Definitions for EEG - EEG
Electroencephalogram
An instrument that generates a record of the electrical activity of the brain by measuring
electric potentials using electrodes attached to the scalp.
Electroencephalograph
A chart of the brain waves picked up by the electrodes placed on the scalp.
10-20 System
A system of electrode application on the scalp using identifiable skull landmarks as
reference.
Distributed using percentages of 10 and 20.
Montage
The particular arrangement by which a number of derivations are displayed
simultaneously in an EEG record.
Bipolar Montage
Chains of derivations that consist of electrodes along the same array, where input 2 in
one channels in input 1 in the next.
Transverse Montage
A montage consisting of derivations from pairs along coronal (transverse) arrays.
Also called a Coronal Bipolar Montage.
Longitudinal Montage
A montage consisting of derivations from pairs of electrodes along longitudinal, usually
anterior to posterior, arrays.
Reference Montage
An arrangement of derivations in which one input 2 is common to all channels.
Derivation
A pair of electrodes recorded in the EEG.
Polarity
The sign of potential different between an electrode affected by the given potential and
another electrode.
Artefact
Any potential difference due to an extracerebral source (either physiological or
mechanical) recorded in EEG tracings.
Frequency
The rhythmic repetitive activity or the equivalent frequency of isolated waves.
Rhythmic
A constant frequency.
Arrhythmic
A sequence of waves of inconstant frequency.
Voltage
, The amplitude of a waveform. Refers to the average voltage or peak voltage of EEG
activity.
Attenuation
The reduction of amplitude of EEG activity resulting from decreased voltage.
Hypersynchrony
An increase in voltage and regularity of rhythmic activity.
Paroxysmal
Activity that emerges from the background with a rapid onset.
Morphology
The shape of a waveform.
Monomorphic
One dominant waveform.
Polymorphic
Multiple frequencies that combine to form a complex waveform.
Sinusoidal
Waves resembling sine waves. Monomorphic activity is usually sinusoidal.
Transient
An isolated wave or pattern that is distinctly different from the background activity.
Spike
A transient waveform with a pointed peak and duration of 20-70 milliseconds.
Sharp wave
A transient waveform with a pointed peak and duration of 70-200 milliseconds.
Complex
A sequence of 2 or more waves, not necessarily of the same frequency, with a distinct
form or pattern different from the background.
Biphasic
A wave or complex having 2 distinct components, one surface positive and the other
surface negative.
Triphasic
A wave or complex with 3 distinct components, such as (+-+) or (-+-).
Quantity
The amount of a particular type of EEG activity with respect to percentage time present
and or voltage.
Continuous
Occurring without interruption.
Discontinuous
Appearing from time to time.
Also called intermittent
Irregular Quantity
Inconsistent frequency
Regular Quantity
Consistent freqency
Location
Refers to the scalp distribution of the EEG rhythms.
Generalized
Electroencephalogram
An instrument that generates a record of the electrical activity of the brain by measuring
electric potentials using electrodes attached to the scalp.
Electroencephalograph
A chart of the brain waves picked up by the electrodes placed on the scalp.
10-20 System
A system of electrode application on the scalp using identifiable skull landmarks as
reference.
Distributed using percentages of 10 and 20.
Montage
The particular arrangement by which a number of derivations are displayed
simultaneously in an EEG record.
Bipolar Montage
Chains of derivations that consist of electrodes along the same array, where input 2 in
one channels in input 1 in the next.
Transverse Montage
A montage consisting of derivations from pairs along coronal (transverse) arrays.
Also called a Coronal Bipolar Montage.
Longitudinal Montage
A montage consisting of derivations from pairs of electrodes along longitudinal, usually
anterior to posterior, arrays.
Reference Montage
An arrangement of derivations in which one input 2 is common to all channels.
Derivation
A pair of electrodes recorded in the EEG.
Polarity
The sign of potential different between an electrode affected by the given potential and
another electrode.
Artefact
Any potential difference due to an extracerebral source (either physiological or
mechanical) recorded in EEG tracings.
Frequency
The rhythmic repetitive activity or the equivalent frequency of isolated waves.
Rhythmic
A constant frequency.
Arrhythmic
A sequence of waves of inconstant frequency.
Voltage
, The amplitude of a waveform. Refers to the average voltage or peak voltage of EEG
activity.
Attenuation
The reduction of amplitude of EEG activity resulting from decreased voltage.
Hypersynchrony
An increase in voltage and regularity of rhythmic activity.
Paroxysmal
Activity that emerges from the background with a rapid onset.
Morphology
The shape of a waveform.
Monomorphic
One dominant waveform.
Polymorphic
Multiple frequencies that combine to form a complex waveform.
Sinusoidal
Waves resembling sine waves. Monomorphic activity is usually sinusoidal.
Transient
An isolated wave or pattern that is distinctly different from the background activity.
Spike
A transient waveform with a pointed peak and duration of 20-70 milliseconds.
Sharp wave
A transient waveform with a pointed peak and duration of 70-200 milliseconds.
Complex
A sequence of 2 or more waves, not necessarily of the same frequency, with a distinct
form or pattern different from the background.
Biphasic
A wave or complex having 2 distinct components, one surface positive and the other
surface negative.
Triphasic
A wave or complex with 3 distinct components, such as (+-+) or (-+-).
Quantity
The amount of a particular type of EEG activity with respect to percentage time present
and or voltage.
Continuous
Occurring without interruption.
Discontinuous
Appearing from time to time.
Also called intermittent
Irregular Quantity
Inconsistent frequency
Regular Quantity
Consistent freqency
Location
Refers to the scalp distribution of the EEG rhythms.
Generalized
