A glossary of terms for EEG findings

In order to read and provide report to patient, Electroencephalographers should know how to write a professional report. The glossary what I list are most commonly used by clinical eclectroencephalographers and proposal for the report form for the EGG findings. Since all report should be decribed as precisely as posible, the students or poeple who work in this field must know all of them.

Absence

Use of term discouraged when describing EEG patterns. Terms suggested, whenever appropriate: spike-and-slow-wave complex; 3/s spike-and-slow-wave complex; sharp-and-slowwave complex

Activation procedure

(1) Any procedure designed to enhance or elicit normal or abnormal EEG activity, especially paroxysmal activity. Examples: hyperventilation, photic stimulation, sleep, injection of convulsant drugs. (2) Induction of an EEG pattern consisting of a low voltage record which becomes apparent upon blocking of EEG rhythms by physiological or other stimuli such as electrical stimulation of the brain (use in this meaning discouraged).

Baseline

1) Strictly: line obtained when an identical voltage is applied to the two input terminals of an EEG ampli®er or when the instrument is in the calibrate position but no calibration signal is applied. (2) Loosely: imaginary line corresponding to the approximate mean values of the EEG activity assessed visually in an EEG derivation over a period of time.

Blocking

(1) Apparent, temporary obliteration of EEG rhythms in response to physiological or other stimuli such as electrical stimulation of the brain (see attenuation). (2) A condition of temporary unresponsiveness of the EEG ampli®er, caused by major overload. Manifested initially by extreme, ¯at-topped trace excursion(s) lasting up to a few seconds (see overload, clipping).

Channel

Complete system for the detection, ampli®cation and display of potential differences between a pair of electrodes. Comment: analog electroencephalographs generally have several EEG channels. Digital EEG machines simulate a multichannel display by tracing several voltage time plots on a visual display.

Coronal bipolar montage

A montage consisting of derivations from pairs of electrodes along coronal (transverse) linear arrays. Synonym: transverse bipolar montage.

Cycle

The complete sequence of potential changes undergone by individual components of a sequence of regularly repeated EEG waves or complexes.

Deep sleep

Non-REM sleep stages 3 and 4 (Rechtschaffen and Kales 1968).

EEG

Abbreviation for electroencephalogram, electroencephalography and electroencephalographic.

Impedance meter

An instrument used to measure impedance (see electrode impedance)

Paper speed

Velocity of movement of EEG paper. Expressed in centimeters per second (cm/s) or millimeters per second (m/s).

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