American Clinical Neurophysiology Society Standardized EEG Terminology and Categorization for the Description of Continuous EEG Monitoring in Neonates:

Flashcards of key vocabulary terms from a lecture on EEG monitoring in neonates.

Postmenstrual Age (PMA)

Gestational age (measured from the last menstrual period) + chronological age at the time of recording.

Term

37 up to 44 weeks of PMA.

Preterm

Less than 37 weeks of PMA.

Post Term

44 to 48 weeks of PMA.

Activité Moyenne

Continuous, low to medium voltage (25-50 mV peak-to-peak) mixed frequency EEG activity with a predominance of theta and delta and overriding beta activity during wakefulness in term infants.

Tracé Discontinu

Normal discontinuous EEG tracing encountered in healthy preterm babies, characterized by bursts of high voltage (50-300 mV pp) activity interrupted by low voltage interburst periods (<25 mV pp).

Interburst Interval (IBI)

Period in which EEG activity is attenuated <25 to 50 mV pp for 2 seconds or more within discontinuous EEG patterns.

Tracé Alternant

Alternating tracing in quiet sleep near term, showing higher voltage bursts (50-150 mV pp) of delta activity alternating with briefer, lower voltage (25-50 mV pp) interburst periods.

Sleep-Wake Cycling

Pattern of alterations among behavioral states, more distinctive and easier to recognize in term babies compared with preterm babies.

Normal Continuity

EEG activity that is continuous when there is uninterrupted, nonstop electrical activity with <2 seconds of voltage attenuation <25 mV pp.

Discontinuity

Higher voltage “bursts” of electrical activity interrupted by lower voltage “interbursts.”

Excessive Discontinuity

Abnormally discontinuous tracings with bursts that contain some normal patterns and graphoelements separated by IBIs that are too prolonged or voltage depressed for PMA.

Burst Suppression

Invariant, abnormally composed EEG bursts separated by prolonged and abnormally low voltage IBIs periods, strictly defined as IBI voltages <5 mV pp.

Normal Symmetry

Electrical voltages, frequencies, and the distribution of specific, named graphoelements should be reasonably equally represented between homologous regions of the two hemispheres.

Normal Synchrony

The percentage of synchronized bursts is not a linear function of PMA, EEG activity is almost completely synchronous before 27 to 29 weeks of PMA.

Normal Asynchrony

Some degree of asynchrony is expected and normal between 30 and 37 weeks of PMA.

Borderline Low Voltage

Continuous EEG background containing some normal activity and graphoelements with representative voltages persistently at least 10 mV but <25 mV.

Abnormally Low Voltage

Persistently low voltage activity without normal background features, the fundamental baseline voltage is <10 mV pp.

Electrocerebral Inactivity (ECI)

Absence of discernible cerebral electrical activity <2 mV pp when reviewed at a sensitivity of 2 mV/mm.

Variability

Conspicuous spontaneous EEG responses to internal stimuli such as that occur during typical sleep–wake cycling.

Reactivity

Conspicuous cerebral EEG response to external stimulation.

Dysmaturity

EEG that would be normal for an infant at least 2 weeks younger than the stated PMA.

Graphoelements

Normal, expected, and specific; named EEG background patterns that first appear peak and then fade during particular epochs of neonatal development.

Monorythmic Delta Activity

Moderately high voltage (up to 200 mV pp) delta activity with a relatively stereotyped morphology, typically synchronous and symmetric.

Delta Brushes

Combination of 0.3 to 1.5 Hz slow waves of 50 to 250 mV pp with superimposed fast activity (8–12 or 18–22 Hz).

Rhythmic Temporal Theta

25 to 120 mV pp theta frequency activity for short (2 seconds) bursts over the temporal region, typically symmetric.

Anterior Dysrhythmia

50 to 100 mV pp delta waves, which may occur in isolation or brief runs for a few seconds over the frontal regions, typically synchronous and symmetric.

Encoches Frontales

50 to 100 mV pp broad diphasic transients (0.5–0.75 seconds) with a small initial negative deflection and a larger positive deflection, typically synchronous and symmetric.

Sharp Wave Transients

Transient EEG patterns that may intermittently punctuate the background, characterized by their negative or positive polarity, duration, abundance, spatial distribution, and repetitive behavior.

Physiologic Negative Sharp Waves

Negative sharp waves lasting 100 to 200 milliseconds, typically observed against the backdrop of a normal EEG background for PMA.

Abnormal Negative Sharp Wave Transients

Sharp waves or true spikes that commonly arise in the context of an abnormal EEG background for PMA.

Positive Sharp Wave Transients

Sharp waves in the rolandic regions (positive rolandic sharp waves), represented by electrodes C3 and C4, although it was later recognized that many were actually maximally situated at the midline vertex.

Brief Rhythmic Discharges (BRD)

Evolving rhythmic patterns of electrical activity that share many characteristics with seizures but are very brief, with a duration of <10 seconds.

Electrographic Seizure

Sudden, abnormal EEG event defined by a repetitive and evolving pattern with a minimum 2 mV pp voltage and duration of at least 10 seconds.

Diffuse Seizure Spread

Asynchronous involvement of all electrodes by focal seizures of extensive geographic distribution.

Lateralized Seizure

All of the seizure propagates within a single hemisphere (left or right hemisphere).

Unifocal Onset Seizures

Multiple seizures arise from a single general region.

Multifocal Onset Seizures

Seizures that originate from at least three independent foci with at least one in each hemisphere.

Status Epilepticus

Summed duration of seizures comprises $ 50% of an arbitrarily defined 1-hour epoch.

Periodic Discharges

Pattern in which waveforms have a relatively uniform morphology and duration with a quantifiable interval between consecutive waveforms and the waveforms recur at nearly regular intervals

Rhythmic Delta Activity

Repetition of a waveform with relatively uniform morphology and duration but without an interval between consecutive waveforms

Spiky Waveforms

Waveforms that have a duration measured at the EEG baseline ,100 milliseconds.

Sharp Waveforms

Waveforms that have a duration of 100 to 200 milliseconds.

Sharply Contoured Theta and Delta Waveforms

Waveforms that have a sharp wave morphology but are too long in duration to qualify as a sharp wave.

Clinical Only Seizure

Sudden paroxysm of abnormal clinical changes that do not correlate with a simultaneous EEG seizure.

Anterior Quadrant

Referring to the Frontal region on an EEG.

Posterior Quadrant

Referring to the Occipital region on an EEG.

Synchrony

Bursts of activity that occur nearly simultaneously between hemispheres in the discontinuous portions of the recording.

Asynchrony

EEG bursts for PMA that occur asynchronously (greater than 1.5 seconds between the onset of activity in each hemisphere) during the discontinuous portions of the recording.

Evolving

Unequivocal evolution in frequency, voltage, morphology, or location of a seizure

Lability

Denotes conspicuous spontaneous EEG responses to internal stimuli such as those that occur during typical sleep-wake cycling.