Continuous EEG (cEEG) allows brain electrical activity to be monitored for hours or days rather than sampled for a short routine recording. In intensive care it is used mainly to detect electrographic seizures, non-convulsive status epilepticus and other clinically important EEG patterns that may have no obvious outward signs.
Why a routine EEG can miss the problem
A routine EEG records only a short period. Critically ill patients can have intermittent seizures that occur outside that window.
Continuous monitoring increases the chance of detecting seizures and shows how patterns evolve after treatment, sedation changes or neurological deterioration.
Who may need cEEG
Common indications include unexplained persistent altered consciousness, failure to wake after convulsive status epilepticus, acute brain injury with concern for seizures, suspected non-convulsive status epilepticus and monitoring during treatment of refractory status.
It may also be used after cardiac arrest and in selected patients with periodic or rhythmic EEG patterns.
Many ICU seizures are invisible
Large observational studies have shown that electrographic seizures are common among critically ill patients selected for cEEG monitoring, and many occur without obvious clinical signs.
This is why observation at the bedside cannot replace EEG when non-convulsive seizures are suspected.
What cEEG can and cannot tell us
cEEG can identify seizures, seizure burden, background organisation and patterns associated with acute brain dysfunction.
It cannot independently determine the cause of coma, establish prognosis with certainty or tell clinicians automatically whether every abnormal periodic pattern should be treated.
Monitoring treatment
When intravenous anaesthetic therapy is used for refractory status epilepticus, clinical movements may disappear even while electrographic seizure activity persists.
cEEG is therefore used to assess whether seizure suppression has actually been achieved and to watch for recurrence during treatment reduction.
Practical limitations
Continuous EEG requires equipment, trained technologists, neurophysiology expertise and reliable systems for reviewing long recordings.
Access remains uneven between hospitals and countries, making critical-care EEG another example of a neurological technology with a global access gap.
Quantitative EEG
Quantitative EEG compresses long recordings into trend displays that can help trained clinicians screen for change and possible seizures.
It supplements rather than replaces review of the underlying raw EEG.
Related reading
Sources and further reading
- ACNS consensus statement on continuous EEG in critically ill adults and children
- Electrographic seizures and ictal-interictal continuum patterns in critically ill patients
- Seizure identification in the ICU using quantitative EEG — 2026 systematic review
Evidence checked: September 2026.