Peds Normal Drowsy and Asleep

Written by Sarah Durica, M.D. and Trent Tollefson, M.D.

Pediatric Drowsiness and Sleep EEG

Normal sleep features also evolve with age. Hypnogogic hypersynchrony is normal in drowsiness beginning around 6 months and is characterized by bursts of high-amplitude delta and theta slowing. Hypnopompic hypersynchrony is similar in appearance but occurs during the transition from sleep to wakefulness.

Figure 1: Normal drowsiness with hypnagogic hypersynchrony, high amplitude delta and theta slowing, in a 2-year-old child. Image credit: Chelsea Ortman.

In term infants, frontocentral sleep spindles appear around 6 weeks to 2 months. Due to immature myelination, early sleep spindles are asynchronous, occurring at different times on the left and the right. They are often longer and higher frequency than adult spindles. Although spindles prior to age 2 appear asynchronously, they should be symmetric. Absence of spindles on one side suggests a focal abnormality. Spindles should be synchronous by age 2. Vertex waves and K‑complexes are present by 6 months in the same regions as adults, though pediatric vertex waves can have a broader spatial distribution, appear in repetitive runs, and look sharp, which may be mistaken for epileptiform activity. By 1 year, all sleep stages should be recognizable.

Figure 2: Normal stage 2 sleep in a 2-month-old term infant. Note the symmetric and asynchronous sleep spindles (brackets). Image credit: Trent Tollefson.

Figure 3: Normal stage 2 sleep in a 2-year-old child. Synchronous and symmetric, high amplitude sleep spindles are seen (brackets). Image credit: Chelsea Ortman.

Figure 4: Normal prominent vertex waves in a 9-year-old patient (brackets). Image credit: Trent Tollefson.