At what age should infant sleep staging rules be used in polysomnography (PSG)?

Infant Sleep Staging Rules in Polysomnography

Infant sleep staging rules should be used in polysomnography for infants from birth to 2 months of age, with transition to pediatric sleep staging rules at 3 months of age when sleep spindles become consistently present. 1, 2

Age-Based Sleep Staging Criteria

• Infants 0-2 months of age should have sleep scored using the specialized infant sleep staging rules that recognize four states: wakefulness (W), REM sleep (R), NREM sleep (N), and transitional sleep (T) 2
• By 3 months of age, sleep spindles are consistently present, allowing for the transition to standard pediatric sleep staging that includes N1, N2, and N3 sleep stages 1, 3
• The prospective longitudinal study by Sankupellay et al. confirmed that stages NREM 2 and 3 sleep could be scored in infants 3 months or older 3

Key Physiological Differences in Infant Sleep

• In infants 0-2 months, regularity (or irregularity) of respiration is the single most useful polysomnographic characteristic for scoring sleep stages 2
• Sleep onset in infants up to 2-3 months post-term more commonly occurs in REM sleep rather than NREM sleep, unlike older children and adults 2
• Trace alternant (TA) is a distinctive EEG pattern characteristic of NREM sleep in young infants that usually disappears by 1 month post-term, replaced by high voltage slow (HVS) patterns 2

Technical Specifications for Infant Sleep Staging

• For infants 0-2 months, a recommended EEG montage includes: F3-M2, F4-M1, C3-M2, C4-M1, O1-M2, O2-M1; with additional C3-Cz, Cz-C4 to help detect early and asynchronous sleep spindles 2
• Sleep should be scored in 30-second epochs as either wakefulness, REM, NREM, or transitional sleep 2
• Visual observation (supplemented by video review) is crucial for determining drowsiness in young infants 2

Transition from Infant to Pediatric Sleep Staging

• Sleep spindles first appear at 44-48 weeks conceptional age (approximately 1-2 months post-term) and when present prompt scoring of NREM stage 2 (N2) sleep 1, 2
• About 50% of sleep spindles within a particular infant's PSG are asynchronous before 6 months of age, decreasing to 30% at 1 year 1
• K complexes first appear at 5 months post-term and are usually present by 6 months post-term 1

Clinical Implications

• The AASM sleep scoring rules better differentiate children with OSA from primary snorers or healthy age-matched controls 3
• When using AASM rules, children with OSA show more NREM 1 and stage shifts per hour of sleep than primary snorers or controls, providing useful markers of sleep fragmentation 3
• For children with suspected sleep-disordered breathing who are candidates for tonsillectomy, laboratory-based polysomnography is recommended when indicated 3

Common Pitfalls and Caveats

• Failing to recognize that sleep spindles may be asynchronous in infants under 6 months, requiring simultaneous recording of left and right frontal and central activity 1
• Misinterpreting respiratory patterns in young infants, when regularity of breathing is a critical determinant of sleep stage 2, 4
• Not accounting for the higher amplitude of slow wave activity in children, which typically ranges from 100-400 μV (much higher than the >75 μV threshold used in adults) 3
• Overlooking that sleep spindles in children occur independently at two different frequencies and locations: 11.0-12.75 Hz over frontal regions and 13.0-14.75 Hz over centroparietal regions 1

In summary, infant sleep staging rules (0-2 months) focus on respiratory patterns, presence of body movements, and specific EEG patterns like trace alternant, while pediatric sleep staging (≥3 months) incorporates more adult-like features including sleep spindles, K-complexes, and slow wave activity, allowing for the scoring of N1, N2, and N3 sleep stages.