Continuous EEG Monitoring

OVERVIEW

• emerging technique for neurological monitoring
• not widely used

USES

• increases sensitivity of detection non-convulsive seizures
• determine depth of sedation
• distinguish epileptic from non-epileptic motor activity
• monitor dynamic changes in brain function e.g. ischemia, vasospasm, rebleeding
• monitor treatment response (e.g. anti-epileptic drugs)
• may have a role in prognostication of hypoxic brain injury, intracranial hemorrhage and TBI

INDICATIONS

Consider in patients at high risk of NCSE (~20% risk):

• patients with seizures
• patients with coma
• intracranial haemorrhage
• SAH
• encephalitis
• TBI
• post cardiac arrest
• hypoxic ischemic brain injury and metabolic disorders in paediatric patients

METHOD OF USE

Duration of monitoring

• 24 hours monitoring if not comatose
• 28-72 hours if comatose
• If PLED present monitor >24 hours

Reducing interference

• use of electrical filter
• may require neuromuscular blockade of movement interference

In some circumstances a modified array or reduced channels may be needed (may reduce sensitivity)

PROS AND CONS

Advantages

• monitors a dynamic situation
• provides information at the bedside
• high sensitivity

Disadvantages

• labour and resource intensive
• requires skilled interpretation
• multiple sources of potential artifact in the ICU setting
  • environmental
    • airflow around bed
    • electrical devices
    • IV drip counters
  • patient factors
    • movements
    • skull defects or hematoma
    • excessive sweating
    • pacemaker interference

OTHER INFORMATION

Non-convulsive seizures

• without cEEG >50% of non-convulsive status epilepticus (NCSE) is missed in ICUs
• Non-convulsive seizures (NCS) occur in about 50% of patients with coma or convulsive status epilepticus
• NCS occur in 8-37% of the general ICU population
• associated with poorer prognosis and surrogates such as increased neuron-specific enolase and hippocampal atrophy

Sensitivity of cEEG

• 56% of seizures occur in the first hour of cEEG
• 88% of seizures occur in the first 24h of cEEG
• 93% of seizures occur in the first 48h of cEEG

30 minute EEG

• lacks sensitivity for detecting NCS and NCSE in ICU settings
• may be used for risk stratification, e.g. if epileptiform discharges then extend monitoring
• may be performed serially, with increased sensitivity the greater the frequency
• an option in the absence of cEEG capacity, but still labour and resource intensive

References and Links

LITFL

• CCC — Non-Convulsive Status Epilepticus (NCSE)
• CCC — Electroencephalogram
• CCC — Continuous EEG Monitoring
• CCC — BIS Monitoring

Journal articles

• Caricato A, Melchionda I, Antonelli M. Continuous Electroencephalography Monitoring in Adults in the Intensive Care Unit. Crit Care. 2018;22(1):75. [pubmed]
• Friedman D, Claassen J, Hirsch LJ. Continuous electroencephalogram monitoring in the intensive care unit. Anesth Analg. 2009 Aug;109(2):506-23.PMID: 19608827.
• Kennedy JD, Gerard EE. Continuous EEG monitoring in the intensive care unit. Curr Neurol Neurosci Rep. 2012 Aug;12(4):419-28. PMID: 22653639.
• Sutter R. Are We Prepared to Detect Subtle and Nonconvulsive Status Epilepticus in Critically Ill Patients?. J Clin Neurophysiol. 2016;33(1):25-31. [pubmed]
• Trinka E, Leitinger M. Which EEG patterns in coma are nonconvulsive status epilepticus?. Epilepsy Behav. 2015;49:203-22. [pubmed]

FOAM and web resources

• ICN Podcast — 85. Flower on Continuous EEG Monitoring(2013)