RF (radiofrequency) signal.
Connected to the sound processor by a coil cable.
Receive signals from the speech processor and convert them into electric impulses.

Question 28

What is the purpose of the electrode array in the CI?

Answer 28

A group of electrodes that collects the impulses from the stimulator and sends them to different regions of the auditory nerve. Stimulate auditory neurons. Configuration of array: Straight or perimodiolar: Contour Array. Stylet holds the array straight and is removed during insertion. The closer the array is the modiolus, lower thresholds and max comfort levels

Question 29

What is the purpose of the transcutaneous/percutaneous Link in the CI?

Answer 29

Power and data transferred by a modulation of a carrier frequency (basically a very small looped system).
Communicate pattern to internal receiver, transmits data which electrode to stimulate, mode of stimulation, amplitude, pulse width and interpulse separation. Magnets in both coil headset and internal receiver. Across the skin.
Advantage is obvious: no break in the skin through which infection can invade.
Disadvantages: Limitations on rate of stimulation.
Repertoire of signal waveforms is limited.
Bi-directional, with minor limitations.

Question 30

What is the purpose of the internal receiver in the CI?

Answer 30

Decodes the signal and controls an electrical current on each electrode
Receive pattern and distribute it to electrodes according to plan. Surgically implanted. Receives code that is transferred via coil
Converts the code into electrical impulses.

Question 31

What is the rate of stimulation?

Answer 31

Defines the number of electrical pulses per second that may be presented across the electrode array.

Question 32

What is telemetry?

Answer 32

Allows information to be transmitted from the device through radio freq. to an external system: ie. Voltages generated by active electrode, impedance to flow of current (as tissue grows, impedance increases). Can be used to monitor the state of the cochlea. CAP can be measured: indicates how much neural activity the stimulation is causing, etc.
The microphone is generally housed in the BTE case.

Question 33

Exception to rule Advanced Bionics (AB): how?

Answer 33

T-mic: microphone that extends from the end of the earhook.

Question 34

What is the purpose of the bi-directional link in the CI?

Answer 34

Information from the implanted components may be read. Status of the receiver/stimulator. Data logging. Impedances of the implanted electrodes. Intracochlear evoked potentials recorded from unstimulated electrodes

Question 35

To determine candidacy, one must consider what?

Answer 35

1. audiometric threshold
2. speech recognition performance
3. age
4. psychological status
5. auditory progress with hearing aids
6. speech/language development
7. medical/surgical considerations
8. radiologic findings
9. type of insurance coverage

Question 36

Official FDA approved age for cochlear implantation is what?

Answer 36

12 months of age.

Question 37

What kind of hearing loss or under-development should be considered for implantation at 12-24 months of age?

Answer 37

1. Profound sensorineural hearing loss bilaterally (PTA of 90 dB or greater)
2. Auditory Neuropathy Spectrum Disorder of severe nature
3. Lack of progress in development of auditory skill with hearing aid or other amplification
4. High motivation and realistic expectations from family
5. Other existing medical conditions won’t interfere with cochlear implant procedure