Evaluation of persons for surgery is generally recommended only after focal seizures persist despite the person having tried at least two appropriately chosen and well-tolerated medications, or if there is an identifiable brain lesion (a dysfunctional part of the brain) believed to cause the seizures.
When someone is considered to be a good candidate for surgery experts generally agree that it should be performed as early as possible.
Surgical evaluation takes into account the following variables:
- the type of seizure
- the brain region involved, and
- the importance of the area of the brain where seizures originate (called the focus) for everyday behavior
Prior to surgery, individuals with epilepsy are monitored intensively in order to pinpoint the exact location in the brain where seizures begin. Implanted electrodes may be used to record activity from the surface of the brain, which yields more detailed information than an external scalp EEG. Surgeons usually avoid operating in areas of the brain that are necessary for speech, movement, sensation, memory and thinking, or other important abilities. fMRI can be used to locate such “eloquent” brain areas involved in an individual.
While surgery can significantly reduce or even halt seizures for many people, any kind of surgery involves some level of risk.
Surgery for epilepsy does not always successfully reduce seizures and it can result in cognitive or personality changes as well as physical disability, even in people who are excellent candidates for it. Nonetheless, when medications fail, several studies have shown that surgery is much more likely to make someone seizure-free compared to attempts to use other medications.
Anyone thinking about surgery for epilepsy should be assessed at an epilepsy center experienced in surgical techniques and should discuss with the epilepsy specialists the balance between the risks of surgery and desire to become seizure-free.
Even when surgery completely ends a person's seizures, it is important to continue taking antiseizure medication for some time. Doctors generally recommend continuing medication for at least two years after a successful operation to avoid recurrence of seizures.
Types of surgical procedures for epilepsy
There are a variety of surgical procedures that may be used for treating epilepsy disorders.
Surgery to treat underlying conditions
In cases where seizures are caused by a brain tumor, hydrocephalus, or other conditions that can be treated with surgery, doctors may operate to treat these underlying conditions. In many cases, once the underlying condition is successfully treated, a person's seizures will disappear as well.
Surgery to remove a seizure focus
Surgery to remove a seizure focus involves removing the defined area of the brain where seizures originate. It is the most common type of surgery for epilepsy, which doctors may refer to as a lobectomy or lesionectomy, and is appropriate only for focal seizures that originate in just one area of the brain. In general, people have a better chance of becoming seizure-free after surgery if they have a small, well-defined seizure focus. The most common type of lobectomy is a temporal lobe resection, which is performed for people with medial temporal lobe epilepsy. In such individuals one hippocampus (there are two, one on each side of the brain) is seen to be shrunken and scarred on an MRI scan.
Multiple subpial transection
Multiple subpial transection may be performed when seizures originate in part of the brain that cannot be removed. It involves making a series of cuts that are designed to prevent seizures from spreading into other parts of the brain while leaving the person's normal abilities intact.
Corpus callosotomy,or severing the network of neural connections between the right and left halves (hemispheres) of the brain, is done primarily in children with severe seizures that start in one half of the brain and spread to the other side. Corpus callosotomy can end drop attacks and other generalized seizures. However, the procedure does not stop seizures in the side of the brain where they originate, and these focal seizures may even worsen after surgery.
Hemispherectomy and hemispherotomy
Hemispherectomy and hemispherotomy involve removing half of the brain's cortex, or outer layer. These procedures are used predominantly in children who have seizures that do not respond to medication because of damage that involves only half the brain, as occurs with conditions such as Rasmussen's encephalitis. While this type of surgery is very excessive and is performed only when other therapies have failed, with intense rehabilitation, children can recover many abilities.
Reference: The National Institute of Neurological Disorders and Stroke
Last updated May 4, 2017