Breach rhythm on EEG

Effect of a skull defect · Benign variants

High-amplitude sharply contoured activity at C4 only: the skull defect, not a focus. Simulated trace, longitudinal bipolar channels. Open in the interactive viewer

What it looks like

Over a craniotomy or burr hole the skull no longer filters the signal, so activity under the defect appears higher in amplitude, faster and sharper: prominent mu-like and beta activity confined to one or two electrodes. ^3,11

What it means at the bedside

Sharp-looking transients inside a breach are over-called. Demand a clear after-going slow wave and a field beyond the defect before calling them epileptiform. Focal slowing in the same place does reflect the underlying lesion.

BenignFocalPost-surgical

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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/

Breach rhythm on EEG

What it looks like

What it means at the bedside

Sources

Related patterns