Main term 2: PDs, RDA, and SW

Criteria & assessment

PDs

name

Periodic discharges

rule

Relatively uniform waveform morphology and duration, a discernible inter-discharge interval, and recurrence at nearly regular intervals.

regularity

Cycle length varies by less than 50% from one cycle to the next in a majority (>50%) of cycle pairs.

discharge

Waveform shorter than 0.5 s irrespective of phases, or at least 0.5 s with no more than 3 phases; must stand out from background.

RDA

name

Rhythmic delta activity

rule

Relatively uniform waveform morphology and duration with no interval between waves; irregular or polymorphic delta is not RDA.

regularity

Period varies by less than 50% from the subsequent cycle in a majority (>50%) of cycle pairs.

frequency hz

min

0.5

max

4

note

Sharp crests or troughs do not prevent a pattern from being rhythmic.

SW

name

Spike-and-wave or sharp-and-wave

rule

Spike, polyspike, or sharp wave consistently followed by a slow wave in a regular alternating repeating pattern, with a consistent component relationship for at least 6 consecutive cycles and no interval between complexes.