Technological improvements in the 1990s and 2000s first permitted the recording of large quantities of digital electroencephalography (EEG) data for subsequent analysis and review. These continuous EEG (cEEG) recordings allowed for improved characterization of electrical patterns that were abnormal but not clearly seizures (eg, on the ictal-interictal continuum), and they showed that more patients were having electrographic seizures than were exhibiting clinical features of seizure activity. Nonconvulsive seizures were found to have an unexpectedly high prevalence in patients with altered mental status1 and in critically ill patients.2,3 Subsequent studies have suggested that these seizures are not simply a marker of an injured brain, but actually may damage the brain itself,4- 6 with longer nonconvulsive seizure activity correlating with worsened outcomes.7,8 Ensuring detection of nonconvulsive seizures has become a priority, as treatment might potentially prevent additional brain injury and improve mentation in an encephalopathic patient with nonconvulsive seizures. However, if we do not want to miss seizures and cannot detect them without EEG, should we order cEEG on every patient with altered mental status? If so, how long should we keep the cEEG on for monitoring? And is this cost-effective? Unfortunately, these questions remain largely unanswered, but we are beginning to understand how the risk of seizures on EEG changes with time, which may help us determine the optimal duration of EEG monitoring for our patients.
Czeisler BM, Claassen J. A Novel Clinical Score to Assess Seizure Risk. JAMA Neurol. Published online October 09, 2017. doi:10.1001/jamaneurol.2017.1922
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