Somnologie

, Volume 21, Supplement 1, pp 9–18

Scoring of pediatric polysomnograms

Theory and practice
Schwerpunkt

DOI: 10.1007/s11818-016-0071-7

Cite this article as:
Scholle, S. Somnologie (2017) 21(Suppl 1): 9. doi:10.1007/s11818-016-0071-7

Abstract

Background

In 2007, the American Association of Sleep Medicine (AASM) published recommendations for recording and scoring polysomnograms. These were revised in 2014 and 2015, and the given rules should be applied to polysomnography in both adults and children.

Objective

The scoring of pediatric polysomnograms is complicated by development-dependent alterations in specific patterns. The present article aims to demonstrate that in particular situations, the AASM rules for scoring and evaluation of sleep and associated events in children are worthy of further discussion.

Materials and methods

The problems associated with performing and evaluating results of sleep studies are illustrated using individual examples. Polysomnography was performed according to AASM rules.

Results and conclusion

This article highlights the problems associated with recording and scoring pediatric polysomnograms according to AASM rules with respect to the number of necessary electrodes, study over one or two nights, scoring of sleep stages (specific patterns for scoring sleep stages and the delta wave amplitude criterion), arousal definition, scoring movements and movement times, and scoring the respiratory pattern. Individual examples are discussed in each case. Beyond the fundamental aspects laid down in the AASM rules, recording and scoring polysomnograms in children necessitates additional understanding of development-specific characteristics.

Keywords

Sleep Polysomnography Child Movement Arousal 

Auswertung von Polysomnographien im Kindesalter

Theorie und Praxis

Zusammenfassung

Hintergrund

2007 wurden von der American Association of Sleep Medicine (AASM) Empfehlungen zur Durchführung und Bewertung von Polysomnographien veröffentlicht, die 2014 und 2015 überarbeitet wurden und sowohl im Erwachsenen- als auch im Kindesalter angewendet werden sollen.

Ziel der Arbeit

Die Bewertung von Polysomnographien ist im Kindesalter durch die entwicklungsbedingte Veränderung von spezifischen Mustern erschwert. Die Arbeit soll zeigen, dass im Einzelfall die Empfehlungen der AASM bezüglich der Mustererkennung und -bewertung im Kindesalter diskussionswürdig sind.

Material und Methoden

In Einzelbeispielen wird auf Probleme bei der Durchführung und Bewertung von Untersuchungen im Schlaf hingewiesen. Die Ableitungen wurden entsprechend der AASM-Regeln durchgeführt.

Ergebnisse und Diskussion

Hinweise zur Problematik der Ableitung und Auswertung von Polysomnographien im Kindesalter nach den AASM-Regeln wurden bezüglich der Anzahl von Messwertaufnehmern, der Untersuchung in 1 oder 2 Nächten, der Bewertung der Schlafstadien (spezifische Muster zur Schlafstadienerkennung und Amplitudenkriterium Deltawellen), der Arousaldefinition, der Bewertung von Bewegungen und Bewegungszeiten und der Bewertung des Atemmusters gegeben. Einzelbeispiele werden jeweils erläutert. Über die AASM-Regeln hinaus erfordert die Durchführung und Auswertung von Polysomnographien im Kindesalter ein zusätzliches Wissen über entwicklungsspezifische Besonderheiten.

Schlüsselwörter

Schlaf Polysomnographie Kind Bewegung Arousal 

The rules on scoring of sleep and associated events published in 2007 by the American Association of Sleep Medicine (AASM) [1] have become widely accepted during recent years. These rules are also applicable to children, providing the development-dependent changes in certain specific patterns are considered.

In 2014 and 2015, the AASM recommendations for scoring of sleep stage in children were revised, and morphologic criteria of the infant sleep electroencephalogram (EEG) were described in detail [2, 3].

Although there are rules governing scoring of sleep, ambiguity—caused by inter- and intraindividual pattern divergence and age-dependent characteristics—is frequently encountered in practice. The current article aims to indicate such pitfalls.

Methods

Using individual examples, potential problems associated with the application of AASM rules for analysis of pediatric sleep are illustrated. Each of the figures depicts the derivations recommended by the AASM [1]. In order to improve comprehensibility, single channels have been blended out in isolated cases.

Regarding polysomnographic montage: the technical specifications for the EEG (derivations F3-M2, F4-M1, C3-M2, C4-M1, O1-M2, O2-M1), electrooculogram (EOG), and the chin electromyogram (EMG) given for adults were observed. In infants and young children, the distance between the EOG and chin EMG electrodes was reduced according to the size of the head.

To record respiration, an oronasal thermal sensor and a nasal pressure sensor were used. Oxygen saturation was measured by pulse oximetry, as specified by AASM rules. Respiratory effort was assessed using respiratory inductance plethysmography (chest and abdomen).

To detect leg movements, the EMG of the left and right tibialis anterior muscle was recorded. According to AASM cardiologic rules, a modified electrocardiograph lead II using torso electrode placement was employed. An audiovisual recording was generally made throughout the PSG. In addition, the behavior was observed by trained personnel.

Results and discussion

Number of electrodes

Compared to polysomnography in adults, polysomnographic evaluation of infants, children, and adolescents is considerably more complicated. Subjects are frequently highly unsettled by the unknown environment and the recoding, such that placement of the electrodes can prove problematic, particularly in infants and small children.

In versions 2.1 and 2.2 [2, 3], the AASM recommends placement of additional electrodes in 2‑year-old children, i. e., F4-M1, C4-M1, O2-M1, F3-M2, C3-M2, O1-M2, C4-Cz, C3-Cz, since sleep spindles often occur asynchronously at this age and are particularly detectable in central derivations C3-Cz, C4-Cz and C3-M2, C4-M1. However, in our experience, the number of electrodes applied to the head should be reduced for routine recordings (e. g., for routine recordings up to the age of 2 years, only C3-M2 and C4-M1) in order to minimize stress. Since high-amplitude delta waves are particularly detectable frontally and centrally from 2 months after birth, as are sleep spindles and K complexes from 3–6 months, a frontal derivation would be recommendable in addition to the central derivation. The occipital derivation provides little additional information in infants and small children [4]. Placing sensors to record oral and nasal respiration is also extremely disturbing for infants; therefore, only an oronasal thermistor or a nasal pressure measurement system should be employed, whereby a nasal pressure sensor is preferred for detection of hypopnea [1].

Study over one or two nights

Due to the well-known first-night effect, the intention should be to evaluate children during the second night. However, if a clear statement on diagnosis can already be made after the first night, the second night may be omitted [5].

Scoring sleep stages

Specific patterns for scoring sleep stages and the delta wave amplitude criterion

The patterns given by the AASM for scoring of sleep stages differ in children in a development-dependent manner [4]. In the first step of scoring a polysomnogram, the investigator should thus orient the analysis toward the age-dependent appearance of distinctive graphic elements of the different sleep stages (e. g., vertex waves, sleep spindles, K complexes) in order to be able to evaluate the curves appropriately (Table 1). This is also particularly true for the amplitude of high-amplitude delta waves in stage N3, which is particularly high during puberty, for example, where it frequently lies between 100 and 400 µV. In manual versions 2.1 and 2.2 [2, 3], it is stated that the amplitude criterion for slow waves in adults is also valid for children (>75 µV peak-to-peak amplitude at a frequency of 0.5–2 Hz). Since basal activity in children is frequently already >75 µV, delineation of sleep stage N3 should, in the author’s opinion, be oriented toward the average height of delta waves in the individual patient (Fig. 1; [4]).
Table 1

Typical electroencephalogram patterns during sleep and their maturation (table modified from [14])

Age

31–44 weeks conceptional age (cA)

First year postpartum

1–3 years of age

3–5 years of age

5–12 years of age

12–20 years of age

Dominant posterior rhythm

Starting at 2–4 months with 2–4 Hz; at 5–6 months, 5–6 Hz

5–6 to 9.5 Hz

6–8 to 7–9.5 Hz

8–10 to 9–11 Hz

10 Hz (8–13 Hz)

Sleepiness drowsiness

Indifferent

At 6 months rhythmic theta activity, increasing amplitude in comparison to wakefulness

Rhythmic theta activity at 4–6 Hz, so-called “hypnagogic hypersynchrony” until 4 years, increasing amplitude in comparison to wakefulness

Rhythmic theta becomes slower and rare, hypnagogic rhythms

Decreasing alpha activity, hypnagogic rhythms (seldom)

Decreasing alpha activity, hypnagogic rhythms more seldom

Trace alternant (TA)

During quiet sleep, after 36 weeks mature pattern

Vanishes in the 1st/2nd month

Sleep spindles

Starting at 6 weeks to 3 months, 12–15 Hz; before 10 weeks: “pre-spindles”: rounded negative, sharp positive component

Progressive increase of inter-spindle intervals with age

Increasing spindle density from 3 years, typical maximum at vertex

From 18–24 months: mature spindles without rounded component; from 2 years: central 14 Hz, anterior 12 Hz

K complexes

From the 3rd to 6th month

High, fully developed with 2 years

High, with increasing steep component

High, with marked steep component

Smaller, steep component less prominent

Vertex sharp waves

From 4 to 6 months onwards

Most prominent at 3–10 years

REMs

Burst pattern after 28 (33–36) weeks cA

High-density bursts with interburst intervals <1 s decrease with age

Fig. 1

Age 8 years: The basal activity in stage N2 shows delta waves ≥75 µV (a). Upon comparison with stage N3 (b), it is clear that in the left side of the figure, no stage N3 should be scored, since the amplitudes are significantly higher in N3

Stage N2 is scored “when at least one sleep spindle or one K complex occurs in the 30-second epoch” [1]. N2 is also scored in the following epochs if a low-amplitude EEG with mixed frequencies is present in the absence sleep spindles or K complexes [1]. It is particularly important to observe this rule between the ages of 1 and 3 years, when sleep spindles are rare [6] and only few typical K complexes are found.

The designation of rapid eye movement sleep (REM) is based, among other things, on eye movements. Particularly in infants, although these movements are visible under the closed eyelids, it is often not possible to reproduce them in the derivations. Eye movements are recorded by electrodes (diagonal derivation E1-M2 and E2-M2) that register changes in the potential between cornea (positive) and retina (negative). If the distance between cornea and retina is very small, the changes in potential are also small, and the typical picture of rapid eye movements is less recognizable. In this instance, stage R should also be scored if the EEG pattern (low-amplitude mixed-frequency, no sleep spindles or trace alternate patterns) and the chin EMG pattern (low tone) are indicative of this stage and no eye movements are present [2, 3].

Particularly in infants but also in children and adolescents, consideration of heart rate is useful, which is less variable NREM (N) than in REM (R) sleep. This enables wakefulness and sleep stages N and R to be roughly determined by simply examining the heart rate pattern in the whole-night overview.

Arousals pattern

The AASM arousal definition only considers cortical EEG arousals. Upon an arousal in stage N2, even in the absence of a change in basal activity, the AASM recommends [1] a change to N1 until a new sleep spindle or K complex occurs. However, upon arousals occurring in stage N3 or during REM sleep, no change in sleep stage is made. In the author’s opinion, this is worthy of further discussion, since although arousals generally trigger lighter sleep, they do not necessarily trigger a sleep stage transition, as is suggested for stage 2. The AASM recommends scoring an arousal in N sleep “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 s, with at least 10 s of stable sleep preceding the change”. Scoring of arousals should incorporate information from both the occipital and central derivations [1]. Arousals in children are generally characterized by a transition to theta frequencies, which are particularly visible frontally and centrally (Fig. 2). Only from the age of adolescence is an occipital shift to an alpha rhythm seen as an arousal pattern [4]. Theta activations occur frequently in childhood, which, although not reaching the 3‑s criterion, are accompanied by an increase in heart rate and/or movements [7]. Arousals between 1 and <3 s are not taken into consideration according to the AASM rules.
Fig. 2

Age 3 years: According to the American Association of Sleep Medicine (AASM) rules, an arousal is scored if an abrupt shift of the EEG frequency for at least 3 s occurs. In this case, two shifts to a theta frequency are easily seen in the frontal and central derivations but not in occipital derivations. The arousals occur in connection with sucking movements (chin EMG). However, the arousals are not 10 s apart, as stipulated by the AASM rules. Both arousals do, however, cause discrete increases in heart rate and should therefore be scored as separate events

The AASM also states: “scoring of arousals may be improved by considering additional aspects of the recorded information, such as respiratory and/or other events.” [1]. No reference is made to movements (motoric arousals) or heart rate responses (autonomic arousals) [7], which considerably simplify scoring of arousal patterns in children. At least 10 s of stable sleep should lie between two arousals [1]. If one considers that according to the AASM a minimum of 5 s pass between two leg movements which are frequently accompanied by cortical arousals—arousals are only partly counted by the AASM rules, since their minimal separation should be 10 s (Fig. 3).
Fig. 3

Age 2 years: Two bilateral leg movements with a separation of 5 s, which are both accompanied by cortical arousals. However, according to the American Association of Sleep Medicine (AASM), these may only be scored as a single arousal, since the minimum separation between two arousals should be 10 s

In children, arousal patterns frequently occur as paroxysmal delta bursts. These are not mentioned in the AASM guidelines [1], although they characterize the disruption of sleep microstructure as well as the typical age-related theta arousals [7].

Scoring leg movements lasting >10 s

According to the AASM manual [1], movement times, as defined by Rechtschaffen and Kales [8], are no longer scored. In children, phases with movement artefacts >15 s, which disturb the EEG but do not lead to a sleep stage transition (Fig. 4; [7]), are frequently observed. According to the AASM, the movement times are added to the subsequent sleep stage, providing no transition to wakefulness occurs.
Fig. 4

Age 8 years: Movement time: More than half of the epoch is disrupted by motor activity, although no transition from the sleep stage to wakefulness is visible. The typical pattern of a cortical arousal (theta activation) is only hinted at. EMG artefacts interfere with the EEG. According to the American Association of Sleep Medicine (AASM), the leg movement should not be scored, since it lasts for longer than 10 s and the sleep stage would be scored as N3. The disruption of sleep by the leg movement would thus not be recognizable in the macrostructure

According to the AASM rules, leg movements (LM) must not be scored as movement if they last longer than 10 s (“the minimal duration of an LM event is 0.5 s, the maximum duration 10 s”) [1]. In children with sleep-disordered breathing or attention-deficit/hyperactivity disorder (ADHD), movements lasting >10 s are also common, i. e., restless sleep is a diagnostic criterion [9]. If AASM rules are observed, this sleep disruption would not be recognized, since movements >10 s are not scored and movement times according to Rechtschaffen and Kales [8] are added to the subsequent stage. The increased incidence of clusters of short-term increases in heart rate, which accompany larger movements, could also not be explained without further evaluation of the events (Fig. 5).
Fig. 5

Age 9 years, attention-deficit/hyperactivity disorder (ADHD): Sleep profile corresponds to age, but disrupted microstructure with clusters of movement times (MT). These are also reflected by the heart rate in the form of short-term increases. According to the American Association of Sleep Medicine (AASM), the disrupted sleep microstructure would not be detected, since movement times according to Rechtschaffen and Kales [8] should be added to the subsequent stage. Further evaluation would be necessary to explain the increases in heart rate

Rules for movements in connection with respiratory events

The AASM rules for scoring a movement correspond to fulfilment of the requirements set for adults [1, 2, 3].

It is stated that leg movements should not be scored if they occur 0.5 s prior to or 0.5 s after an apneic event ([1]; Fig. 6).

Movements occurring prior to a central apnea can trigger a central apnea via pulmonary stretch receptors (Hering–Breuer reflex). From infancy to adolescence, the occurrence of central apneas following movements decreases with increasing age. Therefore, these are age-specific in infants and young children, but not in adolescents. If central apneas following movements occur at an increased rate in older subjects, detection of this pattern could also demonstrate abnormal development.

The AASM [1] also stipulates that central apneas should not be scored when directly preceded by snoring, sighing, a respiratory event (what about periodic breathing? See Fig. 7), or an arousal. Movement is not specifically considered in this listing (Fig. 6).
Fig. 6

Age 7 years: Central apnea following a movement. The movement (light gray) is associated with reflexive closure of the upper airways, not obstructive apnea (see also Fig. 8). The movement is coupled to a cortical (dark green) and an autonomic arousal (first green bar). The movement triggers the Hering–Breuer reflex and a central apnea (dark gray), which presupposes a shift in EEG frequency (second dark green bar). However, according to the American Association of Sleep Medicine (AASM), this is not scored as an arousal, since it lasts <3 s. The central apnea (>2 missed breaths) is not scored according to AASM rules because it is preceded by an arousal and is not terminated by an arousal, since the subsequent shift in EEG frequency lasts <3 s. The increase in heart rate as a consequence of the apnea does, however, suggests an arousal with both cortical and autonomic characteristics

Fig. 7

Age 8 years: Periodic breathing. The central apneas (gray) are each separated by only one breath, are each induced or terminated by a movement (brown), and are accompanied by cortical arousals (orange, shown here in the chin EMG). According to American Association of Sleep Medicine (AASM) rules for central apneas, these apneas should not be scored, since they last <20 s. An expanded AASM pediatric rule allows this pattern to be scored as periodic breathing, but without consideration of movements or arousals

In the AASM rules, central apneas are however scored when an EEG arousal, a transition to wakefulness, or ≥3 % oxygen saturation follows the apnea [1]. A movement following an apnea should be considered a motoric arousal; however, according to AASM, only cortical arousals are considered. In the author’s opinion, it would be contradictory to negate the movement (Fig. 6).

Scoring of respiratory patterns

To record the respiratory signal, the AASM [1] recommends using oronasal thermistors and nasal pressure sensors (for detection of hypopnea), as well as esophageal pressure measurement (invasive methods not really suitable for routine use in children) or dual thoracoabdominal belts (inductance plethysmography) for measurement of respiratory effort. To detect hypoventilation, measurement of arterial pCO2, transcutaneous pCO2, or end-tidal pCO2 is suggested.

Apnea duration is determined with reference to the respiratory rate, which changes in a development-dependent fashion [10].

According to the AASM, at least two missed breaths—based on the preceding pattern of respiration—characterize an obstructive apnea if the amplitude of oronasal airflow is reduced by ≥90 % and a continual increase in respiratory effort is detected [1]. Up to the age of 8 years, this type of pattern is very common in association with movements [10]. Leg EMG records are indispensable for characterization. If such an “obstructive apnea” occurs during a movement, it should not be scored, since it represents a reflexive closure of the upper airways designed to prevent pulmonary aspiration (Fig. 6 and 8). This constraint is not considered in the AASM rules [1].
Fig. 8

Age 2 years: Obstructive apnea following nasal pressure measurement, which occurs during a leg movement (LM-L). This is a reflexive effect and should not be considered pathologic. Determination of this phenomenon requires bilateral tibialis anterior muscle EMGs, shown here for the left leg only

According to AASM rules [1], central apneas in children are only scored from a duration of 20 s, providing they are not terminated by an arousal, an awakening, or an oxygen desaturation ≥3 %. However, if one considers that the cutoff in adults is 10 s, this 20 s duration is set very high, particularly in the case of older children and adolescents. From the age of 8 years, the average duration of central apneas is about 10 s [4, 10]. This should justify scoring central apneas <20 s from this age. In the author’s experience, 20 s apneas are also more than rare in infants with immature respiratory control [4, 10].

Other AASM rules [1] on scoring central apneas also appear worthy of further discussion. Movements prior to and following an apnea should not be scored. So how does one proceed when faced with a pattern such as the one shown in Fig. 7? In this case, a periodic breathing pattern would be scored; however, according to AASM rules [1], events preceding or following the apnea would not be considered, i. e., arousals and leg movements would be ignored. “Score periodic breathing if >3 consecutive episodes of central apnea with duration >3 s are separated by an interval of normal breathing not longer than 20 s.” Disruption of sleep due to cortical arousals and leg movements (motoric arousals) would not be detectable by such an approach.

Children with clinical symptoms of obstructive sleep apnea syndrome (OSAS), who have an abnormal respiratory pattern during sleep, do not have to exhibit apneas/hypopneas that fulfill the AASM criteria [11, 12]. In children, it is important to clarify whether increased respiratory effort is present. Observation by trained personnel cannot always be replaced by audio/video recordings.

Practical conclusion

  • The AASM Manual for the Scoring of Sleep and Associated Events [1, 2, 3] provides rules for scoring polysomnographic patterns also intended for use in children.

  • Age-dependent changes in the patterns representative of sleep stage, in the respiratory pattern, and in the other polysomnographic parameters must be considered, since children up to the age of 14 years pass through key developmental processes [4, 7, 10, 13]. This receives less attention in the AASM rules.

  • The current article presents examples which are intended to facilitate scoring of pediatric polysomnograms beyond the scope of the AASM rules.

  • It is recommended that polysomnographic data be evaluated in their overall context, e. g., when scoring arousals, leg movements, and heart rate responses should also be included.

Compliance with ethical guidelines

Conflict of interest

S. Scholle states that she has no competing interests.

All studies on humans described in the present manuscript were carried out with the approval of the responsible ethics committee and in accordance with national law and the Helsinki Declaration of 1975 (in its current, revised form). Informed consent was obtained from all patients included in studies. Written consent was obtained from the parents of all children.

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Robert-Koch-Krankenhaus Apolda GmbHApoldaDeutschland