What are mu EEG variants?

Updated: Oct 09, 2019
  • Author: Roy Sucholeiki, MD; Chief Editor: Selim R Benbadis, MD  more...
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Mu (rhythm en arceau or wicket rhythm)

  • This waveform is recognized easily and has no pathological significance. The naive may not recognize it and assume it to be abnormal.

  • The mu waveform occurs in the central regions in the awake patient. It is seen best if a bone defect underlies the electrodes.

  • It can be markedly asymmetrical.

  • Often in the alpha range frequency, it has rounded positive aspects on 1 side and sharpened negative aspects on the other (see image shown below). [7]

    Example of mu waveforms. Example of mu waveforms.
  • It is not blocked by eye opening.

  • It becomes obvious when the alpha disappears (ie, alpha blocking).

  • Associated with fast activity, mu has a frequency about half that of fast activity.

  • The most classical feature of mu waveform is that it blocks with motor activity of the contralateral body (or the thought of such movement).

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