The roles of surgery and technology in understanding focal epilepsy and its comorbidities.

Intracranial electrophysiological recording in patients with refractory focal epilepsy is the gold standard for defining epileptogenic tissue. Although the concordance of intracranial electrophysiology, structural MRI, and pathology can identify brain regions for resection, complete seizure control after surgery is not achieved in all patients with focal epilepsy. Repetitive identical behavioural seizures suggest one onset area, but epileptogenesis might be distributed and connected by functional and structural brain networks outside the seizure onset area, which could explain poor postsurgical outcomes in some patients. Similar networks are postulated in neuropsychiatric disorders, such as depression and anxiety, and seem to overlap with posited epilepsy networks, perhaps explaining the high prevalence of comorbid neuropsychiatric disorders in patients with epilepsy. These networks are difficult to verify with available electrophysiological recording approaches. Advances in intracranial technology are needed to confirm the epilepsy network hypothesis and improve surgical outcomes by providing individualised therapies based on specific network contributions.