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UBC Theses and Dissertations

Scalp spreading depression Jafaryrabanybastany, Zoya


Ionic currents in the brain generate voltage oscillations, including ultra-low frequency electroencephalograms (DC-EEG) and standard electroencephalograms (AC-EEG). While AC-EEG is typical for epilepsy diagnosis, recent research highlights DC-EEG's crucial role in epilepsy analysis. AC-EEG filters out DC-EEG using high-pass filters to eliminate slow-wave artifacts, bioelectrodes' half-cell potential asymmetrical changes and prevent instrument saturation. Spreading depression (SD), a significant pathological DC-EEG, encounters challenges in scalp recording due to its ultralow frequency range, necessitating the use of invasive EEG as the sole method to capture this wave. Considering the side effects of invasive methods for epileptic patients, we designed an innovative clinical DC/AC EEG to capture SD from the surface scalp of epileptic patients and extended the clinical EEG lower band to 4mHz. Our device successfully recorded SD waves from the surface scalp of epileptic patient during clinical EEG monitoring for the first time, marking a significant breakthrough [73]. We examined DC and AC EEG in 18 epileptic patients using our innovative system during long-term video EEG monitoring in a clinical trial. Scalp SD preceded seizures with a <30-minute lag. Additionally, using our ictal EEG, SD detections, and customized brain mapping method, we located the responsible brain regions for epilepsy (EZ) and SD, revealing a clear link between scalp SD and EZ [48]. We improved the novel EEG with NIRS (Near-infrared spectroscopy) to measure local tissue oxygen levels during SD and seizures in the clinical video EEG monitoring study. During scalp SD, local tissue oxygenation decreased and returned to normal afterward. Then by using the recorded data (AC EEG, DC EEG, NIRS, synchronized video), we extracted the scalp SD features for the first time. Scalp SD showed an amplitude exceeding 1mV, lasting over 10 seconds (maximum:81s), and propagated through tissue at an average velocity of 5.7 mm/minute. AC EEG diminished during SD and subsequent seizures in epileptic patients. Hemoglobin concentrations changed during SD and seizures. More significantly, using synced video, we detected patients' neurological symptoms during the repolarization stage of SD for the first time. These findings suggest the scalp SD as an innovative biomarker for epilepsy.

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