EEG Sleep Staging and Sleep EEG 5 — Questions and Answers
Question 1: Sleep efficiency is calculated as:
- Total sleep time divided by time in bed × 100 (Correct answer)
- Total sleep time divided by total recording time × 100
- REM time divided by total sleep time × 100
- Sleep onset latency divided by time in bed × 100
Correct answer: Total sleep time divided by time in bed × 100
Sleep efficiency = (TST / TIB) × 100; a value ≥85% is generally considered normal in adults.
Question 2: Which sleep stage is most suppressed by benzodiazepine hypnotics?
- N3 slow-wave sleep (Correct answer)
- N1 sleep
- N2 sleep
- REM sleep
Correct answer: N3 slow-wave sleep
Benzodiazepines markedly reduce N3 (slow-wave sleep) amplitude and duration while increasing spindle activity in N2.
Question 3: A 35-year-old has a sleep onset latency to REM (SOREMP) of 8 minutes on overnight PSG. This finding is most suggestive of:
- Narcolepsy (Correct answer)
- Obstructive sleep apnea
- Idiopathic insomnia
- Delayed sleep phase disorder
Correct answer: Narcolepsy
A REM latency of ≤20 minutes (SOREMP) on nocturnal PSG is a key diagnostic criterion for narcolepsy.
Question 4: In healthy young adults, what percentage of total sleep time is typically spent in REM sleep?
- 20–25% (Correct answer)
- 5–10%
- 45–55%
- 30–35%
Correct answer: 20–25%
REM sleep constitutes approximately 20–25% of TST in healthy young adults, decreasing with advancing age.
Question 5: The phenomenon of 'REM rebound' after REM-suppressing medication withdrawal is best explained by:
- Homeostatic pressure accumulating during REM deprivation (Correct answer)
- Circadian rhythm advancement
- Increased slow-wave sleep drive
- Cholinergic receptor downregulation
Correct answer: Homeostatic pressure accumulating during REM deprivation
When REM-suppressing drugs are withdrawn, accumulated homeostatic REM pressure results in increased REM percentage and shortened REM latency.
Question 6: Which of the following is the correct AASM criterion for scoring N3 sleep?
- ≥20% of the epoch consists of waves 0.5–2 Hz with amplitude >75 µV (Correct answer)
- ≥50% of the epoch consists of waves 0.5–2 Hz with amplitude >75 µV
- Any delta waves >100 µV regardless of proportion
- Continuous delta waves with sleep spindles present
Correct answer: ≥20% of the epoch consists of waves 0.5–2 Hz with amplitude >75 µV
AASM rules require that ≥20% of the 30-second epoch contain slow waves (0.5–2 Hz, peak-to-peak >75 µV) to score N3.
Question 7: During an MSLT nap, a patient falls asleep in 4 minutes and enters REM sleep. How many such SOREMPs across 5 naps are needed to support a narcolepsy diagnosis?
- ≥2 SOREMPs (Correct answer)
- 1 SOREMP
- 3 SOREMPs
- 4 SOREMPs
Correct answer: ≥2 SOREMPs
ICSD-3 criteria require a mean sleep latency ≤8 minutes AND ≥2 SOREMPs across 5 MSLT nap opportunities to diagnose narcolepsy.
EEG Sleep Staging and Sleep EEG 5
Sleep efficiency is calculated as: