Evoked Potentials Flashcards
7 cards from real EEG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Evoked Potentials flashcards as text
For pattern reversal visual evoked potential (VEP) testing, how should each eye be stimulated?
Answer: Monocularly (one eye at a time, other occluded)
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.
What are the typical high-pass and low-pass filter settings used when recording brainstem auditory evoked potentials (BAEPs)?
Answer: 100–3000 Hz
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.
The 'N13' potential recorded at the cervical spine (Cv5 or Cv7 electrode) during median nerve SSEP is generated by which structure?
Answer: Dorsal horn/dorsal column nuclei at the cervicomedullary junction
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.
Approximately how many stimulus repetitions (averages) are typically needed to obtain a reliable, reproducible BAEP waveform?
Answer: 1000–2000
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.
What is the primary clinical advantage of flash VEPs over pattern reversal VEPs?
Answer: Can be performed in uncooperative or visually impaired patients unable to fixate on a pattern
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.
Which peripheral nerve is most commonly stimulated at the ankle when performing lower extremity somatosensory evoked potential (SSEP) testing?
Answer: Posterior tibial nerve
The posterior tibial nerve at the medial ankle is the standard lower extremity stimulus site because it is superficial, easily palpated, and activates large-diameter sensory fibers with reliable cortical responses.
Signal averaging in evoked potential recording improves waveform clarity primarily because:
Answer: The evoked response is time-locked to the stimulus while background EEG cancels out with repeated averaging
The neural response to each stimulus occurs at a fixed latency (time-locked), so it adds coherently across averages; random background EEG noise is uncorrelated and averages toward zero, improving signal-to-noise ratio.