How do we decide who is a good candidate?

Case scenario 1: all seizures arise from the same part of the brain + there in no known function -> focal resection.
A classic example would be epilepsy that arises from the medial part of the temporal lobe in which no more testing would be required. The patient in this case would undergo a resection of part of their brain. In some cases and in some epilepsy centers, a technique called electrocorticogram (which is an EEG that is performed on the surface of the brain) is utilized to tailor the resection. What happens in this situation is that the surgeon performs the resection and then the epilepsy doctor records information from the boundaries of where the brain portion was removed. If there is still epileptic activity showing up, then the surgeon will extend the resection removing that additional part of the brain.

Case scenario 2: all seizures arise from an area of the brain + there is possible function that could be lost.
In this case a second evaluation with electrodes on the brain (subdural strips or grids) or in the brain (depth electrodes) or both combined are needed (called phase II) in order to:
• Localize the seizures even more: this is done with video-EEG, but this time, the recording is coming directly from the brain surface. This gives us the possibility of pinpointing the area that is causing the seizures with more precision so that a smaller and more specific part of the brain is removed (sparing healthy brain).
• “Mapping the brain”: this is done by delivering a small amount of current through each electrode in order to try to “map out” specific functions (i.e. movement, language, sensation, etc.).