ACNS Standardized Critical Care EEG Terminology
1) Start with the Background
To assess the degree of encephalopathy
-Symmetry
>Is it symmetric? Mildly asymmetric? Markedly asymmetric?
>You determine this by comparing amplitude and frequency between hemispheres
-PDR
>Present or absent, and what frequency
-Background frequency
>Delta / Theta / Alpha, or “> Alpha”
-Reactivity
>Does the EEG change with stimulation?
-Voltage
>Normal (>20 μV), low (10–20 μV), or suppressed (<10 μV)
-Continuity
>Continuous; nearly continuous, discontinuous, burst‑suppression, suppressed
2) Label RPPs
Every RPP pattern uses a 2‑term structure:
Main Term 1: Location
G = generalized
L = lateralized
BI = bilateral independent
UI = unilateral independent
Mf = multifocal
Main Term 2: Pattern type
PD = periodic discharges
RDA = rhythmic delta activity
SW = spike‑wave
Example
L-PDs = lateralized periodic discharges
G‑RDA = generalized rhythmic delta activity
3) Add plus (+) modifiers present
These modifiers show increased epileptogenic potential
+F = superimposed fast activity
+R = superimposed rhythmic activity
+S = superimposed sharp waves
EDB = extreme delta brush
Example:
L‑PDs +F = higher risk for seizures than plain L‑PDs
G‑RDA +S
-Frequency (0.5–4 Hz)
-Sharpness (spike, sharp, blunt)
-Amplitude
-Triphasic morphology (yes/no)
-Evolution (evolving, fluctuating, static)
Example:
L‑PDs +F at 1.5 Hz, medium amplitude, sharply contoured, fluctuating
G‑RDA +S at 2 Hz, sharply contoured delta with superimposed sharp waves, fluctuating
a) Is it a szs? (ESz or ECSz)
b) If it lasts longer → status (ESE or ECSE)
c) If it’s short but suspicious → BIRDs
d) If it’s not a seizure but not normal → IIC
