Observational Study of the Structural-functional Connectome in Patients With Epilepsy

Over the past decade, the concept of the brain as a complex network has extremely influenced the way regarding how the latter is studied (Bartolomei et al., 2017). The structure of both structural and functional networks within the brain has been related to optimal brain functioning (Duma et al., 2022). This evolution of methods and approaches of investigation has directly impacted the study of epilepsy. An early conception of focal epilepsy was that it was related to the activity of the epileptogenic zone, which was identified as the generative element of seizures. However, what was previously considered focal was found to be network alterations at various levels, thus moving from the epileptogenic zone to the concept of the epileptogenic network. Alterations in both the structural and functional network, compared with a healthy control population, have been identified in various forms of epilepsy from focal to idiopathic generalized epilepsy (Lariviere et al., 2022, Zhang et al., 2009). Often the identification and removal of the epileptogenic network, turns out to be the elective therapy in drug-resistant focal epilepsies. The process of diagnosing and defining the epileptogenic network is still debated today. One of the most widely used methods is the implantation of intracranial electrodes for electroencephalographic recording of seizures (Bartolomei et al., 2017). This methodology carries with it several, albeit controlled, risks to the patient. New noninvasive approaches are being developed seeking to integrate information from structural neuroimaging and cortical electrical activity measured by high-density electroencephalography with external electrodes (Duma et al., 2021). These new approaches also include simulative approaches that exploit individualized information such as cortex geometry and patient-specific white matter connections (Courtiol et al. 2020). Thus, starting from a simple structural and diffusion MRI, which is done in routine clinical examinations, multiple localizing hypotheses of the epileptogenic network can be tested using simulative models and then compared with the real EEG signal as validation. Of great relevance is also to understand how the structural-functional connectome relates to cognitive function in patients with epilepsy, who have a high probability of presenting impaired functioning in one or more cognitive domains.