Periodic EEG Patterns

Abstract

Periodic and rhythmic patterns are encountered with increasing frequency as continuous electroenchephalography (EEG) monitoring is adopted more widely across hospitals and intensive care units for seizure detection and brain monitoring. A standardized nomenclature has provided a common way to describe these abnormal patterns. Periodic and rhythmic discharges in most cases do not point to a specific underlying diagnosis, but instead represent a common expression of a variety of underlying pathologies. Lateralized periodic discharges in particular may independently impact outcome, and there is mounting evidence that periodic discharges exacerbate underlying acute brain injury. Lateralized and generalized periodic discharges, lateralized rhythmic delta, and stimulus-induced rhythmic, periodic, or ictal discharges are highly associated with electrographic seizures during continuous EEG monitoring, and it is critical to consider any periodic or rhythmic pattern as potentially indicative of an epileptic seizure if there is a clinical correlate, evidence of ongoing neuronal injury, or a positive response to an anti-seizure medication.