RPSGT Best Practices & Methodologies 4 — Questions and Answers
Question 1: Which EEG feature is required to score an epoch as stage N2 sleep?
- At least one K-complex or sleep spindle in the absence of arousal (Correct answer)
- Continuous delta activity comprising >20% of the epoch
- Presence of sawtooth waves
- Alpha activity replaced by theta activity only
Correct answer: At least one K-complex or sleep spindle in the absence of arousal
Stage N2 requires one or more K-complexes or sleep spindles not associated with arousal, in the absence of sufficient slow-wave activity for N3.
Question 2: Stage N3 is scored when high-amplitude slow-wave activity occupies what proportion of an epoch?
- >10%
- >20% (Correct answer)
- >30%
- >50%
Correct answer: >20%
N3 (slow-wave sleep) is scored when ≥20% of the epoch contains waves with frequency 0.5–2 Hz and peak-to-peak amplitude >75 µV.
Question 3: REM sleep is identified by which combination of polysomnographic features?
- Low-amplitude mixed-frequency EEG, low chin EMG tone, and rapid eye movements (Correct answer)
- High-amplitude delta EEG, absent eye movements, and high chin EMG tone
- Sleep spindles, low chin EMG, and slow rolling eye movements
- Alpha EEG, high chin EMG, and REMs
Correct answer: Low-amplitude mixed-frequency EEG, low chin EMG tone, and rapid eye movements
REM sleep is characterized by low-amplitude mixed-frequency EEG, atonic (low) chin EMG, and rapid eye movements.
Question 4: According to AASM rules, an arousal during NREM sleep is scored when there is an abrupt shift in EEG frequency lasting at least how long?
- 1 second
- 3 seconds (Correct answer)
- 5 seconds
- 10 seconds
Correct answer: 3 seconds
A NREM arousal requires an abrupt EEG frequency shift lasting ≥3 seconds, preceded by at least 10 seconds of stable sleep.
Question 5: What EEG waveform defines stage N1 sleep in patients who generate a well-defined alpha rhythm while awake?
- Replacement of alpha rhythm by low-amplitude mixed-frequency activity (Correct answer)
- Presence of K-complexes
- Appearance of sleep spindles
- High-voltage delta waves exceeding 75 µV
Correct answer: Replacement of alpha rhythm by low-amplitude mixed-frequency activity
In patients with alpha rhythm, N1 is scored when alpha is attenuated and replaced by low-amplitude mixed-frequency (predominantly 4–7 Hz) EEG activity.
Question 6: Sawtooth waves are a characteristic EEG feature associated with which sleep stage?
- Stage N1
- Stage N2
- Stage N3
- Stage R (REM) (Correct answer)
Correct answer: Stage R (REM)
Sawtooth waves—serrated, sharply contoured 2–6 Hz waves—are a characteristic EEG feature of REM sleep, often preceding bursts of rapid eye movements.
Question 7: When scoring an epoch that contains both stage N2 features and stage N3 slow-wave activity, which rule applies?
- The stage occupying the majority (>50%) of the epoch is scored
- Score the epoch as N2 if any N2 features are present
- Score N3 if slow-wave activity comprises ≥20% of the epoch (Correct answer)
- Always score the later-occurring stage in the epoch
Correct answer: Score N3 if slow-wave activity comprises ≥20% of the epoch
AASM rules score an epoch as N3 when ≥20% of the epoch contains qualifying slow-wave activity, regardless of co-occurring N2 features.
RPSGT Best Practices & Methodologies 4
Which EEG feature is required to score an epoch as stage N2 sleep?