From the Guidelines
For a possible seizure, an electroencephalogram (EEG) with extended monitoring, specifically to monitor nonconvulsive seizure activity, is recommended. The choice of EEG type is guided by the clinical context and the need to detect seizure activity, which may not be captured by a standard short-duration EEG. According to the clinical practice guidelines for the management of patients in the intensive care unit 1, EEG monitoring is crucial for detecting nonconvulsive seizures in patients with known or suspected seizures. Key considerations in selecting an EEG monitoring approach include:
- The duration of monitoring: Extended monitoring such as 24-hour ambulatory EEG or longer durations like 2-5 days of video-EEG monitoring may be necessary to capture intermittent seizure activity.
- The clinical setting: For patients in the ICU, particularly those with elevated intracranial pressure, EEG can be used to titrate electrosuppressive medication to achieve burst suppression, as recommended by guidelines 1.
- The patient's condition: Sleep-deprived EEGs can be valuable as they may provoke abnormal brain activity in susceptible individuals.
- The need for simultaneous recording of brain activity and physical manifestations: Long-term video-EEG monitoring in an epilepsy monitoring unit is beneficial for correlating electrical abnormalities with clinical symptoms, aiding in the accurate diagnosis and classification of seizure type. Given the importance of detecting and managing seizures effectively to prevent morbidity, mortality, and to improve quality of life, the use of extended EEG monitoring is prioritized based on the most recent and highest quality evidence available 1.
From the Research
Types of EEG for Seizure Diagnosis
The following types of EEG are used for seizure diagnosis:
- Routine EEG: used to evaluate patients with suspected seizures or for seizure management 2, 3
- Sleep-deprived EEG (SDE): used to detect interictal discharges and validate a syndromic classification of epilepsy when standard EEG is negative 4
- Ambulatory EEG (Amb-EEG): used to detect interictal discharges and evaluate treatment efficacy 4
- Long-term video-EEG recording (LTVER): used for pre-surgical evaluation of drug-resistant epilepsy and to analyze electro-clinical correlations 4
- EEG with activation techniques: such as hyperventilation, intermittent photic stimulation, and sleep deprivation, which can help increase the occurrence of interictal epileptiform abnormalities 2, 3, 5, 6
Activation Techniques
Activation techniques used in EEG include:
- Hyperventilation: can help trigger the expression of epileptogenic activity 2, 6
- Intermittent photic stimulation: can help trigger the expression of epileptogenic activity, especially when combined with sleep deprivation 5, 6
- Sleep deprivation: can help increase the occurrence of interictal epileptiform abnormalities 2, 4, 5
Indications for Long-term EEG
Long-term EEG is indicated for:
- Syndromic classification of epilepsy
- Search for interictal discharges when epilepsy is suspected or for therapeutic evaluation
- Positive diagnosis of paroxysmal clinical events
- Pre-surgical evaluation of drug-resistant epilepsy 4