Seizure pathways and seizure durations can vary independently within individual patients with focal epilepsy

Abstract

longer durations than seizures that remain focal (Dobesberger et al., 2015; Kaufmann et al., 2020), and focal seizures tend to be longer if they involve loss of awareness (Dobesberger et al., 2015;. Meanwhile, analysis of chronic intracranial EEG (iEEG) recordings suggests that seizures with different durations have similar onsets, but different terminations (Karoly et al., 2018). Additionally, there is evidence that distinct populations of short and long seizures correspond to different seizure pathways with characteristic durations (Cook et al., 2016;Karoly et al., 2018). These findings suggest that seizure pathways and durations may co-vary within patients, with different seizure durations serving as a proxy for different seizure pathways. However, it is also possible that seizure duration is modulated independently of the seizure's pathway. Two seizures could potentially follow the same pathway, but have different durations due to variable rates of progression (e.g. by "dwelling" in particular EEG activity patterns). In a rodent model, Wenzel et al. (2017) found seizures with consistent recruitment patterns and different rates of seizure spread at a neuronal level, a characteristic termed "elasticity." To our knowledge, no studies have quantitatively explored such temporal flexibility in seizure pathways in human patients. Nonetheless, within-patient seizures with consistent firing patterns, but small changes in duration, have been observed (Truccolo et al., 2011), suggesting that elasticity in the same seizure