What Does “Subclinical Rhythmic Electrographic Discharge of Adults” in EEG Signify?

Abstract

Subclinical rhythmic electrographic discharge of adults (SREDA) is the rarest benign epileptiform variant. It is an established EEG phenomenon that when present may cause confusion with an epileptic discharge for those unfamiliar with the entity. An electronic term search was performed on all EEG reports to identify those records reported as showing SREDA and other benign variants. Serial EEG reports of 5,200 subjects who underwent EEG through our EEG laboratory services between January 2001 and December 2009 were thus scrutinized, and their clinical profile and follow-up data were obtained. A total of four subjects had SREDA (0.07%) in their EEG, and their mean age was 53.7 years. The duration of SREDA ranged from 10 to 60 seconds. SREDA was not associated with any clinical seizures during recording. Two patients remained asymptomatic on long-term follow-up. One patient was found to have idiopathic generalized epilepsy and another patient had Alzheimer disease during the follow-up. Mere presence of SREDA may not have any clinical significance at one point of time. The authors have also highlighted the possible pathophysiological basis of SREDA. Many features of SREDA still remain unresolved: why is it more common in the elderly population, why is its spatial distribution centered over temporoparietal region, why it appears mostly in wakefulness, and what is its pathogenesis? It would be worthwhile if compilation of cases reported world over are performed and further analyzed to reach at a common conclusion on its varied clinical presentations and EEG features.