FIRDA (frontal intermittent rhythmic delta activity)

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  • Frontal
  • Intermittent: In cycles, so not continuous
  • Rhythmic: Repetition of a waveform with relatively uniform morphology and duration, without an interval between consecutive waveforms.
  • Delta: Delta waves
  • Activity


  • The FIRDA can be more specified with the prevalence, duration, frequency, amplitude, stimulus-induced (SI), Evolving OR Fluctuating (both terms refer to changes in either frequency, location or morphology).
  • If a more ictal appearance it can be categorized as FIRDA+:[1]
    • +F: superimposed fast activity.
    • +S: superimposed sharp waves or spikes, or sharply contoured.
    • +FS: superimposed fast activity and sharp waves or spikes, or sharply contoured.


Clinical relevance:

  • Often due to global cerebral dysfunction (e.g. metabolic-, toxic- encephalopathy, traumatic)
  • FIRDA is rarely due to a subcortical dysfunction/lesion (e.g. lewy body dementia) or elevated intracranial pressure.
  • A small amount of FIRDA, especially when it is restricted to drowsiness, can be a normal in elderly or children.



FIRDA in a 70 year old male (source)

FIRDA (source) EEGpedia.png



Notes

  1. ACNS STANDARDIZED ICU EEG NOMENCLATURE v. 2012