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High-frequency activity has been described as having a role in the initiation of epileptic seizures. The case of a patient with refractory bitemporal epilepsy is presented. Extraoperative monitoring with depth and subdural electrodes revealed an ictal pattern with a build-up of high-frequency (> 80 Hz) activity originating in the cortex, with spread to both hippocampi. This observation was only revealed with the use of high-pass filtering, and represented crucial information that significantly influenced the decision about the side, localization and extent of resection. Removal of the cortex generating high-frequency activity, led to cessation of seizures in this patient. Current knowledge about the role of high-frequency activity and the case presented here support the importance of recording with equipment capable of detecting fast activity during the presurgical invasive monitoring. An active search for a high-frequency seizure onset zone in patients with structurally-unaffected hippocampi may improve the outcome beyond that possible with conventional bandwidth, invasive EEG recordings.

Original publication




Journal article


Epileptic Disord

Publication Date





231 - 238


Cerebral Cortex, Electrodes, Implanted, Electroencephalography, Epilepsy, Temporal Lobe, Female, Hippocampus, Humans, Magnetic Resonance Imaging, Middle Aged, Neurosurgical Procedures, Positron-Emission Tomography, Temporal Lobe