Abstracts

Rationale: Nonconvulsive status epilepticus (NCSE) and nonconvulsive seizures (NCSz) are a complication of subarachnoid hemorrhage (SAH). With greater use of continuous EEG (cEEG) to detect NCSE and NCSz, patterns of unclear significance are seen. In 2005, the ACNS Subcommittee on Research Terminology for Continuous EEG Monitoring published proposed standardized nomenclature for these patterns, though the correlation with clinical course and outcome is unknown. Using this nomenclature, our institution created a prospective database using cEEG in patients with aneurysmal SAH and altered mental status.Methods: Patients were enrolled from a single tertiary care center. Inclusion criteria were aneurysmal SAH, Glasgow Coma Scale (GCS) ?8, decrease in GCS of 2 or more points, failure to return to baseline within 12 hours of treatment, or clinical seizure. Treatment of the aneurysm was determined by best clinical judgment. Prospective data included clinical examination, medical history, imaging, angiographic findings, surgical and medical interventions and laboratory values. Outcomes were determined for all patients at the end of the acute hospital stay. Continuous EEG monitoring was performed and scored according to ACNS Research Terminology. All data was collected under approved IRB protocols.Results: From May 2008 through December 2010, 323 patients were admitted with a SAH associated with a ruptured intracranial aneurysm. Of these, 68 met inclusion criteria and underwent cEEG monitoring. The mean age was 56.9 years. Rhythmical and periodic patterns (RPPs) were common occurring in 51 (75%) patients during monitoring. 33 (49%) patients had Periodic Discharges (PD). 4 patients had electrographic seizures, per ACNS terminology. Older patients were more likely to have PDs (64.45 vs 52.22 years, p<0.001). 66 of the patients underwent an intervention for treatment of the aneurysm: 27 had endovascular coiling, 36 had a craniotomy for surgical clipping and 3 had a combined approach. Patients undergoing endovascular coiling were older than those undergoing surgical clipping (64.11 vs 52.36 years, p=0.001). Endovascular patients were more likely to have PDs during cEEG monitoring (p=0.001). However, all patients with electrographic seizures had their aneurysms treated with surgical clipping. Endovascular patients also trended towards having more cardiac complications (p=0.07).Conclusions: Rhythmical and periodic patterns were common in patients with poor grade subarachnoid hemorrhage. There was a positive correlation between both age and endovascular treatment and the presence of PDs. Endovascular patients were also older with more cardiac complications. We postulate the increased frequency of PDs in the endovascular group is secondary to increased age and greater systemic illness - not the result of a certain treatment modality. Though PDs were more frequent in this group, electrographic seizures were not. The ACNS terminology assists in describing patterns, but further work is needed to determine the ictal-ness and treatment implications of the patterns seen.