A decrease of ripples precedes seizure onset in mesial temporal lobe epilepsy
Cenglin Xu1, Shuang Wang2, Yi Wang1
1Department of Pharmacology, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, School of Medicine, Zhejiang University, Hangzhou, China.
Abstract:
High-frequency oscillations (HFOs) are promising biomarkers for epileptic foci; however, their characteristic changes during the preictal period remain unclear. Here, the preictal HFOs were recorded and detected by an automated HFOs detection method in the mouse pilocarpine model as well as in patients with mesial temporal lobe epilepsy (mTLE) and neocortical epilepsy. A total of sixteen low-voltage fast (LVF) and fifty-three hypersynchronous-onset (HYP) seizures were recorded in ten mice. The rate of ripples (80-250Hz) decreased during 1min before the onset of LVF and HYP seizures, which was primarily due to the reduction of type II (independent of epileptiform discharges) rather than type I ripples (superimposed on epileptiform activities). The ripple rate decreased until 30s before HYP seizure, whereas it increased with a peak at 40s during the 1min preictal period of LVF seizures. Furthermore, the "ripple reduction" phenomenon was also observed in all twelve seizures from nine patients with mTLE but not in neocortical epilepsy. These results indicate that ripples may potentially be helpful for understanding the mechanisms of ictogenesis in mTLE, and the different modes of ripple changes during the minute before LVF and HYP seizures might also be beneficial for the diagnosis of seizure types.
Insights
Preictal high-frequency oscillations (HFOs) show distinct patterns before seizures in epilepsy models and patients. Ripple reduction before seizures may aid in understanding ictogenesis and diagnosing seizure types.
Area of Science:
- Neuroscience
- Epilepsy Research
- Biomarker Discovery
Background:
- High-frequency oscillations (HFOs) are potential biomarkers for epileptic foci.
- Understanding preictal HFO changes is crucial for seizure prediction and understanding ictogenesis.
Purpose of the Study:
- To investigate the characteristic changes of HFOs during the preictal period in epilepsy models and patients.
- To explore the utility of preictal HFOs as biomarkers for seizure onset and type.
Main Methods:
- Automated HFO detection methods were employed.
- Recordings were made in a mouse pilocarpine model and in human patients with mesial temporal lobe epilepsy (mTLE) and neocortical epilepsy.
- Analysis focused on ripple rates (80-250Hz) in the minute preceding seizures.
Main Results:
- A decrease in ripple rate was observed in the preictal period for both low-voltage fast (LVF) and hypersynchronous-onset (HYP) seizures in mice.
- This reduction was mainly attributed to type II ripples (independent of epileptiform discharges).
- Distinct temporal patterns of ripple changes were noted before LVF and HYP seizures, and a 'ripple reduction' phenomenon was observed in mTLE patients but not in neocortical epilepsy.
Conclusions:
- Preictal ripple changes may offer insights into the mechanisms of ictogenesis in mTLE.
- Differential preictal ripple dynamics could potentially aid in diagnosing seizure types.
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