EEG Evoked Potentials 3

Question 1

For pattern reversal visual evoked potential (VEP) testing, how should each eye be stimulated?

Accepted Answer

Monocularly (one eye at a time, other occluded)

Answer

Monocular stimulation is essential so that an abnormality in one optic nerve, which lies anterior to the optic chiasm, can be lateralized; binocular stimulation would mask unilateral optic nerve disease.

Question 2

What are the typical high-pass and low-pass filter settings used when recording brainstem auditory evoked potentials (BAEPs)?

Accepted Answer

100–3000 Hz

Answer

BAEP waveforms contain frequencies predominantly in the 100–3000 Hz range; these bandpass settings preserve the fast transient potentials while rejecting low-frequency muscle artifact and EEG.

Question 3

The 'N13' potential recorded at the cervical spine (Cv5 or Cv7 electrode) during median nerve SSEP is generated by which structure?

Accepted Answer

Dorsal horn/dorsal column nuclei at the cervicomedullary junction

Answer

N13 is a stationary far-field potential reflecting synaptic activity at the dorsal column nuclei (cuneate nucleus) in the cervicomedullary junction, serving as an important reference point for central conduction.

Question 4

Approximately how many stimulus repetitions (averages) are typically needed to obtain a reliable, reproducible BAEP waveform?

Accepted Answer

1000–2000

Answer

Because the BAEP signal amplitude is only about 0.1–1 µV, averaging 1000–2000 responses is required to achieve an adequate signal-to-noise ratio and clearly resolve all five waves.

Question 5

What is the primary clinical advantage of flash VEPs over pattern reversal VEPs?

Accepted Answer

Can be performed in uncooperative or visually impaired patients unable to fixate on a pattern

Answer

Flash VEPs require only light perception and no fixation, making them useful in infants, comatose patients, or those with dense media opacities, even though pattern reversal VEPs are more diagnostically sensitive.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG Evoked Potentials 3