MRI scans may show tumors, abnormal blood vessels, cysts, and areas of brain cell loss or other brain damage. An intracarotid sodium amobarbital test locates speech and memory centers. A drug is injected into an artery leading to the brain. It puts half of the brain to sleep for a short period of time. The doctors then check speech and memory on the side of the brain not put to sleep.
PET measures how intensely different parts of the brain use up glucose, oxygen, or other substances.
Even after all the previously described tests are done, additional information may be needed to identify the epileptic area in the brain. This is because the area of seizure activity sometimes can't be found by electrodes attached to the surface of the head. To obtain that additional information, two separate operations may be required. The first operation places electrodes in or on the brain itself. These special electrodes are called depth or subdural electrodes.