Invasive EEG monitoring

Occasionally, the patient’s epilepsy syndrome may require the use of invasive EEG recordings before epilepsy surgery can be considered. Invasive EEG recordings are those recordings that are made with electrodes that have been surgically implanted on the surface or within the depth of the brain. These recordings are done to better localize the region of the brain from which the epilepsy is arising from.

  • Subdural EEG electrodes are those electrodes that sit over the surface of the brain.
  • Depth EEG electrodes are those electrodes that are placed within the substance of the brain (stereo electroencephalography (SEEG)). During SEEG, doctors place electrodes in targeted brain areas, which are then monitored to precisely locate the source of the seizure. A SEEG can find seizure sites deep in the brain that a regular electroencephalography (EEG) test may not reach. It covers both sides (hemispheres) of the brain.

Once enough information about the seizures is collected, patients will return to the operating room and the electrodes and wires are removed. The average recovery time for an intracranial EEG is 1 – 2 weeks. If the source of the seizure is found, another brain surgery can be planned to help get seizures under control. This second surgery is usually done four to eight weeks after the SEEG. The ultimate goal of this surgery is to make the patient seizure-free, even with triggers.

How to prepare for an Intracranial Electroencephalography:

  • Be aware that your surgery will last about 6 – 8 hours.
  • Bring comfortable clothing that can be buttoned or zippered from the front.
  • Bring books, handheld gaming devices, computers, tablets, or cell phones for entertainment.
  • Be aware that electronic equipment may interfere with the EEG recording, in which case you will not be able to use that device. Battery-powered devices are least likely to interfere.