Epilepsy surgery is surgery performed to treat epilepsy, a disorder of recurrent seizures—abnormal electrical activity in the brain.
There are many kinds of epilepsy. They vary by cause, symptoms, severity, brain areas affected, and more. When it comes to surgical treatment, the most useful way to classify seizures is by whether they are focal (also called partial) or generalized. Focal seizures involve only one area of the brain. Generalized seizures involve the entire brain. A seizure that starts as a focal seizure may sometimes progress to become a generalized seizure. Some surgeries aim to cure focal seizures, and some aim to reduce the number or severity of generalized seizures.
Just as there are many types of epilepsy, there are many types of epilepsy surgery. Surgeries can generally be placed into one of three broad categories: resection, disconnection or stimulation.
Resection is a medical term that means “removal.” A resection may be performed if a specific brain area responsible for seizures can be identified and safely removed. Generally, the goal is to remove the cause of the abnormal electrical activity, thereby completely eliminating seizures. One common type of resection that treats temporal lobe epilepsy is a temporal lobectomy. In this procedure, a small part of the temporal lobe is removed. The Columbia Comprehensive Epilepsy Center (CCEC) and a handful of other centers are also pioneering the use of Gamma Knife radiosurgery for seizure foci in the temporal lobes. Radiosurgery uses precise beams of radiation; unlike traditional surgery, it does not require a surgical incision.
The second broad category is disconnection. This type of surgery leaves brain tissue in place but cuts certain nerve connections. It is sometimes an option when seizures do not begin in one specific brain area that can be identified and safely removed. This may be because seizures have no defined initiation points, or have many initiation points, or have a defined initiation point that cannot be safely removed.
A common surgery in this category is the corpus callosotomy. In this procedure, a surgeon cuts the corpus callosum, the bundle of nerves that connect the left and right hemispheres of the brain. Seizures may continue to affect one half of the brain, but they cannot spread to the other half. Another common surgery in this category is the multiple subpial transection. In this surgery, doctors take advantage of the fact that seizures tend to spread along horizontal nerve pathways, while much important nerve communication takes place along vertical nerve pathways. Surgeons sever horizontal connections between nerves to make it harder for seizure to spread.
The third broad category is stimulation. The vagus nerve stimulator is a well-known device that can be surgically implanted near the collarbone; it delivers mild electrical current to the vagus nerve and can help reduce seizures. Responsive brain stimulation (RNS) and Deep Brain Stimulation (DBS) are newer stimulation treatments available at only select centers like the CCEC. DBS can deliver the same style of stimulation as the vagus nerve stimulator, but to precise locations in the brain. RNS consists of a device placed beneath the scalp and thin electrodes that enter the brain. The RNS device continually monitors and records electrical activity in the target area; if it detects a pattern that could lead to a seizure, it automatically delivers a mild electrical current that may stop the seizure.
When is Epilepsy Surgery performed?
In some cases of medically refractory epilepsy, surgery can help establish seizure control.
It is important to understand that surgery is simply another type of treatment—one that may help when non-surgical treatments have failed. Surgery is likely to benefit properly selected patients, but there can be no guarantee that it will. In addition, any type of surgery carries some risk. A doctor can help patients and their families weigh the risks, benefits and quality-of-life considerations of medical and surgical treatments. Additionally, a neurosurgeon can explain whether the goal of an individual’s surgery will be to manage (reduce the number of) or cure (completely eliminate) seizures.
Before surgical planning can begin in earnest, it is critical to understand exactly where the seizures arise. Sometimes an EEG can provide this information. In an EEG, small metal discs called electrodes are placed on the scalp. The electrodes record electrical activity in the brain.
But in some situations, scalp EEGs can’t give enough information about the seizures. In such cases, to get the information required for surgical planning, electrodes can be placed on the surface of or within the brain itself. A neurosurgeon performs an operation either to place subdural electrodes on the surface of the brain, or thin Stereo EEG electrodes deeper in the brain. Information about electrical activity in the brain is gathered by the electrodes, and the area causing the seizures is identified. The electrodes can also be stimulated with a tiny electrical charge. This can give doctors information about the function of the precise area being stimulated by the electrodes, to determine whether or not the area can be removed safely.
After the required information has been gathered, the electrodes are removed.
Studies consistently show that experienced neurosurgeons at neuroscience centers of excellence achieve the best possible patient outcomes. Our neurosurgeons comprise one of the most skilled and experienced epilepsy surgery teams in the world. They are leaders in the use of state-of-the-art technology and techniques, including preoperative and intraoperative brain mapping, deep brain stimulation (DBS) and responsive brain stimulation (RNS) for focal epilepsy, and Gamma Knife radiosurgery for temporal lobe epilepsy. They draw on their deep experience to choose the safest, least invasive techniques likely to provide maximum benefit for each patient.