EEG Evoked Potentials 1 — Questions and Answers
Question 1: What are the three main types of evoked potentials commonly recorded in a clinical neurophysiology laboratory?
- Visual, Auditory, and Somatosensory (Correct answer)
- Motor, Sensory, and Cognitive
- Cortical, Subcortical, and Peripheral
- Pattern, Flash, and Click
Correct answer: Visual, Auditory, and Somatosensory
The three main clinical evoked potentials are Visual (VEP), Auditory (BAEP/ABR), and Somatosensory (SSEP), each assessing a different sensory pathway.
Question 2: Which evoked potential modality is specifically used to assess the integrity of the auditory pathway from the cochlea through the brainstem?
- Visual Evoked Potentials (VEP)
- Somatosensory Evoked Potentials (SSEP)
- Brainstem Auditory Evoked Potentials (BAEP) (Correct answer)
- Motor Evoked Potentials (MEP)
Correct answer: Brainstem Auditory Evoked Potentials (BAEP)
BAEPs (also called ABRs) record far-field potentials generated along the auditory nerve and brainstem from cochlea to inferior colliculus.
Question 3: What is the primary waveform of clinical interest in a pattern reversal visual evoked potential (VEP)?
- N75
- P100 (Correct answer)
- N145
- P200
Correct answer: P100
The P100 is the large positive peak occurring around 100 ms, generated in primary visual cortex, and is the most reliable and clinically significant component of the pattern reversal VEP.
Question 4: Stimulation of the median nerve in a somatosensory evoked potential (SSEP) study produces a cortical response designated N20 at approximately what latency in a normal adult?
- 5–10 ms
- 12–15 ms
- 18–21 ms (Correct answer)
- 30–35 ms
Correct answer: 18–21 ms
The N20 cortical potential following median nerve stimulation peaks at approximately 18–21 ms in normal adults, reflecting conduction time from wrist to primary somatosensory cortex.
Question 5: In brainstem auditory evoked potentials (BAEPs), Wave V is generated primarily by which structure?
- Cochlear nerve (CN VIII)
- Cochlear nucleus
- Lateral lemniscus/inferior colliculus region (Correct answer)
- Primary auditory cortex
Correct answer: Lateral lemniscus/inferior colliculus region
Wave V of the BAEP is generated at or near the lateral lemniscus and inferior colliculus, making it the most robust and clinically important wave.
Question 6: Which measurement is most commonly used to identify BAEP abnormalities related to central conduction?
- Absolute wave I latency alone
- Interpeak latencies (IPLs) between waves (Correct answer)
- Peak-to-trough amplitudes
- Stimulus intensity threshold
Correct answer: Interpeak latencies (IPLs) between waves
Interpeak latencies (e.g., I–III, III–V, I–V) reflect central conduction time between brainstem generators and are the primary diagnostic parameters for central pathology.
Question 7: What is the standard stimulus rate used when performing pattern reversal visual evoked potentials (VEPs) in a clinical setting?
- 0.1–0.5 reversals/second
- 1–2 reversals/second (Correct answer)
- 5–8 reversals/second
- 10–15 reversals/second
Correct answer: 1–2 reversals/second
A reversal rate of approximately 1–2 per second (1–2 Hz) is standard for pattern reversal VEPs; faster rates can cause habituation and distort the P100 latency.
EEG Evoked Potentials 1
What are the three main types of evoked potentials commonly recorded in a clinical neurophysiology laboratory?