LAUSR

Recently, continuous video-EEG (cEEG) recording became a widely used tool to detect and investigate dynamic changes in patients who are critically ill. Altered or fluctuating mental status in these patients could be secondary to various conditions ranging from metabolic encephalopathies to nonconvulsive status epilepticus (NCSE). While some of the EEG patterns are easily recognized as nonictal, others are not as clearly defined. One of the relatively recent EEG phenomena is described by Hirsch et al. (2004) and falls in this “gray zone.” The authors called this activity stimulusinduced rhythmic, periodic, or ictal discharges (SIRPIDs) (Hirsch et al. 2004). CEEG in critically ill patients made it clear that these changes are not spontaneous or state related but indeed triggered by different stimuli. Stimulus types range from normal examination and suctioning to noxious stimuli (Hirsch et al. 2004, Braksick et al. 2016). We observed that even sudden loud noise, such as someone closing the door of patient’s room or turning on a TV, could trigger SIRPIDs. The name of SIRPIDs comprises multiple electrographic phenotypes. As described in the initial article, it is considered to be periodic when the discharges (such as sharp waves, spikes, or polyspikes) recur at somewhat regular intervals (Hirsch et al. 2004). Specific EEG patterns described as rhythmic include periodic lateralized epileptiform discharges (PLEDs), bilateral independent PLEDs (BiPLEDs or BiLPDs), generalized periodic epileptiform discharges (GPEDs or GPDs), triphasic waves, or frontal rhythmic delta activity (Hirsch et al. 2004). This pattern is usually more continuous than a periodic one, with little or no separation between discharges. The third pattern, as the name implies—ictal—is characterized by clear evolution (Hirsch et al. 2004). The duration of SIRPIDs is highly variable, ranging from several seconds to hours. Different examples of SIRPIDs were shown in Figures 1 to 3. The majority of patients lack