EPILEPSY SURGERY FOR UNCONTROLLED SEIZURES
Epilepsy surgery was once thought of as a last resort for the many patients whose seizures are not controlled with medications. Now, teams of epilepsy experts at centers with advanced technologies have greatly improved the effectiveness and safety of epilepsy surgery in adults and children. Epilepsy surgery may be the best option for many patients and should be considered when good medical treatment has failed to control the epilepsy. Evaluation at a high-level epilepsy center is necessary to find out about epilepsy surgery and other options when medications don’t control the seizures.
Epilepsy surgery can fully control seizures in some individuals who continue to have frequent seizures, despite treatment with a variety of anti-seizure medications. Epilepsy surgery usually involves removal of a small part of abnormal brain tissue, which is the site that controls the seizure onset.
Surgery may be an excellent treatment for a person whose:
· Seizures confirmed by EEG are not controllable by the usual anti-seizure medications,
· Seizures begin in one small area of the brain, and
· Seizures begin in an area of the brain that is not needed for movement, feeling, language or memory.
Some of the tests that are used to plan epilepsy surgery are also widely used for evaluating medication choices in seizure treatment. Recordings of brain electrical activity (video-electroencephalography, or video-EEG) often are used to find the site where electrical seizures begin and add the benefit of correlating the person’s clinical symptoms with the electrical signature. Brain imaging such as magnetic resonance imaging (MRI) often shows structural brain tissue abnormalities related to the site where electrical seizures begin. Neuropsychological testing checks on brain areas that are important for normal brain processing, such as thinking, language and memory.
Special tests may be needed to evaluate a person for possible epilepsy surgery – tests that would not be done unless surgery is a strong consideration. (It might fit better to order these test descriptions more in the order that they might be performed, ending with the intracranial EEG as the last step before the resection) One of these tests is intracranial EEG recording, which requires insertion of recording electrodes (depth electrodes, grids, strips) inside the skull in order to improve seizure recording. Another such test is cortical electrical stimulation for functional mapping, in which low levels of electrical current are placed on the brain surface through the intracranial electrodes to map out normal functions for movements, sensation, speech, and other important functions. Functional brain imaging with positron emission tomography (PET) and single photon emission computed tomography (SPECT) are used to map out brain energy use or brain blood flow between seizures or during seizures. Magnetoencephalography and magnetic source imaging (MEG and MSI) evaluate the seizure focus and the functional location using magnetic fields in the brain, in areas where electrical activity may be hidden from the EEG field. Functional MRI (fMRI) may localize language utilizing brain blood flow during a task. The Wada test involves checking parts of the brain for language and memory function by briefly putting these areas to sleep with a medication. No one person is likely to need all of these tests. These tests should be performed only by experts at high-level epilepsy centers.
Extensive testing may show that seizures appear to start in abnormal tissue, which does not appear to be needed for normal brain processing, in some individuals with uncontrolled seizures. These individuals may want to have a team of epilepsy neurologists and neurosurgeon evaluate which area may be removed to control the seizures.
Several types of partial (focal) epilepsy are especially likely to benefit from epilepsy surgery. Over two-thirds of people who have surgery for temporal lobe epilepsy become free of seizures that cause loss of consciousness, and most of the remaining one-third have major reduction in seizure frequency. In temporal lobe epilepsy the results of surgery can be quite good when there is an MRI lesion (such as a scar, an abnormal blood vessel, a benign tumor, or abnormal area of brain development) near the site where the seizures begin and even when the brain tissue looks normal on MRI scans.
When seizures begin outside of the temporal lobes, it is important to determine whether a lesion is present at the site where seizures start. If a lesion is present near the seizure-starting area outside of the temporal lobes, surgical results for seizure control are nearly as good as in temporal lobe epilepsy surgery. If no lesion is present near a seizure-starting area outside of the temporal lobes, surgical planning is based mainly on EEG recordings obtained during the patient having their typical seizure. Unfortunately surgery is less likely to control the seizures fully.
Some types of generalized epilepsy have been treated with surgery that cuts fibers between the two sides of the brain, termed corpus callosum section. Results of this surgery often are not as good as in partial epilepsies, however, and this type of surgery is indicated in a limited type of seizure.
Not everyone who has frequent seizures despite taking anti-seizure medications is able to have epilepsy surgery. Some individuals should not have epilepsy surgery because seizures begin in areas of the brain that are critical to maintain movement, feeling, language or memory functions; in these individuals, removing these brain sites could cause a decrease in or even a loss of these important functions. Some individual have seizures that start in many different parts of the brain, or have seizures that start in parts of the brain that cannot be found with electrical seizure recordings, such that surgery is less likely to stop the seizures. These and many other complex issues require that a highly expert team of neurosurgeons, neurologists, imaging experts, neuropsychologists and other brain specialists in order to achieve safe and effective epilepsy surgery.
If you have uncontrolled seizures, you should be evaluated at a high-level epilepsy center. The experts at the center can determine what might be the best pre-surgical approach for your problem and explain which epilepsy surgery might be best for you. No two people have exactly the same brain problems that cause seizures. Each individual needs to be independently evaluated by the epilepsy team. Surgery may or may not be your best option. There are other nonsurgical options available and in development which the epilepsy physicians can help you evaluate as options.