Class Key points Quiz

Question 1

What is ABR testing for?

Answer 1

ABR is testing neural synchrony

Question 2

what is the main disorder that would result in a abnormal ABR?

Answer 2

ANSD

Question 3

____ and _____ is required to view all evoked responses

Answer 3

Signal averaging and amplification is required to view all evoked responses

Question 4

Evoked potentials (EPs), or evoked responses (ERs), measure the what?

Answer 4

Evoked potentials (EPs), or evoked responses (ERs), measure the electrophysiologic responses of the nervous system to a variety of stimuli

Question 5

SERs are generated by stimulation of what?

Answer 5

SERs are generated by stimulation of afferent peripheral nerve fibers by either physiological or electrical means

Question 6

Somatosensory Evoked Responses (SERs)

Name the Common places to stimulate the nerves in clinical tests

Answer 6

Median nerve (at the wrist)
Common Peroneal nerve (at the knee)
Posterior Tibial nerve (at the ankle)

Question 7

to record the response, electrodes are placed on the:

Answer 7

Scalp (to monitor brain activity),
Spine, and
Nerves near the stimulation site (to track how the signal travels through the nervous system).

Question 8

Somatosensory Evoked Responses (SERs)

These tests are helpful for:

Answer 8

• Neurologic disease
• Prognosis of comatose patients especially after postanoxic coma
• Intraoperative monitoring of “at risk” somatosensory pathways

Question 9

Waveforms are described in terms of what?

Answer 9

• Morphology (shape of the wave),
• Amplitude (size/strength of the signal), ( height of the wave form)
• Dispersion aka Latency (how long it takes for the signal to appear, and whether it’s delayed or spread out)

Question 10

Late evoked responses are generally used for studying ____

Answer 10

Late evoked responses are generally used for studying higher cortical functions

• clinical usefulness is limited, experimental and not routinely used

Question 11

True or false

Advances in imaging technology, especially MRI, have decreased the use of ER testing in clinical practice

Answer 11

TRUE
The use of Evoked Response testing has declined over time because MRI technology has improved a lot.

Question 12

what are the key differences between MRI & Evoked Responses?

Answer 12

• MRI shows detailed pictures of the brain’s structure—it tells doctors what the brain looks like and where any damage or abnormality is. structual/anatomic test
• MRI is usually better for figuring out where something is wrong in the brain or nervous system.
• ERs measure how well certain parts of the brain or nerves are working—so it gives information about function, not structure. assesses funtionality

Question 13

AERs are ____ or _____ that are generated when the ____ system is stimulated by ____

Answer 13

AERs are brain waves or electrical responses that are generated when the auditory system is stimulated by sound

Question 14

What sounds are used to elicit AERs?

Answer 14

• Clicks (abrupt onset, very short duration, and broad band – not frequency specific)
• Tone bursts (short duration, frequency specific sounds)
• Speech sounds (e.g., /ba/ and /da/

Question 15

As a general rule, the louder the stimulus intensity the what?

Answer 15

As a general rule, the louder the stimulus intensity the larger the AER Response

Question 16

Explain the process of how Auditory Evoked Responses are measured?

Answer 16

• sound is presented into the ear by a transducer (insert)
• when the sound enteres the ear it stimulates the cochlea and brain
• The Cochlea & brain activity is picked up by the electrodes place on the scalp (vertex,ear lobes etc)
• An electrode is a wire with a metal disc or sticky patch on the end — the other end of the electrobe wire has a DIN pin (a connector) that plugs into a machine
• The machine amplifies and records the signals

sound goes into the ear → the brain responds → electrodes on the head detect that brain activity → the signal gets sent to the recording equipment.

Question 17

What is a DIN Pin?

Answer 17

• A DIN connector is a type of electrical plug
• For computer keyboard and mouse there are now the Mini-DIN connectors
• The original DIN standards for these connectors are no longer in print and have been replaced with the equivalent international IEC standard

Question 18

The process how the brain responds to sound, recorded and processed.

Answer 18

• sound is played into the ear & activates parts of the auditory system
• deep inside the head, far from the surface electrodes (far-field recording)
• The electrical activity from those internal structures travels through the body’s tissues and fluids and reaches the electrodes on the scalp.
• from there hte signal travels through the electrode wire
• to a preamplifier/amplifier, which boosts the signal
• Through filters, which clean up the signal by removing noise
• Into an analog-to-digital converter, which turns the electrical signal into digital data
• Lastly, computer, where the signal is analyzed and displayed (as waveforms, graphs, etc.)

Stimulus presented → the sound triggers activity in the brain &cochlea → the activity reaches the scalp electrodes →transferred through wire → to preamplifier/amplifier → the signal is amplified, cleaned, digitized, and analyzed on a computer.

Question 19

If the electrodes are so far away from the generator site how do we know the response is coming from the auditory central nervous system (CANS)?

Answer 19

• Exact loaction within the CANS is hard to identify
• but we know the response is within the auditory system since the simulus is a soun
• It takes about 1 second for an AER to occur after stimulus is presented
• analyzing the pattern and timing (latency) we can identify what region & sometimes specific sites within the CANS are generating the response.