EEG Sleep Staging and Sleep EEG 2 — Questions and Answers
Question 1: A K-complex is defined as a well-delineated negative sharp wave followed by a positive component with a total duration of at least:
- 0.5 seconds (Correct answer)
- 1.0 second
- 1.5 seconds
- 0.25 seconds
Correct answer: 0.5 seconds
AASM criteria define a K-complex as a biphasic wave lasting ≥0.5 seconds, maximal over frontal regions.
Question 2: Hypnagogic hypersynchrony in children refers to:
- High-amplitude 3–4.5 Hz rhythmic activity at drowsiness onset (Correct answer)
- Sleep spindles exceeding 15 Hz
- Delta bursts during REM
- K-complexes occurring in clusters
Correct answer: High-amplitude 3–4.5 Hz rhythmic activity at drowsiness onset
Hypnagogic hypersynchrony is a normal pediatric variant of high-amplitude slow rhythmic activity seen during drowsiness that should not be mistaken for a seizure.
Question 3: Sleep spindles are generated primarily by thalamocortical circuits involving which thalamic nucleus?
- Reticular nucleus of the thalamus (Correct answer)
- Lateral geniculate nucleus
- Pulvinar
- Centromedian nucleus
Correct answer: Reticular nucleus of the thalamus
The thalamic reticular nucleus acts as a pacemaker for sleep spindles through rhythmic inhibitory postsynaptic potentials to relay nuclei.
Question 4: During a routine EEG, the patient closes his eyes and 10 Hz activity appears posteriorly. When he opens his eyes this activity disappears. This is consistent with:
- Normal alpha rhythm with eye-opening attenuation (Correct answer)
- Occipital seizure activity
- Posterior slow waves of youth
- Breach rhythm
Correct answer: Normal alpha rhythm with eye-opening attenuation
Alpha rhythm (8–13 Hz) generated in the occipital cortex is reactive to eye opening and represents a normal, awake, relaxed EEG finding.
Question 5: Which of the following best describes POSTS (Positive Occipital Sharp Transients of Sleep)?
- Surface-positive sharply contoured occipital waves occurring in NREM sleep (Correct answer)
- Negative temporal sharp waves in REM
- Frontal spike discharges during N3
- Alpha intrusions during N2
Correct answer: Surface-positive sharply contoured occipital waves occurring in NREM sleep
POSTS are surface-positive sharp waves in the occipital regions during NREM sleep and are a normal variant that must not be misread as epileptiform activity.
Question 6: The cyclic alternating pattern (CAP) in NREM sleep is significant because it:
- Reflects sleep instability and arousal fluctuations (Correct answer)
- Indicates Stage REM entry
- Confirms absence epilepsy diagnosis
- Marks the onset of Stage N3
Correct answer: Reflects sleep instability and arousal fluctuations
CAP is a periodic EEG activity during NREM that reflects cyclic arousal oscillations, and elevated CAP rates are associated with fragmented, non-restorative sleep.
EEG Sleep Staging and Sleep EEG 2
A K-complex is defined as a well-delineated negative sharp wave followed by a positive component with a total duration of at least: