Sleep-Stage Scoring
BY
AHMAD YOUNES
PROFESSOR OF THORACIC MEDICINE
Mansoura 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
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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
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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
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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
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
10
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 N2
B. 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 30sec 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
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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 mixedfrequency 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
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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
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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 Rules
NREM 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.”