- Medically Intractable Epilepsy
If medications do not successfully control seizures, they are called “intractable.” We believe that anyone with epilepsy who is still having seizures despite trying several medications at reasonable doses is intractable. For these individuals, we aggressively search for the area in the brain where seizures originate (the focal point). If the focal point can be identified, then it may be treated surgically to eliminate seizures.
While neurosurgery may seem a radical step for the treatment of epilepsy, it is actually a rather safe and well-tolerated treatment when performed by experienced teams. Although surgery has risks, studies have consistently shown that the benefits outweigh the risks by reducing the number of or completely curing seizures.
Eliminating seizures helps:
The Northwestern Comprehensive Epilepsy Center team is staffed by experienced board-certified physicians who are all fellowship-trained in epilepsy and epilepsy surgery.
Candidates for Epilepsy Surgery
A person is considered to be a potential candidate for surgery if his or her seizures cannot be controlled by medications:
The best candidates for epilepsy surgery are those who do not respond to medication and who also have seizures that originate from a single focal area of the brain. Conditions that often fall into this category include:
Surgery has the highest chance of success if the following two conditions are present:
Note: If the studies are inconclusive regarding the exact location of seizure onset, implanted electrodes may be necessary to more closely localize the seizure focus. Subdural electrodes may be placed on the brain (subdural grids) or into the brain (depth electrodes) to more precisely record the seizure onset.
Pre-surgical evaluation involves many tests that are designed to determine if the seizures are coming from a single location in the brain that may be surgically treated. If all the studies point to a single area as being responsible for the seizures, surgery may drastically reduce, or even eliminate, seizures.
Pre-surgical evaluation involves the following tests:
Patients are admitted the morning of surgery. The procedure to place the electrodes typically lasts about 4 to 5 hours. Joshua Rosenow, MD, and Stephan Schuele, MD, work together to design a custom arrangement of implanted electrodes to maximize safety and the ability to localize the seizure focus. The surgery is performed using state-of-the-art computerized image guidance technology to allow the safest and most minimally invasive approach available. Patients spend one night in the neurosurgical intensive care unit afterwards.
Patients are then transferred to the Epilepsy Monitoring Unit (EMU) for video EEG monitoring for 5 to 10 days. Epilepsy medications are reduced during their stay; after several seizures have been recorded, the medications are restarted. At this time, the doctors decide whether the area causing the seizures has been localized enough to be safely removed. Patients will then return to the operating room for removal of the electrodes, and hopefully, removal or resection of the area causing seizures.
Once all of the testing has been completed, the team discusses each patient’s case in detail at our monthly multidisciplinary Epilepsy Surgery Patient Management Conference. The entire Comprehensive Epilepsy Center team attends this conference. The team reviews each patient’s case individually, and we make a consensus recommendation about further treatment. We then discuss the individual results of this conference in detail with each patient and his or her family.
Epilepsy Surgery Resection
If all of the presurgical studies show that a person’s seizures are coming from a well-defined location that may be safely removed, we often recommend surgery.
The Comprehensive Epilepsy Center team discusses the specific risks of surgery with patients and their families after their case has been reviewed at the multidisciplinary patient management conference.
Patients are admitted the morning of surgery. Surgery may be performed on any region of the brain using state-of-the-art computerized image guidance technology to allow for the safest and most minimally invasive approach available. The procedure typically lasts about 4 to 5 hours and is usually performed under general anesthesia with the patient completely asleep. However, if the area to be removed is very close to 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 sensitive regions while in the operating room to minimize the risk of postoperative disability.
Patients spend one night in the neurosurgical intensive care unit before returning to the regular neuroscience floor where they will stay 4 to 5 more days before going home. Most patients have a slight headache for a week or so after they go home. They also tire easily for several weeks, but we encourage them to take walks and go out.
After surgery, patients remain on the same antiepileptic drugs they were taking before surgery. If they remain seizure-free for 1 to 2 years, we gradually begin to wean them off the drugs.
Epilepsy Surgery Resection Outcomes
Multiple studies have shown that the chance of becoming seizure-free after surgery for temporal lobe epilepsy is about 70 percent for the first 2 years and 50 to 60 percent for life. Please note that some of the patients in these studies who were not considered “seizure-free” had only a single seizure over many years. These studies demonstrate that patients who have good surgical outcomes have better cognitive and memory function than patients who do not have surgery and continue to have seizures.
Outcomes for resection of other areas of the brain are highly variable. These other forms of epilepsy are less common, and the patient population is much smaller. In general, the chance of becoming seizure-free is about 40 to 50 percent, but this may vary depending on each patient’s specific condition.
Vagus Nerve Stimulation (VNS)
Some patients are not good candidates for epilepsy surgery because they have one of the following complications:
For these patients, we sometimes recommend implantation of a vagus nerve stimulator (VNS).
The vagus nerve stimulator is designed to prevent seizures by sending regular, mild pulses of electrical energy to the brain by way of the vagus nerve. The electrical pulses are supplied by a device similar to a pacemaker. The vagus nerve originates in the brain stem and runs down the neck to the chest and abdomen. In the neck, it lies between the carotid artery and jugular vein.
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 of the chest. The wire has enough slack to allow free movement of the head and neck.
The surgery is performed under general anesthesia, and patients go home the same day. The procedure usually lasts about 90 minutes. Two incisions are made: one along the outer side of the chest near the left armpit and a second incision horizontally in the left neck, hidden in a skin crease. The battery is flat and round, about the size of a silver dollar.
The neurologist programs the strength and timing of the impulses according to each patient's individual needs. The settings can be programmed and changed by using a programming wand that transmits the information through the skin to the battery.
For all patients, the device is programmed to go on for a certain period (for example, 7 seconds or 30 seconds) and then to go off for another period (for example, 14 seconds or 5 minutes). The device runs continuously, usually with 30 seconds of stimulation alternating with 5 minutes of no stimulation. Patients may feel a buzz in the throat or detect a slight voice change while the device is on, but not between stimulation periods.
Holding a special magnet near the implanted device causes the device to become active outside of the programmed interval. For people with warnings (auras) before their seizures, activating the stimulator with the magnet when the warning occurs may stop the seizure.
The battery for the stimulator lasts approximately 5 years before it needs to be replaced during a short outpatient procedure.
Vagus Nerve Stimulation Outcomes
Long-term studies of patients undergoing vagus nerve stimulation show that the reduction in seizure frequency is highly variable. Results can range from no reduction to complete elimination of seizures. Most patients experience a 20 to 60 percent reduction in seizures. The effect of vagus nerve stimulation may take up to 2 years to be fully realized.