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Questions and Answers
What does EEG stand for?
What does EEG stand for?
Electroencephalography
What is the main utility of EEG?
What is the main utility of EEG?
What are the characteristic EEG alterations during an epileptic seizure called?
What are the characteristic EEG alterations during an epileptic seizure called?
What is the primary generator of EEG signals?
What is the primary generator of EEG signals?
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EEG can directly record the momentary local field potential changes arising from neuronal action potentials.
EEG can directly record the momentary local field potential changes arising from neuronal action potentials.
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What is a common artifact encountered during EEG?
What is a common artifact encountered during EEG?
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What is the principle behind differential amplification in EEG?
What is the principle behind differential amplification in EEG?
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MEG is more sensitive to biological filters than EEG.
MEG is more sensitive to biological filters than EEG.
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What is meant by the term "calibration" in EEG?
What is meant by the term "calibration" in EEG?
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What is meant by biocalibration?
What is meant by biocalibration?
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What does "10-20" refer to in the 10-20 electrode placement strategy?
What does "10-20" refer to in the 10-20 electrode placement strategy?
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What are the two main types of EEG montages?
What are the two main types of EEG montages?
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What is the term for a standard arrangement and selection of channel pairs and chains for display and review?
What is the term for a standard arrangement and selection of channel pairs and chains for display and review?
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What are the different EEG frequency bands?
What are the different EEG frequency bands?
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What is meant by the term "background" in EEG?
What is meant by the term "background" in EEG?
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What is the term for a normal background EEG in patients with eyes closed?
What is the term for a normal background EEG in patients with eyes closed?
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Alpha rhythm is typically highly symmetrical in amplitude.
Alpha rhythm is typically highly symmetrical in amplitude.
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Where is the alpha generator thought to be located?
Where is the alpha generator thought to be located?
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What is the term for independent alpha activity over the temporal regions, often seen in older patients?
What is the term for independent alpha activity over the temporal regions, often seen in older patients?
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The mu rhythm is reactive to eye opening or closure.
The mu rhythm is reactive to eye opening or closure.
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Excess beta activity is always pathological.
Excess beta activity is always pathological.
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Generalized background slowing is always pathological.
Generalized background slowing is always pathological.
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Focal slowing is always indicative of a focal brain lesion.
Focal slowing is always indicative of a focal brain lesion.
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Triphasic waveforms are considered to be ictal.
Triphasic waveforms are considered to be ictal.
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What is the term for nearly continuous periodic epileptiform complexes that repeat at a slower frequency than those of NCSE, usually 1 Hz or less?
What is the term for nearly continuous periodic epileptiform complexes that repeat at a slower frequency than those of NCSE, usually 1 Hz or less?
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Generalized periodic discharges (GPDs) are considered to represent NCSE.
Generalized periodic discharges (GPDs) are considered to represent NCSE.
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What are the three main types of psychogenic nonepileptic spells?
What are the three main types of psychogenic nonepileptic spells?
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What are the two main types of epileptic seizures?
What are the two main types of epileptic seizures?
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What is the term for absence seizures?
What is the term for absence seizures?
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What is the term for a sudden loss of postural tone, which may lead to falls?
What is the term for a sudden loss of postural tone, which may lead to falls?
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Tonic seizures are always a hallmark of generalized epilepsy.
Tonic seizures are always a hallmark of generalized epilepsy.
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What are the two phases of a tonic-clonic seizure?
What are the two phases of a tonic-clonic seizure?
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Focal seizures always involve impairment of consciousness.
Focal seizures always involve impairment of consciousness.
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What is the term for seizures with no subjective or objective clinical accompaniment?
What is the term for seizures with no subjective or objective clinical accompaniment?
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Focal seizures always result in a change in EEG activity.
Focal seizures always result in a change in EEG activity.
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Generalized slowing on EEG always indicates a focal brain lesion.
Generalized slowing on EEG always indicates a focal brain lesion.
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EEG can be used to confirm a diagnosis of brain death.
EEG can be used to confirm a diagnosis of brain death.
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What is the term for a lack of any detectable brain activity on EEG?
What is the term for a lack of any detectable brain activity on EEG?
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Who is credited with discovering the electrical properties of the brain?
Who is credited with discovering the electrical properties of the brain?
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Who is credited with recording the first human EEGs?
Who is credited with recording the first human EEGs?
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What is the term for the 10 or 20 percent intervals used to position electrodes on the scalp for EEG recordings?
What is the term for the 10 or 20 percent intervals used to position electrodes on the scalp for EEG recordings?
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Digital EEG is the only type of EEG recording method used today.
Digital EEG is the only type of EEG recording method used today.
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EEG is considered a very safe procedure.
EEG is considered a very safe procedure.
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EEG can be used to help determine the depth of anesthesia.
EEG can be used to help determine the depth of anesthesia.
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EEG is often used during the evaluation of patients with suspected seizures.
EEG is often used during the evaluation of patients with suspected seizures.
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Video-EEG monitoring is always necessary when performing a routine EEG.
Video-EEG monitoring is always necessary when performing a routine EEG.
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Video-EEG monitoring is most appropriately reserved for patients needing event characterization or seizure localization in preparation for epilepsy surgery.
Video-EEG monitoring is most appropriately reserved for patients needing event characterization or seizure localization in preparation for epilepsy surgery.
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Interictal EEG findings alone can always be used to determine the diagnosis of epilepsy.
Interictal EEG findings alone can always be used to determine the diagnosis of epilepsy.
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EEG recordings can be used to monitor the effectiveness of anti-epileptic drug treatment.
EEG recordings can be used to monitor the effectiveness of anti-epileptic drug treatment.
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EEG abnormalities cannot be used to differentiate between convulsive and nonconvulsive status epilepticus.
EEG abnormalities cannot be used to differentiate between convulsive and nonconvulsive status epilepticus.
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Video-EEG monitoring has a very high yield, and therefore should be performed routinely on all patients with epilepsy.
Video-EEG monitoring has a very high yield, and therefore should be performed routinely on all patients with epilepsy.
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Video-EEG monitoring can differentiate between psychogenic spells and epileptic seizures.
Video-EEG monitoring can differentiate between psychogenic spells and epileptic seizures.
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The use of computerized seizure and spike detection software is a highly accurate and reliable method for interpreting video-EEG data.
The use of computerized seizure and spike detection software is a highly accurate and reliable method for interpreting video-EEG data.
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Sleep deprivation is never used as a provocative technique in video-EEG monitoring.
Sleep deprivation is never used as a provocative technique in video-EEG monitoring.
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Video-EEG monitoring is always the best choice for diagnosing epilepsy.
Video-EEG monitoring is always the best choice for diagnosing epilepsy.
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Video-EEG monitoring is not helpful for characterizing spells that are non-epileptic in nature.
Video-EEG monitoring is not helpful for characterizing spells that are non-epileptic in nature.
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Video-EEG monitoring is highly specific, meaning that it can reliably distinguish between epileptic and nonepileptic events.
Video-EEG monitoring is highly specific, meaning that it can reliably distinguish between epileptic and nonepileptic events.
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Study Notes
Electroencephalography (EEG)
- EEG is an electrophysiological technique for recording electrical activity arising from the human brain.
- It's useful for evaluating dynamic cerebral functioning, especially in suspected seizures, epilepsy, and unusual spells.
Editors and Contributors
- Erik K. St. Louis, MD, Mayo Clinic College of Medicine, Rochester, Minnesota
- Lauren C. Frey, MD, University of Colorado, Denver, Colorado
- Additional contributors listed include various medical professionals with diverse expertise.
License
- Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License (BY-NC-SA)
- Proper citation of figures, tables, and images necessary when reusing or repurposing content
Table of Contents
- Covers topics like introduction, background, analysis techniques, normal and abnormal EEG patterns in different age groups, and treatment of acute seizures.
- Includes appendices on EEG generation in the brain, digital EEG principles, electrical safety, common artifacts, EEG standards, and history.
Introduction
- The first neurophysiologic recordings of animals were by Richard Caton in 1875.
- Hans Berger pioneered EEG in humans in 1924.
Calibration
- Technologists use a known voltage during EEG recording for checking amplifier fidelity.
- Biocalibration further ensures the fidelity of the cerebral signal (often by having patients open and close their eyes).
Electrode Placement and Montages
- The International 10-20 system for electrode placement is a standard strategy.
- Both bipolar and referential montages are used for different purposes (bipolar connects neighboring electrodes, referential connects each active to a distant reference.)
- A Laplacian or "source derivation" montage is also a common approach for evaluating electrical potentials to localize areas of activity.
Frequency Bandwidths
- EEG waveforms categorized into different frequency bands (e.g., delta, theta, alpha, beta, low and high gamma).
- Ripples refer to frequencies generally over 100Hz.
Common Physiological Artifacts
- Eye movement, blinking, swallowing, and muscle movements create artifacts.
- Posterior dominant rhythm (PDR) - a common, symmetrical, low-amplitude rhythmic pattern seen when eyes are closed (especially in relaxed wakefulness)
- Other normal background rhythms (theta and delta) are also present but can be focal or generalized.
Drowsiness and Sleep
- Drowsiness and sleep characterized by slow frequencies (theta and delta).
- Slow eye movements (SEMS) are a marker for the transition to deeper sleep stages.
- Defining features of sleep stages with their respective EEGs are summarized in a table.
Developmental EEG
- Specialized considerations for monitoring premature, neonatal, infant, and children EEGs.
- Particular note for electrode placement, patient state, and external factors.
- Techniques for assessing development, maturity, and response to treatment are detailed.
EEG in Epilepsies
- Routine interictal EEG in epilepsy used for seizure type diagnosis.
- Interictal epileptiform discharges are helpful, but need to be differentiated from benign variants to avoid misdiagnosis.
Focal and Generalized Slowing
- Focal slowing can be due to a number of pathologies
- Generalized slowing can be due to various etiologies.
Encephalopathy/Delirium
- Characterized by reversible generalized confusion.
- Often manifested as diffuse slowing or epileptiform patterns.
Dementias
- Early stages might be normal appearing.
- Later stages (especially second to third month of symptoms) can include periodic sharp-wave activity, often associated with myoclonus.
Anesthetic Patterns
- EEG commonly used to assess anesthetic depth in surgical procedures, especially cardiovascular and associated surgeries.
- Variations such as unilateral increased slowing or voltage reduction can suggest adjustments for surgical procedure.
Ictal EEG
- Applications of using EEG during surgical procedures are described.
- Long-term monitoring with subdural electrodes is detailed.
Urgent and Emergent EEG
- Urgent cases require particular caution in interpretation given systemic/neurologic conditions.
Pre-Lorazepam and Post-Lorazepam
- Used as an example for assessing the impact of drugs on EEG activity and treatment efficacy for seizure conditions.
Common Artifacts
- Eye movements, tongue movements, and muscle artifacts addressed.
- Electrode related issues like electrode "pop" and sweat artifacts also considered.
EEG Standards and Examples for the Determination of Brain Death
- Criteria and details necessary for confirming brain death using EEG.
Brief History of EEG
- Provides background on the development of the technique.
- Key contributors and milestones are highlighted.
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Description
This quiz provides an overview of Electroencephalography (EEG), an important technique for recording brain's electrical activity. It covers its applications, especially in evaluating seizures and abnormal brain functioning, as well as the analytical techniques used. Explore the normal and abnormal EEG patterns and their significance in various age groups.
