FAQ: Evaluation for Seizure Surgery

Many patients have similar questions about having seizure surgery and what tests may be needed before surgery. The following general information is intended to answer questions you may have. Please keep in mind, however, that each patient is unique and his or her care is individualized. If your questions and concerns are not answered here, we encourage you to contact us for additional information.

What is seizure surgery?

Seizure surgery is an operation aimed at removing the area of your brain that is causing you to have seizures. The goal of surgery is to improve seizure control and when possible, to stop seizures completely. There are several types of seizure surgery. The best option for you will be determined by the seizure type, the seizure history and the results of your test.

When is surgery offered?

When anticonvulsant medications fail to adequately control seizures, you are considered to have seizures that are refractory to medication therapy. Sometimes these seizures may come under control with the addition of surgery. For patients who are open to this option, a surgical evaluation may be initiated.

Results from your video telemetry give the doctors a better understanding of what part(s) of your brain your seizures may be arising from. If most of your seizures are coming from one specific area, it may be possible to safely remove this area (seizure focus) in an effort to control your seizures. There are additional tests that help the epilepsy team determine exactly where your seizures arise from and whether surgery is an option for you.

What type of tests will I need before I can be considered for surgery?

There are several types of tests you may need before being considered for surgery. The epilepsy team will order tests necessary to confirm the origin of your seizures. Some of the tests include:

• Magnetic Resonance Imaging (MRI): a scan that uses a magnet to form detailed pictures of your brain.

• Positron Emission Tomography (PET): a scan that uses an injection of a radioactive tracer to measure brain metabolism in an effort to locate the seizure focus.

• Magnetoencephalography (MEG): MEG identifies brain activity by measuring small electrical currents arising from the neurons of the brain.

• You may need to repeat the video/EEG monitoring if not enough information was obtained originally.

How will the results of these tests help determine if I am a good candidate for surgery?

The information gathered from the tests above are all aimed at better defining and localizing your specific seizure focus and determining if that focus can be safely removed.

In some cases, however, the results of the tests may give the epilepsy team an idea as to where the seizures start, but the results may not be conclusive. If the initial scalp EEG testing doesn’t provide enough localizing information, you may need further evaluation using intracranial monitoring. Intracranial monitoring records brain wave activity using electrodes placed surgically in or on the surface of the brain, rather than just pasting the electrodes to your scalp as you had with your initial video EEG monitoring admission.

What types of intracranial monitoring might be suggested to help better define my seizure focus?

Intracranial monitoring involves the surgical placement of special EEG electrodes onto the surface on the brain, or sometimes into the brain tissue. These surgically placed electrodes may include one or more of the following types:
• Subdural strip electrodes are flexible strands of electrodes placed on the surface of the brain through burr holes. These electrodes are usually placed to better determine of what side seizures are coming from.

• Depth electrodes are fine, rigid electrodes placed guided with imaging into the brain tissue, through burr holes, in order to record brain wave activity from a more precise area of interest in the brain.

• Subdural grid electrodes are an array of electrodes, usually 64-128 electrodes, placed onto the surface of one brain hemisphere via craniotomy. Grid electrodes are sometimes used when the side in which the seizures originate has been determined, but there still exists the need to better define the seizure focus. The grid also allows for additional testing to be done at the bedside, by the epilepsy team, in an effort to better define the brain functions in and around the seizure focus. You will be admitted for video monitoring and if enough information is obtained you will have resective surgery scheduled a week later.

After any of the intracranial electrodes have been placed in the operating room, and you are stable post-operatively, you will be transferred to the EEG-Video Telemetry Monitoring Unit on 8-Long for monitoring. The neurosurgery team will discuss details further with you when you meet with them.

What are the final steps before the surgery?

• Neuropsychological evaluation: This will be done by a neuropsychologist, a psychologist who specializes in the relationship of brain and behavior. This is extensive testing that may determine the site of your seizures as well as predict possible cognitive changes after surgery.

• Wada test: This is a test to evaluate location of speech and memory functions in your brain. This is done by using sodium amytal to sedate one side of your brain while the other side is being tested. The neuropsychologist will be performing these tests. The results of this test determine which side of the brain is the dominant area for these crucial functions, namely speech and memory. It will determine whether you will need to be awake during part of the surgery. Appointments for these tests will be scheduled for you by the Epilepsy Center. You will receive a letter to confirm these appointments and more in-depth information about each study.

Epilepsy Surgery

Once the Epilepsy Team has obtained and reviewed all the tests necessary and have determined that you are a seizure surgery candidate, they will present the results to you. Together, you and your doctors will decide what the next step in your seizure management should be. The risks and benefits of all treatment options will be discussed with you, giving you the opportunity to be able to make an informed decision that best suits your needs and lifestyle.

Before recommending a specific surgical procedure or an individual plan for you, our multidisciplinary epilepsy team will meet to review all of the testing and to discuss potential options.

You will be called within a week after your case is discussed so that an appointment is made to meet your epilepsy doctor and/or neurosurgery team. This will give them the opportunity to talk over the options with you as well as to answer any questions you may have.