Surgical placement of temporary electrodes
Even with all of the testing involved, sometimes the area in the brain causing the seizures cannot be defined enough to be able to do surgery to remove it. These patients may need to have electrodes, or leads, placed to help find the site. These patients are evaluated by the epilepsy team to determine which patients are the best candidates for this invasive procedure.
There are a few surgical options on how to place these leads. This procedure involves placing these electrodes either on the surface of the brain or inside of the brain tissue. When they are placed in these areas, it is closer to the area causing the seizures than the leads that are placed on the scalp. Once the leads are placed in or on the brain, the other end of the electrode lead attaches to an EEG machine where the brain waves can be monitored. Patients are observed in an area where video monitoring is also used.
A subdural electrode grid is a thin sheet of material with many small electrodes in it, all spaced evenly apart. These are placed directly on the surface of the brain, and can record the brain waves much more precisely than the scalp electrodes. These sheets come in different shapes and sizes, and are chosen based on the patient’s needs.
These are small wires which are implanted within the brain tissue itself. Each wire has small electrodes placed at intervals on the length of the wire. These electrodes are able to record brain wave activity along the entire length of the wire. This makes it easier to record brain activity deep within the brain. They can be placed through small openings in the skin.
Sometimes, both the subdural grids and the depth electrodes are used together to monitor a patient’s brain wave activities.