Under what circumstances is data obtained from non-invasive EEG monitoring sufficient for planning resection in a patient with drug-resistant focal epilepsy?

The decision to offer resection to a patient with focal epilepsy is never determined just by scalp EEG monitoring. The data set used to make that decision is based on many other factors, including patient history, seizure semiology, neuropsychological testing, and imaging. When a preponderance of information points to a particular, resectable focus, then invasive EEG is not required. However, when significant doubt about the seizure focus exists, then invasive recordings may offer the kind of information we need to make decisions about the safety and efficacy of resection, or in some cases the utility of neuromodulation (e.g., RNS, DBS).