EP

Question 1

What is the definition of evoked potential?

Answer 1

The average of multiple responses

Question 2

What is the definition of evoked response?

Answer 2

The electrical recording following a single stimulus

Question 3

How does visual input travel?

Answer 3

From the retina to the optic nerve, optic chiasm, optic Tract, lateral geniculate body, and optic radiation and finally reaches the occipital cortex.

Question 4

What is the function of the CNS?

Answer 4

Collects information from environment & body through sensory input, compared and contrast information with past informations, then decides a motor response.

Question 5

What is MUAP?

Answer 5

Motor unit action potential

Question 6

What is the neuro muscular junction (NMJ)?

Answer 6

A chronicle synapse cause by motor neurons & muscle fibers.

Question 7

What does the anterior horn cell do?

Answer 7

Transmits info through nerves to muscles this is the NMJ process

Question 8

What kind of fibers are measured in NCS?

Answer 8

Large mylinated fibers are the fibers that are measured in NCS.

Question 9

Neuropothies that preferentially affect only small fibers may not reveal any abnormalities on NCS

Answer 9

Maybe in EMG

Question 10

The largest & fasted fibers in the peripheral nervous system are not recorded during routine motor or sensory NCS.

Answer 10

These are the muscle afferent, very nosey Like when we test the signal and ask the patient to push against thumb.

Question 11

What is volume conduction?

Answer 11

The process of initial intracellular electrical potential being trans omitted through extracellular fluid & tissue.

Which is essential the process of NMJ (neuro muscular junction)

Question 12

What is a near field potential?

Answer 12

When you are recording close to the source.

Question 13

What is a far-field action potential?

Answer 13

Electrical potentials that are distributed widely & instantly.

Far-field potentials are more often concerned in EP’s but occasional important in NCS’s

Question 14

What is the morphology produced by a near-field potential?

Answer 14

Near-field potentials produce a triphasic waveform as an advancing action potential approached & then passes beneath and away from a recording electrode.

Question 15

What is the definition of “end plate”?

Answer 15

End plate is when the active electrode (recording electrode) is directly over the motor point of the muscle.

Question 16

What will the morphology of the wave look like if the cathode is off the motor point?

Answer 16

A classic triphasic wave.

Depolarization begins distally and then travels under and past the active electrode resulting in initial positive deflection.

Question 17

What will the morphology of the wave look like if the cathode is placed on the end plate?

Answer 17

Initial negative wave followed by subsequent positive wave.

Depolarization occurs first at site, with depolarization subsequently spreading away.

Question 18

What will the morphology of the wave look like of the cathode is place at a distance from the motor point?

Answer 18

Only a small positive wave will be seen

Question 19

Definition of “cathode”

Answer 19

The stimulator

Question 20

Definition of “CMAP”

Answer 20

Compound muscle action potential.

A summation of all underlying individual muscle fiber action potentials

(latency, amplitude, duration)

Question 21

How are far-field potentials recorded?

Answer 21

Far-field potentials are recorded with two recording electrodes, one closer & the other farther from the source, they essentially see the source at the same time.

Question 22

What range are motor response studies typically within?

Answer 22

Millivolts (mV) range

Question 23

What range are sensory and mixed electrodes typically within?

Answer 23

Microvolts (uV) range

Question 24

What is the Belly-tendon montage?

Answer 24

When G1 is placed over the end plate and G2 is placed distally, over the tendon of the muscle.

Question 25

In CMAP what does latency represent?

Answer 25

Latency represents 3 separate process:

1. the nerve conduction time from the stim to the NMJ.
2. the delay across the NMJ.
3. depolarization time across the muscle.

Question 26

In CMAP what is the amplitude and how is it measured?

Answer 26

Amplitude is measured from baseline to the negative peak.

Question 27

What is usually The reason for a CMAP low amplitude wave

Answer 27

Low amplitude is often the result of (axonal loss, demyelination & some NMJ disorders & neuropathies

Question 28

In CMAP what is the area?

Answer 28

The area above the baseline to negative peak

Question 29

In CMAP what is duration?

Answer 29

The duration is a measure from the initial deflections from baseline to the first baseline crossing.

Question 30

How is motor conduction velocity calculated?

Answer 30

Motor conduction velocity is calculated by dividing the distance traveled by the nerve conduction time.

To calculate a true motor conduction velocity, without including NMJ transmission & muscle depolarization times, two stimulation sites must be used, one distal and one proximal.

Question 31

Conduction velocity formula:

Answer 31

Distance between proximal and distal stim site \ proximal latency - distal latency