| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 3043210 | Clinical Neurophysiology | 2015 | 13 Pages |
•Either ictal direct current shifts or high frequency oscillations were observed in more restricted areas than conventional ictal changes.•Both ictal direct current shifts and high-frequency oscillations contributed to delineate the core of tissue generating epileptic seizures.•The earlier occurrence of ictal direct current shifts than high frequency oscillations may suggest an active role of glia in seizure generation.
ObjectiveWe assessed the temporal–spatial characteristics of ictal direct current (DC) shifts (or infraslow activity) and high frequency oscillations (HFOs) in 16 patients with intractable focal epilepsy.MethodsThe underlying etiology consisted of cortical dysplasia, glioma, hippocampal sclerosis, and low-grade neuroepithelial tumor in nine, four, two, and one patients, respectively. The median number of analyzed seizure events was 8.0 per patient (range: 2–10). Chronic electrocorticographic recording was performed with (1) a band-pass filter of 0.016–600 Hz (or 0.016–300 Hz) and a sampling rate of 2000 Hz (or 1000 Hz).ResultsIctal DC shifts and a sustained form of ictal HFOs were observed in 75.0% and 50.0% of the patients, and 71.3% and 46.3% of the analyzed seizures. Visual assessment revealed that the onset of ictal DC shifts preceded that of ictal HFOs with statistical significance in 5/7 patients. The spatial extent of ictal DC shifts or HFOs was smaller than that of the conventionally defined seizure onset zone in 9/12 patients.ConclusionBoth ictal DC shifts and HFOs might represent the core of tissue generating seizures.SignificanceThe early occurrence of ictal DC shifts warrants further studies to determine the role of glia (possibly mediating ictal DC shifts) in seizure generation.
