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    NeuroLogic: ACNS Terminology

    ACNS Terminology

    Learn continuity, attenuation, and the ictal-interictal continuum in EEG Fundamentals first, then use these charts. The IIC walkthrough is at ACNS IIC in Fundamentals.

    All Content Reference Charts Name a Pattern Read the Strip Write the Report Old Terms Training Module

    ACNS Nomenclature Reference Charts

    Choose a chart, then open the full-size image to read small labels. Previous and Next cycle through the four charts and wrap around. Use the final ACNS 2021 paper below for complete definitions and exceptions.

    ACNS Standardized Critical Care EEG Terminology
    A standardized approach to describe EEG patterns in critical care patients.

    Open Final ACNS 2021 Terminology

    Name a Pattern

    ACNS 2021 names a rhythmic or periodic pattern from where it is, what it is, and what rides on top of it. Pick each part to build the name and watch an example page redraw with every choice, then set the frequency and course to see whether it meets the seizure or ictal-interictal continuum criteria.

    The name builder needs JavaScript. Main term 1 (G, L, BI, UI, Mf) + main term 2 (PDs, RDA, SW) + plus modifiers (+F, +R for PDs, +S for RDA), for example LPDs+F.

    A teaching aid, not a reading tool. Duration, prevalence, morphology and the clinical picture also matter; the ACNS 2021 paper is the reference.

    Read the Strip

    Name the pattern on a ten-second page, one part at a time: where it is, what it is, how fast, what rides on it, and whether it changes. Then check it against ACNS 2021. The strips are drawn from a simple field model, so focal discharges reverse phase where they should, but they are teaching sketches, not recordings.

    The strip drill needs JavaScript.

    Write the Report

    Describe what you see in the order a critical care EEG report uses (background, sporadic discharges, rhythmic or periodic patterns, seizures) and get draft wording in ACNS 2021 terms. Each choice shows its definition. Copy the draft and adapt it to your own template.

    The report writer needs JavaScript.

    Numbers into ACNS words

    The quantifiers are defined by numbers. Type what you measured to get the term.

    A teaching aid. The ACNS 2021 paper defines every term; your report is your own clinical interpretation.

    Old Terms to 2021 Terms

    Older reports, and many senior colleagues, still use these names. Translate them when you read and write.

    Older termACNS 2021Note
    PLEDsLPDsLateralized periodic discharges; add +F or +R when present.
    BIPLEDsBIPDsBilateral independent periodic discharges.
    GPEDs, PEDsGPDsGeneralized periodic discharges.
    Triphasic wavesGPDs with triphasic morphologyA description of shape, not a diagnosis of metabolic encephalopathy.
    FIRDA, OIRDAGRDA, frontally or occipitally predominantNot associated with seizures.
    TIRDA, lateralized rhythmic deltaLRDAAssociated with seizures. With a temporal maximum on a routine EEG it is an interictal marker of temporal lobe epilepsy; older reports and papers call it TIRDA. The ACNS terms can be used outside the ICU.
    Periodic epileptiform dischargesPDs"Epileptiform" is left out of the name: PDs describe a pattern, not its meaning.
    Slow spike-and-wave, polyspike-and-waveSW (spike-and-wave or sharp-and-wave), with its frequencyMain term 2 for any repeating spike or sharp wave followed by a slow wave.
    SIRPIDsSI- prefix (for example, SI-LPDs)Stimulus-induced patterns keep their own name with the SI prefix. They do not count as reactivity.
    Burst suppression with identical burstsBurst suppression, highly epileptiform or identical burstsDescribe the bursts; identical bursts after cardiac arrest point to a poor outcome.
    Alpha coma, spindle comaBackground frequency and reactivity described directlyName the predominant frequency, distribution and reactivity instead.
    Nonconvulsive status (loosely used)Electrographic or electroclinical status epilepticus, or IICUse the 2021 seizure and continuum criteria.

    ACNS Training Modules

    These are ACNS's own training modules for the 2021 terminology (Leitinger, Fong and Hirsch for the Critical Care EEG Monitoring Research Consortium), published on acns.org and mirrored here. Each part follows the guideline's sections with an introduction, an EEG example with a question, the annotated answer and a summary. They are PowerPoint files.

    Part 1 of 3

    Background and sporadic discharges

    Guideline sections A and B: the EEG background and sporadic epileptiform discharges. 41 slides.

    Covers
    • Continuity, burst suppression and burst attenuation
    • Highly epileptiform and identical bursts
    • Reactivity, state changes, CAPE and breach effect
    • Spikes and sharp waves, phases, discharge versus burst
    Download Part 1 (PowerPoint, 5.7 MB)
    Part 2 of 3

    Rhythmic and periodic patterns

    Guideline section C: naming a rhythmic or periodic pattern and its modifiers. 82 slides.

    Covers
    • Main term 1 (G, L, BI, UI, Mf) and main term 2 (PDs, RDA, SW)
    • Prevalence, duration, frequency and sharpness
    • Plus modifiers (+F, +R, +S) and extreme delta brush
    • Evolution, fluctuation and stimulus-induced patterns
    Download Part 2 (PowerPoint, 15 MB)
    Part 3 of 3

    Seizures, BIRDs and the continuum

    Guideline sections D to F: the 2021 seizure definitions, BIRDs and the ictal-interictal continuum. 38 slides.

    Covers
    • Electrographic and electroclinical seizures and status epilepticus
    • Brief potentially ictal rhythmic discharges (BIRDs)
    • Ictal-interictal continuum criteria, with worked examples
    Download Part 3 (PowerPoint, 8.1 MB)

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