Overview

Approximately 70% of people with epilepsy have either complete or very good seizure control with medication (see Epilepsy). Approximately 30% of people with epilepsy are not controlled with medication and are considered medically intractable. "Medically intractable seizures" are defined as persistent seizures despite trials of three or more appropriate antiepileptic drugs (1), alone or in combination. People with medically intractable seizures may be candidates for surgical treatment to achieve better seizure control.

What is epilepsy surgery?

Epilepsy surgery is a procedure that removes the seizure-producing region of the brain or limits the spread of the seizure activity. It can be considered a curative procedure (stopping the seizures) or a palliative procedure (restricting the spread of the seizure). Curative procedures such as temporal lobectomy, frontal lobectomy, or hemispherectomy are aimed at removing the area of the brain (seizure focus) causing seizures. Palliative procedures such as corpus callosotomy or vagus nerve stimulation (VNS) limit the spread of the seizure and stop or reduce seizures that cause physical harm.

Am I a candidate for surgery?

Surgery may be an option if you have:

• seizures that are uncontrolled with medications (intractable) or you have severe side effects to the medications
• partial seizures that always start in one area of the brain (localized seizure focus)
• seizures that significantly affect your quality of life
• seizures caused by a lesion such as scar tissue, a brain tumor, arteriovenous malformation (AVM), or birth defect
• seizure discharge that spreads to the whole brain (secondary generalization)

Patients are initially evaluated by an epileptologist. A complete medical history and physical exam helps identify critical information such as age of onset and type of seizures (including frequency, severity, and duration) (see Seizures). The physical exam is usually normal but may show some asymmetries of development compatible with early structural brain lesions such as a difference in the size of one hand or foot compared to the other, which may correlate with atrophy of one hemisphere in the brain.

The following diagnostic studies may be included in a patient's evaluation for epilepsy surgery. Not all tests are required for every patient. The epilepsy team will decide which tests are appropriate.

Continuous video/EEG monitoring requires a hospital stay in an epilepsy monitoring unit. You will be monitored by a video camera and an electroencephalogram (EEG), which uses electrodes placed on your scalp to record the electrical activity of the brain. This monitoring allows observation of the your behavior and EEG activity simultaneously during a seizure. Careful analysis of both seizure activity and "between-seizure" activity can provide critical information about where the seizure starts and spreads.

Magnetic Resonance Imaging (MRI) helps identify structural brain abnormalities that can cause epilepsy such as focal hippocampal atrophy, cavernous angiomas, cortical dysplasias, and gliomas. Functional MRI can create an anatomical and functional model of a patient's brain by combining detailed anatomical information with precise physiological information.

Single-Photon Emission Computed Tomography (SPECT) provides information about blood flow to brain tissue. Analyzing blood flow to the brain may help determine how specific areas are functioning. Blood flow to an area of the brain during a seizure increases while blood flow to an area of the brain when a person is not having a seizure can show a specific area of decreased blood flow.

Neuropsychological testing evaluates your current level of brain functioning including memory and language that might correlate with diagnostic imaging and EEG.

Wada Test (Intracarotid Amytal test) is used to determine which side of your brain is "dominant" for language and memory function. Surgeons need to know this information so that surgery does not affect these functions. It is done as part of a angiogram to detect any vascular or blood flow problems (see Angiogram). Sodium amytal is a short-acting barbiturate that is injected into one of the carotid arteries (right or left) and puts one half of the brain (hemisphere) to sleep. You will not be able to move one side of your body and may not be able to speak. You will be asked to identify pictures, words, objects, or numbers. After the drug wears off in 5-10 minutes you will have to answer questions and remember what was shown. The process is then repeated on the other side. This information is used in conjunction with the neuropsychological testing to help identify memory and language deficits and predict postoperative outcome.

• Subdural electrodes look like a plastic grid and are placed over a specific surface area of the brain. Subdural electrodes allow for a wide area of EEG recording as well as cortical mapping of functional areas. Various sizes and types of electrodes can be used based on the area of brain being studied.
• Intracerebral depth electrodes look like a banded stick and are placed stereotactically deep into the brain tissue, usually the amygdala and hippocampus of the temporal lobe, or the orbital-frontal and cingulate regions. Depth electrodes are indicated for patients with bitemporal, bifrontal, or frontal temporal seizures.

The surgical decision

The epilepsy team meets to review all testing performed to decide if surgery is the best treatment option. All tests should point to a single region in the brain as the source for seizures. If this is the case, the epilepsy team then can recommend surgery as an option to reduce or eliminate seizures.

Who performs epilepsy surgery?

Epilepsy surgery is done by a neurosurgeon specifically trained in this field. The presurgical evaluation is done at a comprehensive epilepsy treatment program that includes a multidisciplinary team of specialists (neurologists, neurosurgeons, neuropsychologists, and nurse clinicians).

What surgeries are available?

There are two kinds of epilepsy surgery: curative procedures, which stop the seizures and palliative procedures, which restrict the spread of the seizure.

Curative procedures are performed if the information obtained in the presurgical evaluation consistently points to a specific area of the brain where the seizure starts. The goal is to completely remove the seizure focus area without causing brain dysfunction.

• Temporal lobectomy is the most common type of epilepsy surgery and is performed for people with temporal lobe epilepsy (TLE). It involves removing the front part of the temporal lobe along with the amygdala and a portion of the hippocampus. A temporal lobectomy leads to a significant reduction or complete seizure control about 70% to 80% of the time (1). The risks of surgery are relatively low. There is a 2% risk of hemorrhage (bleeding into the brain), infection, or visual field problems. Memory and language function can be affected if this procedure is performed on the dominant hemisphere.
• Frontal lobectomy is the second most common type of epilepsy surgery. The success rates are not as good as those for temporal lobectomy. Approximately 30% to 50% of patients have better seizure control. Behavioral changes in personality, motivation, organization, and mood are more common with this procedure.
• Parietal or occipital lobectomies are not commonly performed. Locating a seizure focus in one of these lobes is more difficult and usually requires subdural electrodes. The risks of surgery in the parietal or occipital lobes depend on the area removed.
• Hemispherectomy involves removal of the brain's cortex (outer layer) from a damaged hemisphere (right or left side of brain). This procedure is usually used in children with intractable seizures with weakness of one side of the body and sometimes a smaller hand. Seizures are controlled in about 80% of these patients with surgery. Many patients improve in cognitive functioning, attention span, and behavior.

Palliative procedures are performed when a specific area of brain, or seizure focus, cannot be determined. These procedures such as corpus callosotomy and vagus nerve stimulation do not remove an area of brain instead they prevent the spread of seizures or reduce their frequency.

• Corpus callosotomy prevents the spread of the seizure discharge from one side of the brain to the other across the corpus callosum. It is done to prevent or reduce seizures that may cause injury to the patient (especially drop attacks). A callosotomy is usually done in two stages. The first procedure is to section the front two thirds of the corpus callosum. If the patient improves, a second procedure may not be necessary. If not, a second surgery can be performed to section the posterior one third. Some patients experience disconnection syndrome after a complete callosotomy. This happens because the communication pathways between the left and right sides of the brain are severed. The patient may have difficulty with right-left confusion with motor problems, apathy, and mutism. These can improve with speech and physical therapy.
• Multiple subpial transections involve making small incisions in the brain, which interfere with the spread of seizure impulses. This technique may be used alone or in combination with a lobectomy.
• Vagus nerve stimulation (VNS) is used for treating people over age 12 who have partial seizures. VNS is not a cure for epilepsy, it does not work for everyone, and it does not replace the need for AEDs. This procedure is generally reserved for patients who are not candidates for potentially curative brain surgery. The VNS is similar to a pacemaker. A wire (lead) is wrapped around the vagus nerve in the neck and is connected to a generator/battery implanted under the skin near the collarbone. The doctor programs the generator device (from outside the body) to produce electrical signals that travel along the vagus nerve to the brain at regular intervals. These signals help prevent seizures. The patient is also taught to use a magnet to turn the device on if they feel a warning (aura) that a seizure is about to start. Research has shown the vagus nerve stimulator to reduce seizure frequency by about 30% (similar to the results of the newer AEDs) (2). Common side effects are a tingling sensation in the neck and mild hoarseness in the voice, both of which occur only during stimulation. Initial hiccups or coughing can occur in the early post-operative period (see VNS).

What happens before surgery?

At your office visit the neurosurgeon will discuss with you the procedure's benefits and risks, answer any questions, and have you sign consent forms. Patients are admitted to the hospital the morning of the procedure. No food or drink is permitted past midnight the night before surgery. Take your AED medication as usual. Several routine tests (e.g., blood test, electrocardiogram, chest X-ray) are performed and an intravenous (IV) line is started in your arm. An anesthesiologist will explain the effects of anesthesia and its risks.

What happens during surgery?

There are four main steps of the procedure. The surgery generally takes 3 to 4 hours.

Step 1. Prepare the patient
You will lie on your back on the operative table and be given anesthesia. Once asleep, your head is placed in a skull fixation device attached to the table that holds your head in position during the surgery. Depending on where the incision needs to be made, your hair may be shaved.

Step 2. Perform a craniotomy
After your scalp is prepped, the surgeon will make a skin incision to expose the skull. He will then make a circular opening in the skull with a drill. This bony opening, or craniotomy, exposes the protective covering of the brain, called the dura mater, which is opened with scissors to expose the brain.

Step 3. Expose and remove the seizure focus area
Retractors are used to gently move the brain and open a corridor to the seizure focus area. In the case of a lobectomy, the surgeon uses microsurgical instruments to remove that area of brain (Fig. 5). In the case of a corpus callosotomy, the anterior two-thirds is split to disconnect the left and right sides of the brain.

Step 4. Close the craniotomy
The retractors are removed and the dura is closed with sutures. The bone flap is replaced and is secured to the skull with titanium plates and screws. The muscles and skin are sutured back together.

What happens after surgery?

You will wake up in the recovery area. Your blood pressure, heart rate, and respiration will be monitored, and your pain will be addressed. Once your condition is stable, you will be moved to a room on the Neuroscience floor where you will stay for a week. If you had a VNS, the neurostimulator will be programmed and your medication dosage will be adjusted. It is important to work with your neurologist to adjust your medications and refine the programming of the stimulator.

Recovery

After about 3 to 8 weeks you can usually go back to normal activities. However you cannot drive for at least one year. Doctors usually recommend that surgery patients stay on AEDs for up to two years after the operation. Some people may have to continue with medication indefinitely for seizure control. If language or memory problems continue past the recovery period, your doctor may recommend speech or physical therapy.

Clinical trials

Clinical trials are research studies in which new treatments (e.g., drugs, diagnostics, procedures, vaccines, and other therapies) are tested in people to see if they are safe and effective. Research is always being con­ducted to improve the standard of medical care and explore new drug and surgical treatments. Patients can find information about current clinical investigations nation­wide, including their eligibility, protocol, and participating locations on the web. The National Institutes of Health (NIH), www.clinicaltrials.gov , sponsors many trials; private industry and pharmaceutical compa­nies also sponsor trials, www.centerwatch.com .

Current studies
Click here for information about clinical trials conducted by our doctors at local Cincinnati hospitals or call 1-800-325-7787 ext. 5260.

Sources & Links

If you have more questions, please contact the Mayfield Clinic at 800-325-7787 or 513-221-1100. For information about The Neuroscience Institute's Cincinnati Epilepsy Center in Ohio , call 1-888-797-4TNI. Our team has five full-time epileptologists, one neurosurgeon who specializes in epilepsy surgery, a neuropsychologist, nurse clinician, and a highly skilled team of EEG technicians.

Links
Epilepsy Foundation of America , 800-EFA-1000 www.efa.org
American Epilepsy Society www.aesnet.org
National Society for Epilepsy www.epilepsynse.org.uk
www.epilepsy.com
www.epilepsyandhealth.com

Sources

1. Wiebe S, Blume WT, Girvin JP, Eliasziw M: A randomized, controlled trial of surgery for temporal-lobe epilepsy. N Engl J Med 345:311-8, 2001
2. Schachter SC: Vagus nerve stimulation therapy summary. Neurology 59:S15-20, 2002.
3. Jooma R, Yeh HS, Privitera MD, Rigrish D, Gartner M: Seizure control and extent of mesial temporal resection. Acta Neurochir 133:44-9, 1995.

Glossary

antiepileptic drug (AED): a medication used to control epileptic seizures.

cortical mapping: direct brain recording or stimulation to identify language, motor, and sensory areas of the cortex.

cortex: the outer layer of the brain containing nerve cell bodies.

disconnection syndrome: the interruption of information transferred from one brain region to another.

generalized seizure: a seizure involving the entire brain.

hippocampal atrophy: a wasting or decrease in size of the hippocampus.

hypermetabolism: faster than normal metabolism.

hypometabolism: slower than normal metabolism.

ictal: that which happens during a seizure.

interictal: that which happens between seizures.

intractable: difficult to control.

localization: finding the location in the brain where epileptic seizures start.

lobectomy: surgical removal of a lobe of the brain.

seizure focus: a specific area of the brain where seizures begin.

palliative: to alleviate without curing.

partial seizure : a seizure involving only a portion of the brain.

updated: 6.2004
reviewed by: Hwa-shain Yeh, MD, Maureen Gartner, RN, David Ficker, MD