While surgery may seem like a radical step for the treatment of epilepsy, it has been an accepted form of treatment for over 50 years. While surgery has risks, studies have consistently shown that the benefits of reducing or curing seizures outweigh the risks of surgery. The Northwestern Comprehensive Epilepsy Center is staffed by experienced, board-certified neurosurgeons trained in epilepsy surgery.
Surgical procedures are performed in the operating room, usually under general anesthesia, with the patient completely asleep. However, if the area to be removed is near important brain areas controlling speech or movement, the resection is sometimes performed with the patient awake for a portion of the procedure. This allows for detailed mapping of the brain regions to minimize the risk of postoperative disability. After the operation, most patients are monitored in an intensive care unit for 24 to 48 hours. Patients stay 4 to 5 days in the hospital before going home to recuperate. Most patients have a slight headache for a week or so after they go home. They may also tire easily for several weeks but are encouraged to take walks and go out. Patients will remain on the same anti-epileptic drugs they were taking before surgery. If the patient remains seizure-free for 1 to 2 years, medications may be reduced over time in selected patients.
Patients and family should have a realistic picture of the benefits, the risks and the chances of complete or partial control of seizures. Possible complications of surgery include death, bleeding, stroke and infection. Patients may also experience adverse effects if areas of the brain are removed. These may be temporary or permanent.
Epilepsy Surgery Candidates
Around one-third of people with epilepsy continue to have seizures despite optimal medication and lifestyle changes. They may be candidates for surgery to eliminate the seizures. The pre-surgical evaluation involves many tests that determine the seizure's location and whether it may be surgically treated. The best candidates for epilepsy surgery are those people whose seizures originate from a single location in the brain and the region of the brain can be safely removed without causing significant disability. Conditions that often fall into this category include:
- Mesial temporal sclerosis (hippocampal sclerosis)—this is the most common epilepsy disorder that is surgically curable and is the disorder seen in 75 percent of patients undergoing epilepsy surgery
- Cortical dysplasia—small congenital malformations of the cortex that cause seizures
- Other congenital anomalies of brain development
- Cavernous angioma—benign vascular tumors that are prone to cause seizures
- Other brain tumors
- Brain trauma
Types of Surgical Treatments:
Temporal Lobectomy or Cortical Resection
The most common form of epilepsy surgery is a lobectomy or cortical resection. All or part of a left or right lobe may be removed surgically. The temporal lobe is the most common site of simple and complex partial seizures, some of which may secondarily generalize. Multiple studies have shown that the chance of becoming seizure free after surgery is about 70 percent for the first 2 years and 50 to 60 percent for the patient's lifetime. Some of the patients who were not seizure-free only had a single seizure over many years. These studies also show that patients who have good surgical outcomes have better cognitive and memory function than patients who do not have surgery.
A corpus callosotomy may be performed when partial seizures secondarily generalize and it is not possible to identify a single location or when resection of a localized focus would cause a significant disability. Uncontrolled generalized seizures, especially atonic seizures (drop attacks), may also be treated with this type of surgery. The surgery involves sectioning, or separating, the corpus callosum (a nerve bridge that connects the two halves of the brain and integrates its functions). By separating the cerebral hemispheres, the spread of a seizure can be confined to one side of the brain, thereby reducing generalized seizures.
Some types of seizure activity on one or both sides will continue after the operation, but the effects are generally less severe. The operation may be done in two steps. The first operation partially separates the two halves of the brain, but leaves some connections in place. If the generalized seizures stop, no further surgery is done. If generalized seizures continue, a second operation to complete the separation may be performed.
Vagus Nerve Stimulation (VNS)
Some patients are not candidates for epilepsy surgery because their seizures may be originating from multiple locations, from both sides of the brain, or from an area that is too valuable to remove. For these patients, a vagus nerve stimulator (VNS) may be recommended.
The VNS is designed to prevent seizures by sending regular small pulses of electrical energy to the brain via the vagus nerve, a large nerve in the neck. The electrical pulses are supplied by a device like a pacemaker. The VNS electrode is coiled around the left vagus nerve in the neck, and the wire runs under the skin to the battery, which is placed under the skin on the chest. The battery is flat and round, about the size of a silver dollar. The neurologist programs the electrical impulses according to each patient's individual needs. The settings can be programmed and changed by using a programming magnet. For people who have warnings (auras) before their seizures, activating the stimulator with the magnet when the warning occurs may help stop the seizure.
Patients may feel a buzz in the throat or detect a slight voice change while the device is on, but not between stimulation periods. The battery for the stimulator lasts approximately 5 years. Long-term studies of patients undergoing VNS show that seizure freedom is seldom achieved. The reduction in seizure frequency may range from a 20 to 60 percent. It may take 1 to 2 years for the reduction to be achieved.