If the patient has an indication for epilepsy surgery, a preoperative evaluation is performed. The preoperative evaluation includes a noninvasive (phase I) and an invasive (phase II) assessment. Phase I includes medical history, past treatment, neurological examination, neuropsychological testing, psychiatric and psychosocial evaluation, interictal and interictal EEG, structural imaging such as CT and MRI, and functional imaging such as magnetoencephalography (MEG), magnetic resonance spectroscopy (MRS), functional MRI imaging (fMRI), single photon emission computed tomography ( SPECT) and positron emission computed tomography (PET). If the epileptogenic focus can be identified during the phase I evaluation, the patient can proceed directly to surgery. If the epileptogenic focus cannot be identified during the phase I evaluation, then a phase II evaluation is required. Phase II evaluation includes invasive EEG monitoring, which is achieved by placing electrodes in the subdural, epidural, and deep brain areas; further evaluation is done with barbiturate testing (Wada test).