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EEG Terminology

EEG

Term	Definition
Pseudo-Rhythmic Recurrent Sharp Waves	The term previously used to describe periodic lateralized epileptiform discharges also known as PLEDs. (Chatrian 1961)
PLEDs	Periodic epileptiform discharges that occur in a focal or lateralized manner over one hemisphere.
PRFD	Periodically recurring focal discharges. (Hughes and Schlagenhauff 1965)
Cerebral Bigeminy	Alternating ipsilateral periodic lateralized epileptiform discharges. Two separate foci of periodic activity with alternating amplitudes ad morphology are present over the same area or hemisphere.
PLPD	Pseudoperiodic lateralized paroxysmal discharges. PLEDs in which the repetition rate is not precisely regular.
BIPLEDs	Bilateral PLEDs that occur independently between cerebral hemispheres.
PSPA	Periodic sinusoid paroxysmal activity. Bursts of sinusoid activity around 7-9 Hz, usually followed by a slow wave, lasting less than 500 ms, with a period less than 2 s. Mainly over the posterior head regions, associated with confusional state.
Chronic PLEDs	Persistent PLEDs over long periods of time.
PEDIM	Periodic epileptiform discharges arising from the centro-parietal midline sagittal region.
Poly PLEDs	Periodic lateralized epileptiform discharges followed by after-discharges occurring in clusters.
PLEDs Plus	PLEDs with rhythmical discharges that are more likely to be associated with clinical seizures.
PLEDs Proper	PLEDs with no associated rhythmical discharges.
Sequential PLEDs	PLEDs that occur sequentially between consecutive seizures.
Tri-Focal PLEDs	PLEDs that occur in three independent sites.
Tri-PLEDs	Tri-focal independent periodic lateralized epileptiform discharges occurring in three different areas.
IpsiIPs/Ipsi PLEDs	Periodic discharges arising from ipsilateral independent foci.
Multi-Focal PLEDs	PLEDs that occur in at least three independent site and involve both hemispheres,
EEG (Electroencephalography)	The process of amplification, recording, and analysis of the electrical potentials of the brain,
Electrocorticography	The result of electrical activity directly from the surface of the cerebral cortex either during surgery or post surgery using implanted electrodes.
Lead	A single electrodes placement on the scalp or other recording area. Also used to describe the electrode itself.
Electroencephalograph	The instrument used to amplify and record the electrical potentials of the brain.
Electroencephalogram	The EEG recording itself.
ND (Neurodiagnostics)	An umbrella term that refers to all types of neurophysiologic testing and monitoring.
Sagittal	Relating to or situated on the imaginary plane that divides a human or animal body into right and left halves.
Derivation	One set of 2 electrodes, placed into Grid 1 and Grid 2 of one channel of the electroencephalograph.
Horizontal Dipole	When the surface electrodes are able to record both the negative and positive ends of a generator.
Bipolar	Refers to the montage which consists of chains of electrodes going from anterior to posterior, left over right, in temporal chains and parasagittal chains across the head.
Monatge	An organized combination of electrode derivations recording at the same time on the electroencephalograph.
Dipole	Having two equal and opposite magnetized or electrically charged poles that are separated by a short distance.
Monopolar	Refers to a montage that is referential.
Vertex	The very top. In EEG it is Cz.
Dura Mater	The outer most toughest layer of the meninges.
Arachnoid Mater	The web like middle layer of the meninges.
Pia Mater	The innermost layer of the meninges.
Transverse	In EEG, it is a montage that goes crosswise across the head from left to right.
Discharge	Used to describe paroxysmal patterns such as epileptiform patterns and seizure patterns.
Meninges	The three membranes enveloping the brain and spinal cord. The three layers are called Dura, Arachnoid, and Pia.
Parasagittal	In EEG, the 2 planes running front to back on either side of the midline.
Channel	In EEG, one line of activity derived from 2 electrodes input into a differential amplifier.
Gyrus	One of the elevations in the convolutions of the surface of the brain caused by the in-folding of the cortex.
Gyri	Plural of gyrus.
Cortex	The convoluted layer of grey matter covering the surface of the cerebral hemispheres about half of which is hidden within the folded walls of the sulci.
Central Sulcus aka Rolandic Fissure	The central sulcus is a prominent landmark of the brain, separating the parietal lobe from the frontal lobe and the primary motor cortex from the primary auditory somatosensory cortex.
Extra Cerebral	Term indicating a location not on the head.
Meningitis	Inflammation of the meninges.
Sulcus	Literally a groove, trench, or furrow. A general term used to designate such a depression especially those on the surface of the brain.
Sulci	Plural of sulcus, as in the "sulci of the brain."
Homunculus	A pictorial representation of the anatomical divisions of the primary motor cortex and the primary somatosensory cortex.
Medial	Toward the midline of the body.
Lateral	Away from the midline of the body.
Proximal	Toward a reference point (extremity).
Distal	Away from a reference point (extremity).
Inferior	Lower or below.
Superior	Upper or above.
Cephalad or Cranial	Head.
Caudal or Cauded	Tail, tail end.
Anterior	Toward the front.
Posterior	Toward the back.
Dorsal	Posterior.
Ventral	Anterior.
Dermatomes	An area of skin that is mainly supplied by a single spinal nerve.
Hertz	Unit of frequency. Cycles per second.
Gamma	The frequency band in EEG containing faster frequencies above 30 Hz.
Beta	The frequency band in EEG containing faster frequencies 13 Hz to 30 Hz.
Alpha	The frequency band in EEG containing frequencies from 8-13 Hz.
Theta	The frequency band in EEG containing frequencies from 4 Hz to less than 8 Hz.
Delta	The frequency band in EEG containing frequencies less than 4 Hz.
Cycles per Second	Unit of frequency. Also called Hertz abbreviated Hz.
Cycles	A complete series of changes undergone by a wave or complex before the series of changes are repeated.
Dipole	Having two equal and opposite magnetized or electronically charged poles that are separated by a short distance.
Frequency	Defined as cycles per second.
Monopolar	Literally means having one pole. In EEG it refers to a montage that is referential. The term is misleading because both electrodes in a referential montage contribute electrical potentials to the differential amplifier and are actually active.
Bilateral	Both sides, in EEG is means occurring over both hemispheres.
Lateralized	Occurring only over one hemisphere.
Horizontal Dipole	When surface electrodes are able to record both the negative and positive ends of a generator.
Bipolar	Having two poles. Refers to montages that are "scalp to scalp".
Background Activity	Activity representing normal patterns or the activity present in abnormal patients during resting asymptomatic periods.
Dominant Frequency	The frequency of activity the occupies the greater part of the recording.
Diffuse	Widespread, occurring over large areas of one or both hemispheres.
Bancaud Phenomenon	Uncommon unilateral failure of the alpha to attenuate with eye opening. It may occur in lesions of the temporal or parietal lobes.
Unilateral	Restricted or remaining in one hemisphere.
Sub-harmonic	Frequency that is below the fundamental frequency, a frequency that divides evenly into the fundamental frequency.
Harmonic	A wave or frequency that is an integral multiple of a given fundamental frequency. Seen in photic driving responses and sometimes in electrical noise.
Alpha Squeak	A transient increase in alpha frequency immediately following eye closure.
Photovoltaic	Technically means generating electrical power by converting light energy. In EEG it refers to an artifact caused by the photic stimulator in the frontal leads. The artifact is eliminated by covering the electrode with something to shield the light.
Topography	Refers to the distribution of a pattern or waveform over the surface of the brain.
Focal	In a clearly delineated area of the brain in a focal temporal spike or focal slowing.
Ipsilateral	On the same side. In an Ipsilateral Ear Reference Montage, it refers ti all the electrodes in Grid 1 to the ear of mastoid on the same side of the head.
Contralateral	Relating to the opposite side of the head or body.
Generalized	Occurring simultaneously throughout the recording electrodes. A discharge can be primarily generalized or secondarily generalized.
Multifocal	Having two or more spatially separated sites of origin.
Temporal	Situated in or arising from the temporal lobe.
Central	Situated in or arising from the area of the brain around the central sulcus.
Frontal	Situated in or arising from the front.
Occipital	Posterior portion of the brain just above the cerebellum responsible for the processing of vision.
Parietal	Situated in or arising from the parietal lobe.
Focus	A limited region of the scalp, cerebral cortex or depth electrode recording side displaying a given EEG activity, either normal or abnormal.
Spread	Propagation of EEG waves from one region of the brain to another.
Homologous	Areas sharing common function. The same area on the opposite side or the same area having the same relative position in another organism.
Epileptic Focus	The exact location of the brain from which an underling epileptiform discharge originates.
Asymmetry or Asymmetrical	A change in the appearance of a rhythm on one side.
Symmetry or Symmetrical	The same on both sides, patterns that appear the same over both hemispheres.
Polymorphic	Multiple frequencies together creating complex waveforms.
Monomorphic	Having one dominant pattern of rhythm.
Morphology	The form or shape of EEG waves and patterns.
Biphasic	A waveform having 2 phases or 2 deflections on each side of the baseline.
Sharp Wave	A transient, usually negative in polarity but can be positive, with a duration of greater than 70 msec but less than 200 msec. Voltage is variable but usually is high. Morphology is sharply pointed.
Spike	A transient with a duration of less than 70 msec but more than 20 msec and commonly (though not exclusively) negative in polarity.
Sinusoidal	Having a curved shape as in an "S" or since wave.
Epileptiform	Waveforms often associated with epilepsy such as spikes, sharp waves, or spike and slow wave.
Triphasic	A waveform having 3 phases.
Electrodecremental	An event causing sudden loss of amplitude with abrupt return to the previous pattern.
Organization	The degree to which EEG rhythms conform to a certain ideal characteristic common to subjects in the same age group.
Complex	A waveform made up of more than one frequency and morphology.
Suppression	The attenuation of activity that should be there or is present on the opposite side such as in the suppression of alpha or sleep activity.
Artifact

Created by: akesselman

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