Final Exam Study Guide Flashcards
(140 cards)
1
Q
what is a stacked ABR
A
Run derived bands of ABRs and stack them together to look at amplitude changes as opposed to latency changes
Derived-band method: neural contributions from different frequency regions of the cochlea are obtained
It is the sum of synchronous activity generated from 5 frequency regions across the cochlea in response to a click stimulus and high-pass pink noise masking. Wave V for each waveform is stacked/aligned, added together and the resulting amplitude is measured
Developed based on the 8th nerve compound action potential work done by Teas, Eldredge, and Davis in 1962
2
Q
when can stacked abr be used
A
Stacked is ONLY used for neurological purposes & cannot be used to estimate hearing
3
Q
Traditional Click ABR can be used for
A
neurological purposes and estimating hearing
4
Q
ASSR is used to estimate
A
hearing only
5
Q
why was stacked abr created
A
Wanted to make the ABR more sensitive to small lesions
They were good for medium to large acoustic tumors (>1cm) but had poor sensitivity to small tumors (<1cm in diameter)
This is because ABR relies on latency changes of Wave V and it is primarily influenced by HF fibers and tumors will be missed if those fibers aren’t affected by the lesion
Idea: if we can measure amplitude over successive runs and set cut-off criteria, we can make it more sensitive to detecting small lesions
6
Q
what was the idea of stacked abrs
A
if we can measure amplitude over successive runs and set cut-off criteria, we can make it more sensitive to detecting small lesions
7
Q
what was normal stacked abr
A
sum of stacked would = amplitude of click-evoked ABR
8
Q
what was an abnormal and indicative of a small tumor in stacked abr
A
stacked amplitude reduced when compared to click evoked abr
9
Q
Approximate Generator Sites / Components
of ecochg
A
CM
SP
AP
10
Q
describe the CM seen in ECochG
A
Originates from hair cells, mainly OHCs
An alternating current signal → follows the waveform of the stimulus evoking it
No latency → begins with the stimulus; immediate onset
11
Q
describe the SP seen in ECochG
A
Exact source is unknown, most likely contribution from distortion products associated with basilar membrane and hair cell displacement (most likely IHC involvement)
This is why ECochG is done at high intensity levels → IHCs only activate at higher acoustic stimulation and why with greater amounts of HL it is hard to identify SP (>60-70dB HL, specificall HF HL)
Response viewed as a direct current shift in the ECochG baseline recording
Usually happens in the same direction and before the compound AP of the 8th nerve
12
Q
describe the AP seen in ECochG
A
compound/whole nerve action potential
Easiest to identify due to its amplitude
Comes from the distal 8th nerve (same as wave I of the ABR)
Sometimes referred to as N1
13
Q
anatomical structures of ecochg
A
OHCs → cochlear microphonic
Vibration of the basilar membrane, OHCs
IHCs → summating potential
IHCs are depolarized
Afferent Fibers of CN VIII → action potential
Synapse between IHC & auditory fibers, spiral ganglion
14
Q
Nonpathological Subject Factors
in ecochg
A
Attention and state of arousal has NO effect on obtaining these tests
Drugs
Immune to most drugs and medications because it is a sensory cochlear potential
Sedatives, relaxants, barbituates & anesthesia have no effect
Phenytoin, lidocain and diazepam HAVE an effect
15
Q
why is ecochg not affected by arousal or attention
A
It is an exogenous response → earlier potentials; determined by physical characteristics of the stimulus
Do not have to hear the signal & responses are due to the presentation of the stimulus and organ itself
Good for sedation, coma, asleep, etc.
Elicited by external (environmental) stimuli
16
Q
what is an exogenous response
A
earlier potentials; determined by physical characteristics of the stimulus
Do not have to hear the signal & responses are due to the presentation of the stimulus and organ itself
Good for sedation, coma, asleep, etc.
Elicited by external (environmental) stimui
17
Q
ecochg stimulus factors
A
Click
Alternating polarity
To cancel out CM → this eliminates its interference in recording SP & AP
18
Q
Acquisition Factors for ecochg
A
Analysis time (epoch or window size)
Period after stimuli is presented where the ecochg data is collected and it should normally appear
5-10ms because ecochg typically lasts 2-3ms
19
Q
electrode montage for ecocgh
A
Transtympanic → through the eardrum
Needle electrode inserted through the ™ & placed on the promontory
Nearfield
Extratympanic → outside the eardrum
Tiptrode → in the ear canal
Tymptrode → on the ™
Far field
20
Q
Waveform Analysis (2 Main Outcomes) of ecochg
A
- Present Response → normal SP-AP Ratio = good cochlear function
AP amplitude is much larger than SP (2x) - Absent Response → no SP-AP Ratio measured = cochlear pathology or too much HL
Sensory hearing impairment mainly affecting HF region (>1 kHz) - Elevated Response → SP elevation = Meniere’s/hydrops/build up of endolymph & Third Window Disorder or SCD (superior canal dehiscence)
AP amp is reduced compared to SP
SP amplitude is atypically large = reduced SP/AP ratio
21
Q
SP amplitude is atypically large = reduced SP/AP ratio
A
menieres
or SCD
22
Q
no SP-AP Ratio measured
A
cochlear pathology
Sensory hearing impairment mainly affecting HF region (>1 kHz)
23
Q
discovered really early (before abr by 40yrs) and was the initial/original hearing potential to identify hearing threshold
abr is preferred now
Objective test of hearing
A
ecochg
24
Q
what is abnormal SP/AP ratio in ecochg
A
> 50% = abnormal
25
why and when would we use ecochg testing
Diagnosis of Meniere’s Disease (endolymphatic hydrops)
Intraoperative monitoring
endolymphatic shunts, cochlear implants, etc
SCCD
3rd window disorder
Vemps are preferred method now
Assessment of hearing (NOHL)
Identify wave I in neurodiagnostic ABR
Confirmation and diagnosis of ANSD
26
Ways to optimize and improve abilities to get Wave I
Turn intensity up (louder=larger amp)
Slow the rate
Get closer to the generator site
Push down further in canal or try tymptrode
Really low impedances (since they are tiny potentials)
27
Large SP amplitude relative to AP amplitude (large SP/AP ratio; higher than >50%)
symptomatic MD
28
>50% or higher potentials
active hydrops
29
Variables Affecting Recording ecochg
Montage used
Electrode placement
Best when recorded near field to get more robust and reliable results
30
Why or when might you use ecochg over abr
anesthesia (inhalation agents – isoflurane, sevoflurane, or similar) and body temperature can affect ABRs but not ecochg
ABR is more affected by medication and things and less factors to control it than in ECochG
Ecochg assesses outcomes of MD treatments
Surgical (endolymphatic sac decompression, shunt) & non-surgical (drugs glycerol and mannitor) pre and post
31
biling of ecochg
CPT 92584
All types of setups
Billable once per day of service
32
what is an auditory steady state response (ASSR)
AEP / electrophysiological response
Attempts to estimate the threshold of hearing using electrophysiologic measures similar to behavioral results
Represented as an estimated audiogram with a 95% CI
Doesn't require a clinician's experience in waveform analysis
Statistically based
33
how does ASSR differentiate from ABR
ASSR
Performs multiple frequencies at the same time binaurally
Higher intensities are available (120dB)
Stimulus type: Continuous, modulated tone (like P300)
How response is measured:
Time-locked and sustained neural activity
Response Detection:
Based on amplitude and phase in frequency domain
Purely objective - Statistical analysis of the probability of a response (95% CI)
ABR
Single stimulus per run
Lower intensity (90dB)
Stimulus type: transient (burst, sudden onset, quick rise and fall and offset) & frequency specific tone burst
How response is measured:
Stimulus locked and peaks of neural activity over time
Response Detection:
Based on amplitude and latency in a time domain
More subjective - Subjective analysis of amplitude/latency function
looking at waves and interpreting if it is there or not
34
How are assr & abr similar
Same montage
Both EP
Both used to estimate hearing
Both use inserts
35
anatomical generators of ASSR
Affected by attention, state of arousal and sleep
Slower modulation rates = auditory cortex (<40 Hz)
Becomes more endogenous
Affected by attention, arousal, and awareness
Faster modulation rates = auditory brainstem(>70 Hz)
Becomes more exogenous
Deals more with stimulus parameters and less with patient attention
36
Slower modulation rates =
auditory cortex (<40 Hz)
37
Faster modulation rates
auditory brainstem(>70 Hz)
38
assr norms
40 Hz awake response are w/in 10dB of behavioral thresholds
80 Hz sleep response correlates with behavioral thresholds - better for HF than LF
Better correlation to behavior thresholds with HL (varies bw 5-20dB) than normal hearing (varies bw 10-25 dB)
39
benefits of ASSR
can be useful for determining candidacy for cochlear implants and hearing aids in young ones
This with tone burst ABR can give good info for infants or difficult to test PTs
Provides better estimation of thresholds for HF SNHL than tone bursts
Better frequency specificity
Good for assessing severe to profound HL in kids due to 120 dB HL level limit
Frequency specific signals are used to estimate thresholds from .25-8 kHz
40
Disadvantages of ASSR
Requires quiet state of arousal: movement can mess up results
Sleeps naturally or with sedation
Sedation and anesthesia invalidates threshold estimations for ASSR evoked with slow modulation frequencies (e.g., < 60 Hz)
cannot be used to differentiate sensory versus neural auditory dysfunction
Absence of ASSR does not differentiate between profound sensory hearing loss versus ANSD.
No CPT billing code
41
what factors affect ASSR
Maturational effects for the first 12 months of life
<14yrs - do not use 40 Hz stimulus (cortical response and longer maturation than BS)
Premies have higher thresholds caused by immature auditory systems
High intensity stimulation with 500 Hz interpreted with caution
Can be a myogenic response similar to VEMP
42
HF BC thresholds worsen with age
false
improve
43
LF BC thresholds improve with age
false
worsen
44
what is Electroneuronography
A neurological non-invasive test used to study facial nerve in cases of muscle weakness on one side of the face or with Bell’s palsy
Tests the FN and been around since the 70s (Esslen & Fisch
45
Study of the FN
enog
46
Study of other nerves
nerve conduction
47
Closely related to electromyography (EMG)
electrical activity of muscles
48
why perform enogs
Used as a marker to determine course of ation in managing a disease or to monitor the status
Based on the ENOG resonse, physicians may continue to monitor or recommend surgery to address the damage
49
FN disorder etiologies
Bell’s palsy, trauma during surgery, temporal bone fractures, neuromas (pressing on fn), MS, otitis media, mumps, mastoiditis, glomus jugulare, meningioma, mastoiditis, CVA, Guillan Bare syndrome, Herpes zoster oticus, Melkersson-Rosenthal syndrome, chicken pox, idiopathic, other, FN neuroma
50
what is ASSR (lab definition)
electrophysiological response generated by the brain in reaction to a rapidly repeating auditory stimulus
51
stimulus is a continuous tone that can be modulated in amplitude and frequency with signal averaging time locked to a period of sustained neural activity
ASSR
52
Performed at slower modulation rates leads to an ________ which is affected by the patient's attention/arousal/awareness
endogenous response
53
Perfromed at faster modulation rates leads to an ___________
exogenous response
54
why is ENOG performed
Used as a marker to determine course of ation in managing a disease or to monitor the status
Based on the ENOG resonse, physicians may continue to monitor or recommend surgery to address the damage
55
what is denervation
any loss of nerve supply regardless of the cause
losing the nerve supply to a part of the body, no matter what caused it
If those nerves help control a certain function, like moving a muscle or sensing touch, then losing them can change or stop how that part of the body works
56
what is wallerian degeneration
happens when a nerve is cut or damaged
The part of the nerve that’s farther from the main cell (the part past the injury; axon distal to the injury) breaks down as part of a clean-up and healing process
57
when does wallerian degneration occur
Starts 24-36 hours after injury (in the axon stump distal to the injury site)
Before this the axon is still excitable & complete denervation takes 72 hours (remains active for up to 72 hours)
58
when is the ideal time to perform ENOG
ENOG should be performed no earlier than 3 days and no later than 21 days (might be too late for intervention)
IDEALLY between 3 & 21 days after the onset of symptoms for the best prognosis
59
how is nerve injury classified
Sunderland and Seddon Injury Classification
Neuropraxia
Neurotmesis
Axonotmesis
Level 1: mild & level 5: most severe
House-Brackmann Facial Nerve Grading
Standard by medical professionals
Measure of the range of intentional motion PTs facial mucsles have
Level 1: healthy & level 6: total impairment
60
methodology behind ENOG
Electrodes placed on the main trunk & distally
Most accurate, qualitative measurement
Measures the compound action potential
Compares the magnitude of the response on the normal side to that on the impaired side
Only useful once WD has occurred
61
what is the key component of ENOG
amplitude
62
what is the equation for amp of ENOG
Dysfunctional Side (volts) / Healthy Side (volts) = Percentage of Response
63
<90% amp decrease in ENOG
good prognosis for spontaneous recovery (on impaired side)
Probably won’t do anything
Any response level above 10%
64
>90% amp decrease
indicator for medical intervention (on impaired side)
Anything below the thresholds requires active and invasive means to correct it
65
what is the montage for ENOG
low forhead - common ground
low nostril (ipsilateral nasolabial fold)
- electrode
corner smile
+ active electrode
horizontal stimulating electrode just under ear (red + in front of lobe & blue - base of mastoid)
66
what are good words to use with PTs for ENOG
“Tapping Sensation” NOT “Shocking”
“Discomfort” NOT “Painful”
“Movement” NOT “Jerking/Twitching”
67
FN response
8ms
68
masseter response
5ms
69
what peaks are seen in ENOG
N1, P1 and N2
Negative peak / deflection (N1) followed by a large positive deflection (P1) followed by a final negative deflection (N2)
70
Is NOT a test of conscious hearing but can be used to infer the peripheral auditory sensitivity
abr
71
test of neural syncrhony
abr
72
main clinical applications of the ABR
threshold search to establish hearing sensitivity
neurological assessment / rate study
73
when would a threshold abr be performed
newborn hearing assessment, adult hearing assessment (for those that cannot complete traditional testing such as cognitively impaired) and for those with which behavioral thresholds are felt to be unreliable or show poor test agreement
74
when would a rate study abr be performed
For those with known (reliable) hearing thresholds, what we are typically using ABR for in adults is a neurological assessment to evaluate integrity of the auditory system
cases of asymmetric or sudden hearing loss, unilateral tinnitus, poor word recognition relative to tonal thresholds and/or abnormal acoustic reflex patterns
75
what are the main clinical applications to using an ABR
cochlear pathologies, ANSD, & NOHL
76
wave I of abr
1.5 (+/- 2 SD)
Distal VIIIth N (lateral portion; spiral ganglion, 1st order response)
77
wave II of abr
Proximal VIIIth N w/ some from Distal 8 N: root entry zone
78
wave III of abr
3.5 (+/- 2 SD)
Neurons in cochlear nucleus (CN) and possibly fibers entering CN
79
wave IV of abr
Unknown, 3rd-order neurons in SOC most likely
80
wave V of abr
5.5 (+/- 2 SD)
May be related to activity in lateral leminiscus and inferior colliculus
81
Most robust & reliable characteristic in clinical interpretation of ABRs
absolute latency
82
what is absolute latency
time between stimulus onset and peak of the waveform
when stimulus starts to when the peak arrives
83
Provides mainstay of ABR interpretation - key component for repeatibility
absolute latency
84
what is Interwave latency intervals (IWI) or interpeak latencies (IPL)
time period bw peaks; distance between waves
Wave I - III: ≈ 2.0 msec
Wave III-V: ≈ 2.0 msec
Wave I-V: ≈ 4.0 msec
85
Interaural latency differences
ear to ear differences
latency of Wave V in each ear should be <.2-.4 difference (normal)
86
what is a Latency-Intensity Function (LIF)
Plots absolute latencies of Wave V as a function of intensity (stimulus level it is done at) to see if it is in the normative range & determine type of HL
87
axis of LIF
X-axis = stimulus
Y-axis = Wave V latency
88
As stimulus intensity increases latencies decrease and amplitudes increase
true
89
As stimulus intensity decreases latencies increase and amplitude decreases
true
90
what happens with stimulus rate changes
Amp of Wave 5 stays consistent with rate increase but amplitude of earlier waves decreases
91
normal amplitudes of abrs
normal ranges from 0.1 to 1.0 µV
Lower intensities result in smaller amp peaks of earlier waves (I and II) that become obscured in the background of noise but wave V should remain
92
LIF characterization for CHL
characterized by prolonged absolute latencies of ALL waves due to intensity of the stimulus reaching the cochlea being decreased due to the conductive component
All absolute latencies are delated/shifted ot the right but interwaves are not affected
Cannot tell difference bw CHL & retro based on just the above
Need to do BC ABR - normal bone & abn air
93
LIF characterization for retrocochlear disorders
Wave V latency prolongation (same as CHL)
earlier peaks (I and/or III) may be within normal limits
94
LIF characterization of cochlear HL
Steeper than normal LIF with normal latencies at higher intensities and prolonged latencies at lower intensities
95
What are the two types of ABRs?
neurodiagnostic abr
threshold abr
96
how would you perform a neurologic abr ( (i.e., what stimulus factors would you change and what would you leave alone) for it?
10-20 montage, 2-channel
click stimulus, 80 dB nHL
rarefaction & condensation to r/o ANSD then either one, 11.1 then 57.7, then 77.7 rates, replicate
epoch 10-15ms
97
What would you look for when analyzing a neurodiagnostic abr?
look at peak and interpeak latencies to determine normalcy
98
what is a neurodiagnostic abr
used to identify space occupying lesions or identify demylenating conditions
99
what is a threshold abr
used to estimate hearing sensitivity
100
how would you perform a threshold abr ( (i.e., what stimulus factors would you change and what would you leave alone) for it?
10-20 montage, 2-channel, toneburst or NB chirp at 80 dB nHL, 33.3 rate
perform rarefaction & condensation clicks to r/o ANSD then use alternating for the rest
replicate
1000 sweeps
epoch 10-15ms
101
What would you look for when analyzing a threshold abr?
102
sensory HL abr patterns
Wave I small, absent or slightly delayed
Interpeak latencies normal
Poor waveform morphology
Wave V can be delayed beyond normal
103
CHL ABR pattern
Peak waveforms proportionally delayed
Normal (equal) interpeak latencies
104
neural/retro HL ABR pattern
Wave I normal typically (can be prolonged)
Interpeak latencies of I-III or III-V or both delayed
Absence of wave III and/or wave V
Replication difficult or absent
105
ANSD ABR pattern
using rarefaction & condensation polarity
OAEs are usually present but can disappear over time
ABR peaks are generally absent or abnormally delayed
Audiogram
Normal to profound
Rising LF configuration
Poor speech discrim even w/ normal audio
Normal CM in ECochG
Abnormal ART
Normal MRI bilaterally
106
what is a horizontal montage
test ear – to non-test ear +, ground forehead
107
what can you do to avoid noisy recordings
Tightly braid electrode leads (leads short as possible)
Impedance equals 5 kohms or less
Make sure amp cable not crossing over stimulus cable
Amp at least 3 feet away from the base
Increase number of averages
Turn off “noise checking” (artifact reject – must increase # of averages to 8000)
Try another room and/or outlet
Make sure patient is comfortable and breathing slowly out of mouth
108
components in an ECochG
CM
SP
AP (wave I at 1.5ms)
109
components in an ABR
Waves I, II, III, IV, V
Wave I - 1.5 (+/- 2 SD)
Distal VIIIth N (lateral portion; spiral ganglion, 1st order response)
Wave II
Proximal VIIIth N w/ some from Distal 8 N: root entry zone
Wave III - 3.5 (+/- 2 SD)
Neurons in cochlear nucleus (CN) and possibly fibers entering CN
Wave IV
Unknown, 3rd-order neurons in SOC most likely
Wave V - 5.5 (+/- 2 SD)
May be related to activity in lateral leminiscus and inferior colliculus
110
components in AMLR
Po ~10ms (1st + peak, transition from ABR)
Na~20 ms (major wave in kids)
Pa ~25-30 ms
(most important wave & largest +)
Nb~40 ms
P1 (PB) ~50 ms (P1 or P50 of ALR)
111
which waveforms are prominent/present for children in AMLR
P1 or Pb (P50)
112
which waveforms are prominent/present for adults in AMLR
Pa
113
which waveforms are prominent/present for children vs adults in abr
Wave V
114
Evoked (Event-Related Potentials - ERP)
External stimulus is required
Conscious awareness is needed
Example tests → ECochG, ABR
115
Non-evoked (Non-Event Related Potentials)
Reflects ongoing brain activity in the absence of stimuli
External timulus is not required; spontaneous
No conscious awareness is needed
116
electrodes are at a distance from the generator
far field
117
Causes a reduced response amplitude
far field
118
electrodes are near the generator
near field
119
Amplitude is high when very close but even just a slight distance away it reduces a lot
near field
120
click vs toneburst
click (BB bandwidth, rapid onset, short duration, ECochG & ABR, not frequency specific, large amps thresholds bw 2-4kHz)
Tone burst/pip (frequency specific, smaller amps, hearing thresholds ABR, long duration)
121
better neural synchrony worse frequency specificity; good for early AEPs
short duration
122
better frequency specificity and worse clear, synchronized responses
long duration
123
faster rates
shorter interstimulus levels & can increase latency and decrease amplitude
124
slower rates
decreased latency & increased amp, better waveform for middle & lates, less stress on system, useful for neurdiagnostics
125
initial movement is away from ™ (stapes away from oval window = short latency and higher amp of early components of AEP)
rarefaction
126
initial movement is toward ™ (stapes into oval window = longer latency & larger Wave V amp)
condensation
127
stimulus pressure wavefront is alternated on successive trials bw the 2 above
alternating
128
alternating is most commonly used in which testing
ECochG & BC ABR
129
If ISI > refractory period
neurons fully recover = strong response
130
If ISI < refractory period
neurons have incomplete recovery = weak or a missed response
131
what is Interstimulus Interval (ISI)
time bw each stimulus
132
1 vs 2 channel
1-Channel → 3-4 electrodes → basic ABR testing
Good for threshold estimation and more basic clinical needs or screenings; slower
Records 1 ear at a time & gives 1 waveform at a time (e.g., Cz-A1 or Cz-A2)
2-Channel → 4+ electrodes → neurodiagnostic use (gets both ipsi & contra responses)
Used for neurodiagnostic testing, ANSD evals and more detailed; adv diagnostics & differentiating lesions
C3/C4 or T3/T4
Contra responses
Will not see wave I or wave III (attentuation; crossing over and traveling further)
133
inverting and noninverting electrodes
Inverting Electrode → on earlobe or mastoid of the stimulus side (A1 or A2)
Polarity of the signal coming from this electrode IS inverted
Takes the AEP coming into the electrode and before signal processing happens it flips the whole thing 180 deg into the mirror image reference
The signal flipping causes phase cancellation and leaves us with the signal of interest
Non-Inverting Electrode → electrode located on Cz or midline forehead near Fz
Polarity of the signal coming from this electrode is NOT inverted
Takes AEP signal coming into the electrode, goes into pre-amp box and signal processing, is analyzed and stays the same → how it comes in is how it stays and there is no manipulation of the signa
134
ABR becomes adult like around
2-3yrs+
135
What to do if impedances are poor?
Prep small area where electrodes are to be placed vs forehead to nasion – help with electrodes and area acting as a large antenna
Always check electrode leads for small breaks and adequate gel on pads
You should have minimum 3cm distance between electrodes
Infant skin is very thin and does not hold much fluid. Fluid is needed to conduct the electrical response. With high impedance and adequate prep you can try placing a saline soaked gauze pad over area or re-apply conductive gel to electrode
Do not use fast rates for premature infants or with known neurological disease (61.1 rate for TB 2k/4k)(39.1 for 500/1k)
136
What to do if you have noisy recordings?
Tightly braid electrode leads (leads short as possible)
Impedance equals 5 kohms or less
Make sure amp cable not crossing over stimulus cable
Amp at least 3 feet away from the base
Increase number of averages
Turn off “noise checking” (artifact reject – must increase # of averages to 8000)
Try another room and/or outlet
Make sure patient is comfortable and breathing slowly out of mouth
137
ECochG & ABR are endogenous responses
FASLE
exo
138
can get as early as 27wks conceptual age
ecochg
139
what time period does the ABR occur after stimulus onset
0-20 ms
140
