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(Abst. 3.121), 2015

Ictal and Nonictal Patterns in Subarachnoid Hemorrhage :Is it a seizure or is it vasospasm
Authors: Jeffrey Politsky, Sloka Iyengar, Igor Ugorec, Preeti Puntambekar
Content: Rationale: Subarachnoid hemorrhage (SAH) is a major cause of morbidity and mortality despite aggressive medical and surgical treatment. Continuous Video EEG (cVEEG) monitoring with or without quantitative EEG has been used to identify seizures, non-convulsive status epilepticus, vasospasm and also secondary complications such as delayed cerebral ischemia (DCI) in SAH patients (1). There are rhythmic and periodic EEG patterns that have been reported in SAH patients, however, with uncertain clinical significance.Methods: This is a retrospective data analysis of ictal and nonictal patterns associated with SAH at our institution from 2011-2014. These patients were on cVEEG monitoring for detection of seizures and vasospasm. EEG patterns were reviewed periodically in conjunction periodic clinical neurologic examination. EEG pattern changes considered to be compatible with vasospasm were reported to the intensivist and the patient was sent for confirmatory angiography.Results: The incidence of patients that developed angiographically confirmed vasospasm was 34.5%. EEG pattern changes correctly anticipated the diagnosis and treatment of vasospasm in over 80% of patients evaluated. The most prevalent early identifying pattern on cVEEG was rhythmic delta activity (RDA). There were patterns on the interictal ictal continuum seen as RDA plus superimposed sharp waves or spikes (RDA+S), multifocal spike/sharp wave (SW) and generalized periodic discharges (PDs). Unambiguous ictal patterns were present in a smaller percentage of patients (15%) were treated with anti-seizure medications. Improvement and subsequent worsening of cVEEG patterns were also monitored as response to conventional treatment (triple H) for SAH-induced vasospasm and a change in the EEG pattern was equally accurate in predicting the effectiveness and loss of efficacy of triple H therapy.Conclusions: Based on this evaluation our data suggests that rhythmic and periodic patterns on the interictal-ictal continuum occur frequently in SAH patients and are not straightforward. Proper interpretation of these patterns and distinguishing between ictal and non-ictal (vasospasm) patterns is integral to appropriate management strategy in an effort to optimize patient outcome. Continuous EEG can identify and help guide treatment in SAH patients and should be used in concert with frequent clinical examination and angiography. 1. Claassen J et al., Quantitative continuous EEG for detecting delayed cerebral ischemia in patients with poor-grade subarachnoid hemorrhage. Clin Neurophysiol. 2004 Dec;115(12):2699-710.