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Breach is not just for babies!

EEG has many descriptions and patterns related to the electrical activity in the brain. Breach is simply one of them. Most of us recognize the term "breach" as a deliver position for babies in the womb. But if you are in the Neurodiagnostic field, you know this is also an electrical discharge pattern coming from the brain. More specifically related to trauma cases where the skull barrier to the brain is missing or has an abnormality.

To understand what this pattern is and why we see this in EEG, we need to understand the basic principals of EEG and how it is preformed. EEG is a non invasive diagnostic tool. A precise measurement of the patient's head is done to locate and place individual electrodes on the scalp over specific areas of the brain to measure electrical impulses. As trained EEG technicians, we learn to read these electrical impulses and the patterns they create.

Why would we see this pattern in EEG. This pattern is produced when the skull barrier is missing or has a defect eliminating or reducing the skull thickness. In normal scalp EEG, we have the skull barrier that impedes the electrical impulses uniformly. If there is a skull defect or damage from surgery or trauma, there is no uniform barrier to impede the electrical impulses. This creates a focal point over the area of defect with much larger amplitudes. This is most commonly asymmetrical due to the location of surgery or trauma.


You may also hear different descriptions for this pattern such as Breach Rhythm or Breach Effect used to describe this distinct pattern. This is simply describing the same electrical impulse created by the skull defect. While this pattern is very distinct and can mimic an abnormality in the EEG findings due to the sharp contours, high amplitudes and irregular morphology, it is in fact benign. This pattern has no clinical significance to diagnosis, but can be easily mistaken for an abnormality if the technician does not document the skull defect or surgical site.


Some causes of Breach Rhythm may be evident by recent surgery or trauma as we treat inpatients. However, taking a good patient history is also important in the clinical setting. Patients may present with Breach Rhythm as outpatients as well. This can be due to artificial skull replacement materials used to repair the skull defect. This can also lead to misdiagnosis of epileptiform if a proper history is not documented. When in doubt always go back to basics:

  • Age

  • level of consciousness

  • medical history

  • medication

  • location of activity

  • Verify the EEG findings by changing montage (this pattern will remain in the same channels no matter what montage you change to due to the skull defect)

Breach Rhythm is specific to a skull defect and is not used to describe neonatal EEG or infant EEG patterns. We need to recognize also the development in the skull to determine an abnormality. Neonate and infant EEG are normally high amplitude. This is in part due to the brain development as well as the skull development. We need to recognize that age and physiological development also have a role in EEG and how the activity is interpreted as normal or abnormal. Always go back to basics to determine if what you are seeing is abnormal or normal.






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