Mu rhythm on EEG

Central arciform rhythm · 7–11 Hz · Normal

Arciform central rhythm. The left central mu blocks when the right fist is clenched. Simulated trace, longitudinal bipolar channels. Open in the interactive viewer

What it looks like

Arch-shaped 7–11 Hz activity over the central region (C3, C4), often asymmetric or one-sided. It does not react to eye opening; it attenuates with movement, or thought of movement, of the opposite hand. ^3,11

What it means at the bedside

Its sharp contour and asymmetry invite over-reading as epileptiform. Ask the patient to make a fist: mu disappears, a focus does not.

Normal variantCentral

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Sources

Kane N, et al. A revised glossary of terms most commonly used by clinical electroencephalographers and updated proposal for the report format of the EEG findings (IFCN, 2017). Clin Neurophysiol Pract 2017;2:170–185. doi.org/10.1016/j.cnp.2017.07.002
Britton JW, et al. Electroencephalography (EEG): An Introductory Text and Atlas of Normal and Abnormal Findings in Adults, Children, and Infants. American Epilepsy Society, 2016 (free, NCBI Bookshelf). www.ncbi.nlm.nih.gov/books/NBK390354/

Mu rhythm on EEG

What it looks like

What it means at the bedside

Sources

Related patterns