An 84-year-old woman had recurrent spells of right upper limb weakness and numbness. There were prior left parietal and right occipital strokes and metastatic breast cancer with skull involvement (figures 1 and 2). The diagnosis was focal epilepsy.
Figure 1. CT head study.
Large osteolytic lesion in the right frontal bone. Calcification in the left superior parietal lobe is secondary to prior infarction.
Figure 2. EEG recording.
High-amplitude, high-frequency activity confined to the right frontocentral region consistent with breach rhythm.
Breach effect is defined as a focal increase in amplitude of α, β, and µ rhythms detected at or near the site of a bony skull defect,1 usually seen with surgical skull defects but also with osteolytic lesions of the skull.2 There is no association with epilepsy, but the EEG alteration may be confused with focal epileptiform discharges.
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STUDY FUNDING
No targeted funding reported.
DISCLOSURE
C. O'Gorman reports no disclosures relevant to the manuscript. Dr. Cascino is a member of the American Academy of Neurology Board of Directors, an Associate Editor of Neurology®, and supported by Mayo Foundation—Mayo Medical Ventures and NIH grant—Epilepsy Phenome Genome Project: R01NS053998. Go to Neurology.org for full disclosures.
REFERENCES
- 1.Cobb WA, Guiloff RJ, Cast J. Breach rhythm: the EEG related to skull defects. Electroencephalogr Clin Neurophysiol 1979;47:251–271 [DOI] [PubMed] [Google Scholar]
- 2.Radhakrishnan K, Silbert PL, Klass DW. Breach activity related to an osteolytic skull metastasis. Am J EEG Technol 1994;34:1–5 [Google Scholar]
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