Reproducibility of Temporally Evolving Seizure Patterns and Network Connectivity in Focal Epilepsy

Yaohong Wei^1,2Wei Zhang³Sinclair Liu³Biao Han^1,2*Qi Chen^1,2*

• ¹Country Center for Studies of Psychological Application, South China Normal University, Guangzhou, China, Guangzhou, China
• ²School of Psychology, South China Normal University, Guangzhou, China
• ³Department of Neurology, Beijing Tsinghua Changgung Hospital, School of Clinical Medicine, Tsinghua University, Beijing, China, Beijing, China

Clinical semiology, waveform patterns, frequency band characteristics, neuronal spiking activity, and connectivity network dynamics exhibit notable reproducibility across seizures in the same patient. However, whether these reproducible features distinctly delineate the epileptogenic zone, propagation zone, and non-involved zone and the underlying temporal dynamics remain unclear. In this study, we included 14 patients with focal epilepsy characterized by low-voltage fast activity and with pre-LVFA patterns of rhythmic spikes and/or burst of polyspikes. We examined the reproducibility of raw signals, power spectra, and connectivity patterns across multiple seizures during the interictal, pre-LVFA, and ictal periods. During the ictal phase, raw signals and power spectra in both the high (gamma and ripple) and low (delta) frequency bands demonstrated greater reproducibility in epileptogenic zone than propagation zone. Since the high and low frequency bands during seizure onsets have been associated with fast inhibitory interneuron activity and principal neuron activity, respectively, the present results imply that activity of different neuronal populations in the epileptogenic zone may remain stable across seizures. More importantly, during the pre-LVFA period, the reproducibility of beta band power spectra in epileptogenic zone, the connectivity patterns within epileptogenic zone and between epileptogenic zone and propagation zone could already discriminate the epileptogenic zone from the propagation zone prior to the low-voltage fast activity onset. Taken together, the reproducibility of raw signals and power spectra in high and low frequency bands during the ictal period could help to improve diagnostic precision of epileptogenic zone, and the reproducibility of pre-LVFA beta band power spectra, the connectivity within epileptogenic zone and between epileptogenic zone and propagation zone would aid in predicting seizure onsets.