Atypical Presentation of Subclinical Rhythmic Electrographic Discharge of Adults (SREDA) in a Patient with Idiopathic Generalized Epilepsy

Subclinical rhythmic electrographic discharge of adults (SREDA) is considered a benign EEG pattern of uncertain significance, although it may closely resemble an electrographic seizure pattern. SREDA was first described by Westmorland and Klass in 1981 as a distinctive rhythmic and rare EEG pattern primarily seen in older subjects. The typical pattern consists of sharp contoured, non-evolving 5 to 7 Hz theta rhythm with a widespread bilaterally synchronous distribution, but maximal over the parietal and posterior temporal regions. It usually lasts for a few seconds to several minutes without clinical association. Later in 1997, several unusual variants of SREDA were reported consisting of variations in frequency, morphology, topographic distribution, duration, and stage of alertness. We report SREDA in a patient with idiopathic generalized epilepsy which shows some atypical features (such as asynchronous onset, bifid waveforms, asymmetry, and fragmentation) and mimics a secondarily generalized partial seizure. It is important to successfully identify SREDA to avoid misdiagnosis and incorrect treatment. The technologist's contribution is essential and valuable. EEG technologists and interpreters should be aware of typical and atypical features of SREDA and its wide spectrum. KEY WORDS. Atypical features, benign variants, EEG, electrographic seizure, hyperventilation, subclinical rhythmic electrographic discharge of adults (SREDA).

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