Epilepsy surgery

At Providence Brain and Spine Institute, surgery to treat epilepsy usually occurs after several tests have been performed. Together these tests provide a thorough understanding of your seizures. The goal is to identify an area in the brain that causes seizures and to determine whether this area can be removed safely without causing new neurologic problems. For patients for whom this is the case, this evaluation may ultimately result in either an open surgery to remove part of the brain that causes seizures (a craniotomy), or a procedure that uses a laser probe to burn part of the brain that causes seizures (a stereotactic laser ablation procedure). For patients for whom either a specific area of seizure onset is not identified, multiple areas are identified or who cannot have one of these surgeries without causing new neurologic problems, other options are available including the Neuropace procedure or Vagus Nerve Stimulation.

Preoperative evaluation before epilepsy surgery

Surgery to treat epilepsy usually occurs after several tests have been performed. Together these tests provide a thorough understanding of your seizures. These tests may include:

High resolution MRI of the brain: This is performed to provide the best view of brain anatomy, to determine whether there are any abnormalities in the brain that may be the cause of your seizures.

Functional MRI: This is a special MRI that is performed to study the function of specific parts of the brain. You will be asked to perform simple tasks during the MRI scan, which helps the radiologist to identify which parts of your brain are important for normal brain functions such as language, control of muscle activity or processing of sensory input. This information is used to develop a surgical plan that avoids these critical areas.

Epilepsy monitoring unit/Long-term video EEG monitoring: If you experience frequent seizures, you may be referred to an epilepsy monitoring unit for evaluation. This evaluation determines if your seizures are caused by epilepsy and where they start in the brain. If you are admitted to an epilepsy monitoring unit, you will stay for several days. During this time, you will be continuously monitored with a combination of video and electroencephalogram (EEG).

While the EEG records your brain’s electrical activity, the video recording shows how your behavior is affected during a seizure. A neuropsychologist may be called in consultation to determine how well the individual parts of your brain are functioning. The EEG results, video recording and neuropsychology exam help make the most accurate diagnosis possible. A treatment plan will be designed for you based on the information gathered during your stay.

Positron emission tomography/CT (PET) is a test that uses a combination of CT scan and a special type of camera to detect a tracer within the brain. During the test, the tracer liquid is put into an IV in your arm. The tracer moves through your body and collects in the brain as a function of its activity level, which can provide information about areas that cause seizures. The tracer gives off tiny positively charged particles (positrons). The camera records the location of positrons and turns the recording into pictures on a computer.

Wada testing: The Wada test checks to see which side of your brain is responsible for language and memory. A cerebral angiogram is performed as part of the Wada test. A neuroradiologist places a catheter into an artery in your leg and directs the catheter to the right or left carotid artery. Then the neuroradiologist injects a dye into the carotid artery and a special x-ray machine takes pictures of your brain’s blood vessels. At the start of the Wada test, the neuroradiologist will inject sodium amytal into the catheter that is in the carotid artery to put part of your brain to sleep. While one side of the brain is asleep you will be shown flashcards asked to name and remember objects or pictures. After a few minutes, the side that was asleep wakes up. You will be asked to recall what pictures or objects were shown. The same procedure is repeated on the other side. The Wada test is an outpatient procedure, you are able to leave the hospital the same day.

Invasive seizure monitoring (grid and depth electrodes): for some patients, the location of seizure onset within the brain cannot be determined by noninvasive tests like EEG or MRI. For these patients, a surgical procedure is required to implant electrodes on the surface of the brain (referred to as electrode grids) or within the brain (referred to as depth electrodes) to better understand the precise location of seizures within the brain. These electrodes are implanted with you asleep in the operating room. After you wake up from surgery the electrodes are connected to an EEG machine to monitor your brain activity, typically for several days. If this process demonstrates an area that causes your seizures that can be treated with surgery, you may have a epilepsy surgery procedure at the same time that your electrodes are removed, or at a later date.

Cortical mapping: this is an inpatient procedure conducted for patients who have a grid or depth electrodes placed inside the brain. During the procedure, a neurologist stimulates each electrode placed within the patient’s brain individually. This can help determine which areas are causing seizures, and which parts are important for normal functions such as language or control of your muscles. The result is a "map" of the brain’s normal activity and seizure focus areas, which allows the surgeon to know precisely which part of the brain to remove during surgery.

What to expect with craniotomy for epilepsy

A craniotomy to remove an area of the brain that causes seizures has the highest likelihood of seizure freedom for patients with medically resistant epilepsy.

  • Temporal lobe epilepsy is the most common form of medically-resistant epilepsy that can be treated with surgery. If it is possible to localize seizure onset to one side of the brain, within the temporal lobe, it is possible to remove that portion of the brain and prevent further seizures. This is called a craniotomy for anterior temporal lobectomy. Patients with temporal lobe epilepsy will undergo several studies to help determine whether they may be a candidate for surgery (see “Preoperative evaluation before epilepsy surgery”). This may or may not include invasive electrode placement to help identify the location of seizure onset if this is not clear with noninvasive studies. It will usually also require Wada testing to determine location of language and memory within the brain before surgery.
  • Non-temporal lobe epilepsy may also be treated surgically if the location for seizure onset can be determined. This frequently requires invasive electrode placement to help localize the source of seizures (see “Preoperative evaluation before epilepsy surgery”). If an area of the brain is identified that causes seizures and that area can be removed safely without causing new neurologic problems, then a craniotomy for resection of seizure focus will be recommended.

A craniotomy is usually performed under general anesthesia. The procedure involves making an incision in the scalp to expose the skull. A piece of the skull is removed with a special drill to expose the underlying brain. Computer navigation is registered to your MRI scan and used during surgery to precisely determine the area of brain to remove. In specific situations other techniques may also be used during surgery to further identify the area that causes seizures and/or areas to avoid that are critical for normal brain activity. This may include intraoperative brain wave monitoring (electrocorticography), brain cortex stimulation or even an awake craniotomy when surgery is very close to critical brain regions such as the motor or language centers. At the end of the procedure the skull that was removed is replaced and secured with small plates and screws. The skin is closed with sutures and staples.

After surgery you will recover in the neurocritical care unit for the first 1-3 days. You will be monitored closely for new neurologic problems and postoperative seizures. You will be given medication for pain and other discomfort after surgery. Once appropriate you will be gradually returned to normal activity. Most patients can be discharged home 2-5 days after surgery, infrequently patients will require a short course of therapy at an inpatient rehabilitation center. Typically no changes will be made to your seizure medications for the first few months after surgery. You will have scheduled follow up with both your neurosurgeon and your neurologist.

What to expect with Stereotactic Laser Ablation Surgery

Some forms of medically-resistant epilepsy that can be treated with surgery. If it is possible to localize seizure onset to one area within the brain, you may qualify for a minimally invasive procedure known as a stereotactic laser ablation. Patients with epilepsy will undergo several studies to help determine whether they may be a candidate for this surgery (see “Preoperative evaluation before epilepsy surgery”). This may or may not include invasive electrode placement to help identify the location of seizure onset if this is not clear with noninvasive studies. It will may also require Wada testing to determine location of language and memory within the brain before surgery.

Stereotactic laser ablation is typically performed under general anesthesia. The entire procedure occurs through a half-inch incision in the scalp. A small hole is then drilled through the skull and a fiber optic laser probe is passed through this hole to reach the area of brain tissue that causes seizures. Using the Providence Brain and Spine Institute intraoperative MRI, we are able to watch in real-time as we use the laser to selectively burn tissue in the area of the brain that causes seizures. Once the procedure is complete the laser fiber is removed and the incision is closed with a single stitch. For some procedures, this process is repeated with multiple laser fibers from different trajectories to create a more complex brain ablation.

You will be monitored in the hospital after surgery. Most patients are able to go home the next day after the procedure. Typically no changes will be made to your seizure medications for the first few months after surgery. You will have scheduled follow up with both your neurosurgeon and your neurologist.

What to expect with Neuropace Surgery

Neuropace is a responsive neurostimulator that monitors your brainwaves, looking for unusual activity that may lead to a seizure. The device is personalized to recognize the electrical patterns specific to your brain, rapidly identifying unusual activity that can lead to a seizure. After detecting unusual activity, the device sends brief electrical pulses to disrupt this activity and normalize your brainwaves, often before you can feel seizure symptoms. The Neuropace system has been shown to significantly reduce seizures, with continued improvement over time. Patients also report better cognitive function, quality of life, and mood. The device works without producing the side effects associated with many antiseizure medications, such as dizziness, drowsiness, or cognitive impairments.

The Neuropace device can be a good option for patients who are not candidates for other epilepsy brain surgeries (see “Preoperative evaluation before epilepsy surgery”). Patients most frequently do not qualify for other epilepsy brain surgeries because multiple areas of seizure onset are identified in the brain or because the area of the brain that causes seizures is also important for normal brain function and therefore cannot be removed.

Neuropace implantation is typically performed under general anesthesia. The device has two components: a neurostimulator that is imbedded in the skull and two electrodes that are placed on or within the brain at locations where seizures begin. An incision is made over the area where the neurostimulator will be implanted and a piece of skull is removed to accommodate the neurostimulator. Separate small incisions are made at the locations where the electrodes will enter the skull. These electrodes are placed precisely to best recognize and respond to seizure activity. The wires are tunneled under the skin to reach the neurostimulator and then connected to the device. The incisions are closed with sutures and staples.

You will be monitored in the hospital after surgery. Most patients are able to go home the next day after the procedure. Typically no changes will be made to your seizure medications for the first few months after surgery. You will have scheduled follow up with both your neurosurgeon and your neurologist. Typically the device is set to record your seizures for the first several weeks, then your neurologist will begin to adjust the device to best recognize and respond to your seizures. Seizures will gradually improve over several months after surgery as the device is optimized.

What to expect with Vagus Nerve Stimulation surgery

Vagus nerve stimulation is designed to prevent seizures by sending regular pulses of electrical energy to the brain via the vagus nerve. These pulses are supplied by a neurostimulator that looks like a cardiac pacemaker. The neurostimulator is placed under the skin on the chest wall and an electode (wire) runs from it to the vagus nerve in the neck. The vagus nerve passes through the neck as it travels from the brain to the chest and abdomen.

VNS surgery is performed under general anesthesia. An incision is made in the left chest near the collar bone to create a pocket for the neurostimulator. A second incision is made horizontally on the left side of the neck, within a crease in the skin. The vagus nerve is identified and dissected away from the surrounding structures within the left side of the neck. Helical electrodes are then wound around the vagus nerve and secured in place. The wires of the electrode are passed under the skin from the neck to the chest and then connected to the neurostimulator. The neurostimulator is then placed in the chest pocket. Both incisions are closed with suture and surgical glue.

The procedure usually takes about 90 minutes. Typically you can leave the hospital the same day after surgery. The stimulator cannot be turned on immediately because of changes related to surgery. It will be turned on 2-3 weeks later when you follow up with your neurologist. Your neurologist will determine the appropriate strength and timing of impulses delivered by your VNS system to meet your needs. The settings can be programmed and changed by your neurologist through the skin with a wand that is placed over the neurostimulator.

Holding a special magnet near the implanted device (generator) triggers the device to deliver another burst of stimulation. For people with warnings (auras) before their seizures, activating the stimulator with the magnet when the warning occurs may help to stop the seizure. The battery for the stimulator usually lasts about 5 years, depending on the settings used. When the battery runs low, it can be replaced with a brief outpatient surgical procedure.

Referring physicians about epilepsy surgery at the Providence Brain and Spine Institute

At the PSBI we value our network of referring physicians, and make every effort to tailor epilepsy surgery to the patient and to the practice of their managing neurologist. We strive to actively communicate before and after surgery regarding the individual needs of patients undergoing epilepsy surgery. We make it a priority to streamline the preoperative evaluation process, to minimize perioperative stress and discomfort and to facilitate recovery after surgery.

It is our goal to be your partner as your patient goes through epilepsy surgery, and to transition the patient back to your care once appropriate. However, if you would prefer, our epileptologists can also assume patient management before and/or after epilepsy surgery. For device implantation surgeries such as Neuropace or VNS we can also make arrangements for device representatives to assist you in person for the initial programming sessions as necessary.

For patients traveling a significant distance to Portland, our goal is to minimize their transportation burden. We can help direct local pre-surgical evaluations and coordinate appointments across disciplines when a visit to Portland is necessary.