Abstracts

Rationale: To review in a retrospective fashion the frequency and clinical significance of stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) in patients who are comatose and being monitored in the intensive care setting. Methods: We reviewed a total of 60 patients undergoing video EEG monitoring in the intensive care setting during a 12-month period from April 2006 - April 2007. We limited our analysis to comatose patients with the intent to find patients with and without SIRPIDs. SIRPIDs were defined as periodic, rhythmic, or ictal-appearing discharges that were repeatedly induced by environmental stimuli.Results: Of the 60 patients reviewed we identified 19 comatose patients. Four of the patients were found to have SIRPIDs (21%) as defined in the literature1. Of the patients analyzed two patients had several electrographic seizures in response to varied stimuli. One patient had multiple episodes of stimulus induced bilateral independent periodic discharges (BiPEDS) in addition to other non-stimulus induced sharp activity. One patient had stimulus induced frontal intermittent rhythmic delta activity (FIRDA) and frequent left temporal spikes independent of specific stimuli. Further data analysis revealed that none of these patients had a prior diagnosis of epilepsy. Structural brain lesions occurred in three patients (75%) with SIRPIDs (1 CVA, 1 diffuse head injury, 1 large intraparenchymal hemorrhage). Although seizure activity was focal in onset in one patient there was no structural lesion on neuroimaging. All patients with SIRPIDs were treated with antiepileptic medication once diagnosed. One of the four (25%) patients found to have SIRPIDs died as a result of the diffuse traumatic brain injury. The other three had better outcomes and were discharged from the hospital. Of the comatose patients in the non-SIRPIDs group, 6 (40%) had seizure activity (2 developed subclinical status epilepticus). Conclusions: Stimulus-induced rhythmic, periodic, or ictal discharges have been defined in the literature and are of unclear clinical significance. Our data suggests that the phenomenon occurs in patients with severe brain injury. Further prospective analysis will be conducted at our center to help elucidate further the prognostic and therapeutic significance of SIRPIDs.