EEG Sleep Staging and Sleep EEG 4 — Questions and Answers
Question 1: Which EEG feature is pathognomonic of N2 sleep and must be present for stage scoring?
- Sleep spindles or K-complexes (Correct answer)
- Delta waves >75 µV
- Sawtooth waves
- Vertex sharp waves
Correct answer: Sleep spindles or K-complexes
N2 sleep requires the presence of sleep spindles (12–14 Hz bursts) or K-complexes; delta waves define N3, sawtooth waves occur in REM, and vertex sharps mark N1.
Question 2: A patient shows repeated brief arousals out of N3 sleep in the first third of the night without awakening. This pattern is most consistent with:
- Sleep terror disorder (Correct answer)
- REM sleep behavior disorder
- Sleep-onset insomnia
- Narcolepsy
Correct answer: Sleep terror disorder
Sleep terrors (NREM parasomnias) classically arise from N3 slow-wave sleep in the early part of the night with partial arousals and autonomic activation.
Question 3: During polysomnography, the minimum duration of a K-complex to be scored as such is:
- 0.5 seconds (Correct answer)
- 0.25 seconds
- 1.0 second
- 2.0 seconds
Correct answer: 0.5 seconds
Per AASM scoring rules, a K-complex must have a duration of ≥0.5 seconds to be distinguished from other sharp transients.
Question 4: Which of the following best describes the EEG during phasic REM sleep?
- Bursts of sawtooth waves coinciding with rapid eye movements (Correct answer)
- High-amplitude delta waves with superimposed spindles
- Continuous 12–14 Hz spindle activity
- Diffuse alpha rhythm with occasional vertex sharps
Correct answer: Bursts of sawtooth waves coinciding with rapid eye movements
Phasic REM is characterized by sawtooth waves (2–6 Hz, notched appearance) that typically precede or accompany bursts of REMs.
Question 5: In the AASM 2007 rules, slow-wave sleep (SWS) replaced which older Rechtschaffen & Kales (R&K) staging terminology?
- Stages 3 and 4 combined into N3 (Correct answer)
- Stage 2 renamed to N2
- Stage 1 renamed to N1
- Stage REM renamed to R
Correct answer: Stages 3 and 4 combined into N3
The AASM 2007 manual merged R&K stages 3 and 4 into a single stage N3, collectively called slow-wave sleep.
Question 6: A sleep technologist notices that chin EMG amplitude has dropped to its lowest level of the night, eye movements are present, and EEG is low-voltage mixed frequency. The patient is most likely in:
- REM sleep (Correct answer)
- N1 sleep
- N2 sleep
- N3 sleep
Correct answer: REM sleep
REM sleep is defined by muscle atonia (very low chin EMG), rapid eye movements, and low-voltage mixed-frequency EEG without spindles or K-complexes.
Question 7: Which electrode placement is standard for detecting eye movements during sleep staging PSG?
- E1-M2 and E2-M2 (outer canthi referenced to contralateral mastoid) (Correct answer)
- F7-F8 bipolar pair
- Fp1-Fp2 bipolar pair
- C3-A2 and C4-A1
Correct answer: E1-M2 and E2-M2 (outer canthi referenced to contralateral mastoid)
EOG channels placed at the outer canthi (E1, E2) referenced to mastoids capture horizontal and vertical eye movements needed for sleep staging.
EEG Sleep Staging and Sleep EEG 4
Which EEG feature is pathognomonic of N2 sleep and must be present for stage scoring?