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October 13, 2023
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Resource Learning EEG

Yamada, Thoru, and Elizabeth Meng. Practical Guide for Clinical Neurophysiologic Testing: EEG.

Available from: Wolters Kluwer, (2nd Edition). Wolters Kluwer Health, 2017.

Greenfield, John, L. et al. Reading EEGs: A Practical Approach. Available from: Wolters Kluwer, (2nd Edition). Wolters Kluwer Health, 2020.

Frontal intermittent rhythmic delta activity (FIRDA) suggests a cerebral dysfunction of nonspecific etiology. This pattern is commonly seen in patients with metabolic or toxic encephalopathies of various severities, bifrontal or multifocal lesions, and dementia. The paroxysmal nature of FIRDA can make it difficult to differentiate from epileptiform activity in some cases, especially when associated with sharp or “spiky” components and a triphasic appearance.

In FIRDA the bifrontal delta activity does not reach the posterior regions; as the name infers, the intermittent rhythmic delta activity is often maximal over the frontal regions. FIRDA is synchronous and often of high amplitude. This delta slowing can be enhanced with hyperventilation and drowsiness in normal children and can be attenuated with light sleep and may return in REM sleep.

Which of the following delta range activities has a direct correlation with temporal lobe epilepsy?
Arrhythmic delta activity
Frontal intermittent delta activity
Temporal intermittent delta activity
Occipital intermittent activity
Correct Answer: 

FIRDA is a nonspecific abnormality associated with a variety of brain disorders. However, the presence of temporal intermittent rhythmic delta activity (TIRDA) strongly suggests temporal lobe epilepsy. It is associated with temporal epilepsies in up to 80% of patients and can last 3-20 seconds.

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