invasive preoperative exploration invasive subdural grid monitoring true Subdural grid recordings provide more accurate delineation of regions of eloquent cortex and epileptogenic foci than do noninvasive strategies or awake craniotomy. The information derived from chronic subdural recordings can be used to plan an aggressive approach to the epileptogenic focus to maximize favorable outcomes https://www.ncbi.nlm.nih.gov/pubmed/12744361 Modified definition