What are electrode artifacts on EEG?

Updated: Oct 09, 2019
  • Author: Selim R Benbadis, MD; Chief Editor: Helmi L Lutsep, MD  more...
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Answer

The most common electrode artifact is the electrode popping. Morphologically this appears as single or multiple sharp waveforms due to abrupt impedance change. It is identified easily by its characteristic appearance (ie, abrupt vertical transient that does not modify the background activity) and its usual distribution, which is limited to a single electrode. In general, sharp transients that occur at a single electrode should be considered artifacts until proven otherwise.

Sweat artifact. This is characterized by very low- Sweat artifact. This is characterized by very low-frequency (here, 0.25- to 0.5-Hz) oscillations. The distribution here (midtemporal electrode T3 and occipital electrode O1) suggests sweat on the left side. Note that morphology and frequency are also consistent with slow rolling eye movements, but distribution is not.

At other times, the impedance change is not so abrupt, and the artifact may mimic a low-voltage arrhythmic delta wave.

Electrode artifact at frontal pole electrode Fp1. Electrode artifact at frontal pole electrode Fp1. The duration is too short ("narrow") for any cerebral potential, and the distribution is limited to a single electrode (Fp1). In general, activity that affects a single electrode (ie, without the expected drop off and activity at neighboring electrodes or "plausible field") should be considered an artifact until proven otherwise.
Electrode artifact at occipital electrode O1. The Electrode artifact at occipital electrode O1. The morphology is very unusual for any cerebral waveform, and the distribution is limited to a single electrode. In general, activity that affects a single electrode (ie, without the expected drop off and activity at neighboring electrodes or "plausible field") should be considered an artifact until proven otherwise.
Electrode artifact at frontal electrode F3. This s Electrode artifact at frontal electrode F3. This should not be misinterpreted as a spike. This sharply contoured transient clearly occurs at only one electrode, as confirmed on the referential montage.
Electrode (impedance) artifact at parietal electro Electrode (impedance) artifact at parietal electrode P3. Initially, a slow artifact is followed by a more abrupt one at the seventh second. This commonly is referred to as an electrode pop. Note again the unusual morphology of the sharp component and that it is at a single electrode. Also note an eye blink in the third second and slight electromyogram artifact in the frontal regions in the first 2 seconds.
Just as electrode artifacts can simulate intericta Just as electrode artifacts can simulate interictal spikes, they also can mimic an ictal pattern. This rhythmic artifact may be mistaken for an electrographic seizure or subclinical rhythmic epileptiform discharges of adults (SREDA). However, this is confined to a single electrode (posterior temporal electrode T6), as can be confirmed on a referential montage. This artifact often is confirmed by the presence of other definite electrode pops in the same electrode.

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