From the Guidelines
An Electroencephalogram (EEG) is indicated for evaluating several neurological conditions, primarily seizures and epilepsy, as well as altered mental status, encephalopathy, or unexplained coma, with the most recent guidelines recommending its use in patients with spontaneous intracerebral hemorrhage and impaired or fluctuating level of consciousness 1. The indications for an EEG can be broadly categorized into several key areas, including:
- Diagnosis and characterization of seizure types and epilepsy
- Evaluation of altered mental status, encephalopathy, or unexplained coma to identify potential causes such as non-convulsive status epilepticus or metabolic disturbances
- Diagnosis of brain death
- Monitoring depth of anesthesia or sedation in critical care settings
- Evaluation of sleep disorders
- Assessment of dementia or encephalitis
- Monitoring patients with cerebrovascular disorders In children, EEG may be used to evaluate developmental delays, autism spectrum disorders, or genetic syndromes with neurological manifestations. The test works by recording electrical activity in the brain through electrodes placed on the scalp, detecting abnormal patterns that correlate with specific neurological conditions, and is non-invasive, painless, and can be performed as a routine study (20-40 minutes), prolonged recording, or continuous monitoring depending on the clinical question being addressed. Recent guidelines, such as those from the American Heart Association/American Stroke Association, recommend the use of continuous EEG monitoring for at least 24 hours in patients with spontaneous intracerebral hemorrhage and impaired or fluctuating level of consciousness, as seizures are often detected after at least 24 hours of monitoring 1. Additionally, the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care recommends the use of EEG in patients with acute brain injury and unexplained and persistent altered consciousness, as well as in patients with convulsive status epilepticus that do not return to functional baseline within 60 minutes after seizure medication 1. However, the most recent and highest quality study, published in 2022, provides the strongest evidence for the indications of EEG in patients with spontaneous intracerebral hemorrhage 1.
From the Research
Indications for EEG
The indications for an Electroencephalogram (EEG) include:
- Seizure disorders, such as first seizure or known epilepsy 2, 3, 4, 5, 6
- Cognitive change 2
- Syncope 2
- Movement disorder 2
- Psychogenic non-epileptic events 2
- Unresponsiveness or intensive care unit admission 2
- Psychiatric presentation 2
- Diagnosis of epilepsy syndrome 3, 4, 6
- Presurgical evaluation of epilepsy 3
- Detection of subclinical seizures as a cause of coma 3
- Classification of seizures and epilepsy syndromes 4
- Prognostic information regarding seizure recurrence after a single unprovoked attack and following antiepileptic drug withdrawal 4
- Localization of the seizure focus for epilepsy surgery 4, 5
Specific Uses of EEG
EEG can be used to:
- Determine if attacks are of epileptic origin 3
- Estimate the recurrence risk after a first seizure 3
- Aid in the diagnosis of the epilepsy syndrome 3
- Represent the gold standard in the presurgical evaluation of epilepsy 3
- Detect subclinical seizures as a cause of coma 3
- Provide useful prognostic information regarding seizure recurrence after a single unprovoked attack and following antiepileptic drug withdrawal 4