15 Types of Epilepsy Surgery
15.1 An overview
Epilepsy surgery is not one thing. It is a family of procedures, each suited to a different situation. They can be divided into a few broad categories1–3:
- Resective surgery: removing the area of brain tissue where seizures start
- Disconnection surgery: cutting connections so seizures cannot spread, without removing tissue
- Ablative surgery: destroying a small, precise target using heat (laser) rather than cutting
- Neuromodulation: implanting a device that uses electrical stimulation to reduce seizures (an option covered in the chapter on vagus nerve stimulation)
The first question your team tries to answer is this: can we identify the exact area where seizures start, and is it safe to remove or destroy it? If the answer to both is yes, resective or ablative surgery offers the best chance of becoming seizure-free1,3. If the answer to either is no, disconnection or neuromodulation may be more appropriate.
Surgery is considered once epilepsy is drug-resistant, and deciding whether it is right for a given person is the subject of the chapter on when to consider surgery.
15.2 Resective surgery
Resective surgery means surgically removing brain tissue. It is the most common type of epilepsy surgery and, when the conditions are right, gives the highest chance of stopping seizures altogether4,5.
15.2.1 Temporal lobe resection
The temporal lobe, located on each side of the brain roughly behind the temple, is the most common site of drug-resistant focal epilepsy. The most frequent cause is hippocampal sclerosis, a scarring of the hippocampus (the seahorse-shaped memory structure deep in the temporal lobe) that shows up on MRI as shrinkage and signal change1,6.
When seizures arise from this area, the standard operation is called an anterior temporal lobectomy (ATL) or, in a more targeted version, a selective amygdalohippocampectomy (SAH). In ATL, the front portion of the temporal lobe is removed, including the hippocampus and amygdala. In SAH, a surgeon takes a more targeted path to remove primarily the hippocampus and amygdala while preserving more of the outer temporal cortex7,8.
Either way, these are the surgeries with the best-established outcomes in all of epilepsy surgery. Roughly 60 to 80% of people with hippocampal sclerosis become seizure-free after temporal lobe surgery1,6–8. The memory structures being removed are already damaged and not functioning normally, which is why the operation is possible without causing significant new memory problems in most cases, although this is carefully evaluated beforehand3,9.
15.2.2 Lesionectomy
Sometimes the culprit is a visible abnormality on MRI: a tumour (usually benign and slow-growing), a cortical malformation, a blood vessel abnormality (like a cavernoma), or scar tissue. When that lesion is the seizure source and can be safely removed, the operation is called a lesionectomy.
Outcomes from lesionectomy depend heavily on the type and location of the lesion and whether seizure activity is confined to it. Slow-growing tumours (particularly gangliogliomas and DNET) have excellent surgical outcomes, with seizure freedom rates above 70 to 80% common10,11. Cortical malformations (such as focal cortical dysplasia) are more variable because the boundaries of the abnormal tissue can be difficult to define precisely on imaging2,11,12.
15.2.3 Extratemporal resection
When seizures start outside the temporal lobe, in the frontal, parietal, or occipital lobes, surgery is called an extratemporal resection or lobar resection. These operations follow the same principle: remove the area generating seizures if it can be done safely.
Outcomes are generally somewhat lower than for temporal lobe surgery, in the range of 40 to 70% seizure freedom, and they vary considerably with the location of the focus and the underlying cause13–15. Results in more recent series have tended to be better than in older ones14. Part of the reason for the wider range is that the seizure focus in extratemporal epilepsy can be harder to pinpoint, and part is that these areas may involve functions such as movement, language, or vision that limit how much can be removed2,15.
When seizures arise from a large area spanning more than one lobe, a multilobar resection may be performed, removing portions of two or more adjacent lobes. These are less common and require careful planning with invasive monitoring to define exactly which tissue needs to go.
15.3 Hemispheric surgery
When seizures arise from one entire half of the brain, or when one hemisphere is so severely damaged that it is generating seizures continuously and dragging the other side down, the solution may be to address the whole hemisphere at once.
This is most common in children with conditions such as16,17:
- Rasmussen’s encephalitis (a progressive inflammation of one hemisphere)
- Hemimegalencephaly (abnormal overgrowth of one hemisphere)
- Large stroke or injury in infancy affecting one side
- Sturge-Weber syndrome affecting one hemisphere
- Widespread cortical malformation on one side
There are two main approaches.
15.3.1 Hemispherectomy
An anatomical hemispherectomy removes most of the affected hemisphere. The temporal lobe and most of the cortex are removed, while structures like the brainstem and deep brain nuclei are left intact.
Because of concerns about long-term complications with a very large surgical cavity, most centres today prefer a functional hemispherectomy or hemispherotomy instead16.
15.3.2 Hemispherotomy
A hemispherotomy achieves the same effect, disconnecting the damaged hemisphere from the rest of the brain, but removes far less tissue. The surgeon makes precise cuts to sever the connections between the two hemispheres and between the damaged hemisphere and the deep structures, while leaving most of the brain in place. The isolated hemisphere can no longer generate or spread seizures even though the tissue is still physically present.
Seizure freedom rates after hemispheric surgery are in the range of 60 to 80%16,17. The best outcomes are seen when the underlying cause is a stroke or injury (rather than a malformation) and when surgery is performed earlier in life16–18. Because the brain is being disconnected from the already-damaged side, children often continue using the hand on the affected side just as they did before, though weakness or loss of fine hand movements on the opposite side may occur or worsen. The brain’s ability to reorganize and compensate is extraordinary, particularly in younger children16,17.
15.4 Disconnection surgery
Disconnection surgery works differently from resection. Instead of removing the seizure-generating tissue, it cuts the pathways that allow seizures to spread, limiting the impact of seizures even if they cannot be stopped entirely.
15.4.1 Corpus callosotomy
The corpus callosum is a thick band of nerve fibres connecting the two halves of the brain. In some types of epilepsy, seizures start on one side and rapidly spread to the other, causing the whole brain to be involved and causing falls, which are among the most dangerous and injurious seizure types.
In a corpus callosotomy, surgeons cut some or all of the corpus callosum. This does not stop seizures from starting, but it prevents them from crossing over and involving the whole brain19,20. The most dramatic effect is on drop attacks (atonic or tonic seizures causing sudden falls). Roughly 50 to 80% of people who have the operation get a meaningful reduction in these falls, and about half stop having them altogether19,21,22. For someone who was previously falling and injuring themselves daily, that change can be life-changing.
Corpus callosotomy is most often considered for people with Lennox-Gastaut syndrome or similar severe epilepsies with multiple seizure types including drops21,22. It is palliative, meaning it improves quality of life rather than aiming for seizure freedom.
15.5 Laser ablation (LITT)
Laser interstitial thermal therapy, usually called LITT or laser ablation, is a minimally invasive procedure that uses heat to destroy a small, precisely defined target deep in the brain2.
The procedure works like this: under MRI guidance, a neurosurgeon passes a thin probe (about the width of a pencil lead) through a small hole in the skull and into the target area. Through the probe, a laser fibre heats the surrounding tissue to a temperature that destroys it. The whole time, real-time MRI images show the surgeon exactly how much tissue is being affected, allowing very precise control2,23.
LITT is particularly well-suited to2:
- Mesial temporal structures (hippocampus and amygdala) when the seizure focus is in that area
- Deep lesions, such as hypothalamic hamartomas, which cause gelastic seizures (laughing seizures) and sit in an area that is very difficult to reach with open surgery
- Nodular heterotopias (clusters of misplaced neurons deep in the brain)
The key advantages of LITT are that it requires only a small hole in the skull (no large incision), hospital stays are typically 1 to 2 days, and recovery is faster than open surgery23. The trade-off is a slightly smaller margin for re-doing the surgery if the first ablation is not complete, and that some targets are not safely reachable with a probe.
Seizure freedom rates for LITT depend heavily on the target. For mesial temporal sclerosis, roughly 50 to 60% of people become seizure-free2,23–25. This is somewhat lower than an anterior temporal lobectomy, which remains the more effective operation, but it is comparable to a selective amygdalohippocampectomy, and it comes with a much easier recovery2,24. Choosing between them is a real trade-off worth discussing openly with your team rather than a question with one right answer.
For hypothalamic hamartomas, results are excellent, with 60 to 80% of patients becoming free of gelastic seizures, and LITT is now considered the first-line treatment for this condition26–29.
15.6 Radiosurgery
Stereotactic radiosurgery (most commonly delivered by a device called the Gamma Knife) uses highly focused beams of radiation to damage or destroy a precise brain target, without any incision at all. It is not surgery in the traditional sense, since no instruments enter the brain, but it achieves a similar effect to ablation over a longer time frame15,30.
The limitation is that the treatment effect takes months to develop (the tissue gradually dies off), and outcomes for epilepsy, particularly for mesial temporal targets, are somewhat lower than those of direct surgery or LITT5,30–32. It is used in specific situations, for example for cavernous malformations in difficult locations, or for patients who cannot tolerate a surgical procedure15.
15.7 What about the risk of affecting normal function?
This is one of the most important questions families ask, and your team will spend a great deal of time addressing it before recommending any procedure.
The brain is not uniform. Different areas control different functions: speech, movement, vision, memory. Surgery near these areas carries a risk of affecting them. This is called eloquent cortex, meaning cortex that controls an essential function.
The presurgical evaluation is designed specifically to map where these functions are in your brain, because there is more individual variation than most people realize, and to determine how much the tissue that needs to be removed overlaps with areas you depend on. Techniques like functional MRI, Wada testing, and sometimes direct cortical stimulation during stereo-EEG are used to do this mapping3,9,33.
In children especially, the brain has remarkable ability to reorganize. Functions that are located in tissue that needs to be removed can sometimes shift to nearby areas, particularly when surgery is performed at a younger age16,18.
The goal is always to weigh the real and specific risks of surgery against the real and ongoing risks of uncontrolled seizures, which include injury, cognitive effects over time, and sudden unexpected death in epilepsy (SUDEP). This is a genuine and sometimes difficult conversation, and it is one your team should walk through with you in detail.
15.8 Key points
- Epilepsy surgery includes several different types of procedures, not just one operation.
- Resective surgery (removing tissue) gives the highest chance of seizure freedom when the focus is clearly identified and safely removable.
- Disconnection surgery reduces how seizures spread rather than stopping them at the source, and is particularly helpful for drop attacks.
- LITT is a minimally invasive alternative to open surgery for specific deep targets, with faster recovery, and is now the first choice for hypothalamic hamartomas.
- Hemispheric surgery offers very good outcomes for children with severe one-sided epilepsy.
- Neuromodulation devices are the next option when resection or disconnection is not possible.