TIRDA (temporal intermittent rhythmic delta activity)

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  • Temporal
  • 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


  • Short burst of rhythmic delta activity in the temporal region
  • Amplitude of 50-100 microV
  • The TIRDA 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 TIRDA+:[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

  • Strong association with temporal lobe epilepsy
  • Occurs in 28% of patients with temporal lobe epilepsy [2]


Other intermittent rhythmic delta activity:


TIRDA in a 72 year old female with left temporal epilepsy (average)

TIRDA in a 72 year old female with left temporal epilepsy (average) EEGpedia.png




Notes

  1. ACNS STANDARDIZED ICU EEG NOMENCLATURE v. 2012
  2. Geyer JD et al. Significance of interictal temporal lobe delta activity for localization of the primary epileptogenic region. Neurology. 1999 Jan 1. 52(1):202-5.