To identify clinical characteristics of patients associated with delayed seizure detection on cEEG who will benefit from longer than 24-48 hours of monitoring

Studies have been done to identify duration of cEEG before seizures are excluded. However, it is unclear how long cEEG should be continued in different patients based on their reason for presentation, interictal finding and neurological status in order to exclude subclinical seizures

Baseline demographic,clinical, and EEG findings were recorded for all patients who underwent cEEG at our hospital during a single calendar year. Data was analyzed using Mann-Whitney U tests, Pearson Chi-square tests and Logistic regression analysis.

Among 2425 patients monitored on cEEG,14%(n=339) were found to have seizures. Median age of seizure patients was 60(45.5-72)years with 46.9%(n=159) females.

Characteristics more likely to be associated with seizures detection were altered mentation(coma, stupor or obtundation;p<0.001),presence of  any type of epileptiform abnormalities(sharp waves, PLEDs and periodic pattern, p<0.001),presence of any acute or remote brain insults and witnessed seizure-like event as the primary indication for cEEG.

80.5%(n=273) of seizures were detected during the first 24 hours of monitoring. Patients who were obtunded, stuporous or comatose (p=0.005), had PLEDs, acute brain insults (p=0.025), SDH, SAH or more than one type of hemorrhage (p=0.015), patients on AEDs (> 24 hours, p<0.001 and >48 hours, p=0.049) and patients with primary indication of cEEG of altered mental status as against witnessed seizure like events (p<0.001) were more likely to have delayed seizure detection after 24 or 48 hours.

Stuporous, obtunded or comatose patients, those with LPDs,acute brain insults,altered mental status as the primary indication for cEEG and those with SDH, SAH or more than one type of hemorrhage and those one AEDs are more likely to have delayed seizure detection and hence are likely benefit from  longer cEEG (>24-48 hours)  to detect subclinical seizures.