Prior to admission for intracranial electrodes or epilepsy surgery, an appointment will be made for you to see your neurosurgeon. You will be able to discuss the surgical procedure in detail and the neurosurgeon will go over the possible risks and complications.
What is the purpose of intracranial electrodes?
Intracranial EEG electrodes are necessary when the scalp EEG recordings of your seizures do not give us the information needed to localize your EEG focus. The intracranial electrodes are placed on the surface of the brain or are implanted deep into the brain where seizures often begin. The number, type and placement of electrodes is decided at the team conference based on the appearance of your seizures. The names of the different types of intracranial electrodes that may be used are depth electrodes, subdural strips, and subdural grids.
What are depth electrodes?
They are very fine electrodes (wires) that are placed inside the brain to record electrical activity.
What are subdural strips?
They are strips of six to eight contact points from which electrical activity from your brain is recorded. They lie on the surface of the brain rather than in the brain tissue.
What are subdural grids?
A subdural grid is an array of up to 64 contact points from which we can record the brain's electrical activity. It is placed on the surface of the brain through a craniotomy incision. The grid can also be used to map out speech and motor areas to help guide the surgeon in the resection.
How do they put the electrodes in?
You are taken to the operating room where part of your hair will be shaved. This is done to reduce the risk of infection. If you are having depth electrodes placed, you will be fitted with a stereotactic head frame and taken to the MRI (Magnetic Resonance Imaging) room. The MRI will help the neurosurgeon map out the coordinates so that the electrodes are placed in the correct position. You will then return to the operating room where the neurosurgeon will make several (depending on the number of electrodes) small holes in your skull, through which electrodes are placed. The electrodes are then sutured in place and your head wrapped in a bandage for protection and padding. For subdural strips or grids, you are taken directly to the operating room. A small hole may be drilled in the skull in order to place the strip electrodes. A circle of skull (craniotomy) is temporarily removed in order to place grid electrodes.
Who puts them in?
How many electrodes will I have?
Each person is different, but most have patients have between 30 and 120 electrodes placed.
How will I feel after the electrodes are placed?
If only strips and depth electrodes are placed, you may have a headache for the first day or two. If you have a grid implantation with a craniotomy incision, your headaches may last longer (on average 1-7 days, although there is tremendous individual variability).
What do I have to do to prepare for the surgery?
You cannot eat or drink anything after midnight the night before surgery. You should continue to take your regular medications with a small sip of water.
How long does the surgery last?
From the time you leave your room until the time you are in recovery will be approximately four to six hours.
What can I do after the surgery?
Generally, after 24 to 72 hours, you will be able to get out of bed and sit in a chair or take a walk with a nurse.
When will the EEG recording begin?
Usually, within 24 to 48 hours after the electrodes are inserted.
Are there any risks?
There is a small risk of infection and brain hemorrhage or swelling that may result in weakness. As with any surgery, there is a very small risk of complications from the anesthesia. You may also have difficulty opening your mouth wide for two to three days after surgery.
How long will I be in the hospital?
That will depend on the number of seizures you have. The usual length of stay is two weeks, but it could be longer or shorter.
What if I do not have any seizures?
Your medication will be reduced and stopped just as in Phase I. Seizures may also be induced by hyperventilation or sleep deprivation.
What other tests will be done during this phase?
We may stimulate the electrodes with tiny electrical currents in order to map out important areas of function in your brain such as speech and motor areas. This is done by the doctor in your room. You will be asked to read and do certain tasks to help define these areas.
When will the electrodes be removed?
The electrodes will be removed once you have had enough seizures to determine the area where the seizures begin. This will be done in the operating room.
When can I go home?
Once you are taken off the monitoring system, your medicine will be adjusted. If you do not have your surgery at this time, you will be discharged once the blood level of your medicine is adequate.
What can I do when I go home?
You can do anything you wish as long as you feel up to it. You can return to work and/or school after several days.
What happens next?
Within two to three weeks of your discharge, there will be another team conference to review all of the findings from your hospitalization. The team will decide at this time whether you are a candidate for epilepsy surgery.