All epilepsy surgery involves the brain. However, different types of operations may be done. In general they fall into two main groups: - Removal of the area of the brain that is producing the seizures.
- Interruption of nerve pathways along which seizure impulses spread.
Lobectomy
Seizures that begin in one or more areas of the brain are known as simple or complex partial seizures. The seizures can take on different forms, depending on where they originate in the brain. The brain is divided into areas called lobes. There are temporal lobes, frontal lobes, parietal lobes and occipital lobes. There are two of each lobe on either side of the head. An operation to remove all or part of these areas is called a lobectomy. This type of surgery may be performed when a person has seizures that start in the same lobe every time. It is sometimes possible to stop the seizures by removing the seizure-producing area if it can be safely done without damaging vital functions.
Hemispherectomy
A lobectomy removes a fairly small area of the brain. However, in rare cases a child may have severe brain disease on just one side of the brain which produces uncontrollable seizures and paralysis on the opposite side of the body.
When this happens, a much more extensive operation may be considered.
It is called a hemispherectomy. It removes all or almost all of one side (hemisphere) of the brain.
It seems impossible that someone could function with only half a brain, but in children the half that is left may take over some of the functions of the part that was removed. However, there will be weakness and loss of some movement on the opposite side of the body. There will also be a loss of peripheral (side) vision.
Corpus Callosotomy
Another kind of surgery for epilepsy is called a corpus callosotomy (split brain surgery).
The corpus callosotomy operation does not take out brain tissue. Instead, it interrupts the spread of seizures by cutting the nerve fibers connecting one side of the brain to the other. This nerve bridge is called the corpus callosum.
The seizures which may respond to this type of surgery include uncontrolled generalized tonic clonic (grand mal) seizures, drop attacks, or massive jerking movements.
These seizures affect both sides of the brain at once and there is usually no one area which can be removed to stop them from happening.
Seizures are usually not stopped entirely by the operation. Some type of seizure activity on one side of the brain or the other is likely to continue, but the effects are generally less severe than the repeated drop attacks or convulsions.
The corpus callosotomy operation is often done in two steps. The first operation partially separates the two halves of the brain but leaves some connections in place.
If the generalized seizures stop, no further surgery is done. If they continue, the doctors may recommend a second step that completes the separation.
Multiple Subpial Transection
Some seizures originate in or spread to parts of the brain that are responsible for functions such as movement or language. Removing these areas would lead to paralysis or loss of language function.
A surgical technique called multiple subpial transection (MST) may be performed in these situations. It involves making small incisions in the brain which interfere with the spread of seizure impulses.
This technique may be used alone or in addition to a lobectomy.
