We employ a multiscale symbolic analysis to investigate the complex dynamics associated with temporal lobe refractory epilepsy using high-resolution intracranial EEG (iEEG). Our focus is on the basal and preictal phases of epilepsy, examining frequency bands up to 240 Hz to uncover key periodicities and time scales in neural activity. By applying band-pass filtering to the signals, we isolate components within the delta, theta, alpha, beta, gamma, and high-frequency oscillations (HFO) bands, allowing us to analyze distinct nonlinear dynamics.

Our approach involves identifying critical time lag scales (τ) within these frequency bands, which are essential for understanding refractory epilepsy. We utilize metrics such as permutation entropy (H), Fisher information (F), and complexity (C) to reveal nonlinear patterns and determine intrinsic τ that optimize complexity. A comparative analysis of basal and preictal signals highlights significant differences in the delta and 200-220 Hz (HFO 6) bands. Notably, variations in Fisher information observed before seizures emphasize the role of delta oscillations and HFO waves as potential biomarkers, offering novel insights into the dynamics of focal epilepsy.