The extension of epileptogenicity as the driving force of the epileptogenic network evolution and complex symptoms

The concept of epileptogenic network was proposed with epilepsy increasingly understood as the result of network disorder. These alterations of networks proved to be associated with the increased seizure susceptibility in response to external stimulus or internal noise. However, the driving force behind its evolution is unclear. Substantial epilepsy research suggested that the epileptogenicity could be observed beyond clinically defined epileptogenic zone. Therefore, the mechanism of the epileptogenic network evolution may be related with the extension of epileptogenicity. In this paper, a small-world network with each node represented by a bistable computational model was established. Furthermore, part of the nodes connected with the primary epileptogenic zone would be transformed into secondary epileptogenic nodes during the evolution of networks, which represents the formation of secondary epileptogeniciy due to the kindling-like effect. Escape time was defined to quantify the likelihood of a node to develop into epileptic state. Meanwhile, phase synchronization was introduce to analyze the synchronization patterns in simulated multiunit systems. Results showed that the extension of epileptogenicity could increase the seizure likelihood of almost all nodes. Particularly, the synchronization patterns were significantly changed with the occurrence of the secondary epileptogenicity, which might imply the variation of functional connectivity between areas. Meanwhile, the reversal of nonspontaneous epileptogenicity could lead to running-down phenomenon. The extension of epileptogenicity seemed to provide novel insights into the diagnosis and treatment, indicating the possible minimum resection to reach excellent long-term surgical outcomes.