What causes EEG artifacts?

Updated: Oct 09, 2019
  • Author: Roy Sucholeiki, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Answer

Forehead, jaw, and eyelid muscle movements can cause artifacts by moving the electrodes. Movements in the surroundings produce disturbances by altering the ambient electrical fields. Moreover, the tongue and eyes have their own dipole electric charge. Therefore, their movement can get recorded by the electrodes. This, in turn, can affect the recorded brain wave.

Artifact produced by tongue movement. The person w Artifact produced by tongue movement. The person was asked to say LILT, which caused the waves to slightly undulate.
EEG artifact of eye blinking. EEG artifact of eye blinking.

ECG may contaminate the recording.

Sweating produces electrical disturbances by shorting electrode pairs.

Other sources of artifacts include ambient electrical waves from respirators, intravenous pump machines, televisions, and other electrical equipment.

  • Many are recognized by their characteristic appearance on the tracing, but others are identified by direct inspection and reported by the technologist or identified on the video tracing in video-EEG recording.

  • Artifacts show great variation because of their protean origin.

  • They may be single waves or recurrent waves (eg, intravenous infusion running), while others are prolonged disturbances (eg, sweating).

  • The specifics of each are not reviewed here because of their variability.

  • The following can be regarded as clinically insignificant:

    • Chewing produces spurious spike and wave runs in the frontal and temporal regions from the temporalis muscles (see image below).

      Example of EEG chewing artifact. Example of EEG chewing artifact.
    • Sweating produces very slow waves, because the salt solution shorts out pairs of adjacent electrodes.

    • Eye movements occur with blinking and result from the electrical charge of the eye itself (see image below). They are frontal. Nystagmus also produces artifactual waves.

      EEG artifact of eye blinking. EEG artifact of eye blinking.
    • ECG and pulse motion produce unusual waveforms. ECG produces small spikes that are recurrent and are especially evident in the monopolar montages. Pulse artifacts occur with recurrent motion of electrodes sitting over a bounding pulse, which alters the contact with the skin. This causes a rhythmic disturbance that is synchronous with the heart but rounded rather than sharp in form.

    • Tremor and movement of the head or body may cause electrodes to move.

    • Electrode pops or movements can produce sudden, recurrent, or continuous electrical waves.

    • Electrical fields result from electrical devices and televisions.

    • ICU special waveforms may result from respirator-induced movements, intravenous drips and drip pumps, electrical fields, or cautery (eg, Bovie) in the operating room or emergency department.


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