EEG terminology for age and state

Published: 2026-09-28 23:05:56

EEG Terminology for Age and State

John Giang, MD

Why it matters

Two readers describing the same neonatal record should use the same age and the same state names; otherwise "normal for age" has no fixed meaning. The ACNS neonatal guideline requires the report to state the postmenstrual age at recording and to label each behavioral state present.

Key points

Age terms (AAP/ACNS usage)

Gestational age (GA): time from the mother's last menstrual period to birth; length of the pregnancy.
Chronological (postnatal) age: time since birth.
Postmenstrual age (PMA) = GA + chronological age; the age used for all neonatal EEG norms. A 4-week-old born at 34 weeks is 38 weeks PMA. Term = 37 to <44 weeks PMA, preterm <37, post-term 44–48.
Corrected (adjusted) age: chronological age minus the weeks born before 40; used after the neonatal period for developmental and EEG milestones in former preterm infants (a 6-month-old born at 28 weeks has a corrected age of 3 months).
Conceptional age: older literature counted from conception, about 2 weeks less than PMA; ACNS now uses PMA and the two should not be mixed.

State terms (neonatal)

Wakefulness: eyes open; continuous mixed-frequency 25–50 µV activity (activité moyenne) with irregular breathing and movement; continuous by 34 weeks PMA.
Active sleep (REM precursor): eyes closed, rapid eye movements, irregular respirations, small and large body movements; EEG is activité moyenne, indistinguishable from wakefulness, so polygraphy decides.
Quiet sleep (NREM precursor): eyes closed, no REMs, regular breathing, occasional startles; EEG is tracé discontinu in preterms, tracé alternant near term (bursts 50–150 µV alternating with 25–50 µV interburst activity), replaced by continuous slow-wave sleep by 46 weeks.
Transitional and indeterminate sleep: periods that do not meet full criteria for one state; brief transitions are normal, but a large proportion of indeterminate sleep at term is abnormal.
Drowsiness: not a defined neonatal state; from infancy onward it is recognized by slowing of the background by 1–2 Hz with fronto-central high-amplitude theta/delta, later as hypnagogic hypersynchrony.
Distinct states emerge at about 29–30 weeks PMA; before that the record looks the same in all states. Sleep–wake cycling is the alternation among these states and is a key marker of a healthy brain.

Consistent reporting language

Header: "GA 34 wk, chronological age 4 wk, PMA 38 wk", plus medications, temperature management, and recording duration. An example of concise reporting language for neonatal age: “Currently 39w+4d PMA, previously 34w+0d GA.”
Name states with the neonatal terms (awake, active sleep, quiet sleep, transitional, indeterminate) until about 44–46 weeks PMA, then switch to wake, drowsy, N1–N3, REM.
Describe each state's background with the standard descriptors: continuity, voltage, synchrony, symmetry, graphoelements, reactivity, variability, and sleep–wake cycling present or absent.
Use "appropriate for PMA" or "dysmature by ≥2 weeks" rather than "normal" or "slow" without an age anchor.

Common pitfalls

Using the baby's date of birth (chronological age) as the age in the header, which overstates maturity in a preterm infant.
Mixing conceptional and postmenstrual age, shifting all norms by two weeks.
Continuing to use "corrected age" beyond 2–3 years, or forgetting to use it in the first two years for former preterm infants.
Calling a term baby "awake" or "asleep" from the EEG alone; wake and active sleep have the same EEG and are separated only by eye, respiratory and EMG channels.
Applying adult sleep-stage names (N2, spindles, K-complexes) to a neonatal record before those features exist.
Reporting a short routine study as "no sleep–wake cycling" when the recording was too brief to capture a full cycle.