Clinical reference

EEG & qEEG

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17 entries · Neonatal EEG
Neonatal EEG

ACNS neonatal monitoring indications

Current ACNS guidance on indications for continuous EEG monitoring in neonates.

Criteria & assessment

  • Consult the final January 2025 guideline linked from the ACNS index.

Editorial draft · clinical review pending

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Neonatal EEG

Background symmetry and interhemispheric synchrony

Symmetry compares homologous content and voltage; synchrony compares burst onset timing and has a non-linear developmental course.

Criteria & assessment

  • Persistent >2:1 voltage difference between homologous regions, or persistent disparity in frequency or graphoelement distribution, is abnormal asymmetry; fleeting differences may remain normal.
  • A burst pair is synchronous when left and right onsets differ by <=1.5 seconds; report the percentage of synchronous bursts.
  • Near-complete synchrony is expected before roughly 27-29 weeks and again near term; about 70% synchrony may occur around 29-30 weeks and some asynchrony is expected from 30-37 weeks.
  • After 38 weeks PMA, substantial asynchrony is not expected; abnormal asynchrony means a clearly excessive PMA-adjusted proportion of bursts with onset difference >1.5 seconds.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 9 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Background variability and reactivity

Variability is spontaneous change from internal state; reactivity is cerebral EEG change after external stimulation.

Criteria & assessment

  • A qualifying response is a conspicuous change in frequency, continuity, or voltage.
  • Record each feature as yes, no, or unclear/unknown/not applicable.
  • Variability first appears near 25 weeks PMA, increases by 28 weeks, and is well established around 30-31 weeks.
  • Reactivity first appears around 30-32 weeks PMA; record stimulus type and strength.
  • Separate cerebral change from movement, EMG, crying, and respiratory artifacts; arousal-related voltage attenuation is not automatically discontinuity.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 11 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Behavioral state and sleep-wake cycling

State assignment combines EEG and polysomnographic behavior and is interpreted relative to PMA.

Criteria & assessment

  • A state requires its defining features for >=60 seconds.
  • Allowed states are awake, active sleep, quiet sleep, transitional sleep, and indeterminate sleep; transitional sleep mixes features of the states on either side, while indeterminate sleep cannot be assigned to active or quiet sleep.
  • Term awake and active sleep use continuous low-to-medium voltage mixed-frequency activité moyenne; active sleep additionally has closed eyes, REM, irregular respiration, and body movement.
  • Term quiet sleep has closed eyes, absent REM, little movement, and near term commonly tracé alternant; mature continuous high-voltage slow activity and 10-12 Hz spindles emerge around 46 weeks PMA.
  • Sleep-wake cycling records orderly alteration among states: term complete sleep-wake cycles are typically 3-4 hours and sleep-only cycles 40-70 minutes; preterm sleep cycles are 30-50 minutes below 35 weeks PMA and 50-65 minutes beyond 35 weeks PMA.
  • Unspecified state change requires distinct EEG patterns differing in discontinuity, voltage, or frequency, with each state lasting >=60 seconds.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 4 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Brief rhythmic discharge

An evolving rhythmic neonatal discharge resembling seizure activity but lasting less than ten seconds.

Criteria & assessment

  • Rhythmic electrical activity shows evolution and duration <10 seconds.
  • Record accompanying background abnormality and confirmed seizures; these are common contexts but not stated as mandatory criteria.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 14 ↗

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Neonatal EEG

EEG dysmaturity

The EEG background appears developmentally appropriate for an infant at least two weeks younger than the actual PMA.

Criteria & assessment

  • Difference between actual PMA and EEG-implied PMA is >=2 weeks.
  • Persistent dysmaturity is abnormal; the source frames the concept longitudinally.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 12 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Excessive discontinuity and neonatal burst suppression

Separates PMA-inappropriate discontinuity that retains normal elements from invariant burst suppression lacking normal graphoelements.

Criteria & assessment

  • Excessive discontinuity has IBIs too long or too voltage-depressed for PMA while bursts retain some age-appropriate patterns or graphoelements.
  • Burst suppression has invariant abnormal bursts separated by prolonged IBIs with voltage <5 µV peak-to-peak.
  • Permitted activity within burst-suppression IBIs is limited to sparse activity up to 15 µV in one electrode, transient activity up to 15 µV for <2 seconds, or the source-described >2:1 voltage asymmetry in multiple electrodes.
  • Burst suppression is unreactive and lacks spontaneous lability; bursts lack recognizable normal graphoelements and should be described as >100 µV or <100 µV, with typical burst and IBI durations and burst-component sharpness recorded.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 8 ↗

Editorial draft · clinical review pending

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Neonatal EEG

ILAE neonatal seizure framework

The neonatal framework emphasizes EEG-confirmed seizures and distinguishes electrographic-only from electroclinical events.

Criteria & assessment

  • Document EEG evidence and available clinical correlate.

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Neonatal EEG

Neonatal recording context and daily reporting

Minimum context needed to interpret each 24-hour neonatal continuous video-EEG period and its clinically relevant changes.

Criteria & assessment

  • Record postmenstrual age (PMA) at acquisition; PMA is gestational age from last menstrual period plus chronological age.
  • Source categories are preterm <37 weeks PMA, term 37 up to 44 weeks PMA, and post-term 44 to 48 weeks PMA; the literal wording overlaps at 44 weeks and does not state whether 48 weeks is inclusive.
  • Record neuroactive medications and ideally administration times, including sedatives, hypnotics, anxiolytics, anesthetics, and antiseizure drugs.
  • Record hypothermia depth, duration, and whether spontaneous or induced; record major hemodynamic, respiratory, or cardiorespiratory changes.
  • Record hours uninterpretable for technical reasons; characterize the first hour, one background hour in each later 24-hour period, and additional epochs after relevant change.
  • Record seizure onset, burden, resolution, and status epilepticus onset and resolution.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 3 ↗
Generation & measurement notes
  • Pending Craig: encode term as the half-open interval [37,44) weeks and post-term as beginning at 44 weeks; the upper 48-week boundary remains unresolved.

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Neonatal EEG

Neonatal rhythmic and periodic patterns of uncertain significance

Non-seizure periodic discharges and rhythmic delta activity are described by waveform organization, minimum cycles, onset, spread, and neonatal location terms.

Criteria & assessment

  • Periodic discharges have relatively uniform morphology/duration, a measurable interdischarge interval, and near-regular recurrence: cycle length varies <50% between adjacent cycles in >50% of cycle pairs.
  • A discharge has <=3 phases or lasts <=0.5 seconds regardless of phases; a burst lasts >0.5 seconds and has >=4 phases.
  • RDA repeats relatively uniform waveforms without an inter-wave interval and has cycle-length variation <50% in >50% of adjacent cycle pairs.
  • PD or RDA must persist for >=6 cycles.
  • Location is lateralized, diffuse with asynchronous all-electrode involvement, bilateral independent, or multifocal; report onset focus, maximal spread, and F/C/T/O/Z or hemispheric predominance as applicable.
  • For diffuse patterns, frontal, occipital, or midline predominance requires amplitude >=50% greater than the comparison region in an appropriate referential montage.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 17 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Neonatal rhythmic/periodic duration, polarity, and sharpness modifiers

Neonatal RPPs use a limited modifier set with neonatal duration boundaries and bipolar polarity measurement.

Criteria & assessment

  • Record typical duration and preferably longest continuous duration: very long >=1 hour; long 5-59 minutes; intermediate 1-4.9 minutes; brief 10-59 seconds; very brief <10 seconds without evolution.
  • Determine predominant-phase polarity in a traditional bipolar montage as positive, negative, or unclear.
  • Measure sharpness at baseline for predominant and sharpest phase: spiky <100 ms; sharp 100-200 ms; sharply contoured theta/delta is >200 ms with steep or pointed morphology; blunt is smooth or sinusoidal.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 18 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Neonatal seizure burden and status epilepticus

Seizure burden is quantified over an explicit denominator; neonatal status is defined by seizure occupancy of a one-hour epoch.

Criteria & assessment

  • Clinical burden may be reported as seizure count per hour or total seizure duration divided by the duration of the epoch of interest.
  • Research temporal-spatial burden sums seizure duration per hour in five non-overlapping neonatal montage regions so each electrode is counted once; the source lists Fp3-T3, C3-O1, Fp4-T4, C4-O2, Fz-Pz or an alternate pairing.
  • Status epilepticus is present when summed seizure duration is >=50% of any defined 60-minute epoch.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 16 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Neonatal seizure type, electrographic definition, and spread

A neonatal electrographic seizure is a sudden abnormal repetitive evolving EEG event meeting voltage and duration thresholds; clinical coupling is classified separately.

Criteria & assessment

  • Electrographic seizure is repetitive and unequivocally evolves in frequency, voltage, morphology, or location, reaches >=2 µV peak-to-peak, and lasts >=10 seconds; there is no minimum electrical frequency.
  • The 2 µV threshold marks seizure beginning and end; two events are separate only when the inter-event interval is >=10 seconds.
  • Electroclinical seizure has definite simultaneous clinical seizure signs; electrographic-only seizure has no specific visible clinical sign; clinical-only events have no simultaneous EEG seizure.
  • Spread classes are diffuse asynchronous involvement of all electrodes, bilateral independent, migrating between hemispheres, lateralized within one hemisphere, unifocal onset, or multifocal onset from >=3 independent foci with >=1 in each hemisphere.
  • Restricted locations may be frontal, central, temporal, occipital, vertex, anterior quadrant, posterior quadrant, or hemispheric left/right.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 15 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Neonatal sharp-wave transients

Distinct positive or negative transients are classified using baseline duration, abundance, spatial distribution, repetition, PMA, and background context.

Criteria & assessment

  • A spike lasts <100 ms at baseline; a sharp wave lasts 100-200 ms; the transient must stand apart from background rather than be only sharply contoured background.
  • Physiologic negative sharp waves are usually 100-200 ms, solitary, symmetric, and mid-temporal/central/centro-temporal against a PMA-normal background; frontal, vertex, and occipital locations are uncommon.
  • Abnormal negative transients are supported by abnormal background, concentration in one region or hemisphere, atypical location, high abundance, or repetitive runs; source-cited outcome data call rates >11/hour preterm and >13/hour term abnormal.
  • Positive Rolandic/vertex sharp waves are centered at C3/C4 or vertex with adjacent field; excessive positive mid-temporal waves can indicate focal pathology, while cited upper normal observations are 3/hour preterm and 1.5/hour term.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 13 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Normal continuity, tracé discontinu, and tracé alternant

Normal neonatal continuity and discontinuity are PMA- and state-dependent rather than fixed adult categories.

Criteria & assessment

  • Continuous activity has no interruption and <2 seconds of attenuation below 25 µV peak-to-peak.
  • An interburst interval (IBI) is attenuation below an age-dependent level described broadly as <25-50 µV peak-to-peak for >=2 seconds; Table 1 supplies the age bins.
  • Normal maximum IBI/voltage by PMA: <30 weeks, 35 seconds and <25 µV; 30-33 weeks, 20 seconds and <25 µV; 34-36 weeks, 10 seconds and approximately 25 µV; 37-40 weeks, 6 seconds and >25 µV.
  • Tracé discontinu contains 50-300 µV bursts with low-voltage IBIs and age-appropriate graphoelements; it is developmentally expected mainly from 26-40 weeks PMA and becomes confined to quiet sleep with maturation.
  • Tracé alternant occurs only in quiet sleep: 50-150 µV delta bursts lasting roughly 4-10 seconds alternate with 25-50 µV mixed theta-delta periods that never fall below 25 µV; it appears around 34-36 weeks, is minimal by 42 weeks, and is absent by 46 weeks PMA.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 5 ↗

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Neonatal EEG

Normal neonatal graphoelements

Named developmental background hallmarks whose morphology, state, distribution, and expected PMA window jointly determine normality.

Criteria & assessment

  • Monorhythmic delta: 24-34 weeks PMA, up to 200 µV peak-to-peak, stereotyped delta usually occipital, temporal, or central and rarely frontal; typically symmetric, synchronous, and often surface positive.
  • Delta brushes: most prominent 24-36 weeks, 0.3-1.5 Hz slow waves at 50-250 µV with superimposed 8-12 or 18-22 Hz activity; peak expression 32-34 weeks, with state distribution changing by PMA and occasional quiet-sleep occurrence through 40 weeks.
  • Rhythmic temporal theta: 24-34 weeks, 25-120 µV theta in approximately 2-second temporal bursts, typically symmetric and maximal at 29-32 weeks; similar activity may occur at vertex or occipital sites.
  • Anterior dysrhythmia: 32-44 weeks, 50-100 µV frontal delta waves singly or in brief runs, typically symmetric and synchronous.
  • Encoches frontales: 34-44 weeks, 50-100 µV broad diphasic frontal transients lasting 0.5-0.75 seconds with small initial negative and larger positive phase; typically symmetric/synchronous and enriched during transition from active to quiet sleep.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 12 ↗

Editorial draft · clinical review pending

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Neonatal EEG

Term background voltage and electrocerebral inactivity

Voltage categories for term neonatal background plus the separately standardized technical claim of electrocerebral inactivity (ECI).

Criteria & assessment

  • Normal term background has most activity >=25 µV peak-to-peak in every behavioral state.
  • Borderline low voltage is continuous, retains normal activity and graphoelements, and is persistently >=10 and <25 µV peak-to-peak.
  • Low-voltage suppressed background lacks normal features, has fundamental baseline <10 µV peak-to-peak, permits >=10 µV transients only when <2 seconds, and is invariant and unreactive.
  • ECI means no discernible cerebral activity at or above 2 µV peak-to-peak when reviewed at sensitivity 2 µV/mm and only when ECI technical standards were met; otherwise report only that the record may be consistent with ECI.
Source · 2012 guideline / 2013 publicationACNS neonatal terminology, official PDF · PDF p. 10 ↗

Editorial draft · clinical review pending

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