Abstracts

Rationale: Subarachnoid hemorrhage (SAH) affects close to 30,000 individuals per year in the United States and is a major cause of morbidity and mortality despite current medical and surgical treatments. Reports of seizure prevalence rates vary from 3-26% (1, 2). This may be reflective of population differences, referral bias, age group and availability of continuous EEG at different centers. Patients who survive the initial hospital course and treatment are at risk for development of late onset seizures. There is insufficient data on the occurrence of both early and late onset seizures after SAH.Methods: This is a retrospective analysis of seizures associated with SAH in our institution from 2011-2014. These patients were on continuous video EEG monitoring (cVEEG) for detection of seizures and vasospasm. Seizure occurrence was defined as either early (first 14 days after SAH) or late (any time after 14 days). Grade of SAH (Hunt-Hess Scale) and radiographic findings were analyzed along with EEG characteristics and compared amongst all patients with early and late onset seizures and those with no seizures.Results: 330 patients with SAH underwent cVEEG monitoring from 2011-2014. The annual incidence of seizures in SAH patients was 15%. The greatest percentage of patients developed early onset seizures from day 1-3 (10.7%) compared with an occurrence rate for late onset seizures in 5%. For example, the 2014 cohort of 4/84 patients that developed late onset seizures had high grade (grade 4 or 5) SAH and were being treated aggressively for vasospasm. They developed late onset seizures from Day 14-80 after the typical risk period for vasospasm. Initial cVEEG patterns for these patients showed generalized rhythmic delta activity (RDA), rhythmic delta activity with superimposed sharp waves or spikes (RDA+S), quasi-rhythmic delta activity, lateralized or multifocal spike/sharp wave (SW) and lateralized or generalized periodic discharges (PDs).Conclusions: Based on this evaluation there were both early and late onset seizures that occurred in SAH patients. The mechanisms for development of late onset seizures may be different from acute early onset seizures. Based on existing data the clinical risk factors for the development of early onset seizures included intra-parenchymal and subdural hemorrhage, whereas the risk factors for late onset seizures also included the presence of vasospasm, cortical infarcts, ventriculitis and hydrocephalus. Presently no distinctive background EEG patterns were identified that definitively predicted the development of early versus late seizure occurrence. Patients with SAH are likely to have both acute and delayed or late onset seizures as a consequence of SAH. 1. Choi K et al., Seizures and epilepsy following aneurysmal subarachnoid hemorrhage: incidence and risk factors. J Korean Neurosurg Soc. 2009;46:93–8. 2. O’Connor et al., High Risk for Seizures Following Subarachnoid Hemorrhage Regardless of Referral Bias Neurocrit Care (2014) 21:476–482