About Epilepsy Surgery
Epilepsy surgery is performed with the goal of curing or significantly improving epilepsy. Epilepsy surgery requires careful planning to remove or disconnect the parts of the brain that are causing seizures without damaging healthy, normal functioning brain tissue. With careful planning, patients may do well with epilepsy surgery and have seizure freedom. Epilepsy surgery is generally performed by a team that includes an epileptologist, neurosurgeon, neuropsychologists, nurses, and technologists. These health care professionals often work closely together to see the patients being considered for epilepsy surgery, look at their scans, discuss options with families and plan the operations. All team members help plan and carry out the surgery to ensure that the procedure is safe and effective.
In this section you will learn about:
- The different types of epilepsy surgery and who is a good candidate
- What tests you should undergo before planning for surgery
- Important terms to know
- Questions to ask your health care provider
- Frequently Asked Questions
Types of Epilepsy Surgery
There are three basic types of epilepsy surgery: resection, disconnection, and ablation.
Resection Surgery
A resection surgery is the most traditional type of surgery. A surgeon makes precise cuts with surgical tools and removes unhealthy brain tissue.
Many different areas of the brain can be resected. The reason behind the surgery is important to consider. In some cases, lesions, or the identifiable unhealthy areas of the brain that are causing the seizures, may be very close to important brain structures and resection may not be able to be pursued.
The neurosurgery team will plan the resection and explain the process to you. The team will use images or scans to plan the operation. Generally, a surgical window for the operation is created by removing part of the skull, which is safely stored. The operation proceeds and the resected tissue is often sent to a pathology lab, where it is closely examined under a microscope by experts. The skull bone that was taken off for surgery is then put back, and the patient is monitored in the hospital before going home.
Epilepsies that may be eligible for this type of surgery: Patients with focal epilepsy are candidates for resective surgery. Compared to disconnection surgeries, patient with lesions seen on brain MRI may be better suited for resective surgery.
Potential complications of resection surgery include: bleeding, infection and swelling. There is also a small risk that not enough tissue is resected, and seizures may continue.
Disconnection Surgery
A disconnection surgery is a surgery where the unhealthy brain tissue causing the seizures is disconnected from healthy brain tissue. The idea is that the seizure will no longer be able to spread from the unhealthy brain tissue into the healthy brain tissue and cause problems.
Many areas of the brain can be disconnected to stop the spread of seizures and keep seizures away from healthy brain tissue. Disconnections can be one lobe of the brain (temporal or occipital) or may involve more than one lobe, or, in certain circumstances, one-half of the brain. A unique type of disconnection is called a “callosotomy,” where the two halves of the brain are disconnected to stop dangerous seizures, such as prolonged convulsions and drop seizures, from occurring.
There are two ways to disconnect the unhealthy part of the brain from the healthy part of the brain. Option 1: The neurosurgeon carefully cuts the connections with surgery or Option 2: The neurosurgeon uses laser therapy, which disrupts the connections through intense heat directed at specific fibers and tracts in the brain.
Epilepsies that may be eligible for this type of surgery: Patients with focal epilepsy are candidates for disconnection surgeries. Generally, focal seizures that spread quickly and involve the entire brain may be good candidates for this type of surgery.
Potential complications of disconnection surgery: Complications depend on what part of the brain is being disconnected and through what method (traditional vs. laser). It is always important to consider that healthy brain may be disconnected in the process. This is an important topic to discuss with the surgical team. With any procedure there is the risk of swelling, bleeding, and infection. Another risk is that the area disconnected may not in fact stop or help seizure control, although this is becoming more rare.
Laser Ablations
A laser ablation surgery is a surgery where the surgical team uses an advanced laser to treat unhealthy brain tissue. The laser works by heating the area of unhealthy brain tissue until it goes away.
Many regions of the brain can be considered for laser ablation. One of the more common areas is the deep part of the temporal lobe, called the mesial temporal lobe. The mesial temporal lobe can be a common source of focal epilepsy, particularly in older children, teenagers, and young adults.
Areas of the brain will be laser ablated by the laser being directed to heat the unhealthy brain tissue in that area. The applied heat destroys the unhealthy brain without damaging healthy brain nearby.
Epilepsies that may be eligible for this type of surgery: Laser ablation works well for patients with focal epilepsy. It is well tolerated in patients who have tubers from tuberous sclerosis. It also works well in patients who have mesial temporal lobe epilepsy. It is becoming increasingly used in disconnections. One of the major advantages of laser surgery is that the patient’s skull bone does not need to be removed. Patients may often be discharged from the hospital in 24-48 hours following the surgery.
Potential complications of laser ablation: Complications would likely mostly be swelling with a rare risk of infection and seizures continuing despite undergoing ablation.
Pre-Epilepsy Surgery Diagnostic Tests
Electroencephalogram (EEG)
EEG is a brain wave test used by neurologists to record or see evidence of seizures. EEGs are helpful when they record a seizure, which will manifest as changes in the brain waves, but are also helpful even when they do not record the actual seizures. Small discharges can be seen at rest, which can provide clues about the presence and location of seizures. These small discharges are referred to as epileptiform discharges.
MAGNETIC RESONANCE IMAGING (MRI)
MRI is a scanner that takes pictures or images of the brain. MRI technology does not use radiation to take a picture. CT scans (commonly referred to as CAT scans) do use radiation. MRI images are very detailed and require patients to hold very still or undergo light sedation. An MRI is used to make sure that there are no problems with the structure of the brain. Problems with structure are often referred to as “lesions” by neurologists. Lesions can include birth defects, scars, strokes, or tumors.
ADDITIONAL TESTING
Additional tests that may be required or provide additional information include:
NEUROPSYCHOMETRIC
Neuropsychometric testing is often referred to as neuropsych testing or IQ testing. Neuropsych testing is often performed by a neuropsychologist who is trained in administering a series of tests that give information about baseline cognitive abilities such as thinking, attention, problem-solving skills, and memory. Neuropsycholigcal testing is often performed before and after surgery to compare results.
POSITRON EMISSION TOMOGRAPHY (PET)
PET is a type of scan that takes pictures of the metabolic activity of the brain. If a region of the brain is overly active, it may be so energized that it demands more nutrition, which can be seen in this type of metabolic scan. Similarly, a region of the brain that is underactive may not use normal amounts of nutrition. A PET scan uses radioactive tracers to see which parts of the brain are active. The amount of radioactive tracer used is minimal. PET scans are good at pointing to the relative region of the brain that is involved, but do not have high-definition capabilities.
SINGLE PHOTON EMISSION COMPUTER TOPOGRAPHY (SPECT)
SPECT is a technique where a scanner provides a snapshot of blood flow in the brain. SPECT scans are used to find where seizures are originating from but can be technically challenging to perform. A SPECT scan is performed in a hospital while a patient is connected to an EEG. This type of scanning relies on the patient having a seizure. Once the seizure happens, the tracer is injected, and the patient is brought to the scanner to see where the seizure originated. The tracer will travel to the area of the brain that is most active, which occurs during a seizure.
MAGNETOENCEPHALOGRAPHY (MEG)
MEG is a type of brain wave test that measures brain waves. The test is like an EEG but measures the magnetic brain waves instead of electric brain waves. The test helps neurologists locate the areas of the brain where seizures may be coming from. It can also tell neurologists what part of the brain (importantly, which side) controls talking and understanding language. MEG can provide a map for movement and sensory function in the brain. MEG can be useful in epilepsy surgery if there is a concern that the seizures are coming from a spot that is near important, normal functioning brain tissue. This important, normal functioning brain tissue is often referred to as “eloquent cortex” by neurologists.
Learn more about MEG scans here.
FUNCTIONAL MRI/ FUNCTIONAL MAGNETIC RESONANCE IMAGING
fMRI is a type of scan that creates a map of the regions of the brain responsible for different types of actions and thinking. fMRI measures differences in blood flow in the brain. When the brain plans an action for the body, there is increased blood flow. In this way a map can be created. This map is often helpful for neurologists to make a map of what parts of the brain are responsible for moving, talking, sensing, or planning. fMRI is also useful for determining what part of the brain helps with memory function. The scan’s ability to create a map is useful, like an MEG, in determining where healthy parts of the brain are so that safe surgeries can be performed.
STEREO EEG
Stereo EEG is a surgically implanted EEG that is used in determining if a patient is a candidate for epilepsy surgery. Stereo EEG uses small probes which are inserted into the brain to measure deep parts of the brain which normal EEG cannot reach. These small probes are inserted into the brain under careful guidance by a team of neurologists and neurosurgeons in the operating room. The patient will then spend a few days in the hospital with the probes inserted into the brain to measure the brain waves and determine if the team can locate the source of seizures. If the seizures can be pinpointed a surgery can be planned and discussed following.
PRE-SURGERY RELATED QUESTIONS TO ASK YOUR DOCTOR
- Is the purpose of the surgery to cure epilepsy or decrease the number of seizures?
- Is memory, motor function or language at risk with the proposed surgery?
- Do seizures need to be captured on EEG before surgery?
- What type of planning will take place to map out the surgery? Will a clear zone be identified to operate on?
- What other tests will be necessary before surgery? Do any tests need to be repeated?
EPILEPSY SURGERY-RELATED TERMINOLOGY
Lesion: A lesion is a term used by neurologists to describe an area of identifiable unhealthy brain that is typically causing seizures. Lesions can mean small scars, brain malformations, old strokes or tumors.
Cortical dysplasia: A cortical dysplasia is a type of lesion in the brain that can cause seizures. Cortical dysplasias often occur while the brain is forming. Sometimes a cortical dysplasia can be seen on MRI and high-definition imaging. Other times, even with high-definition imaging, it can be difficult to be seen.
Seizure onset zone: Neurologists will describe the area of the brain where the seizure is coming from as the seizure onset zone.
Eloquent cortex: Eloquent cortex refers to healthy brain tissue that is responsible for highly important functions such as movement, vision, sensing or talking.
Phase 1 surgery: A phase 1 surgery is an epilepsy surgery where neurologists are clearly able to identify the area of problematic brain causing seizures. The team can pinpoint this area with EEG and MRI. If the MRI can reveal an area of brain that could be safely removed and the EEG points to that area being problematic, a phase 1 surgery is possible.
Phase 2 surgery: A phase 2 surgery is an epilepsy surgery where neurologists are not clearly able to determine the location where the seizures are coming from based on imaging and regular EEG. Phase 2 planning generally involves putting EEG electrodes directly on to the surface of the brain or into the brain tissue. This is done by using something called a “grid,” which is a term used to describe EEG electrodes which record directly from the brain surface. Electrodes that record from inside brain tissue are referred to as stereo electrodes. A phase 2 surgery can also be planned through stereo EEG, or a combination of both.
Seizure capture: Seizure capture refers to recording a seizure, typically in a hospital setting by using EEG or stereo EEG.
Hemispherectomy: A hemispherectomy is a surgery in which one half of the brain is disconnected and removed. A similar term (hemispherotomy) may involve disconnecting one unhealthy half of the brain from the healthy half. These surgeries typically are pursued for very serious conditions or extremely hard to control epilepsy.
Lobectomy: A lobectomy is a term used to describe the removal of one lobe of unhealthy brain. Most commonly this involves the temporal lobe. These surgeries are used for very difficult to control epilepsy.
Lesionectomy: A lesionectomy is a term used to describe the removal of a brain lesion. A brain lesion is a part of the brain that is unhealthy that is causing problems. These include tumors, scars and areas of dysplasia.
Corpus Callosotomy: A corpus callosotomy is a surgery that involves disconnecting the right half of the brain from the left half of the brain. By doing so, generalized seizures can ideally be stopped. This procedure is often recommended for patients with dangerous seizure types such as convulsions and drop seizures. This surgery does not stop seizures, but is an effort to make them less dangerous.
SEEKING A SECOND OPINION
Families should be aware that second opinions are NOT frowned upon by the medical community. Second opinions can be suggested by family members or by primary neurologists. A second opinion does not mean that the patient’s care is being abandoned by the primary neurologist. Often, these two neurology teams will work together to provide the best care for the patient. Second opinions are becoming more common with the ability to seek consultation through telemedicine, which is a good option to consider.
ADDITIONAL RESOURCES
Learn more about epilepsy surgery from a patient perspective here and from a clinician in our webinar, “Epilepsy Surgery: Advancements, Options, & Considerations”. You can also learn about even more recent advances in diagnostics and surgical tools here.
Frequently Asked Questions (FAQs)
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When should epilepsy surgery be considered?
Epilepsy surgery should be considered after two medications (with appropriate trials) have been trialed without success for patients. Considering epilepsy surgery does not mean that you will undergo epilepsy surgery. There are patients who may not respond to medications that could do very well with surgery, and the purpose of considering epilepsy surgery is to identify those patients and give them the option.
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What happens post-operatively?
Patients often remain in the hospital under close observation after surgery to ensure that there are no complications. Members of the team will update you about how the operation went and what the next steps will be.
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What is the success rate for epilepsy surgery?
The success rate of epilepsy surgery is variable and depends on the type of surgery that can be offered. It is important to discuss with your team if seizure freedom or seizure reduction is the goal. It is also important to weigh these decisions on a case-by-case basis for patients and families.
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Do surgery patients stay on their antiseizure medications?
Often directly following surgery patients will remain on their medications. There is not a consensus about how to take medications off or when to take them off. Most patients stay on medications for a few months/years and then slowly wean to assess tolerability afterward.
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What is on the horizon for epilepsy surgery?
As newer technologies become available, these will be used in epilepsy surgery. Higher power scanners will be able to take better pictures so that problematic brain tissue can be better identified. Laser ablation and disconnection will likely also increase in the future as patients tolerate it very well and it does not require the skull bone being removed.
Treatment of epilepsy with gamma knife radiosurgery may be on the horizon, particularly for lesion-based epilepsy. Gamma knife is a type of radiation technology that allows beams of radiation to be directed towards an area of unhealthy brain, thereby ideally stopping its ability to cause seizures. Another new technology, called low intensity focused ultrasound, may be used for neuromodulation (similar to RNS and VNS). Directed ultrasound waves may be theoretically able to alter networks that are causing seizures and thereby suppress them. Low intensity focused ultrasound is not to be confused with high intensity focused ultrasound, which is a technology where ultrasound waves can be used as a way to ablate areas that cause seizures in the brain.