Risk Factors Predict Delayed Seizure Detection on Continuous EEG for Some

for a scientific experiment, a man connected with cables to a computer sits in front of a screen, EEG for research
In a retrospective study, researchers sought to identify risk factors that are predictive of delayed seizure detection on continuous electrocephalogram among patients who are critically ill.

A number of risk factors have been shown to be associated with delayed seizure detection on continuous electroencephalogram (cEEG) among patients who are critically ill, according to a retrospective study published in the journal Epilepsia Open.

Previous research has identified risk factors that have shaped the current monitoring recommendations. At least 48 hours of monitoring is recommended for patients who are comatose and have a history of seizures, while 24 hours is recommended for most patients.

The objective of the current study was to identify additional risk factors that are predictive of delayed seizure detection and to establish the optimal cEEG duration for a variety of patient subpopulations.

They obtained EEG and clinical data on all patients who experienced a seizure in the calendar year 2016 via use of the cEEG Cleveland Clinic database. Patients’ electronic health records were reviewed and demographic data were collected.

The mental status (ie, wakefulness, lethargy, stupor, and coma) of all patients was recorded at the time of initiation of the cEEG. Wakefulness was defined as a “fully alert and responsive state.” Lethargy was described as a “hypersomnolent state with reduced alertness but arousable to minimal stimuli.” Stupor was defined as “unresponsiveness where patients could only be aroused to vigorous, repeated stimuli.” Coma was described as “unarousable unresponsiveness with no understandable response to stimuli.”

A total of 2402 patients 18 years of age and older met the study inclusion criteria. Among these individuals, 13.2% (316 of 2402) experienced subclinical seizures. Of the participants who experienced a seizure, 79.4% (251 of 316) had their initial seizure during 24 hours of cEEG monitoring. Among patients who experienced seizures, 20.6% (65 of 316) had their seizures detected after 24 hours, 13.6% (43 of 316) had their seizures detected between 24 and 48 hours, and 7.0% (22 of 316) had their seizures detected after 48 hours.

Study findings revealed showed seizure detection increased linearly until 36 hours of monitoring, with the likelihood of seizure detection increasing by 46% for each additional day of monitoring.

Risk factors for significantly delayed seizure detection included stupor (13.2% after 48 hours, P =.031); lethargy (25.9%, P =.013); lateralized periodic discharges (27.7%, P =.029); generalized periodic discharges (33.3%, P =.022); acute brain  insults (25.5%, P =.036); brain bleeds (32.8%, P =.014); multiple concomitant brain bleeds (61.1%, P <.001); altered mental status as a primary indication f or cEEG (34.7%, P =.001); and use of antiseizure medications at initiation of cEEG (27.8%, P <.001).

Study limitations included the study’s retrospective nature, several neurologic diagnosis, and varying monitoring duration—patients with seizure vs patients without seizure had a longer median monitoring duration. Furthermore, the statistical threshold for multiple comparisons was not adjusted.

The researchers concluded, “The aforementioned patient subpopulations are at risk of delayed seizure detection. Longer cEEG (≥48 hours) is suggested for these high-risk patients.”

Disclosure: None of the study authors has declared affiliations with biotech, pharmaceutical, and/or device companies.


Zawar I, Briskin I, Hantus S. Risk factors that predict delayed seizure detection on continuous electroencephalogram (cEEG) in a large sample size of critically ill patients. Epilepsia Open. Published online December 16, 2021. doi:10.1002/epi4.12572