Sleep-Stage Scoring

BY

AHMAD YOUNES

PROFESSOR OF THORACIC MEDICINEMansoura Faculty Of Medicine

Definition• Sleep is an ACTIVE process. • Sleep: is a state of behavioral quiescence accompanied

by an elevated arousal threshold and a species-specific sleep posture (recumbent sleep posture, closed eyes, diminished responsiveness to external stimuli and decrease in or absence of movements)

• It is a reversible state of unresponsiveness to stimuli of the outside world and to responses within the brain which underlie perception. 

Sleep Architecture 

  

Beta Activity

• A waveform of 14 to 30 Hz• Originates in the frontal and central regions• Present during wakefulness and drowsiness• May become persistent during drowsiness,

diminish during SWS, and reemerge during REM sleep

• Enhanced or persistent activity suggests use of sedative-hypnotic medications

Alpha Activity• A waveform of 8 to 14 Hz• Originates in the parieto-occipital regions bilaterally• Seen during quite alertness with eyes closed• Eye opening causes the alpha waves to decrease in

amplitude • Has a crescendo decrescendo appearance• Has diminished frequency with aging

Theta Activity

• A waveform of 3 to 7 Hz• Originates in the central vertex region• The most common sleep frequency

Delta Activity• A waveform of 0.5 to 2 Hz• Seen predominantly in the frontal region• Delta activity has an amplitude criterion of 75 µV• Stage-3 sleep defined when 20% to 50% of the

epoch is scored as delta activity• Stage-4 sleep defined when >50% of the epoch is

scored as delta activity• In AASM ,stage 3,4 are named N3

Sleep Spindles

• A waveform of 12 to 14 Hz• Originates in the central vertex region• Has a duration criterion of 0.5 to 1.5 seconds• Typically occurs in stage-2 sleep but can be seen in

other stages

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K Complexes

• Defined as slow waves, with a biphasic morphology (first negative and then positive deflection)

• Predominantly central vertex in origin• Duration must be at least 0.5 seconds• Indicative of stage-2 sleep

Vertex sharp wave :• Sharply contoured waves

• Duration < 0.5 sec

• Maximal over the central region (derivations containing C3, C4, Cz) and distinguishable from the background activity (higher amplitude).

• Occurs in stage N1 often near transition to stage N2

Saw-tooth waves • Saw-tooth waves occur during REM sleep,

although they are not always present during this sleep stage.

• They are triangular waves of 2 to 6 Hz of highest amplitude in the central derivations.

• The presence of saw-tooth waves is not required to score stage R.

Stage W Rules (2007)A. Score epochs as stage W when > 50% of the epoch

has alpha rhythm over the occipital region.• EOG: SEM are characteristic of eyes-closed stage W

but are not required criteria for scoring stage W.• Chin EMG: The chin EMG amplitude is variable but is

often higher than during sleep.

B. Score epochs without visually discernible alpha rhythm as stage W if any of the following are present:

• Eye blinks are present at a frequency of 0.5–2 Hz.• Reading eye movements are present.• Irregular conjugate REMs are present associated with

normal or high chin muscle tone

• Stage W. A 30-second epoch is shown containing REMs, blinks, relatively high chin electromyographic (EMG) activity, and the absence of discernible alpha activity.

. Note that alpha rhythm is more prominent in the occipital derivation and present for more than 50% of the epoch. Slow eye movements (SEMs) are present in this epoch. Although characteristic, they are not a criterion for scoring stage W or N1 in patients producing alpha rhythm with eye closure.

•Stage N1Non Rapid Eye Movement

A. In subjects who generate alpha rhythm with eye closure, score stage N1 if

1. EEG: Alpha rhythm is attenuated and replaced by low amplitude mixed-frequency (4–7 Hz) activity for > 50% of the epoch (<50% of the epoch has alpha rhythm).

a. EEG: Vertex sharp waves may be present but are not required for scoring stage N1.

2. EOG: Slow eye movements may be present in N1, but these are not required for scoring N1.

3. Chin EMG: Variable amplitude, often lower than wake.

Stage N1 Non Rapid Eye Movement

B. In subjects who do NOT generate alpha rhythm with eye closure, score stage N1 commencing with the earliest of any of the following phenomena:

• The EEG shows 4- to 7-Hz activity with slowing of background frequencies by 1 Hz or greater from those of stage W.

• Vertex sharp waves.• Slow eye movements

Transition between wake and stage N 1 sleep

Stage-1 Sleep: Low-voltage, mixed-frequency theta activity is present, as demarcated by the arrows (1). Slow rolling eye movements are evident (2) and so is a more substantial reduction in chin EMG tone (3), which happens to capture activity from the ECG leads in the form of an ECG artifact (4).

Stage N2 A. RULE DEFINING THE START OF N2 SLEEP

1. EEG: Begin scoring stage N2 (in the absence of evidence of N3, SWA < 6 sec) if one or both of the following occur during the first half of the current epoch or the last half of the previous epoch:

– One or more K complexes unassociated with arousals or– One or more trains of sleep spindles.

2. EEG: If the only K complexes present are associated with arousal, continue to score stage N1.

3. EOG: Usually no eye movements, slow eye movements have ended.

4. Chin EMG: Variable, usually less than wake.

Stage N2B. RULE DEFINING THE CONTINUATION OF STAGE N2 SLEEP

1. Continue to score epochs with low-amplitude mixed-frequency EEG activity without K complexes or sleep spindles as stage N2 if they are preceded by an epoch containing:– K complexes unassociated with arousals or– Sleep spindles.

C. RULE DEFINING THE END OF STAGE N2 SLEEP

1. End stage N2 sleep when one of the following events occurs:• Transition to stage W, stage N3, or stage R.• An arousal (change to stage N1 until a K complex unassociated

with an arousal or a sleep spindle occurs).• A major body movement followed by SEM and low-amplitude

mixed-frequency EEG without non-arousal associated K complexes or sleep spindles then score epochs after the major body movement as N1.

i. If no slow eye movements follow the major body movement, score the epoch as stage N2.

ii. The epoch containing the body movement is scored using criteria for major body movements.

Summary of scoring N2

The dark horizontal bars at the top denote the presence of slow wave activity (>75 μV peak to peak, 0.5–2.0 Hz). The total duration of slow wave activity is less than 6 seconds. The dotted lines in F4-M1 are 75 μV apart.

End of Stage N2: Effect of MBM

Stage N3 Rules (previously stage 3,4)A. Score stage N3 when 20% or more of an epoch

consists of SWA, irrespective of age (20% of 30-sec epoch = 6 sec).

1. EEG: SWA ≥ 20% of the epoch (≥6 sec), sleep spindles may be present in stage N3.

2. EOG: Eye movements are not typically seen during stage N3 sleep.

3. EMG: In stage N3, the chin EMG is of variable amplitude, often lower than in stage N2 sleep and sometimes as low as in stage R sleep.

Stage R Rule A (Definite REM Sleep)A. Score stage R sleep in epochs with all the following phenomena (definite or

unequivocal REM epochs):• Low-amplitude mixed-frequency EEG.• Low chin EMG tone (usually at the lowest level of the entire recording).• REMs.

Notes:– Low chin EMG tone: The baseline EMG activity in the chin derivation is

no higher than in any other sleep stage – REMs: Conjugate, irregular, sharply peaked eye movements with an

initial deflection usually lasting < 500 m sec.– Definite stage R (unequivocal stage R) = EEG without spindles or K

complexes, REMs, low chin EMG activity (at REM level).

REM sleep is sometimes divided into

•

Phasic-REM (P-REM) sleep is characterized by phasic twitching in the EMG channel occurring concurrently with bursts of REMs, suggestively correlated with dream content. The phasic EMG twitching in this stage involves very short muscle twitches that may occur in the middle ear muscles, genioglossal muscle, and facial muscles.

• Tonic-REM (T-REM) sleep generally consists of low-voltage activated EEG and is characterized by a marked decrease in skeletal muscle electromyographic activity, without obvious EOG activity.

Continuation and End of Stage R (REM Rules B and C)

B. Continuation of stage R: Continue to score stage R sleep, even in the absence of REMs, for epochs following one or more epochs of stage R as defined above (unequivocal REM epochs), if:-

– EEG continues to show low-amplitude mixed-frequency activity without K complexes or sleep spindles.

– Chin EMG: Tone remains low (at REM level).

C. End of stage R.1. Stop scoring stage R sleep when one or more of the following occur:• There is a transition to stage W or N3.• An increase in chin EMG tone above the level of stage R is seen and criteria

for stage N1 are met.• An arousal occurs followed by low-amplitude mixed-frequency EEG and SEM

(score as stage N1; if no SEM and chin EMG tone remains low, continue to score as stage R).

• A major body movement followed by SEM and low-amplitude mixed-frequency EEG without non-arousal-associated K complexes or sleep spindles (score the epoch after the major body movement as stage N1; if no SEM and the EMG tone remains low, continue to score as stage R; the epoch containing the body movement is scored using major body movement criteria).

• One or more non-arousal-associated K complexes or sleep spindles are present in the first half of the epoch in the absence of REMs, even if chin EMG tone remains low (score as stage N2).

Transitions between Stage N2 and Stage R (REM Rule D):-

D. Score epochs of transition between stage N2 and stage R as follows:• In epochs between definite N2 and definite stage R, score stage R (even

in the absence of REMs) if:– There is a distinct drop in the chin EMG to the REM level in the first half of

the epoch.– There is absence of non-arousal-associated K complexes and sleep

spindles.

• In epochs between definite stage N2 and definite stage R, score stage N2 if all the following are met:– There is a distinct drop in the chin EMG to the REM level in the first half of

the epoch.– There is the presence of non-arousal-associated K complexes and sleep

spindles.– Absence of REMs.

• In epochs between definite N2 and definite stage R, score stage R even in the absence of REMs if:– There is a low chin EMG activity (at the REM level) for the entire epoch.– There is absence of nonarousal-associated K complexes and sleep spindles.

Epochs with a Mixture of Sleep Spindles/K Complexes and REMs

• Epochs with REMs and low chin EMG tone (at the REM level) that would be scored as stage R except for the presence of either K complexes or sleep spindles are still scored as stage R.

• Subsequent contiguous epochs without REMs but continued low chin EMG are scored by the REM continuation and end rules (REM rules B and C,) or stage N2 rules.

Scoring Rules for Major Body Movements

• Score stage W if alpha rhythm is present for part of the epoch (even if < 15 sec in duration).

• Score stage W in the absence of alpha rhythm if an epoch scorable as stage W either precedes or follows the epoch with the major body movement.

• If neither A or B apply, score an epoch with a major body movement as the same stage as the epoch that follows it.

Arousal RulesNREM AROUSAL CRITERIA• Score an arousal during sleep stages N1, N2, and N3 if there is an

abrupt shift of EEG frequency including alpha, theta, and/or frequencies greater than 16 Hz (but not spindles) that lasts at least 3 seconds, with at least 10 seconds of stable sleep preceding the change.

REM AROUSAL CRITERIA• Score an arousal during sleep stage R if there is an abrupt shift

of EEG frequency including alpha, theta, and/or frequencies greater than 16 Hz (but not spindles) that lasts at least 3 seconds, with at least 10 seconds of stable sleep preceding the change. AND

• There is a concurrent increase in submental EMG lasting at least 1 second in addition to the required EEG changes.

COMMON VARIANTS SEEN DURING SLEEP MONITORING

1-Alpha Non–Rapid Eye Movement Sleep Anomaly

The finding of prominent alpha activity (8–13 Hz) during non–rapid eye movement (NREM) sleep is often called alpha sleep, alpha intrusion, or alpha-delta sleep (if noted in association with stage N3).

It makes sleep staging more challenging.

The alpha activity may be more prominent in frontal than occipital regions in contrast to the typical alpha rhythm.

2-Drug Spindles

• Patients who are taking benzodiazepine receptor agonists (BZRAs) often have increased sleep spindle activity

• Sleep spindle activity has a frequency of 11 to 16 Hz.

• Drug spindles often have a frequency in the higher end of the range.

• Benzodiazepines are associated with a decrease in slow wave amplitude (less stage N3 sleep) and an increase in higher EEG frequencies.

Eye Movements Associated with Selective Serotonin Reuptake Inhibitor

• Slow eye movements are typically present during stage W with the eyes closed and during stage N1. They typically vanish with the onset of stage N2.

• In patients taking selective serotonin reuptake inhibitors (SSRIs), a mixture of slow and more rapid eye movements may persist into stage N2 or stage N3. Because this phenomenon was first described with patients on fluoxetine, such eye movements are often called “Prozac eyes.”