Epilepsy Surgery

Epilepsy Surgery Overview

Epilepsy surgery is a treatment option for individuals who have epilepsy that doesn’t respond to medications (drug-resistant epilepsy). While anti-seizure medications adequately control most people’s seizures, up to one in three people will not be helped enough by medical management. In these patients, epilepsy surgery can significantly improve their quality of life and even result in freedom from seizures.

The first step for people considering epilepsy surgery is a thorough evaluation, which entails various tests such as electroencephalography (EEG) and magnetic resonance imaging (MRI). These tests help tailor the surgical treatment plan for individual patients by pinpointing where in the brain seizures originate (known as the seizure focus) and how they propagate throughout the brain.

Categories of Epilepsy Surgery

There are several types of epilepsy surgery, which can be divided into three categories.

Surgical Resection

Surgery to eliminate the seizure focus, which includes brain tissue or structural brain lesions (such as tumors or malformed blood vessels) that are causing your seizures, is called surgical resection. In general, the goal of these is seizure freedom. However, outcomes are known to vary depending on the type of surgery and each person’s epilepsy.

Neurosurgeons typically perform resective surgery through a traditional brain surgery approach, in which the seizure focus is removed (resection) under direct visualization through a small window that is temporarily created in the skull (craniotomy). Sometimes, the seizure focus can be eliminated via a minimally invasive approach, using laser (laser interstitial thermal therapy, LITT) or radiofrequency energy to heat and destroy (ablation) the seizure focus. These techniques are especially beneficial for targeting seizure foci that are small and deep inside the brain. Neurosurgeons can perform ablation through a small opening through the scalp and skull, in which laser energy delivery is monitored in real time using MRI.  

You might not be a candidate for surgery to eliminate your seizure focus based on your specific situation, treatment goals, preferences, and the nature of your epilepsy. In these cases, there remain two other categories of surgery, which include surgery to disconnect the seizure focus from the rest of the brain or surgery to implant neuromodulation devices. While these surgeries can lead to seizure freedom, the more likely outcome is a significant reduction in the number, duration, and severity of seizures.

Neuromodulation

Neuromodulation involves placing electrodes in specific brain areas or the vagus nerve. These electrodes are connected to a battery-operated device called an implantable pulse generator (similar to a cardiac pacemaker), all placed underneath the skin. The implantable pulse generator delivers electrical impulses to the regions where the electrodes are placed. This therapy is known as neuromodulation because its effects on epilepsy symptoms improve with time and adjustments made to the device settings. Your seizures can respond as early as within the first few months of stimulation, but the effects of stimulation typically improve over the years.

Specific outcomes vary depending on the type of neuromodulation device and each person’s epilepsy. Moreover, to benefit from these procedures, you must follow up with your neurologist after surgery to customize device settings in order to achieve optimal symptom reduction with minimal side effects. This process of fine tuning the device settings is known as programming and can take several weeks to months. Following the initial programming, you will need ongoing adjustments based on your specific needs as monitored by your neurologist.

The three types of neuromodulation devices used in epilepsy are:

• Deep Brain Stimulation (DBS): A neurosurgeon places electrodes in deep brain structures, with one electrode in either side of the brain. The electrodes are connected to an implantable pulse generator placed in the upper chest region.
• Responsive Neurostimulation (RNS): Electrodes are placed in brain structures involved in your epilepsy. Unlike DBS, the implantable pulse generator is embedded within the skull. This device actively senses brain activity, which is used to dynamically trigger electrical stimulation when it detects epileptic activity.
• Vagus Nerve Stimulation (VNS): Electrodes are placed on the vagus nerve, one of the twelve cranial nerves that originate directly from the brain (as opposed to most nerves in the body that arise in the spinal cord). Specifically, electrodes are implanted deep inside the neck, where the vagus nerve travels. In addition to epilepsy, the FDA has also approved this therapy for the treatment of treatment-resistant depression and for upper extremity motor rehab following a chronic ischemic stroke.

While the prospect of brain surgery can be daunting, many patients who undergo these procedures see a significant reduction in their seizure burden and a significant improvement in their quality of life. However, as with any surgery, there are risks involved. These include risks of infection, bleeding, neurologic impairment, and device problems requiring additional surgery. Deciding on epilepsy surgery involves careful consideration and discussions with your healthcare team. This decision is deeply personal and requires weighing the potential benefits against the risks.

The recovery process following epilepsy surgery can vary. VNS is performed on an outpatient basis, whereas DBS and RNS generally require an overnight stay in the hospital to monitor your recovery and manage any immediate postoperative symptoms. Surgeries to eliminate or disconnect seizure foci may similarly require an overnight hospital stay or a hospital admission lasting a few days. Most people are discharged directly back home, although some may benefit from inpatient rehabilitation before returning home. You can expect to return to your job and usual activities as quickly as one to two weeks, depending on the nature of your work and lifestyle.

The first step is to understand your epilepsy. This usually involves reviewing your medical history and any prior and current treatments for epilepsy. It also includes a review of how well medications control your seizures. Your neurologist will only refer you to a neurosurgeon after a comprehensive trial with at least two anti-seizure medications (either in succession or together) that did not result in adequate control of symptoms.

If your epilepsy care team thinks that epilepsy surgery could help you, they will schedule a series of diagnostic tests divided into Phase 1 and Phase 2 evaluations.

Phase I Epilepsy Surgery Evaluation

Phase I evaluation aims to characterize your seizure focus with respect to your brain’s unique structure and function mainly using non-invasive tests (except the Wada test, which is minimally invasive). The specific tests that are required will vary for each person. Some Phase I tests include:

• EEG: This test records the electrical activity in your brain using electrodes placed on your scalp. It helps doctors see the patterns of your brain waves and get a general idea of where your seizures might begin. You can undergo EEG in the outpatient setting or while admitted to the hospital in the epilepsy monitoring unit. In general, EEG in the context of a pre-surgical workup will require admission to the epilepsy monitoring unit to record your seizures adequately. 
• High-density EEG (HD EEG): This type of EEG involves using a cap containing a much larger number of scalp electrodes than traditional EEG—typically 128—to record electrical activity in the brain with higher spatial resolution. It provides complementary information to identify areas of the brain where epileptic activity originates.
• Magnetoencephalography (MEG): Akin to HD EEG, MEG provides complementary information to identify epileptic brain regions using a vastly different technique. The device measures the tiny magnetic fields produced by neural activity in the brain that are billions of times smaller than the Earth’s magnetic field. The comprehensive Epilepsy Center at Barrow Neurological Institute is the only center to offer MEG tests in Arizona. The MEG can also map which area of the brain controls speech, language, and other functions.
• MRI: This imaging test provides detailed images of your brain. It helps identify any structural abnormalities that might be causing your seizures. Functional MRI may also be obtained, which shows brain areas that support essential neurologic functions, such as language, memory, vision, and others.
• Neuropsychological evaluation: This is a battery of standardized questionnaires and surveys administered by a neuropsychologist to assess your brain function, including memory, language, mood, and ability to think and solve problems.
• Wada: Also known as the intracarotid sodium amobarbital procedure, this test involves temporary anesthetization of one hemisphere of the brain by injecting a drug into the carotid artery. It allows neuropsychologists to assess the function of each hemisphere, helping them identify the side of your brain responsible for language and memory functions. It is a minimally invasive outpatient procedure in which an endovascular neurosurgeon or neuro-interventionist accesses the large vessels in your legs with a needle puncture and threads a catheter up toward the vessels in your brain, where the drug is delivered. Only a subset of patients who are being evaluated for epilepsy surgery will need the Wada test. In particular, it can be critical for planning surgeries in which the seizure foci are eliminated.
• Additional tests might include a PET or SPECT scan, which also provide complementary information to identify epileptic brain regions.

Our multidisciplinary team of epilepsy specialists, including neurologists, neurosurgeons, neuroradiologists, neuropsychologists, and social workers, conduct a sophisticated and detailed analysis of the information obtained during Phase 1 during our surgical epilepsy conference. If you are a good candidate for epilepsy surgery, the team will generally recommend proceeding to Phase II evaluation, which involves a surgical procedure called stereo EEG (SEEG), to finalize plans for the therapeutic surgery.

Your neurologist will share and discuss these recommendations with you after the conference, and you will have the option to further discuss the potential benefits and risks of SEEG as well as potential therapeutic surgical options for your epilepsy with your neurosurgeon during a clinic consultation. The decision to proceed is made with your input, ensuring you are comfortable with and understand the surgical options and alternatives.

While most patients will first require a Phase II evaluation prior to the therapeutic surgery, some patients may be able to move directly to therapeutic surgery. People can skip to therapeutic surgery if Phase I provides sufficient information to identify a personalized surgical treatment plan that will be safe and effective.

Phase II Epilepsy Surgery Evaluation

Phase II evaluation focuses on further understanding the seizure focus and surrounding brain functions to inform personalized treatment recommendations for individuals that maximizes both efficacy and safety of therapeutic surgery.

This phase consists of SEEG, which entails a minimally invasive surgery to implant electrodes within the brain, followed by admission to the epilepsy monitoring unit for one to two weeks. Your neurosurgeon will perform this surgery in the operating room under general anesthesia. During the procedure, your neurosurgeon implants tiny electrodes with a diameter of less than 1 mm into brain regions implicated by Phase I tests to obtain a much more detailed map of epileptic activity as it starts and propagates throughout your brain. This surgery does not require any large openings or incisions of the scalp. Furthermore, it requires only minimal hair removal around the entry points of each electrode.

After the electrodes are in place, your neurologist may also perform functional mapping in the EMU, during which you perform simple tasks while electrical stimulation is delivered through the implanted electrodes. This allows your epilepsy team to map critical brain functions to optimize the safety of any ensuing epilepsy surgery.

Steps of Epilepsy Surgery

Epilepsy surgery involves several critical steps designed to ensure the best possible outcomes while minimizing risks:

1. Pre-surgical Assessment: This initial step (described above) involves a series of tests to create a detailed map of your seizures to evaluate whether you’re a good candidate for surgery. The specific tests you will need will be customized and may include Phase II evaluation with SEEG.
2. Surgical Planning: Based on the findings from the pre-surgical assessment, your surgical team, including neurologists and neurosurgeons, will decide which therapeutic surgeries are most appropriate for your case.
3. The Surgery: The procedure can vary depending on the type of epilepsy surgery (described in detail above) you decide to proceed with (if you are a candidate for more than one type of epilepsy surgery).
4. Recovery: After surgery, you’ll spend time in the hospital under observation to manage any immediate postoperative symptoms and to begin recovery. The length of hospital stay can vary based on the type of surgery and your specific health needs.
5. Follow-up Care: After surgery, ongoing follow up is crucial. This includes regular check-ups to monitor your health and surgical recovery, adjust medications, and, in some patients, to program your device. The goal is to manage changes to your condition, monitor seizure response, and support your overall recovery and quality of life.

Your healthcare team will be closely involved throughout these steps, ensuring you receive comprehensive care and support tailored to your needs.