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Cochlear Implants > midterm > Flashcards

midterm Flashcards

1
Q

what is the limitation of hearing aids?

A

relies on the integrity of the hair cells; the more severe the HL, the less effective a hearing aids will be

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2
Q

what are CIs?

A

sophisticated implantable device that attempts to restore useful hearing to severely hearing impaired individuals

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3
Q

goal of CI

A

acoustic input –> convert to electrical signal –> interpreted by brain as sound

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4
Q

how do CIs send signals via the aud nerve to the brain?

A

by electrically stimulating the surviving nerve fibers in the cochlea w/ an electrode array

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5
Q

what are the 3 dimensions sound are distinguished by?

A

amplitude (intensity)
frequency (spectral)
time (temporal)

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6
Q

frequency is conveyed by

A
  • place in the cochlea that is stimulated

- enables pitch perception by stimulating the aud neurons in localized, narrow regions of the spiral ganglion

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7
Q

amplitude is encoded by

A
  • current level

- enables intensity (loudness) perception by changes in amplitude of stimulus current

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8
Q

temporal cues extracted from input and are conveyed by

A
  • stimulation rt and pattern of stimulation

- enables processing of temporal cues

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9
Q

primary benefits of a CI

A

increased aud perception (mild HL range)

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10
Q

secondary benefits of a CI

A
  • enhancement of lip reading skills, speech perception and speech production
  • psychological effects
  • lifestyle and social effects
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11
Q

possible limitations of CI

A

potential loss of residual hearing

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12
Q
  • provides electrical stimulation to one point of contact in the cochlea using one electrode
  • more aware of environmental sounds
A

single channel CI

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13
Q

electrical stimulation to multiple points of contact in the cochlea using multiple electrodes

A

multi-channel CI

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14
Q
  • picks up sound from environment
  • transduces the sound to an electrical signal
  • sends signal to sound processor
A

microphone

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15
Q
  • sound goes from pre-amplifier to processor, where sound is analyzed and converted to digital signal
  • selects and arranges sounds picked up by mics
A

sound processor

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16
Q

send electromagnetic signal through skin to the receiver under the skin

A

transmitter cable (and the electromagnetic RF coil)

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17
Q

converts electromagnetic signal to digital code/electric pulses, which are then sent to the electrode array

A

receiver coil

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18
Q

stimulate the aud nerve directly, which sends signal to brain where it is perceived as sound

A

electrodes

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19
Q

located in center of external coil and internal coil, adheres to the external RF coil to the head and directly over the internal coil

A

magnets

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20
Q

RF signal serves as

A

power supply for the internal stimulator

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21
Q

receives signals from speech processor and converts them into electric impulses

A

transmitter and receiver/stimulator

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22
Q
  • group of electrodes that collects the impulses from the stimulator and sends them to different regions of the aud nerve
  • contains metal electrode contacts placed in ionic fluid (perilymph)
  • controlled amount of current applied to electrode contact causes ionic current to flow causing potential changes in fluid immediately surrounding electrode
A

electrode array

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23
Q

official FDA approved age for CI’s in children is

A

12 months of age

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24
Q

12-24mos candidacy audiometric criteria

A

profound sensorineural HL bilaterally

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25
Q

> 2yrs-17yrs candidacy audiometric criteria

A

severe-to-profound sensorineural HL bilaterally

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26
Q

adults: 18yrs + candidacy audiometric criteria

A
  • AB and Med-EL: severe-to-profound SNHL bilaterally
  • Cochlear and Medicare: moderate to profound SNHL bilaterally (PTA 70 or greater)
  • 50% or less on sentence recognition tests in ear to be implanted and 60% or less on non-implanted ear
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27
Q

less than 40% correct in best aided condition on a sentence recognition test

A

medicare criteria

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28
Q

audiometric candidacy recommended test battery

A

az bio sentences (in quiet and noise +10/+5)
CNC monosyllabic words
BKB-SIN

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29
Q

term to describe implanting those pts that do not fall within the general candidacy guidelines

A

off-label implanting

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30
Q

does candidacy = success?

A

no, success is measured against individualized goals based on the pt

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31
Q

what does the FDA say you must do to assess candidacy for CI?

A
  • unaided audiogram
  • hearing aid trial
  • sentence recognition test with hearing aids
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32
Q

a patient’s best listening condition, the condition that yields the highest % correct scores on listening tests

A

best aided condition

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33
Q
  • assesses the performance of adults with cochlear implants and to improve comparability of performance results across centers
A

minimum test speech battery original (MTSB)

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34
Q
  • provide a reliable and efficient measure of speech reception threshold for sentences in quiet and in noise
  • determines the reception threshold for sentences
A

HINT

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35
Q

harder than HINT

10 talker babble noise by different talkers

A

az bio sentences

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36
Q

has a modified adaptive approach

sentences are presented at a fixed level and four talker babble is presented increasingly more difficult SNRs

A

BKB SIN

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37
Q
  • not required for FDA candidacy but gives a good picture of aided ability w/o context cues
  • develop lists of monosyllabic words
A

constant/nucleus/constant test (CNC)

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38
Q

degree of HL implant ear

A

poorer hearing ear

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39
Q

speech reception scores implant ear

A

poorer wrs

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40
Q

duration of HL implant ear

A

most recent onset of deafness is often selected

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41
Q

anatomical considerations implant ear

A

most normal appearing scala tympani

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42
Q

vestibular weakness implanted ear

A

implant ear with weakness

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43
Q

most systems place the electrode array in the

A

scala tympani through round window or fenestration near the round window

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44
Q

why scala tympani?

A

accessible & relatively close to the spiral ganglion cells

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45
Q

depth that electrode array is inserted into scala tympani?

A

22-30mm within the cochlea

46
Q

of fibers activated is a function of

A

the amplitude of the stimulation current

47
Q

loudness can be controlled by

A

varying amplitude of the stimulation current

48
Q

primary goal of electrode arrays

A

sufficient insertion while reduction insertional trauma

49
Q

magic # of electrodes

A

8

50
Q

what can too many electrodes lead to?

A

redundancy btwn electrodes and decrease their ability to deliver distinct sound frequencies

51
Q

close placement to what is desirable in getting better selectivity?

A

modiolus

52
Q
  • pre-curved shape for intention to maintain proximity to modiolus, placed along the medial wall of the cochlea
  • can result in greater insertion trauma
  • shorter (inserted 360-420º)
  • lower current levels; more efficient battery life
A

perimodialar array

53
Q
  • insertion along the lateral wall of the scala tympani
  • do not damage the modiolus or spiral ganglia (more preserved residual hearing)
  • can be inserted up to 720º (can reach apical end of cochlea)
  • requires greater power
A

straight (lateral wall) electrode array

54
Q

frequency coding is constrained by

A
  • # of surviving aud neurons

- spread of excitation associated with electrical stimulation

55
Q
  • remote reference electrode serves as reference, current flows btwn them
  • spread of excitation is larger
  • all electrodes are activated at the same time
A

monopolar

56
Q
  • two intracochlear electrodes reference each other
  • active and reference (ground) electrodes are placed close to each other
  • more localized stimulation
  • some electrodes are simultaneous and some are sequentially stimulated
A

bipolar

57
Q

goal of spatial specificity of electrodes

A

maximize the # of non-overlapping populations of neurons to be stimulated

58
Q
  • all electrodes are activated at the same time

- monopolar

A

fully simultaneous

59
Q
  • some electrodes are simultaneous and some are sequentially stimulated
  • bipolar
A

partially simultaneous

60
Q
  • occurs when electrodes are activated in sequence, one after another
  • requires pulsatile stimulation
A

non-simultaneous/pulsatile

monopolar or bipolar

61
Q

simultaneous stimulation drawback in CI?

A
  • limited frequency specificity

- channel interaction

62
Q

in CI, channels are defined by

A

bandpass filters

63
Q

when two adjacent electrodes are stimulated simultaneously with complimentary waveforms, effectively targeting the area btwn them

A

virtual channel

64
Q

signal processing goals

A
  • maximize speech understanding

- make all sounds as naturally sounding as possible

65
Q

overview of processing

A

4 BPF –> 4 channels –> rectifier –> LPF –> generate pulses –> amplitudes proportional to envelope

66
Q

types of pulses used to be delivered to the electrodes?

A

biphasic pulses

67
Q

why do CIs use biphasic pulses?

A

to achieve the non-simultaneous stimulation by varying the timing

68
Q
  • non-simultaneous processing strategy
  • frequency of pulse train is fixed
  • all electrode contacts are stimulated in each cycle of stimulation
A

continuous interleaved sampling (CIS)

69
Q

neural responses to stimuli from one electrode may be significantly distorted by stimuli from other electrodes

A

channel interaction

70
Q

number of electrodes stimulated =

A

of bandpass filters

71
Q

electrodes can be stimulated in ______ in order of six-three-five-two-four-one which maximizes the spatial separation btwn stimulated electrodes

A

staggered order

72
Q

2 methods that can be used to extract the envelopes of filtered waveforms

A
  • rectification

- hilbert transform (med-el) = feature extraction

73
Q
  • high-rate CIS strategy
  • can be delivered non-simultaneous or partially simultaneous to 16 electrode contacts
  • uses higher cut off frequencies for low pass filters
  • uses half-wave rectification rather than full wave rectification
  • all electrode contacts are stimulated in each cycle of stimulation
A

HiRes

74
Q

goal of Hi-Res

A

improvement in provision of fine temporal structure

75
Q
  • stimulate on the channels with highest amplitude inputs

- goal: capture strongest components of a speech signal and discard low fluctuations in amplitude

A

N of M strategy

76
Q
  • larger # of bandpass filters
  • produces better spectral representation but poorer temporal
  • uses up to 20 filters that span a wider frequency range
  • stimulates as many as 10 electrodes in a cycle
  • adaptive stimulation rt in order to preserve spectral as well as temporal info
  • based on temporal frame
A

SPEAK

77
Q
  • fast rate SPEAK strategy

- higher stimulation rt typical of CIS and the methodology of SPEAK to highlight specific frequencies

A

ACE

78
Q

key difference between SPEAK and ACE

A
  • rt of stimulation

- ACE is high (more similar to CIS)

79
Q

CIS type signal coding that provides better access to fine temporal structure

A

fine hearing processing (FSP)

80
Q

dynamic range of aud thresholds vs electrical pulses

A

100dB vs 10-20dB

81
Q
  • shift everything up

- everything sounds higher pitched

A

frequency mismatch

82
Q

rt that would result in aud nerve response more typical to that of a normal aud system

A

2000 pps

83
Q

speech is audible yet comfortable, and provide loudness perception of speech and environmental noise

A

stimulation level

84
Q

setting lower limits of electrical dynamic range

A

stimulation threshold

85
Q

an estimation of the threshold

A

interpolation

86
Q

to increase stimulus intensity

A
  • increase the amplitude by increasing the upper limit of stimulation
  • widen/lengthen the pulse width bc the stimulus then stays on longer - temporal summation
87
Q

equal sense of loudness across electrode array

A

loudness balancing

88
Q

ensure that stimulation does not result in loudness discomfort, unfavorable sound quality, or non-auditory percept

A

sweeping

89
Q

info critical speech understanding

A

high frequency

90
Q

fine structure info, needed for localization of sound and appreciation of music

A

low frequency

91
Q

can make gain modifications on an individual electrode or successive electrodes

A

frequency shaping

92
Q

allows 2-way transmission of data through radio frequency communication to and from the internal implant

A

telemetry

93
Q

what is electrode impedance influenced by?

A

cochlear fluid

94
Q
  • excessively low impedance
  • there’s not enough resistance
  • two electrodes touching each other
A

short

95
Q
  • excessively high impedance
  • too much resistance
  • ossification; physical barrier
A

open circuit

96
Q

T or F: normal electrical impedances do not imply that the electrode contacts are in the cochlea

A

T

97
Q

what can we do if electrodes are out of voltage compliance?

A

lower the amplitude of the stimulation current

98
Q

what if you dont want to change the loudness?

A

widen/lengthen the pulse width - provide more stimulation to your pt without having to increase the current level

99
Q

when programming or mapping a pt, what is the goal?

A

setting the electrical dynamic range

100
Q

what measure do we set on each electrode to achieve this?

A

EDR allows us to ensure sounds are audible, make sure sounds are comfortable, and adequate loudness growth

101
Q

when would subjective measures (setting threshold and upper limits of stimulation) in a CI user not be possible or reliable?

A

younger pts and those that are cognitively impaired

102
Q
  • early latency evoked potential from electrically stimulated aud nerve fibers
  • stimulation is a biphasic pulse
  • measured through telemetry
A

ECAP

103
Q
  • represents the lowest level at which electrical stimulation elicits a stapedial reflex
  • most commonly used objective measures
A

ESRT

104
Q

after cochlear implantation, ABR can be performed by electrical stimulation through the cochlear implant

A

EABR

105
Q

CI surgery

A
  • incision behind ear
  • mastoidectomy
  • drill the facial recess for access to promontory and round window
  • two structures you must drill btwn is the facial nerve and chorda tympani
  • surgeon places receiver stimulator
  • electrode array is inserted through an opening in cochlea
106
Q

opening or hole in cochlea

A

cochleostomy

107
Q

benefits of round window insertion

A
  • accurate placement: directly to scala tympani

- no drilling in cochlea

108
Q

chorda tympani

A

regulates taste

109
Q

risk of surgery

A
  • anesthesia (issues w pts w cardiac problems)
  • injury to facial nerve
  • meningitis
  • CSF leak
  • perilymph fluid leak
  • infection
  • blood or fluid collection
  • attacks of dizziness or vertigo
  • tinnitus
  • taste disturbances
  • numbness
  • reparative granuloma
110
Q

must have what vaccination before surgery?

A

meningitis

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