[EEG under the surface]

Epilepsy work-up is based on history and scalp EEG. Drug resistant epilepsy should be evaluated in a dedicated epilepsy surgery unit. Sometimes non-invasive studies fail to localize the epileptogenic area in focal epilepsy and then the work up can be complemented with intracranial EEG. Intracranial electrodes are implanted either in the subdural space or intraparenchymally. This is followed by one to two weeks of EEG monitoring in a specialized videotelemetry unit. Intracranial EEG helps to define the borders of the epileptogenic area for resection. The ultimate objective is to render the patient seizure free. The outcome of resective epilepsy surgery depends on the etiology of epilepsy, localization of the epileptogenic area and MR image yield.