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Practical aspects of scoring sleep in children
PAEDIATRIC RESPIRATORY REVIEWS (2006) 7S, S50–S54
D – Sleep: A Primer For Beginners
Practical aspects of scoring sleep in children Leila Kheirandish-Gozal* Division of Pediatric Sleep Medicine, Department of Pediatrics, University of Louisville, 571 S. Floyd Street, Suite 419, Louisville, KY 40202, USA Summary As the indications for pediatric polysomnography expand, and the high prevalence of sleep disorders in childhood becomes increasingly recognized, there is a need for enabling practicing physicians to identify correctly events occurring in polysomnographic tracings. A summary description of the most salient features of the various sleep states and of the characteristics and visual patterns corresponding to frequent events among several recognized diseases is provided. ß 2006 Published by Elsevier Ltd.
DIAGNOSTIC SLEEP STUDY Sleep recordings are usually conducted in a sleep laboratory. The overnight polysomnogram (PSG) is by definition the continuous and simultaneous recording of physiological variables, i.e., EEG, EOG, EMG, EKG, respiratory air flow, gas exchange measurements, respiratory effort, limb movements, and other electrophysiological variables. At least 6 hours of sleep are needed for adequate evaluation of sleep complaints. All recorded data is then analyzed in 30 second epochs, and this selection is more out of convenience rather than be based on any scientific evidence, since the process of sleep represents a continuum as well as a dynamic process. Each 30-sec epoch is then assigned a particular sleep stage, with sleep being divided into two states: Rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. NREM sleep is further subdivided into four NREM stages 1, 2, 3, and 4 (with stages 3 and 4 being also termed Slow-Wave Sleep). The typical polysomnographic montage recommended for use in children is provided in more detail in Table 1.
SLEEP CYCLES As mentioned above, sleep is a dynamic process and consists in periodic alternation of sleep stages in a very deterministic * Tel.: +1 502 852 5262; Fax: +1 502 852 5264. E-mail address: [email protected]. 1526-0542/$ – see front matter ß 2006 Published by Elsevier Ltd. doi:10.1016/j.prrv.2006.04.176
fashion. The first REM sleep period usually occurs about 70 to 90 minutes after sleep onset. In a healthy child, the first cycle begins by moving from wakefulness to non-REM sleep. The first REM period follows the first period of non-REM sleep. The two sleep states continue to alternate throughout the night with an average period of about 90–120 minutes intervals. A night of normal sleep usually consists of 4– 6 non-REM/REM sleep cycles. A complete sleep cycle takes Table 1
Typical Polysomnographic Montage In Children
Electroencephalogram - minimum 2 channels (central and occipital leads); ideally 4-8 channels Chin EMG Anterior tibial EMG – left and right Electro-oculogram – left and right Electrocardiogram Pulse oximeter and pulse waveform Oronasal airflow thermistor Nasal pressure catheter End-tidal capnography and waveform Chest and abdominal respiratory inductance plethysmography Body position sensor Tracheal sound sensor or microphone Time-synchronized video recordings Notes: In younger children, consider transcutaneous carbon dioxide tension measurements. Esophageal catheters are used in some laboratories instead of nasal pressure catheters to assess respiratory effort.
PRACTICAL ASPECTS OF SCORING SLEEP IN CHILDREN
S51
Figure 1 Polysomnographic record illustrating the transition from waking to sleep stage 1 in a child. Please note the hypnic jerk and the slow eye movements that follow.
90 to 110 minutes on average. As the night progresses, REM sleep periods increase in length while the density of slow wave sleep decreases. Past infancy, about 50% of the total sleep duration will be spent in stages 1–2, NREM, with REM sleep occupying about 20–25% of the total sleep time, and the remaining 20–30% represented as slow wave sleep. However, infants spend about half of their sleep time in REM sleep. The polygraphic characteristics that allow for designation of a particular sleep stage are provided as follows: NREM sleep is characterized by slower and larger brain waves:
Figure 2
Stage 1 - During stage 1, slow rolling eye movements and reductions in muscle activity are observed. Theta brain waves with a frequency of greater than 13 Hz (Hertz) are dominant. Patients awakened from stage 1 sleep often remember fragmented visual images. Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall. See example in Fig. 1. Stage 2 - Is characterized by occasional bursts of rapid frequency waves called sleep spindles (10–13 Hz) and K complexes (sharp, negative, high-voltage EEG waves, followed by a slower, positive component) against a relatively low-voltage, mixed-frequency EEG background. The EMG
Polysomnographic record illustrating sleep stage 2 in a child. An example of a K complex is provided within the circle.
S52
L. KHEIRANDISH-GOZAL
Figure 3 Polysomnographic record illustrating sleep stage 4 in a child. Note dominating slow wave pattern and regular cardiac and respiratory features.
signal will be present but reduced compared to wakefulness. (See Fig. 2) Stages 3–4 - Are defined by high -amplitude delta waves occupying at least 20% of 30 sec epoch in stage3 and more than 50% of the epoch in stage 4. Deep sleep usually happen in the first third of the sleep period and It is very difficult to wake someone during stages 3 and 4. There is no eye movement or muscle activity. Children often experience sleep-related enuresis, night terrors and sleep walking during deep sleep. See Fig. 3. REM sleep - Rapid eye movement is characterized by a low voltage, fast frequency brain waves which resemble an active, awake EEG pattern. The electromyogram (EMG) shows inactivity of all voluntary muscles except the extra
ocular muscles and diaphragm. The lack of appropriate muscle atonia during REM sleep is considered abnormal, and may cause REM Behavior Disorder. (See Fig. 4 for typical REM stage) Arousal - Abrupt shift in EEG frequency, which may include theta, alpha and /or frequencies greater than 16 Hz, but not spindles’’, which is at least three seconds in duration (see Fig. 5).
RESPIRATORY EVENTS Central apnea - absence of airflow and inspiratory effort for at least 10 sec.
Figure 4 Polysomnographic record illustrating sleep stage REM in a child. Note dominating high frequency EEG pattern, rapid eye movements in the EOG channels and very low to near absent EMG activity.
PRACTICAL ASPECTS OF SCORING SLEEP IN CHILDREN
S53
Figure 5 Polysomnographic record illustrating an obstructive hypopnea in a child. Please note paradoxical breathing (in square frame) and EEG arousal (circle frame and reduced pulse oximeter plethysmographic signal in bottom channel) followed by irregular breathing.
Obstructive apnea - cessation of airflow (at least 2 breaths) in the presence of continued inspiratory effort during sleep. Mixed apnea - central apnea then becoming an obstructive apnea or vice-versa. Hypopnea - Reduction of airflow >30% associated with oxygen desaturation or arousal (see Fig. 5).
PERIODIC LIMB MOVEMENT PLM is defined as the occurrence of periodic episodes of repetitive and highly stereotyped limb movements
Figure 6
during sleep. The movements are often associated with a partial arousal or awakening. Between the episodes, the legs are still. Periodic Limb Movement Disorder (PLMD), also called nocturnal myoclonus, is a sleep disorder where the patient moves involuntarily during sleep. It can range from a small amount in the ankles and toes to wild flailing of all four limbs. These movements, which are more common in the legs than arms, occur for between 0.5 and 5 seconds, recurring at intervals of 5 to 90 seconds (Fig. 6). A formal diagnosis of PLMD requires a PLM index >5/hr sleep with evidence for partial arousals or awakenings after such events.
Polysomnographic record illustrating a cluster of periodic leg movement events (one of the events is shown within the circle).
S54
L. KHEIRANDISH-GOZAL
Figure 7
Polysomnographic record illustrating bruxism in a child. Note intense EMG activity in all channels.
Figure 8 Polysomnographic record illustrating EEG patterns in a child with spike and wave activity. Please note that these events (an example is shown in the circle) do not coincide in time with the ECG channel (top channel in the recording).
OTHER POTENTIAL FREQUENT FINDINGS Bruxism The habitual involuntary grinding or clenching of the teeth, usually during sleep. It is characterized mainly by rhythmic masticatory muscle activity (see Fig. 7).
Spike and wave Recognition of spike and wave patterns potentially suggestive of seizure activity is an important element in the scoring of sleep studies (see example of EEG recording in Fig. 8)
D – Sleep: A Primer For Beginners
Practical aspects of scoring sleep in children Leila Kheirandish-Gozal* Division of Pediatric Sleep Medicine, Department of Pediatrics, University of Louisville, 571 S. Floyd Street, Suite 419, Louisville, KY 40202, USA Summary As the indications for pediatric polysomnography expand, and the high prevalence of sleep disorders in childhood becomes increasingly recognized, there is a need for enabling practicing physicians to identify correctly events occurring in polysomnographic tracings. A summary description of the most salient features of the various sleep states and of the characteristics and visual patterns corresponding to frequent events among several recognized diseases is provided. ß 2006 Published by Elsevier Ltd.
DIAGNOSTIC SLEEP STUDY Sleep recordings are usually conducted in a sleep laboratory. The overnight polysomnogram (PSG) is by definition the continuous and simultaneous recording of physiological variables, i.e., EEG, EOG, EMG, EKG, respiratory air flow, gas exchange measurements, respiratory effort, limb movements, and other electrophysiological variables. At least 6 hours of sleep are needed for adequate evaluation of sleep complaints. All recorded data is then analyzed in 30 second epochs, and this selection is more out of convenience rather than be based on any scientific evidence, since the process of sleep represents a continuum as well as a dynamic process. Each 30-sec epoch is then assigned a particular sleep stage, with sleep being divided into two states: Rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. NREM sleep is further subdivided into four NREM stages 1, 2, 3, and 4 (with stages 3 and 4 being also termed Slow-Wave Sleep). The typical polysomnographic montage recommended for use in children is provided in more detail in Table 1.
SLEEP CYCLES As mentioned above, sleep is a dynamic process and consists in periodic alternation of sleep stages in a very deterministic * Tel.: +1 502 852 5262; Fax: +1 502 852 5264. E-mail address: [email protected]. 1526-0542/$ – see front matter ß 2006 Published by Elsevier Ltd. doi:10.1016/j.prrv.2006.04.176
fashion. The first REM sleep period usually occurs about 70 to 90 minutes after sleep onset. In a healthy child, the first cycle begins by moving from wakefulness to non-REM sleep. The first REM period follows the first period of non-REM sleep. The two sleep states continue to alternate throughout the night with an average period of about 90–120 minutes intervals. A night of normal sleep usually consists of 4– 6 non-REM/REM sleep cycles. A complete sleep cycle takes Table 1
Typical Polysomnographic Montage In Children
Electroencephalogram - minimum 2 channels (central and occipital leads); ideally 4-8 channels Chin EMG Anterior tibial EMG – left and right Electro-oculogram – left and right Electrocardiogram Pulse oximeter and pulse waveform Oronasal airflow thermistor Nasal pressure catheter End-tidal capnography and waveform Chest and abdominal respiratory inductance plethysmography Body position sensor Tracheal sound sensor or microphone Time-synchronized video recordings Notes: In younger children, consider transcutaneous carbon dioxide tension measurements. Esophageal catheters are used in some laboratories instead of nasal pressure catheters to assess respiratory effort.
PRACTICAL ASPECTS OF SCORING SLEEP IN CHILDREN
S51
Figure 1 Polysomnographic record illustrating the transition from waking to sleep stage 1 in a child. Please note the hypnic jerk and the slow eye movements that follow.
90 to 110 minutes on average. As the night progresses, REM sleep periods increase in length while the density of slow wave sleep decreases. Past infancy, about 50% of the total sleep duration will be spent in stages 1–2, NREM, with REM sleep occupying about 20–25% of the total sleep time, and the remaining 20–30% represented as slow wave sleep. However, infants spend about half of their sleep time in REM sleep. The polygraphic characteristics that allow for designation of a particular sleep stage are provided as follows: NREM sleep is characterized by slower and larger brain waves:
Figure 2
Stage 1 - During stage 1, slow rolling eye movements and reductions in muscle activity are observed. Theta brain waves with a frequency of greater than 13 Hz (Hertz) are dominant. Patients awakened from stage 1 sleep often remember fragmented visual images. Many also experience sudden muscle contractions called hypnic myoclonia, often preceded by a sensation of starting to fall. See example in Fig. 1. Stage 2 - Is characterized by occasional bursts of rapid frequency waves called sleep spindles (10–13 Hz) and K complexes (sharp, negative, high-voltage EEG waves, followed by a slower, positive component) against a relatively low-voltage, mixed-frequency EEG background. The EMG
Polysomnographic record illustrating sleep stage 2 in a child. An example of a K complex is provided within the circle.
S52
L. KHEIRANDISH-GOZAL
Figure 3 Polysomnographic record illustrating sleep stage 4 in a child. Note dominating slow wave pattern and regular cardiac and respiratory features.
signal will be present but reduced compared to wakefulness. (See Fig. 2) Stages 3–4 - Are defined by high -amplitude delta waves occupying at least 20% of 30 sec epoch in stage3 and more than 50% of the epoch in stage 4. Deep sleep usually happen in the first third of the sleep period and It is very difficult to wake someone during stages 3 and 4. There is no eye movement or muscle activity. Children often experience sleep-related enuresis, night terrors and sleep walking during deep sleep. See Fig. 3. REM sleep - Rapid eye movement is characterized by a low voltage, fast frequency brain waves which resemble an active, awake EEG pattern. The electromyogram (EMG) shows inactivity of all voluntary muscles except the extra
ocular muscles and diaphragm. The lack of appropriate muscle atonia during REM sleep is considered abnormal, and may cause REM Behavior Disorder. (See Fig. 4 for typical REM stage) Arousal - Abrupt shift in EEG frequency, which may include theta, alpha and /or frequencies greater than 16 Hz, but not spindles’’, which is at least three seconds in duration (see Fig. 5).
RESPIRATORY EVENTS Central apnea - absence of airflow and inspiratory effort for at least 10 sec.
Figure 4 Polysomnographic record illustrating sleep stage REM in a child. Note dominating high frequency EEG pattern, rapid eye movements in the EOG channels and very low to near absent EMG activity.
PRACTICAL ASPECTS OF SCORING SLEEP IN CHILDREN
S53
Figure 5 Polysomnographic record illustrating an obstructive hypopnea in a child. Please note paradoxical breathing (in square frame) and EEG arousal (circle frame and reduced pulse oximeter plethysmographic signal in bottom channel) followed by irregular breathing.
Obstructive apnea - cessation of airflow (at least 2 breaths) in the presence of continued inspiratory effort during sleep. Mixed apnea - central apnea then becoming an obstructive apnea or vice-versa. Hypopnea - Reduction of airflow >30% associated with oxygen desaturation or arousal (see Fig. 5).
PERIODIC LIMB MOVEMENT PLM is defined as the occurrence of periodic episodes of repetitive and highly stereotyped limb movements
Figure 6
during sleep. The movements are often associated with a partial arousal or awakening. Between the episodes, the legs are still. Periodic Limb Movement Disorder (PLMD), also called nocturnal myoclonus, is a sleep disorder where the patient moves involuntarily during sleep. It can range from a small amount in the ankles and toes to wild flailing of all four limbs. These movements, which are more common in the legs than arms, occur for between 0.5 and 5 seconds, recurring at intervals of 5 to 90 seconds (Fig. 6). A formal diagnosis of PLMD requires a PLM index >5/hr sleep with evidence for partial arousals or awakenings after such events.
Polysomnographic record illustrating a cluster of periodic leg movement events (one of the events is shown within the circle).
S54
L. KHEIRANDISH-GOZAL
Figure 7
Polysomnographic record illustrating bruxism in a child. Note intense EMG activity in all channels.
Figure 8 Polysomnographic record illustrating EEG patterns in a child with spike and wave activity. Please note that these events (an example is shown in the circle) do not coincide in time with the ECG channel (top channel in the recording).
OTHER POTENTIAL FREQUENT FINDINGS Bruxism The habitual involuntary grinding or clenching of the teeth, usually during sleep. It is characterized mainly by rhythmic masticatory muscle activity (see Fig. 7).
Spike and wave Recognition of spike and wave patterns potentially suggestive of seizure activity is an important element in the scoring of sleep studies (see example of EEG recording in Fig. 8)