Abstracts

Rationale: Periodic and rhythmic EEG patterns have been associated with risk of developing seizures in critically ill patients. However, specific pattern characteristics that confer risk for seizures have not been well defined.Methods: We conducted a retrospective, 3-center review of 3460 consecutive critically ill adult patients undergoing continuous EEG monitoring between 2013 and 2014. A multivariate analysis was performed to determine features of periodic and rhythmic patterns that were associated with seizures. Patient monitoring sessions containing a periodic or rhythmic pattern were compared to sessions with no specific pattern present.Results: Periodic or rhythmic patterns were documented in 1513 (44%) of patient monitoring sessions and electrographic seizures were recorded in 482 (14%). Lateralized periodic discharges (LPD) conferred the highest risk for seizures regardless of frequency (45% of sessions with LPDs had seizures, p<0.001) and was greatest when the “plus” modifier was present (64%, p<0.001 vs. 35%, p<0.001 without plus). Both generalized periodic discharges (GPDs) and lateralized rhythmic delta activity (LRDA) were associated with seizures in a frequency dependent manner (GPDs- 1.5-2 Hz : 22%, p=0.05, ≥ 2 Hz: 33%, p<0.001 and LRDA- 1.5-2 Hz: 25%, p=0.05, ≥ 2 Hz: 44%, p<0.001), as well as at any frequency when associated with “plus” modifier (GPDs plus: 27%, p=0.001 and LRDA plus: 49%, p<0.001). Generalized rhythmic delta activity (GRDA) was not associated with seizures regardless of frequency or presence of “plus” modifier.Conclusions: LPDs, LRDA and GPDs are highly associated with seizures while GRDA is not. LPDs are associated with seizures at all frequencies both with and without “plus” modifier but LRDA and GPDs were found to be associated to seizures when frequency were 1.5 Hz or faster or when associated with a “plus” modifier in this cohort.