Breach Rhythm

The skull acts as a high-frequency and high voltage filter. A breach rhythm results from a skull defect, indicative of a bone abnormality, not an EEG abnormality. The lack of bone allows more fast activity and sharper or spiky-appearing cortical activity to be recorded. The skull defect may be due to a brain surgery or a previous skull trauma. 

Breach rhythm is typically focal, asymmetrical, high-voltage activity in the beta frequency range. It often has arch-like waveforms, sometimes having spiky morphology. It can manifest as an irregular rhythm sometimes associated with sharp activity. Breach rhythm is most prominent when recorded over central and temporal regions. Breach rhythm can be identified easily when it occurs in serial trains.