RST Sleep Stage and Event Scoring Questions and Answers — Questions and Answers
Question 1: A 30-second epoch of sleep contains a clear K-complex in the first 10 seconds. The remainder of the epoch is characterized by low-amplitude, mixed-frequency EEG, a sustained low chin EMG tone, and intermittent rapid eye movements. How should this epoch be scored?
- Stage N2
- Stage R (Correct answer)
- Stage N1
- Stage W
Correct answer: Stage R
According to the AASM Manual, if the criteria for Stage R (low-amplitude, mixed-frequency EEG; low chin EMG; and rapid eye movements) are met for more than half of an epoch, the epoch is scored as Stage R. This rule takes precedence even if hallmark features of other stages, such as a K-complex from Stage N2, are also present within the same epoch.
Question 2: According to the AASM Manual for the Scoring of Sleep and Associated Events, which of the following criteria must be met to score an epoch as Stage N3?
- The epoch contains at least 3 K-complexes and 2 sleep spindles.
- At least 50% of the epoch contains EEG activity of 0.5 Hz or less with amplitudes of at least 50 µV.
- At least 20% of the epoch contains EEG activity of 2 Hz or less with peak-to-peak amplitudes of at least 75 µV. (Correct answer)
- The epoch contains at least one delta wave with a frequency of 1 Hz and an amplitude of 100 µV.
Correct answer: At least 20% of the epoch contains EEG activity of 2 Hz or less with peak-to-peak amplitudes of at least 75 µV.
The AASM defines Stage N3 (slow-wave sleep) as an epoch in which 20% or more (i.e., 6 seconds or more) of the epoch consists of slow-wave activity. Slow-wave activity is defined as waves with a frequency of 2 Hz or less and a peak-to-peak amplitude of 75 µV or greater, measured over the frontal EEG derivations.
Question 3: A technologist is scoring a respiratory event and observes a >30% drop in the nasal pressure signal for 12 seconds. This event is associated with a 4% oxygen desaturation from the pre-event baseline. According to the AASM's acceptable scoring criteria, how should this event be scored?
- Obstructive Apnea
- Respiratory Effort-Related Arousal (RERA)
- Hypopnea (Correct answer)
- Central Apnea
Correct answer: Hypopnea
The AASM's acceptable criteria for scoring a hypopnea include a drop in the nasal pressure signal by ≥30% of the pre-event baseline for a duration of ≥10 seconds, associated with a ≥4% oxygen desaturation. Since this event has a >30% signal drop for >10 seconds and is associated with a 4% desaturation, it meets the criteria for a hypopnea.
Question 4: Which of the following is a required criterion for scoring a series of events as Periodic Limb Movements in Sleep (PLMS)?
- A minimum of 2 consecutive limb movements.
- The period between consecutive movements must be less than 5 seconds.
- The series must be associated with an oxygen desaturation of at least 3%.
- The duration of each limb movement must be between 0.5 and 10 seconds. (Correct answer)
Correct answer: The duration of each limb movement must be between 0.5 and 10 seconds.
According to AASM scoring rules, a PLMS series requires a minimum of 4 consecutive limb movements. Each individual limb movement must have a duration of 0.5 to 10 seconds. The period between the onsets of consecutive movements must be between 5 and 90 seconds. There is no requirement for an associated oxygen desaturation.
Question 5: During Stage N2 sleep, a technologist observes an abrupt shift in EEG frequency to alpha activity lasting for 4 seconds. This shift is preceded by at least 10 seconds of stable sleep. How should this 4-second event be scored?
- Arousal (Correct answer)
- Epoch should be rescored as Stage W
- EEG artifact
- Micro-sleep
Correct answer: Arousal
The AASM defines an arousal during NREM sleep as an abrupt shift in EEG frequency (including alpha, theta, and/or frequencies greater than 16 Hz) that lasts for at least 3 seconds and is preceded by at least 10 seconds of stable sleep. This 4-second event meets these criteria perfectly.
Question 6: When scoring for sleep bruxism, what is the minimum required increase in chin EMG amplitude above baseline to score a phasic (rhythmic) bruxism event?
- At least 10% of the maximum amplitude seen during calibration.
- An amplitude that is at least twice the amplitude of the background EMG. (Correct answer)
- A sustained amplitude of at least 50 µV for 2 seconds.
- An amplitude that is at least 50% greater than the amplitude during REM sleep.
Correct answer: An amplitude that is at least twice the amplitude of the background EMG.
The AASM criteria for scoring phasic sleep bruxism require bursts of EMG activity that are at least twice (a 100% increase) the amplitude of the background chin EMG. These bursts must also occur rhythmically (at least 3 in a series), with each burst lasting 0.25-2.0 seconds.
RST Sleep Stage and Event Scoring Questions and Answers
A 30-second epoch of sleep contains a clear K-complex in the first 10 seconds.
The remainder of the epoch is characterized by low-amplitude, mixed-frequency EEG, a sustained low chin EMG tone, and intermittent rapid eye movements.
How should this epoch be scored?