The visual scoring of sleep and arousal in infants and children

Abstract

Age is probably the single most crucial factor determining how humans sleep. Age and level of vigilance significantly influence the electroencephalogram (EEG) and the polysomnogram (PSG). The Pediatric Task Force provide an evidence-based review of the age-related development of the polysomnographic features of sleep in neonates, infants, and children, assessing the reliability and validity of these features, and assessing alternative methods of measurement. We used this annotated supporting text to develop rules for scoring sleep and arousals in infants and children. A pediatric EEG or PSG can only be determined to be normal by assessing whether the EEG patterns are appropriate for maturational age. Sleep in infants at term can be scored as NREM and REM sleep because all the polysomnographic and EEG features of REM sleep are present and quiet sleep, if not NREM sleep, is at least "not REM sleep." The dominant posterior rhythm (DPR) of relaxed wakefulness increases in frequency with age: (1) 3.5-4.5 Hz in 75% of normal infants by 3-4 months post-term; (2) 5-6 Hz in most infants 5-6 months post-term; 3) 6 Hz in 70% of normal children by 2 months of age; and 3) 8 Hz (range 7.5-9.5 Hz) in 82% of normal children age 3 years, 9 Hz in 65% of 9-year-olds, and 10 Hz in 65% of 15-year-old controls. Sleep spindles in children occur independently at two different frequencies and two different scalp locations: 11.0-12.75 Hz over the frontal and 13.0-14.75 Hz over the centroparietal electrodes; these findings are most prominent in children younger than 13 years. Centroparietal spikes are often maximal over the vertex (Cz), less often maximal over the left central (C3) or right central (C4) EEG derivation. About 50% of sleep spindles within a particular infant's PSG are asynchronous before 6 months of age, 30% at 1 year. Based on this, we recommend that: (1) sleep spindles be scored as a polysomnographic signature of NREM stage 2 sleep (N2) at whatever age they are first seen in a PSG, typically present by 2 to 3 months post-term; (2) identify and score sleep spindles from the frontal and centroparietal EEG derivations, especially in infants and children younger than 13 years. NREM sleep in an infant or child can be scored if the dominant posterior rhythm occupies <50% of a 30-second epoch, and one or more of the following EEG patterns appear: (1) a diffuse lower voltage mixed frequency activity; (2) hypnagogic hypersynchrony; (3) rhythmic anterior theta of drowsiness; (4) diffuse high voltage occipital delta slowing; (5) runs or bursts of diffuse, frontal, frontocentral, or occipital maximal rhythmic 3-5 Hz slowing; (6) vertex sharp waves; and/or (7) post-arousal hypersynchrony. K complexes first appear 5 months post-term and are usually present by 6 months post-term, whereas clearly recognizable vertex sharp waves are most often seen 16 months post-term. Vertex sharp waves are best seen over the central (Cz, C3, C4) and K complexes over the frontal (Fz, F3, F4) electrodes. Slow wave activity (SWA) of slow wave sleep (SWS) is first seen as early as 2 to 3 months post-term and is usually present 4 to 4.5 months post-term. SWA of SWS in an infant or child often has a peak-to-peak amplitude of 100 to 400 microV. Based on consensus voting we recommended scoring N1, N2, and N3 corresponding to NREM 1, 2, and SWS whenever it was recognizable in an infant's PSG, usually by 4 to 4.5 months post-term (as early as 2-3 months post-term). Epochs of NREM sleep which contain no sleep spindles, K complexes, or SWA would be scored as N1; those which contain either K complexes or sleep spindles and <20% SWS as N2, and those in which >20% of the 30-second epoch contain 0.5 to 2 Hz >75 microV (usually 100-400 microV) activity as N3. The DPR should be scored in the EEG channel that is best observed, (typically occipital), but DPR reactive to eye opening can be seen in central electrodes. Because sleep spindles occur independently over the frontal and central regions in children, they should be scored whether they occur in the frontal or central regions. Because sleep spindles are asynchronous before age 2 years, simultaneous recording of left and right frontal and central activity may be warranted in children 1-2 years of age. Simultaneous recording of left, right, and midline central electrodes may be appropriate because of the asynchronous nature of sleep spindles before age 2 years, but reliability testing is needed. Evidence has shown that the PSG cannot reliably be used to identify neurological deficits or to predict behavior or outcome in infants because of significant diversity of results, even in normal infants. Normal sleep EEG patterns and architecture are present in the first year of life, even in infants with severe neurological compromise. Increasing evidence suggests that sleep and its disorders play critical roles in the development of healthy children and healthy adults thereafter. Reliability studies comparing head-to-head different scoring criteria, recording techniques, and derivations are needed so that future scoring recommendations can be based on evidence rather than consensus opinion. We need research comparing clinical outcomes with PSG measures to better inform clinicians and families exactly what meaning a PSG has in evaluating a child's suspected sleep disorder.