Presurgical localization of epilepsy

Appropriate selection of potential candidates for epilepsy surgery is critical to successful outcomes. After determining that a patient has drug-resistant epilepsy, a sequence of diagnostic investigations is pursued. Several steps in the diagnostic process are standard to all patients being evaluated for epilepsy surgery. If data from standard evaluations are concordant and a radiologically visible epileptogenic lesion is present, patients may often proceed directly to surgery. If data are discordant, or if more precision is needed in identifying the bounds of the epileptogenic zone or neighboring eloquent cortex, additional studies are tailored to the needs of the individual. Some variability between epilepsy surgical centers is expected, as local expertise and access to diagnostic procedures may vary. Some aspects of the evaluation rely on expert opinion in the absence of a strong evidence base. Ultimately, localization of the epileptogenic zone-for either surgical resection or responsive neurostimulation-relies on the principle of convergence of evidence. The ultimate decision of whether to pursue invasive therapy rests on the integrity of this process and requires an assessment of risk and benefit and the ability to engage the patient in meaningful decision-making.