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

Identification of regional alteration in the value of functional connectivity

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.