Spatio‐temporal characterizations of non‐linear changes in intracranial activities prior to human temporal lobe seizures

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Abstract
Recent studies have shown that non‐linear analysis of intracranial activities can detect a ‘pre‐ictal phase’ preceding the epileptic seizure. Nevertheless, the dynamical nature of the underlying neuronal process and the spatial extension of this pre‐ictal phase still remain unknown. In this paper, we address these aspects using a new non‐linear measure of dynamic similarity between different parts of intracranial recordings of nine patients with medial temporal lobe epilepsy recorded during transitions to seizure. Our results confirm that non‐linear changes in neuronal dynamics allow, in most cases (16 out of 17), a seizure anticipation several minutes in advance. Furthermore, we show that the spatial distribution of pre‐ictal changes often involves an extended network projecting beyond the limits of the epileptogenic region. Finally, the pre‐ictal phase could frequently (13 out of 17) be characterized with a marked shift toward slower frequencies in upper delta or theta frequency range.