Types of Epilepsy Surgery
What are the different types of surgery used to treat epilepsy?
Different surgeries are available for different types of epilepsy. These include
- Focal Resection
- Multiple Subpial Transections
- Laser Interstitial Thermal Therapy
- Anatomical or Functional Hemispherectomy and Hemispherotomy
- Corpus Callosotomy
- Stereotactic Radiosurgery
- Neurostimulation Device Implantations, including
- Vagus Nerve Stimulation (VNS)
- Responsive Neurostimulation (RNS)
- Deep Brain Stimulation (DBS)
Surgery that removes the area of the brain causing seizures is called a focal resection. The area of brain being removed is referred to as the “seizure focus,” meaning the place where seizures begin.
- Removing the seizure focus is the most common type of epilepsy surgery. It is an excellent treatment option for people who have seizures arising from one area of the brain.
- The chances of success are highest in people who have an abnormality on MRI (magnetic resonance imaging) that matches the area where seizures start on EEG (electroencephalogram) monitoring.
- Since it involves removing a part of the brain, it is reserved for people whose seizures arise from non critical brain regions. Examples of critical brain regions include areas that control speech, movement, memory, and vision.
Temporal Lobe Resection
Temporal lobe resection is removing a portion of the temporal lobe of the brain. The most common type of epilepsy surgery is an anterior temporal lobectomy. It has the highest rate of success. After surgery, approximately
- 60% to 70% of people are free of seizures that impair consciousness or cause abnormal movements.
- 20% to 25% of people may still have seizures that affect their awareness (focal impaired awareness or tonic-clonic seizures). Although this group continues to have seizures, the majority of people show a large decrease, more than 85%, in the number of seizures they have.
- 10% to 15% of people do not have improvement in seizure control.
Overall, in people who are good candidates for a temporal lobectomy, more than 85% will have a significant improvement in seizure control. Most people will need to continue taking anti-seizure medications. Often, over time with the guidance of their epilepsy team, they are able to lower the dose of the medicine they need to take. About 25% of the people who become seizure free eventually can stop taking all of their seizure medications. Read a study about the long-term outcome after epilepsy surgery.
Frontal Lobe Resection
Frontal lobe resection refers to removing an area in the frontal lobe where seizures begin. It is the second most common location for epilepsy surgery.
- The frontal lobes of the brain control functions like motivation, attention, concentration, organization, planning, mood, and impulse control.
- People who have frontal lobe seizures may have problems with these functions before surgery.
- It is important to understand there may also be changes seen in these brain functions after surgery.
The success rates for frontal lobectomy are not as high as those for temporal lobectomy. It is still for many people who have drug resistant epilepsy. After surgery:
- Up to 50% of people are free of seizures that impair consciousness or cause abnormal movements.
- 20% to 40% of people may still have seizures that affect their awareness (focal impaired awareness or tonic-clonic seizures). Although this group continues to have seizures, the majority of people have a large decrease in the number of seizures.
- A small number of people do not have any improvement in seizure control.
Although the success rate for frontal lobe surgery is not as high when compared to people who have temporal lobe surgery, there are still 70% of people who do have a great improvement in seizure control. Most people will need to continue taking anti-seizure medications. Often, over time with the guidance of their epilepsy team, they are able to lower the dose they need to take.
Parietal and Occipital Lobe Resection
In most cases, this type of surgery is performed when an area in these lobes is found to contain abnormal structure or a lesion. This type of epilepsy surgery is more likely to be successful when it involves a structural abnormality like a tumor of scar tissue.
Removing a lesion that causes focal seizures is called a lesionectomy. People with a focal (well defined) structural abnormality in the brain causing their seizures, such as a tumor or vascular malformation (abnormal blood vessel group), may be considered for this type of surgery. This operation involves removing the lesion and the area of surrounding brain tissue that is causing seizures.
Multiple Subpial Transections (MST)
Multiple subpial resections are an alternate type of surgery that is used if seizures begin in a region of the brain that cannot be removed safely. This would include areas in the brain that control speech or movement.
This surgical procedure involves the neurosurgeon opening the skull and making a series of fine shallow cuts (transections) into the brain’s gray matter just below the pia mater. The pia is a delicate membrane that surrounds the surface of the brain. The cuts (transections) work by interrupting fibers that are thought to be involved in the spread of electrical seizure activity.
Sometimes MST are done in combination with a surgical resection when a part of the seizure focus is in a critical region (speech or movement) of the brain and a complete resection of the seizure focus is not possible.
Laser Interstitial Thermal Therapy (LITT)
Laser interstitial thermal therapy is sometimes called laser ablation surgery. During the surgery, a MRI (magnetic resonance imaging) is used to precisely map out the exact area of the brain to operate on. Laser is then delivered with pinpoint accuracy to this area to eliminate the seizure focus. All of this is done without needing to open the skull, making it a minimally invasive procedure.
This minimally invasive surgery can be effective for drug resistant focal epilepsy due to small lesions. This treatment has been used most commonly in people with temporal lobe epilepsy from mesial temporal sclerosis (scar tissue in the temporal lobe). People most appropriate for this type of surgery include
- People who have a clearly defined area of brain where seizures begin
- People who would benefit from a less invasive approach to epilepsy surgery
The advantages of this therapy compared to invasive epilepsy surgery include
- Shorter procedure
- No craniotomy (opening skull to access brain) required
- Shorter hospital stay
- Possibly, a reduction in complications and side effects
Early data on laser ablation surgery shows more than half of people treated with LITT achieve freedom from seizures.This type of surgery continues to be carefully studied. A multicenter clinical trial is ongoing to assess the safety and effectiveness of this procedure in individuals with mesial temporal sclerosis.
Anatomical or Functional Hemispherectomy and Hemispherotomy
These types of epilepsy surgery are almost exclusively performed in children with seizures coming from a large area on one side of the brain (hemisphere). The procedures involve separating the area of seizure onset from the rest of the brain. This typically is reserved for children with very large areas of seizure onset.
- Anatomic hemispherectomy involves removing the frontal, parietal, temporal, and occipital lobes on one side of the brain. Deeper brain structures (basal ganglia and thalamus) are left in place. This type of hemisphere surgery has higher risk and is usually considered for people with hemimegalencephaly (a rare condition where one side of the brain is abnormally larger than the other).
- Functional hemispherectomy involves removing a smaller area of the affected hemisphere and disconnecting the remaining brain tissue. This surgery involves less risk but is only helpful in a select group of people.
- Hemispherotomy is different than hemispherectomy as less brain tissue is removed to decrease the risk of complications from surgery. In this type of surgery, the surgeon is makes a hole or several holes in the hemisphere instead of removing large sections of the brain.
The results of these surgical procedures are very good. Generally over 80% of people have markedly improved seizure control and many are able to be free of seizures. The outlook for seizure control may be lower if a person has a progressive disorder, such as Rasmussen’s syndrome.
Corpus callosotomy is usually reserved for people with severe generalized epilepsy (meaning seizures involve both sides of the brain) who are subject to drop attacks (atonic seizures) and falls. The procedure involves splitting the main connection pathway between the two cerebral hemispheres (sides of the brain).
Individuals being considered for this operation usually have
Stereotactic radiosurgery uses many precisely focused radiation beams to treat the area of the brain where seizures begin (seizure focus). There are several different types of stereotactic radiosurgery. They are considered minimally invasive as the surgeon does not have to open the skull for the procedure. Stereotactic radiosurgery uses 3-D imaging to target high doses of radiation to the seizure focus with minimal impact on the surrounding healthy tissue.
Three neurostimulation devices are approved for the treatment of drug resistant epilepsy. These are vagus nerve stimulation (VNS), responsive neuro stimulation (RNS) and deep brain stimulation (DBS).
- VNS is approved for treatment of focal epilepsy when surgery is not possible or does not work. A small electrical generator is implanted under the skin over the chest. A wire, called a “stimulator lead,” is then attached onto the vagus nerve located in the neck. The generator stimulates the vagus nerve on a set schedule. Over time this helps to reduce the number and severity of seizures a person has. It is effective in over half the people who try it.
- RNS is a device that can record seizure activity directly from the brain and delivers stimulation to stop seizures. The device, also called an electrical generator, is implanted in the skull. Electrodes are placed on or in the brain in the area where seizures begin. The device detects seizure onset and then delivers an electrical stimulation to stop the seizure.
- DBS surgery involves implanting an electrode into the brain and placing a stimulating device under the skin in the chest. The brain electrode is implanted through a small hole made in the skull. Advance magnetic resonance imaging (MRI) and a computer navigation system are used to guide the electrode to the exact “target” position deep in the brain. The stimulator device placed in the chest is similar to a pacemaker and is connected to the brain electrode. The device sends signals to the brain electrode to stop signals that trigger a seizure. DBS surgery for treatment of seizures was approved by the U.S. Federal Drug Administration (FDA) in 2018. It has been approved in Europe, Australia and Canada for several years.
In summary, there are several different types of surgery that are available to treat people with drug resistant seizures. Your epilepsy team will discuss what options are possible for you and will help guide you through the proper evaluation and testing prior to making a decision about surgery.
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