Definitions for EEG - EEG
Terms in this set (113)
An instrument that generates a record of the electrical activity of the brain by measuring electric potentials using electrodes attached to the scalp.
A chart of the brain waves picked up by the electrodes placed on the scalp.
A system of electrode application on the scalp using identifiable skull landmarks as reference.
Distributed using percentages of 10 and 20.
The particular arrangement by which a number of derivations are displayed simultaneously in an EEG record.
Chains of derivations that consist of electrodes along the same array, where input 2 in one channels in input 1 in the next.
A montage consisting of derivations from pairs along coronal (transverse) arrays.
Also called a Coronal Bipolar Montage.
A montage consisting of derivations from pairs of electrodes along longitudinal, usually anterior to posterior, arrays.
An arrangement of derivations in which one input 2 is common to all channels.
A pair of electrodes recorded in the EEG.
The sign of potential different between an electrode affected by the given potential and another electrode.
Any potential difference due to an extracerebral source (either physiological or mechanical) recorded in EEG tracings.
The rhythmic repetitive activity or the equivalent frequency of isolated waves.
A constant frequency.
A sequence of waves of inconstant frequency.
The amplitude of a waveform. Refers to the average voltage or peak voltage of EEG activity.
The reduction of amplitude of EEG activity resulting from decreased voltage.
An increase in voltage and regularity of rhythmic activity.
Activity that emerges from the background with a rapid onset.
The shape of a waveform.
One dominant waveform.
Multiple frequencies that combine to form a complex waveform.
Waves resembling sine waves. Monomorphic activity is usually sinusoidal.
An isolated wave or pattern that is distinctly different from the background activity.
A transient waveform with a pointed peak and duration of 20-70 milliseconds.
A transient waveform with a pointed peak and duration of 70-200 milliseconds.
A sequence of 2 or more waves, not necessarily of the same frequency, with a distinct form or pattern different from the background.
A wave or complex having 2 distinct components, one surface positive and the other surface negative.
A wave or complex with 3 distinct components, such as (+-+) or (-+-).
The amount of a particular type of EEG activity with respect to percentage time present and or voltage.
Occurring without interruption.
Appearing from time to time.
Also called intermittent
Refers to the scalp distribution of the EEG rhythms.
Not limited to a specific area of the brain.
Coming from one side of the head; asymmetric.
Coming from both sides of the head (homologous areas; symmetric).
Coming from a local region of the brain.
Equal amplitude and frequency of EEG activity over homologous areas on opposite sides of the head; bilateral.
The simultaneous occurrence of EEG activity on the same or opposite sides of the head.
The distribution of patterns or elements in time.
The reaction of the EEG to stimulation or to a stimulus-related change in morphology.
The increase of amplitude of EEG activity.
Alpha Squeak Phenomenon
A phenomenon that occurs at the moment of eye closure on the EEG. The alpha frequency temporarily increases for a very short period of time.
Alpha rhythm that appears with eyes open. Usually occurs in a drowsy, relaxed state.
A phenomenon that occurs when only one side of the posterior dominant rhythm attenuates with eye opening.
Higher amplitude waveforms compared to the background that appear because of decreased impedance pathways due to a skull defect.
High amplitude, rhythmic theta activity appearing in the central regions of children who are drowsy.
Posterior slow waves of youth
Posterior delta activity intermixed with alpha that appears in children and adolescents as a normal phenomenon.
Sharp theta transients that appear in the occipital head regions when the eyes are open and scanning detailed images.
Rhythmic theta/alpha activity that appears in some patients when lying still and motionless. Attenuates with body movement or the thought of movement.
Also called en arceau
A normal EEG phenomenon whereby the frequency of the activity recorded over the parietooccipital regions is time locked to the flash frequency during photic stimulation.
Also called the following response
Rhythmic Mid-Temporal Theta of Drowisness
A variant pattern consisting of rhythmic, notched theta that appears in the temporal regions during drowsiness.
Also called psychomotor variant or rhythmic temporal theta bursts of drowsiness.
An apiculate variant pattern seen in the temporal regions during drowsiness.
Either slower or faster patterns in the posterior head regions that have the same activation procedures as regular alpha rhythm.
Either a harmonic (faster) or subharmonic (slower)
Subclinical Rhythmic EEG Discharges in Adults
An abrupt or gradual rhythmic pattern appearing in the posterior quadrants of the head in older patients that resembles a seizure discharge but is a normal phenomenon.
14&6 Hz Positive Spikes
An arciform pattern appearing in the posterior temporal head regions in children and adolescents in drowsiness and light sleep.
Also called ctenoids.
Small Sharp Spikes
A low voltage, fast transient that occurs in drowsiness and light sleep mainly in the frontotemporal regions and tend to have a dipole.
Also called Benign Epileptiform Transients of Sleep/Benign Sporadic Sleep Spikes
6 Hz Spike and wave
A variant theta pattern occurring mainly in the frontal or posterior head regions (WHAM or FOLD).
Also called phantom spike and wave
Diphasic waveforms appearing in the frontocentral head regions during the lighter stages of sleep.
The hallmark feature of stage 2 sleep. Consists of an alpha/beta frequency pattern in the frontocentral head regions. Attenuates with deeper sleep.
Also called sigma
High voltage, diphasic complexes of the frontocentral region that emerge from the background with auditory or tactile stimulation. Tend to have overriding spindle activity.
Positive occipital sharp transients of sleep. Occur in the lighter stages of sleep and may occur in trains.
Delta with overriding theta activities in the parasaggital head regions in deeper stages of sleep. Take the shape of mittens.
Periodic lateralized epileptiform discharges. These are sharp complexes that are non-reactive to stimulation and are more pronounced with drowsiness. Tend to occur with cerebral infarction or severe damage.
PLEDs that occur in both hemispheres but tend to be independent from one another. This pattern carries a poor prognosis and indicates diffuse cerebral dysfunction.
Bilateral PLEDs that occur synchronously. Indicate diffuse cerebral dysfunction.
Generalized complex waveforms with 3 phases of polarity. Tend to have an anterior to posterior lag in the brain and occur mainly with metabolic dysfunction.
Also called liver waves
Generalized alternating periods of inactivity/low voltage activity with bursts of high voltage polyspikes, sharp waves or slow transients. Occurs with anoxic brain damage and reversible causes such as severe hypothermia, deep anaesthesia, and drug induced coma.
Intermittent rhythmic delta activity. Most common with diffuse encephalopathies than structural lesions. It is also a normal phenomenon during hyperventilation, if bilateral.
Electrocerebral inactivity. This is considered when there is no detectable EEG activity over 2 uV/mm.
Lack of EEG activity due to reversible causes, such as severe hypothermia, depressant drugs, and circulatory shock.
Any procedure designed to enhance or elicit normal or abnormal EEG activity, especially epileptiform activity.
Abnormally fast or deep respiration, which results in the loss of carbon dioxide from the blood, thereby causing a fall in blood pressure, tingling of the extremities, and sometimes fainting.
A state in which the level of carbon dioxide in the blood is lower than normal; can result from deep or rapid breathing.
The decrease in the diameter of blood vessels
Intermittent Photic Stimulation
A form of visual stimulation used in conjunction with EEG to investigate anomalous brain activity triggered by specific visual stimuli, such as flashing lights or patterns.
Abnormal EEG discharges activated by photic stimulation.
Electromyographic potentials that are intensified by photic stimulation.
An artefact due to voltage created by the photic stimulation on the electrodes.
A stage of sleep in neonates that consist of continuous EEG activity, irregular respiration, frequent body movements, decreased body tone, and eye movements.
A stage of sleep in neonates that consist of no eye or body movements, regular respirations, tonic EMG, and trace discontinu.
EEG activity of a neonate consisting of long intervals of flattening and bursts of delta activity. Intervals become higher voltage and shorter with age.
Occurs in quiet sleep up until 35 weeks conceptional age.
EEG activity of a neonate that is formed from trace discontinu. Has higher voltage and shorter intervals of flattening.
Occurs in quiet sleep up until 38-40 weeks conceptional age.
A hallmark EEG feature of prematurity. Consists of delta with superimposed beta and lasts until the neonate is about term.
High impedance crystal electrodes that are sensitive to motion and monitor respiration by placing a single electrode on the side of the chest wall and one on the abdomen.
A device that responds to the change in distance of the chest electrodes while monitoring respiration. Can also monitor movement like jerking.
A device that records the changes in temperature of air; warm coming out, cold going in.
Also called thermistors
A device that records both EKG and respirations.
Age since the mother's last menstrual period.
Gestational age + chronological age
Age since birth
A newborn infant, especially one less than four weeks old.
An event in the brain caused by excessive and/or hypersynchronous electrical neuronal activity.
A disorder of the central nervous system in which abnormal electrical activity in the brain causes seizures.
Describes the seizure itself.
The period of time right after a seizure has occurred.
The period of time in between seizures.
Epileptic seizures occurring in response to specific sensory stimuli.
A clinical entity with relatively consistent clinical features including seizure type, etiology, EEG features, neurologic status, prognosis and in some cases response to specific AEDs.
A sensation that precedes and marks the onset of a neurological condition, particularly an epileptic seizure or migraine.
Also called a warning symptom
A seizure that involves the entire brain and is characterized by general rather than localized neurologic symptoms. May be tonic-clonic, and may progress from a focal seizure.
A seizure that originates from a localized area of the cerebral cortex, involves neurologic symptoms specific to the affected area of the brain, and may progress to a generalized seizure.
Also called focal seizures
Simple partial seizures
Focal seizures within the brain that occur without altered awareness.
Complex partial seizures
Focal seizures within the brain that occur with altered level of consciousness.
Temporary paralysis that occurs in the limb or limbs involved in the jacksonian convulsions of epilepsy after the attack is over.
The progression of electrical activity through the motor cortex.
Epileptia Partialis Continua
Partial seizure status
Paroxysmal events that mimic an epileptic seizure but do not involve abnormal, rhythmic discharges of cortical neurons.