Evoked Responses Quiz Shortened

Question 1

What is an amplifier?

Answer 1

a device that increases the strength of a signal and is critical in the AEP system
-important as the signals that we are capturing are from the cochlea or 8th nerve and are very small, so without the amplifier, we could not see them

Question 2

Amplifiers for AEPs need 2 things, these are

Answer 2

Input impedance: trying to figure out how clean the measurements are by running an impedance measurement

Common mode rejection (CMR): the process of identifying what is common between electrodes and throwing out those common aspects so all that is left is what is different (the true response)
-The thought behind this is that those common signals are the noise in the environment

Question 3

When using amplifiers what would happen if 2 electrodes were places next to each other in the same location?

Answer 3

The result would be nearly a flat line because of the CMR cancelling out the commonalities

Question 4

What is a filter?

Answer 4

Remove part (or parts) of something from the whole, and within the AEP measurement, they reject electrical activity at certain frequencies while passing energy at other frequencies

Question 5

What are filters used to do?

Answer 5

eliminate as much internal noise as possible and to eliminate as much external electrical noise as possible

Question 6

What are the types of filters?

Answer 6

high pass : rejects lows, allows highs to pass
low pass : rejects highs, allows lows to pass
bandpass : rejects energy below and above a certain cutoff, allows those between the cutoffs to pass. good filter for AER.
band reject : rejects a very specific range between two cutoffs (not typically used in AER recordings)

Question 7

How can an inaccurate amount of filtering impact a recording?

Answer 7

-too much can eliminate the AER response
-too little can lead to high noise levels and poor AER recordings

Question 8

What is a filter slope?

Answer 8

a specified cutoff frequency. this does not happen abruptly but rather at a slope. can play a critical role in AER recordings particularly in the mid and late AERs

Question 9

Our reference electrode will be a ___________ electrode

Answer 9

inverting

Question 10

Exogenous vs Endogenous?

Answer 10

exogenous: does not have to hear the signal
-earlier responses are this type
endogenous: must hear the signal
-all cortical potentials and later responses are this way

Question 11

Electrode Generator sites: tell me the difference between near field and far field

Answer 11

Near field: electrodes are in close proximity
-uncommon as the electrode needs to be directly on the nerve
Far field: electrodes are some distance away
-Typically what is used as the electrodes will be placed on the skull
- The closer you are to the signal, the better

Question 12

Evoked vs Non-Evoked Potentials

Answer 12

remember, these electrical potentials can be recorded both in response to stimulus and in ongoing manner without presence of external stimuli
-evoked is those such as the ECochG or ABR
-non evoked is those such as the EEG

Question 13

What is an Auditory Evoked Potential (AEP)?

Answer 13

represents electrical responses of the nervous system to externally presented stimuli; most will be hidden in the EEG response within the brain
-in simple words, represents brain waves generated in response to sound

Question 14

How do we classify AEP’s?

Answer 14

characteristics determined by external or internal processes, based on the time epoch following the stimulus, based on relation of electrodes to generator site and based on structures in the auditory system that generates them

Question 15

What are electrodes? where does it send information?

Answer 15

A sensing device that detects bioelectric activity and sends it to the pre-amplifier. AERs are recorded by attaching electrodes to the scalp, mastoid, earlobes, external ear canal, or TM. Designed to conduct electrical activity in the frequency range of the evoked responses.

Question 16

How do you prep the skin for an electrode?
whats the goal?

Answer 16

scrub with mildly abrasive liquid substance to remove dead skin, debris, and oil that might interfere with the electrical activity. the aim is to get the impedance below 5 ohm. alcohol pads may only be used to remove vernix prior to ABR on neonates. if using alcohol, make sure skin is completely dry or impedances might be slightly higher.

gently pull electrode a few seconds after application and it should remain tightly adhered to the skin

Question 17

How long is the lead wire that connects the electrode to the DIN pin?

Answer 17

Typically 1 meter or 36 inches. A shorter wire (1 ft) reduces electrical interference but is not commonly used.

Question 18

Tell me about Disc-Type/Cup Electrodes

Answer 18

• conventionally used for AERs
• metal: tin, silver, gold, or platinum
• a hole of about 2 mm in the center to inject/release conducting paste/gel
• Silver chloride coated electrodes are useful for very low frequency.
• best to use electrodes made of the same metal to avoid imbalance
• expected to have a higher impedance than disposable

Question 19

Tell me about Disposable Electrodes

Answer 19

• commonly used for infants
• not sterile but maybe more hygienic
• skin still needs to be prepared by cream/gel is not required
• connected with a snap lead wire of alligator clip lead wire or the whole electrode and wire can be disposable
• should be possible to achieve impedances b/w 1-5 ohms

Question 20

What is electrode impedance? What are we shooting for?

Answer 20

impedance is a materials resistance to flow of electrical current. it is measured in ohms. should be measured before and after AER recording if there is reason to suspect change such as excessive patient movement, increased electrical artifact, and when switching b/w ears.

desired impedance is b/w 1 to 5 ohms, 0 is not desirable bc it may lead to a short circuit at the amplifier or reflect a connection b/w 2 closely placed electrodes

Question 21

how to reduce impedance

Answer 21

turn off unnecessary computer monitors, turn off phones, unplug the chair they are in if it can be operated, always use the largest size ear tip to reduce the risk of stimulus leakage, braid or tape electrode, do not mix electrode types, do not place ground electrodes near the heart, ensure electrodes are symmetrical b/w ears, all electrode leads should run toward the top of the patients head, pressing on the electrode for several minutes, moving it slightly to get better contact, adding more gel, securing it snug with additional tape, and removing electrodes with higher impedance and reprepping skin

Question 22

what does it mean if the electrode impedance is reading “open”?

Answer 22

means it is greater than 80kOhm. this can happen if there is a faulty electrode or if no electrode is plugged in.

Question 23

The more soft tissue the ____ the impedance values

Answer 23

better

Question 24

How do you choose which electrode will be used?

Answer 24

dictated by the type of AER to be recorded and the patient population

Question 25

What is the difference between non-inverting vs. inverting electrodes?

Answer 25

Non-inverting: the signal is coming in and is going to be left alone (how it comes in is how it stays). Located at Cz. Inverting: the signal is coming in and gets flipped 180 degrees before it reaches the processor (takes the signal and flips its 180 degrees). Located at earlobe or mastoid.

Question 26

Tell me about the electrode montage

Answer 26

Some evoked reponses like ABR are recorded with 3-4 electrode sites whereas cortical AER are sometimes recorded simultaneously with 20-30 electrodes facilitated by an electrode cap. Cz = very top of head Fz = high forehead Fpz =how forehead A1 = right ear A2= left ear M1 & M2 = mastoids Odd #s = left Right #s = even

Question 27

What are common sources of artifact? How do you get rid of an artifact?

Answer 27

electrical = activity within the electrical circuit electromagnetic = generated from an external or non-patient source electrophysiologic = originating from the patient To get rid of these, you can remove the source of the artifact (turn off the phone/machine), modify test parameters (increase intensity, change filters) or artifact rejections (any voltage exceeding designated voltage is not sent to the computer)

Question 28

What is signal averaging?

Answer 28

what is sounds like, it averages the electrical activity. used to increase the size of the AER and reduce the size of the noise.

Question 29

What is an auditory evoked repsonse (AER)?

Answer 29

brain waves or electrical responses that are generated when the auditory system is stimulated by sound, but can also be through electricity or a mechanical stimuli

Question 30

What are the sounds used for AERs?

Answer 30

clicks, tone bursts, and speech sounds

Question 31

Tell me about clicks for AERs

Answer 31

abrupt onset, very short duration and broadband -not a frequency specific signal as it contains energy from various frequencies, but most energy is within 1 and 4 kHz

Question 32

Tell me about tone bursts for AERs

Answer 32

short duration -frequency specific with more energy hanging around the frequency of interest

Question 33

What is the general rule with AERs and their stimulus intensity with response

Answer 33

the louder the stimulus intensity, the larger the AER response will be

Question 34

What is polarity? (stimulus factor)

Answer 34

The initial direction of the pressure wavefront in the stimulus waveform, measured at the face of the transducer. There are 3 types: rarefaction polarity, condensation polarity, & alternating polarity.

Question 35

What is rarefaction polarity?

Answer 35

- polarity that causes the pressure wavefront of a transducer to move away from the eardrum - the early components of the AEPs latency is slightly shorter and amplitude is higher for

Question 36

What is condensation polarity?

Answer 36

- a polarity that initially causes the pressure wavefront of a transducer to move toward the eardrum - the early components of the AEPs latency may be slightly longer - wave 5 amplitude tends to be larger for normal hearing subjects

Question 37

What is alternating polarity?

Answer 37

- a polarity that is alternated on successive trials (between rarefaction & condensation) - at high intensities, alternating polarities are sometimes used to reduce stimulus artifact

Question 38

What are the factors that affect AEPs?

Answer 38

stimulus factors, acquisition factors, non-pathologic subject factors, and waveform analysis

Question 39

What are stimulus factors for AEPs?

Answer 39

stimulus type (click/burst), duration, polarity, intensity & rate.

Question 40

What are acquisition factors for AEPs?

Answer 40

type of electrode, filter, amplifiers, artifact rejection, signal averaging,

Question 41

What are non-pathologic subject factors for AEPs?

Answer 41

gender, age, body temp. typically dont make a difference

Question 42

What is waveform analysis for AEPs?

Answer 42

looking at several factors of a waveform over time: latency, amplitude, morphology, & polarity direction

Question 43

Tell me about waveform analysis LATENCY

Answer 43

time b/w stimulus presentation and the appearance of a change. measured in msec.

Question 44

Tell me about waveform analysis AMPLITUDE

Answer 44

the difference b/w the peak of a wave and the following valley. measured in microvolts.

Question 45

Tell me about waveform analysis MORPHOLOGY

Answer 45

pattern/shape of the waves. morphology can be poor even if latency and amplitude are deemed normal.

Question 46

Tell me about waveform analysis POLARITY DIRECTION

Answer 46

which way is up? polarity of an AEP depends on the electrode location relative to the generator of the response & which electrode is plugged into the positive and negative volate inputs of the differential amplifier

Question 47

What are the components of instrumentation?

Answer 47

stimulus generators, electrodes, filters, amplifiers, a signal average with artifact rejection, response delay (trigger), response processing, & a means to print or display test results

Question 48

What transducer is recommended when conducting AEPs?

Answer 48

Inserts because they make wave 1 more visible, prevent canal collapse, increase interaural attenuation, and attenuate environmental noise

Question 49

AERs can be used on patients who cannot be assessed validly with behavioral audiometry such as:

Answer 49

newborns, difficult to test children, developmental disorders, cognitive impairments, false/exaggerated hearing loss, sick or sleeping patients, comatose

Question 50

AERs may be useful for?

Answer 50

evaluating hearing sensitivity, evaluating CANS pathology, evaluation of CANS including auditory processing, evaluation of children with language cognitive or other developmental disorders, and monitoring effectiveness of intervention such as CIs or HAs

Question 51

What is the 10-20 International Electrode nomenclature?

Answer 51

each site is located to a given patient reference by well defined anatomic landmarks. this can make the difference b/w recording well formed responses vs non-observable ones. elecrodes are 10% or 20% of the distance from skull front to back away from eachother. nasion = bridge of nose inion = occipital protuberance f = frontal c = coronal p = parietal o = occipital t = temporal

Question 52

What is a ground electrode, and where is it located?

Answer 52

necessary in order to record consistent responses n varied test conditions. can be located anywhere on the body

Question 53

What are the 3 receptacles/jacks an electrode box has?

Answer 53

non-inverting, inverting, and ground = a one channel recording, meaning the inputs for channel 2 are not used. Two-channel recording = 5 or 6 electrode receptacles, allowing you to perform ipsi and contra recordings simulatenosly. if this has an Cz or Fz site, to avoid placing 2 non-inverting electrodes on a patient (1 for each channel) the receptacles are linked by a jumper cable. one side goes in input 1 for channel 1 and the other side goes in input 1 for channel 2.

Question 54

how do we recognize an ipsi response from a contra response?

Answer 54

you will have an absent/reduced wave 1 and 2 in a contra response

Question 55

What is on the x and y axis of an AER?

Answer 55

x axis = latency in ms y axis = amplitude in microvolts (µv)

Question 56

What is the interplay b/w latency, amplitude, and intensity?

Answer 56

if you decrease intensity, latency will increase, and amplitude will decrease.

Question 57

Is short or long more frequency specific?

Answer 57

long

Question 58

Regarding electrode impedances, which of the following is INCORRECT? - Low inter-electrode impedance is important for the common mode rejection (CMR) to work well - Under some circumstances, a reasonable electrode impedance even if > 5 kOhms in conjunction with low interelectrode impedances, can result in good AERs recordings - An impedance of 0 kOhms is most desirable for the best evoked potential responses - Low and balanced electrode impedances limit external and internal noise (interference) - An impedance of 0 kOhms may reflect a direct connection between two closely spaced electrodes resulting in superior AER recordings

Answer 58

An impedance of 0 kOhms is most desirable for the best evoked potential responses

Question 59

Which of the following filters should generally be avoided in recording auditory evoked responses?

Answer 59

Notch Filter

Question 60

Audi Bel, a recent AuD graduate, is getting ready to perform an ABR on an adult. She is receiving an OPEN message when measuring electrode impedances. What is her MOST likely error?

Answer 60

Selecting a two-channel recording option for a one-channel recording montage

Question 61

The best assessment technique to diagnose auditory neuropathy spectrum disorder is?

Answer 61

Auditory brainstem responses

Question 62

What is the term for the technique used in obtaining an adequate signal-to-noise ratio (SNR) in AER recordings?

Answer 62

Signal averaging

Question 63

What information is critical for filter settings used in recording AERs?

Answer 63

Frequency of the stimulus

Question 64

The auditory evoked response is better at assessing _______________ of the auditory system and the MRI is better at assessing structural problems within the system.

Answer 64

function

Question 65

________________ are generated by stimulation of afferent peripheral nerve fibers (e.g., Median nerve) by either physiological or electrical means and are used in intraoperative monitoring.

Answer 65

Somatosensory evoked responses (SERs)

Question 66

A _______________ electrode does not undergo polarity reversal; it is simply amplified.

Answer 66

non-inverting

Question 67

Inter-electrode impedances should be balanced at about _________________ kOhms.

Answer 67

2

Question 68

A ground electrode placed low such as on the shoulder of a baby may record an _________________ response instead of an AER.

Answer 68

EKG/Heart beat

Question 69

Auditory evoked potentials can be recorded from which of the following? - The vestibulo-cochlear nerve (CN VIII) - The brainstem - The ear (cochlea) - The cerebral cortex - All of the above

Answer 69

All of the above

Question 70

Evoked potentials recorded by electrodes close to the potential field or where the potential is generated are called _____ responses whereas those recorded by electrodes at a distance from where the potential is generated are called _____ responses. Responses recorded from electrodes placed on the scalp are considered ______ responses, whereas those recorded from intratympanic needle electrodes or on the promontory of the cochlea would be considered _____ responses.

Answer 70

near field, far field, far field, near field

Question 71

Which of the following regarding exogenous and endogenous responses are TRUE. - Endogenous potentials are influenced by cognitive processing whereas exogenous are more related to the physical characteristics of the evoking stimulus - Endogenous responses do not require conscious “hearing” of the evoking stimulus and can be recorded on individuals who are asleep, sedated or unconscious - Exogenous responses require special participation from the patient such as reading a book, watching a movie or counting stimuli - ABR, OAE and ECochG are examples of endogenous potentials - ABR, OAE and ECochG are examples of exogenous potentials

Answer 71

- Endogenous potentials are influenced by cognitive processing whereas exogenous are more related to the physical characteristics of the evoking stimulus - ABR, OAE and ECochG are examples of exogenous potentials

Question 72

Based upon the concept of near-field vs far-field responses, for which of the following ABR setups would you expect to obtain the best (largest amplitude, most detail) response? - Inverting electrodes placed on the scalp - Inverting electrodes placed on the earlobes - Inverting electrodes placed against the tympanic membrane (TM-trode or tymptrodes) - Inverting electrodes placed on the mastoids - Inverting electrodes placed anterior to the tragus

Answer 72

Inverting electrodes placed against the tympanic membrane (TM-trode or tymptrodes)

Question 73

Which of the following is NOT true regarding latency? - Latency is dependent upon a number of factors including stimulus type and polarity - Latency can be defined by the time it took for a specific wave or landmark to occur after stimulus onset (absolute latency) or the time interval from previous landmark (interpeak/interwave latency) - Latency is typically described in milliseconds - Latency is unaffected by age with most AERs occurring at the same time interval across the lifespan (from newborns to elderly) - For most AERs, latency tends to increase as you decrease intensity

Answer 73

Latency is unaffected by age with most AERs occurring at the same time interval across the lifespan (from newborns to elderly)

Question 74

Match these to the image? -earclip (lobe) electrode - tiptrode (canal) electrode - snap electrode/disposable electrode - tymptrode or TM-trode (wick or gel) electrode - cup (disk) electrode

Answer 74

A: tiptrode (canal) electrode B: tymptrode or TM-trode (wick or gel) electrode C: earclip (lobe) electrode D: cup (disk) electrode E: snap electrode/disposable electrode

Question 75

Which of the following is an example of a Non-Evoked or non-event-related potential? - Auditory Middle Late Response (AMLR) - Neurologic Auditory Brainstem Response (ABR) - Threshold Auditory Brainstem Response (ABR) - Electrocochleography (ECochG) - Electroencephalography (EEG)

Answer 75

Electroencephalography (EEG)

Question 76

Which of the following is FALSE regarding AERs? - AERs are all separate and distinct potentials without any anatomical or waveform overlap. - When recording AERs, amplitude or peak voltage is typically displayed on the y-axis - When recording AERs, latency is typically displayed on the x-axis - Early AERs typically mature or reach adult configuration faster than late or cortical potentials - In AERs, latency is typically denoted by msec and amplitude in microvolts

Answer 76

AERs are all separate and distinct potentials without any anatomical or waveform overlap.

Question 77

What is an Epoch and why is it an important consideration when recording AERs?

Answer 77

An Epoch is a length of time (in msec) relative to a specific auditory event. If you choose an Epoch that is too short, you may not see your entire response. If you choose an Epoch that is too long your response may get lost in the bigger display with limited detail. You want to choose the best time frame for the potential of interest.