Final Exam ECochG,ENOG,ASSR & Stacked ABR Flashcards
(102 cards)
1
Q
What does ECochG Stand for?
A
Electrocochleography
2
Q
Evoked ECochG consists of what?
A
Cochlear Microphonic (CM)
Summating Potential (SP)
Action Potential (AP)
3
Q
In order and site of origin for the three components of The ECochG
A
- Cochlear Microphonic (CM): Hair Cells (Mostly OHC) occurs first b4 1ms
- Summating Potential (SP): within the cochlear, mostly IHC’s depolariztion
- Action Potential (AP): Whole nerve action potential, synapse between IHC and auditory fibers, spiral ganglion
4
Q
ECochG
Nonpathologic Subject Factors
A
- Attention & State of Arousal have no effect on the result of the test
-
Drugs:
No Affect - Sedatives, relaxants, barbiturates, or anesthesia.
Yes Affects - Phenytoin, lidocaine and diazepam
5
Q
Do drugs have an affect on ECochG and if so what kind?
A
YES
* Phenytoin, lidocaine and diazepam
6
Q
ECochG
Simulus
A
- Click is preferred stimulus
- The CM,SP & AP respond differently depending on the stimulus frequency used.
- The CM waveform mimics the waveform of a single polarity pure tone stimulus.
- When two polarity (alternating) = canceled
7
Q
ECochG, Acquisition Factors
Analysis Time
A
Epoch: 5 - 10 msec for ECochG
8
Q
ECochG, Acquisition Factors
Electrode Montage
A
- Transtympanic – through the eardrum
- Extratympainc – outside the drum → TM trode
To reduce electrical interference from environment, we want electrode to be as close to generator site as possible
9
Q
ECochG, Acquisition Factors
What are the two waveform outcomes?
A
- Little or no response under typical clinical measurement conditions = Cochlear Pathology (SNHL, above 1khz)
- Clear SP & AP but SP abnormally larger in amplitude (reduced SP/AP ratio) = Meniere’s
10
Q
ECochG
Clinical Contributions of ECochG
A
- Assessment of hearing (identifying non-organic loss)
- Identify Wave 1 in Neurodiagnostic ABR
- Confirmation and diagnosis of ANSD
- Diagnosis of Meniere’s Disease (Endo Hydrops)
- Intraoperative monitoring
- SCCD
11
Q
ECochG
explain ECochG’s clinical contribution of
* Assess hearing.
A
- ECochG used to determine hearing threshold in young children and difficult to test patients before ABR
- The recording technique used in ECochG (Electrocochleography) allows for a stronger or larger Wave I response to be seen on the waveform.
- Wave I can sometimes appear even more clearly than Wave V, especially as the sound gets softer (closer to the hearing threshold).
12
Q
ECochG
explain ECochG’s clinical contribution of
* Identify Wave 1 in Neurodiagnostic ABR
A
- Useful for Pt’s W/SNHL especially HFSNHL to distinguish between cochlear VS Neural Auditory dysfunction
- AP amplitude decreases with hearing loss in 2 to 8 khz rage but no affect on SP
- Good for patients with neurological disorders (retrocochlear) where waves III or V are not identifiable
13
Q
ECochG
explain ECochG’s clinical contribution of
* Confirmation and diagnosis of ANSD
A
- OAE’s Present (but disappear later)
- ABR absent or abnormal
- CM present & varified w/reversal
- ECochG is useful in diagnosis of ANSD and monitoring of cochlear function of patients with suspected ANSD
- Estimated up to 10% of permanent hearing loss in infants associated w/ ANSD
- Combined w/ other electrophysiological tests, distinct patterns have emerged
14
Q
ECochG
explain ECochG’s clinical contribution of
* Diagnosis of Meniere’s Disease (Endo Hydrops)
A
- Large SP normal AP = reduced SP/AP ratio
- Diagnostic specificity of this test is poor from 20%-65% in the literature
- Variability exists due to episodic nature of the disease, differences in protocols and especially recording electrode locations
15
Q
ECochG
explain ECochG’s clinical contribution of
* Intraoperative monitoring
A
- ECochG Combined with ABR used in surgeries w/ ear and auditory risk
- ECochG & various ABR techniques can be recorded in the OR on sedated infants or difficult to test children when behavior testing is not possible
- Anesthesia (inhalation agents – isoflurane, sevoflurane, or similar) and body temperature can affect ABR but NOT ECochG
- ECochG has been suggested for assessing MD treatment outcomes.
16
Q
ECochG
explain ECochG’s clinical contribution of
* SCCD
A
17
Q
ECochG
What factors affect Menieres recording?
A
- Choice of Electrodes
- Best recorded in near field closer to generator site the better, more robust and reliable
- Montage Used
18
Q
____ and _____ can affect ABR but NOT ECochG
A
Anesthesia (inhalation agents – isoflurane, sevoflurane, or similar) and body temperature can affect ABR but NOT ECochG
19
Q
ECochG Recording Parameters
A
- Transducer: Insert earphones (tiptrodes/TM electrode)
- Stimulus: Click
- Duration: 0.1ms
- Polarity: Alternative (Rarefaction 1st average, Condensation 2nd average)
- Rate: 8.1/sec
- Intensity: 95-100 dBnHL
- Masking: None
20
Q
ECochG Normative Data
A
Normative Data
SP/AP ratios:
* Tiptrodes > 50% = Abnormal
* Tympanic Membrane Electrode > 35% = Abnormal
* Transtympanic Needle Electrode > 30% = Abnormal
* AP latency condensation – Rarefaction: > 0.38 msec
21
Q
What is ECochG’s Preffered Montage?
A
The preferred montage is ear to ear (horizontal recording)
* to enhance wave 1
22
Q
List ECochG’s
* Filters
* Epoch & Pre-stimulus baseline
* Averages
* Sensitivity
A
- Filters: 5-1500 Hz
- Epoch: 5 msec Pre-stimulus baseline: -1 msec
- Averages: 1000-1500
- Sensitivity: 50 uV
23
Q
With moderate to severe HFSNHL, record ECochG with what electrode type & why?
A
With moderate to severe HFSNHL, record ECochG with TM electrode (tiptrode adequate for detection of AP-wave I if attempting to enhance for neuro evaluation)
* Enhance wave 1
24
Q
For ECochG what montage do you use to enhance wave1?
A
Use horizontal montage to enhance wave 1
* ear to ear
* Ex: left ear Non-invert & right ear Inverting
25
To improve your wave I (AP) particularly when greater amounts of SNHL are present, you can attempt any of the following:
* Increase stimulus intensity
* Slow stimulus rate
* Move electrode as close to generator site as possible
26
ECochG impedance values
Electrode Impednace:1 - 5
Interelectrode Impedance: 3 or less
27
for ECochG why do we Always record pre-stimulus?
Always record pre-stimulus (10% of timebase) to **determine level of background noise, will see CM immediate w/ stimulation**
28
# ECochG
SP is more prominent using what stimulus?
SP is more prominent using **high frequency Tonebursts** (1kHz or 2kHz)
29
What filter is important for recording SP
High pass filtering important for recording SP
30
Change intensity to ____ level to ensure greatest opportunity of recording CM, SP and AP
Increase intensity to **maximum** level to ensure greatest opportunity of recording CM, SP and AP (SPs cannot be recorded below 50 dB)
31
SP cannot be recorded below what db?
SPs cannot be recorded below **50 dB**
32
# ECochG
SP is affected by ____ and AP by ___
SP is affected by **intensity** and AP by **rate**
33
What happens when you Add rarefaction and condensation averages together?
Add rarefaction and condensation averages together **CM and stimulus artifact will disappear; SP and AP easier to identify**
34
What do you do if the SP is Not identifiable?
If the SP is not identifiable, **increase the stimulation rate to 91.1; AP disappears but SP remains**
35
ECochG CPT Code
ECochG
* CPT 92584
36
ASSR stands for what?
Auditory Steady State Response (ASSR)
37
What is the ASSR?
* ASSR is an Auditory evoked potential / electrophysiological response similar to ABR
* Provides another method of auditory threshold estimation beyond typical click & tone burst ABR
38
In what main way does ASSr differ from ABR?
* Stimulus type
* How the response is measured
* How the response is detected
39
# ASSR VS ABR
Stimulus
* **ASSR** uses continuous tone with variations in amplitude and frequency modulation
* **ABR** uses transient stimuli, frequency specific tone burst
40
# ASSR VS ABR
Response Measurement:
* **ASSR** averaging time is locked to a period of time and sustained neural activity
* **ABR** averaging time is locked to a stimulus and peaks of neural activity over time
41
# ASSR VS ABR
Response Detection
* **ASSR** is based on *amplitude* and phase in *frequency domain* with an objective response detection algorithm
* **ABR** is based on *amplitude* and *latency* in a time domain with subjective response detection
42
# ASSR VS ABR
List the similarities between ASSR & ABR
Both..
* are AEP's
* record bioelectric activity from eletrodes
* use acoustic stim delivered though insert
* Used to estimate hearing threshold
43
# ASSR VS ABR
ASSR looks at ___ and ___ in the __ ___ ___ rather than at amplitude and latency.
ASSR looks at **amplitude** and **phases** in the **spectral (frequency) domain** rather than at amplitude and latency.
44
# ASSR VS ABR
ASSR depends on peak detection across a ___ rather than across a time vs. amplitude waveform.
ASSR depends on **peak detection** across a **spectrum** rather than across a time vs. amplitude waveform.
45
# ASSR VS ABR
ASSR is evoked using ___ ___ stimuli presented at a ___ repetition rate rather than an abrupt sound at a relatively low repetition rate.
ASSR is evoked using **repeated sound stimuli** presented at a **high repetition** rate rather than an abrupt sound at a relatively low repetition rate.
46
# ASSR VS ABR
ABR typically uses click or tone-burst stimuli in one ear at a time, but ASSR can be used how and at what frequecnies?
ABR typically uses click or tone-burst stimuli in one ear at a time, but **ASSR can be used binaurally while evaluating broad bands or four frequencies (500, 1k, 2k, & 4k) simultaneously**.
47
# ASSR VS ABR
ABR estimates thresholds from ____ hz in typical mild-moderate-severe hearing losses. ASSR can also estimate thresholds in the ___ range, but offers more __ __ info more quickly and can better estimate hearing in the severe-to-profound ranges.
ABR estimates thresholds from **1-4kHz** in typical mild-moderate-severe hearing losses. ASSR can also estimate thresholds in the **same** range, but offers **more frequency specific** info more quickly and can better estimate hearing in the severe-to-profound ranges.
48
# ASSR VS ABR
Stimulus intensity level is limited to about __ dB nHL for clicks and tone bursts used to evoke the ABR
90dbnHL
49
# ASSR VS ABR
Since ASSR is elicited by steady state (sinusoid) signals with maximum intensity levels of ___ dB HL or ___ , it is the technique of choice for obtaining what?
Since ASSR is elicited by steady state (sinusoid) signals with maximum intensity levels of **120 dB HL or higher**, it is the technique of choice for obtaining vital **information on auditory sensitivity required for definition of candidacy for cochlear implantation**.
50
# ASSR VS ABR
ABR depends highly upon a ___ analysis of the amplitude/latency function. The ASSR uses a statistical analysis of the probability of a response (usually at a 95% confidence interval).
ABR depends highly upon a **subjective** analysis of the amplitude/latency function. The ASSR uses a statistical analysis of the probability of a response (usually at a 95% confidence interval).
51
# ASSR VS ABR
ABR is measured in ___ and the ASSR is measured in ___
ABR is measured in **microvolts** (millionths of a volt) and the ASSR is measured in **nanovolts** (billionths of a volt)
52
Does state of arousal affect ASSR's?
YES
* ASSR's are affected by attention, state of arousal and sleep
53
# ASSR
Can you alter where the anatomical generator is for the ASSR?
Yes, by changing the rate speed
* Slower modulation rates (40Hz and slower) = auditory cortex
* Faster modulation rates (>70 Hz) = brainstem
54
# ASSR
Does rate matter for state of arousal for ASSR?
Yes
* slower rates response becomes more endogenous and affected by patient attention / arousal / awareness
* faster rates response becomes more exogenous (obligatory) and having to do more with stimulus parameters and less w/ patient attention
55
# ASSR
For ASSR what happens with a rate of 40hz and slower?
* Slower modulation rates (40Hz and slower) = auditory cortex
* endogenous and affected by patient attention / arousal / awareness
56
# ASSR
For ASSR what happens with a rate of 70hz and faster?
* Faster modulation rates (>70 Hz) = brainstem
* exogenous (obligatory) and having to do more with stimulus parameters and less w/ patient attention
57
How does ASSR estimate hearing?
* ASSR tries to estimate hearing by using an electrophysiological method designed to be similar to behavioral hearing test
* reported in estimated Hearing Level (dB eHL).
* represented as an “estimated audiogram” with confidence range
* Does not require clinician experience in waveform analysis (statistically based)
58
How is ASSR Normative Data provided?
* ASSR Test sets come with normative data that show how things like arousal and sleep can affect the results
* a probability plot is used to determine whether a brain response is real or just random EEG noise
* Probability of 95–99% = considered valid (not EEG brain activity).
* Plot of probability (95-99% then response confirmed and not random EEG). High limit due to limited samples and in order to reduce false negative
59
What are the benefits of ASSR?
* Determine Candidacy for CI and HA's in infants and young children.
* In combination with tone burt ABR it can provide clinically significant info for Infant & child
* provides better estimation of thresholds for *high frequency* hearing loss than tone burst (Tone burst better at estimating low freq)
60
# True or false
ASSR is more accurate in estimating thresholds in people with hearing loss than in people with normal hearing.
TRUE
ASSR is more accurate in estimating thresholds in people with hearing loss (threshold estimation range is 5–20 dB) than in people with normal hearing (threshold estimation range is 10–25 dB).
61
For ASSR what frequency & state of arousal is best for hearing estimation?
**40hz & awake - Adult = within 10db**
* 80hz stim, sleep,adult = still correlate with behavioral thresholds → better at HF’s
62
for the ASSR you will see maturational affect for the first __ months of life
maturational affect on ASSR for the first **12** months of life
63
40hz for ASSR is great on adults but should not be used on children below what age and why?
* 40 Hz stimulus should not be used on children **below age of 14**
* becuase 40 Hz cortical response, longer maturation than brainstem
64
# ASSR
for ASSR Premature infants have higher thresholds caused by what?
Premature infants have higher thresholds caused by **immature auditory system**
65
ASSR High intensity stimulation at ___ Hz responses should be interpreted with caution due to artifact potential – may be a ___ response similar to ___
High intensity stimulation at **500 Hz** responses should be interpreted with caution due to artifact potential – may be a **myogenic** response similar to **VEMP**
66
what are the 4 main factors affecting ASSR?
* Sleep
* Anesthesia
* Attention
* Internal Noise
67
for bone condution ASSR why do false responses occur & what is reccomended to overcome that?
false responses occur due to stimulus artifact and possibility of vestibular response at frequencies below 1000 Hz
* SAL technique recommended to overcome effects)
68
# BC ASSR
___ frequency BC thresholds improve with age; ___ frequency BC thresholds worsen with age
**High** frequency BC thresholds **improve** with age; **Low** frequency BC thresholds **worsen** with age
69
what are the benefits of sound field ASSR?
* Better stimulus for sound field – less distortion with speakers and amplification
* infants with hearing aids when behavioral data is not possible
* Studies support reasonable correlation between aided ASSR thresholds and behavioral data
70
Correction tables are provided for ASSR but it is typically within how many db and what affects correction data?
* within 10 to 15db
Correction data depends on
* equipment used
* frequencies collected
* collection time
* age of subject
* sleep state of subject
* stimulus parameters
71
ASSR Correction data depends on what variables?
Correction data depends on
* equipment used
* frequencies collected
* collection time
* age of subject
* sleep state of subject
* stimulus parameters
72
ASSR Clinical Advantages
* Frequency-specific threshold estimation at freq 250 Hz to 8000 Hz.
* thresholds can be estimated with AC & BC signals.
* Useful for assessment of severe to profound HL w/ Stim intensity levels up to 120 dB HL
* detection and analysis is automated and statistically based.
* Clinician experience in analysis is not necessary.
73
# Just name 4
Clinical Disadvantages of ASSR
* requires quiet state of arousal
* requires that the patient sleep naturally or with sedation.
* Discrepancies between ASSR thresholds and behavioral thresholds are possible for patients with conductive hearing loss.
* BC requires masking to non-test ear
* little site-specific information for patients with hearing loss
* does not differentiate between profound sensory hearing loss versus ANSD.
74
# true or false
ASSR and ABR are competitive electrophysiological procedures. In the decision to record tone burst ABR or to record ASSR.
FALSE
* ASSR and ABR are **not** competitive electrophysiological procedures.
* The **two procedures are complementary.** Diagnosis of hearing loss and plans for intervention are often based on results of some combination of ABR recordings and ASSR recordings in the same patient.
75
Traditional ABR testing has what 2 primary clinical applications?
* Auditory Threshold Estimation (Threshold ABR)
* Site of Lesion (Neuro-diagnostic ABR for neural synchrony)
76
# True or False
ABR has been shown to be sensitive to acoustic tumors as small as <1cm in diameter
FALSE
ABR has been shown to be sensitive to large acoustic tumors but has poor sensitivity to small tumors (<1cm in diameter)
77
why ABR does not identify small tumors?
ABRs rely on latency changes of wave (peak) V . Wave V is primarily influenced by high-frequency fibers and tumors will be missed if those fibers aren't affected by the lesion.
78
What is the staked ABR?
The stacked ABR is the sum of the synchronous neural activity generated from five frequency regions across the cochlea in response to click stimulation and high-pass pink noise masking.
79
Who developed Staked ABR technique?
Teas,Eldredge, and Davis
* 1962
80
Why was Derived-band ABR and Stacked ABR created?
to **improve the detection of *small* acoustic tumors**, especially those that might be missed by traditional ABR.
81
What is ENOG?
Electroneuronography
* ENOG is a neurological non-invasive test used to study the facial nerve in cases of muscle weakness in one side of the face or with Bell's palsy.
82
What is the current use of ENOG?
Study of the facial nerve
83
What is ENOG mostly used for?
ENOG is typically concerned with the amount of deterioration in facial nerve function.
84
# Name 4
Facial Nerve Disorder Etiologies
* Bell’s Palsy (most common)
* CVA (stroke)
* Otitis media
* Multiple Sclerosis (MS)
* Chicken pox
* Glomus Jugulare
* Meningioma
* Facial Nerve neuroma
* Herpes Zoster Oticus
85
ENOG's Clinical Use
ENOG is used to determine course of action
in managing disease or to monitor status.
* based on ENOG physican may reccomened monitoring or reccomend surgery to address the damage.
86
# Define
any loss of nerve supply regardless of the cause. If the nerves lost to ____ are part of the neuronal communication to a specific function in the body then altered or a loss of physiological functioning can occur.
DENERVATION
* loss of nerve supply to a body part.
* The Function controlled by that denervated nerve will be altered/weakened or lost completely .
87
An active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (i.e. farther from the neuron's cell body) degenerates.
Wallerian Degeneration
* nerve fiber is damaged or cut — the part of the nerve farther from the injury starts to break down.
88
Denervation
Denervation any loss of nerve supply regardless of the cause. If the nerve is lost to denervation are part of the neuronal communcation to a specific funtion in the body then altered or a loss of physiological functioning can occur.
* loss of nerve supply to a body part. regardless of the cause
* The Function controlled by that denervated nerve will be altered/weakened or lost completely .
89
Wallerian Degeneration
Wallerian Degeneration an active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury degenerates.
* nerve fiber is damaged or cut — the part of the axon farther from the injury starts to break down.
90
Process of Wallerian Degeneration
* Begins 24-36 hours after injury in the axon stump distal to site of injury
* Prior to degeneration, axon remains excitable
* Complete denervation takes 72 hours
* ENOG should be performed between 3 days to 21 day after onset of symptoms for best prognosis.
91
Wallerian Degeneration Begins how long after?
Begins 24-36 hours after injury in the axon stump distal to site of injury
* Prior to degeneration, axon remains excitable
92
How long does complete denervation to occur for Wallerian Degeneration
Complete denervation takes 72 hours
93
for Wallerian Degeneration when should ENOG be performed?
ENOG should be performed between **3 days to 21 day** after onset of symptoms for best prognosis.
* Earlier than 3 days, Wallerian Degeneration may not be complete, After 21 days may be too late for intervention
* 72 hours is the sweet spot
94
What is used to classify nerve injury?
* Sunderland and Seddon Injury Classification
* House-Brackmann Facial Nerve Grading
95
ENOG Methodology
* Electrodes placed over the main trunk and distally
* Most accurate, qualitative measurement
* Measures the Compound Action Potential
* Magnitude of response on normal side is compared to impaired side
* Not useful until Wallerian Degeneration has occurred
96
ENOG Usage & Criteria
* Determine if facial nerve is intact
* Monitor facial nerve function
Improvement
Progression of impairment (tested every 3 days typically)
* <90% decrease in amplitude on impaired side is good prognosis for spontaneous recovery. (less than 90)
* >90% decrease in amplitude on impaired side is indicator for medical intervention (greater than)
97
What does an ENOG of < 90% (less than) indicate?
< 90% decrease in amplitude on the impaired side = good prognosis → spontaneous recovery likely
* facial nerve response drops by less than 90% compared to the healthy side, there’s a good chance the nerve will heal on its own
98
What does an ENOG of >90% (greater than) indicate?
> 90% decrease in amplitude on the impaired side = medical intervention needed
* If the response drops by more than 90%, it’s a sign of severe nerve damage → medical or surgical treatment indication.
99
ENOG
* Transducer
* Montage:
* Duration
* Sweeps:
* Rate:
* Intensity:
* Filter:
* Impedance:
* Epoch:
* Transducer: stimulating electrodes located at the stylomastoid foramen (+) anterior (-) posterior
* Montage: recording electrode is located near the ipsilateral nasolabial fold, corner smile and ground on forehead
* Duration: 200 microseconds
* Sweeps = 5
* Rate: 1.7/sec
* (replicate response)
* Intensity: 10mA
* Filter: 3-3000 Hz
* Impedance: <5 kOhms
* Epoch: 20 msec
100
ENOG Montage
Transducer: stimulating electrodes located at the stylomastoid foramen (+) anterior (-) posterior
Montage: recording electrode is located near the ipsilateral nasolabial fold, corner smile and ground on forehead
101
# Offical Definition
What is Sensory Gating?
Sensory gating is a preattentive natural response
* It is the ability of the **brain to attenuate irrelevant sensory stimuli to prevent sensory overload and subsequent cognitive disturbances** and to respond to a novel stimulus or a change in an ongoing stimulus
* Pb or P50
102
# My Definition
What is Sensory Gating?
* Sensory Gating: Sensory gating is the brain's natural filtering system.
* It helps the brain ignore unimportant or repetitive sounds so that it can focus on new or important ones.
* It happens before we’re even consciously aware — this is why it’s called "preattentive."
* It protects the brain from becoming overwhelmed by too much sensory input (like background noise)
