Electrographic seizures and ictal-interictal continuum (IIC) patterns in critically ill patients

Area of Science:

• Neuroscience
• Critical Care Medicine
• Clinical Neurophysiology

Background:

• Continuous electroencephalogram (cEEG) monitoring has advanced significantly, revealing high seizure incidence in critically ill patients.
• Approximately 20% of critically ill patients on cEEG experience seizures, with ~75% having only electrographic seizures (no clinical signs).
• The ictal-interictal continuum (IIC) framework describes EEG patterns like lateralized periodic discharges (LPDs) and generalized periodic discharges (GPDs) that blur the line between ictal and interictal states.

Purpose of the Study:

• To review recent advancements in practical aspects of cEEG use in critical care.
• To discuss current treatment strategies for seizures and IIC patterns.
• To examine the association between IIC/seizures and adverse clinical outcomes.

Main Methods:

• Review of recent observational studies and clinical findings in critical care EEG.
• Analysis of the ictal-interictal continuum (IIC) conceptual framework.
• Synthesis of evidence regarding risk factors, optimal cEEG duration, pathophysiology, and treatment strategies.

Main Results:

• Seizures are common in critically ill patients, frequently presenting as electrographic seizures.
• EEG patterns within the IIC spectrum (LPDs, GPDs) are prevalent and require careful interpretation.
• Growing evidence links IIC patterns and seizures to poor neurological outcomes and potential epilepsy development.

Conclusions:

• cEEG is crucial for detecting seizures in critically ill patients, many of whom lack clinical manifestations.
• Understanding the IIC is vital for accurate diagnosis and management of these complex EEG patterns.
• Further research is needed to optimize cEEG use, treatment, and to elucidate the long-term impact on patient outcomes.