Characterization of Breach Rhythm on Scalp EEG
Abstract number :
1.548
Submission category :
3. Neurophysiology / 3C. Other Clinical EEG
Year :
2025
Submission ID :
1302
Source :
www.aesnet.org
Presentation date :
12/6/2025 12:00:00 AM
Published date :
Authors :
Presenting Author: Siefaddeen Sharayah, MD – Washington University School of Medicine
Doyle Yuan, MD – University of Texas Southwestern Medical Center
Adam Greenblatt, MD – Washington University School of Medicine
Wei Zhao, MD, MSc – McGovern Medical School, UTHealth Houston
M. Brandon Westover, MD, PhD – Beth Israel Deaconess Medical Center
Sándor Beniczky, MD, PhD – Aarhus University Hospital, Member of European Reference Network EpiCARE and Danish Epilepsy Centre
Fábio Nascimento, MD – Washington University School of Medicine
Rationale: Breach rhythm is an EEG pattern recorded over or near a skull defect due to reduced attenuation of cortical signals. It demonstrates relatively higher amplitude than surrounding cerebral potentials, often with sharp or spiky components and faster embedded frequencies (e.g., beta). Accurate recognition is critical to avoid EEG misinterpretation such as overcalling sharp transients as epileptiform discharges or misidentifying background changes as focal slowing. We aimed to characterize breach rhythm on scalp EEG by analyzing a large consecutive series of outpatient studies whose reports included this finding.
Methods: We retrospectively reviewed outpatient scalp EEGs (January 2020–April 2024) in the adult EEG laboratory at Washington University in St. Louis. The study was approved by the institution’s review board. Inclusion required breach rhythm in the clinical EEG report. Clinical data included age, epilepsy diagnosis, seizure semiology, procedure type, lesion characteristics, defect location, and time from surgery/trauma to EEG. Studies were reviewed via our online platform (EEGHub) with adjustable settings, voltage maps, and spectrograms. Three experts (DY, FA, AG) reviewed EEGs with skull defect location known and recorded breach rhythm presence/absence, lateralization, and the following features: (1) amplitude ≥50% greater than the contralateral homologous site, (2) increased local faster frequencies (beta), and (3) local sharp or spiky morphology.
Results: We analyzed 117 EEGs from 115 patients (mean duration 40.8 minutes, range 20.6–64.3). Skull defects followed neurosurgical procedures (109/115) or traumatic brain injury. Mean time from surgery/trauma to EEG was 9.1 years (range 0–35). Interrater variability included 24 disagreements on breach presence and 3 on lateralization. Breach rhythm was identified in 85/117 cases (73%) (Figure 1). Among these, 15% showed one feature, 48% two, and 36% all three. Single-feature cases included increased beta (54%) or higher amplitude (46%); sharp/spiky morphology alone was not observed. When two features co-occurred, combinations were higher amplitude plus sharp/spiky morphology (68%), higher amplitude plus beta (27%), and beta plus sharp/spiky morphology (4.9%). Overall, higher amplitude was most prevalent (89%), followed by sharp/spiky morphology (72%) and beta activity (60%).
Conclusions: Breach rhythm was not identified by expert raters in over a quarter of cases with skull defects. While higher amplitude was the most consistently identified feature of breach, the overall appearance of breach did vary across cases. This variability supports the idea that breach rhythm exists on a spectrum.
Funding: None
Neurophysiology