Termination patterns of stimulus-induced rhythmic, periodic, or ictal patterns and spontaneous electrographic seizures

•Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) are difficult to distinguish from spontaneous seizures.•We identified a termination pattern of SIRPID activity, distinct from that of spontaneous seizures.•The termination pattern has high accuracy for distinguishing SIRPIDs from spontaneous seizures.

ObjectiveTo investigate the ability of the evolution and termination patterns to distinguish stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) from spontaneous electrographic seizures, a challenge to the neurophysiologist and clinician.MethodsWe screened the prospectively collected database of patients undergoing continuous EEG (cEEG) and identified 25 cases of SIRPIDs. We compared patients with SIRPIDs to 25 patients with spontaneous seizures. Two experienced neurophysiologists graded the termination pattern of both on fast fourier transform (FFT) as “abrupt” or “sputtering.”ResultsThe identification of a “sputtering” or cyclical tapering pattern accurately discriminated SIRPIDs from spontaneous seizures with 88% sensitivity and 87% specificity, yielding a positive predictive value of 82% for SIRPIDs when the pattern was present (negative predictive value 87% when the sputtering termination was not seen). Similarly, the identification of an “abrupt” termination pattern identified clinically determined seizures with 84% sensitivity and 88% specificity.ConclusionsThe termination pattern quickly and accurately distinguishes SIRPIDs from spontaneous seizures, suggesting that at least some SIRPIDs have an underlying mechanism distinct from that of spontaneous seizures.SignificanceIf validated in other studies, the use of evolution and termination patterns to classify EEG patterns as epileptiform seizures versus SIRPIDs will help guide treatment of these patients.