Absence of early epileptiform abnormalities predicts lack of seizures on continuous EEG

Abstract

In patients without epileptiform abnormalities during the first 4 hours of recording, no seizures were subsequently detected. Therefore, EEG features early in the recording may indicate a low risk for seizures, and help determine whether extended monitoring is necessary.

Baseline EEG Pattern on Continuous ICU EEG Monitoring and Incidence of Seizures

“…Seizure frequencies in certain patient populations in our study were similar to previous reports: central nervous system infection (30% vs. 25%-33% in the literature) (Claassen et al, 2004;Jordan, 1995;Shafi et al, 2012), postoperative from a neurosurgical procedure (29% vs. 18%-23%) (Claassen et al, 2004;Shafi et al, 2012), hypoxic ischemic encephalopathy (29% vs. 20%-54%) (Claassen et al, 2004;DeLorenzo et al, 1998;Shafi et al, 2012), patients with brain tumor (27% vs. 17%-54%) (Claassen et al, 2004;DeLorenzo et al, 1998;Jordan, 1995;Shafi et al, 2012), epilepsy-related (25% vs. 24%-56%) (Claassen et al, 2004;FIG. 2.…”

“…These data suggest that it may not be necessary to perform cEEG monitoring for 24 to 48 hours on patients who have generalized slowing as the only abnormality on the initial 30 minutes of cEEG recording. A recent study by Shafi et al (2012) found similar results in that the lack of epileptiform discharges early in cEEG monitoring (within 4 hours) predicted the absence of seizures on subsequent cEEG monitoring. With the data we present, providers can make an early determination of a patient's seizure risk based on their baseline EEG pattern, rather than waiting to determine when/if the first epileptiform discharge will appear.…”

“…Interestingly, a recent case-control study revealed that although GPDs were strongly associated with NCS and NCSE, the presence of GPDs were not independently associated with a worse outcome when compared with controls who were matched for age, etiology, and level of consciousness (Foreman et al, 2012). Although the new ACNS terminology guidelines place triphasic waves as a subcategory of GPDs, we chose to differentiate these two groups because patients with triphasic waves have been found to have a low incidence of NCS (4%) (Shafi et al, 2012), despite the fact that it is often difficult to discriminate between triphasic waves and NCSE (Kaplan, 2007).…”

“…One study found that the lack of epileptiform discharges early in cEEG monitoring (within 4 hours) predicted the absence of seizures on subsequent cEEG monitoring (Shafi et al, 2012). The primary goal of our study was to determine if certain EEG patterns detected on the initial 30 minutes of cEEG recordings of adult patients are unlikely to be associated with the development of NCS, therefore justifying quicker termination of cEEG monitoring.…”

“…Previous retrospective and prospective studies have shown the prevalence rate of seizures in neurologic intensive care units to be 8% to 48% (Claassen et al, 2004(Claassen et al, , 2007DeLorenzo et al, 1998;Jordan, 1995;Oddo et al, 2009;Pandian et al, 2004;Privitera et al, 1994;Towne et al, 2000;Vespa et al, 1999;Vespa et al, 2003;Shafi et al, 2012). Of patients with NCS identified on continuous EEG (cEEG), 14% to 76% will have NCSE (DeLorenzo et al, 1998;Jordan, 1995;Pandian et al, 2004;Privitera et al, 1994).…”