Kyoko Kanazawa1, Riki Matsumoto2, Hisaji Imamura1, Masao Matsuhashi3, Takayuki Kikuchi4, Takeharu Kunieda4, Nobuhiro Mikuni5, Susumu Miyamoto4, Ryosuke Takahashi1, Akio Ikeda6. 1. Department of Neurology, Kyoto University, Kyoto, Japan. 2. Department of Epilepsy, Movement Disorders and Physiology, Kyoto University, Kyoto, Japan. 3. Human Brain Research Center, Kyoto University, Kyoto, Japan. 4. Department of Neurosurgery, Kyoto University, Kyoto, Japan. 5. Department of Neurological Surgery, Sapporo Medical University, Sapporo, Japan. 6. Department of Epilepsy, Movement Disorders and Physiology, Kyoto University, Kyoto, Japan. Electronic address: akio@kuhp.kyoto-u.ac.jp.
Abstract
OBJECTIVE: We 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. METHODS: The 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 0.016-600Hz (or 0.016-300Hz) and a sampling rate of 2000Hz (or 1000Hz). RESULTS: Ictal 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. CONCLUSION: Both ictal DC shifts and HFOs might represent the core of tissue generating seizures. SIGNIFICANCE: The early occurrence of ictal DC shifts warrants further studies to determine the role of glia (possibly mediating ictal DC shifts) in seizure generation.
OBJECTIVE: We 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. METHODS: The 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 0.016-600Hz (or 0.016-300Hz) and a sampling rate of 2000Hz (or 1000Hz). RESULTS: Ictal 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. CONCLUSION: Both ictal DC shifts and HFOs might represent the core of tissue generating seizures. SIGNIFICANCE: The early occurrence of ictal DC shifts warrants further studies to determine the role of glia (possibly mediating ictal DC shifts) in seizure generation.
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