Abstract, published in Proceedings of the National Academy of Sciences of the United States of America
Epilepsy is an episodic disease characterized by brief periods of abnormal brain activity, known as seizures, that often have clinical correlates. In many patients, seizures preferentially happen during certain stages of daily and multiday cycles. However, it is unclear whether and how seizures themselves change over time, even though such variability may have clinical implications.
To address this knowledge gap, this research team quantitatively analyzed the nature of within-patient variability in seizure networks using intracranial electroencephalographic (iEEG) recordings of over 500 seizures from 31 patients with focal epilepsy (average of 16.5 seizures per patient). An iEEG is a type of EEG in which electrodes are placed directly on the brain, and a focal seizure is one in which the seizures starts from a single location in the brain.
Contrary to common expectations, this study found seizure variability throughout our group of patients. Importantly, the team demonstrated that seizures do not change randomly; instead, they also appear to fluctuate over daily and slower timescales. These results suggest that various modulatory processes, operating at different timescales, appear to lead to variable seizure pathways in individual patients. Ultimately, we may improve treatments by tailoring interventions to the full range of seizures in each patient.