What is epilepsy surgery?
If anti-epileptic medications do not control epilepsy seizures, brain surgery can be considered for some patients.
The most commonly performed type of brain surgery is called Resective Brain Surgery. Resective surgery for epilepsy is used to remove the part of the brain that is causing the seizures. This means that it can only be used for people where the seizures start in one area of the brain. When seizures start in one part of the brain only, this is called Focal Epilepsy.
There are different kinds of Resective Brain Surgery that occur in different parts of the brain, depending on where the seizures start. Some surgeries mainly involve removing a lesion as seen on the MRI - this is called a lesionectomy. Other surgeries involve larger parts of the brain. They may involve all or most of one of the lobes of the brain. The brain is divided into four paired sections:
- The frontal
- Temporal lobes
Temporal lobe surgery
The most common type of Resective Brain Surgery in adult epilepsy is performed in the temporal lobe. The temporal lobe is located on either side of the brain just above the ear. It plays an important role in language, hearing and memory, and many people with temporal lobe epilepsy therefore also suffer particularly from memory problems.
A temporal lobe resection means that brain tissue in the temporal lobe is resected, or cut away, to remove the seizure focus. The anterior (front) part of the temporal lobe and the deep part and mesial (deep middle) portions of the temporal lobe are the areas most often involved. The deep portions contain a structure called the hippocampus, which is involved in forming memories.
A temporal lobe resection requires exposing an area of the brain using a procedure called a craniotomy. After the patient is put to sleep with anaesthesia, the surgeon makes an incision in the scalp, removes a piece of bone and pulls back a section of the dura, the tough membrane that covers the brain. This creates an opening in which the surgeon inserts special instruments for removing the brain tissue. Surgical microscopes are also used to give the surgeon a magnified view of the area of the brain involved. The surgeon utilises information gathered during the pre-operative evaluation - as well as during surgery - to define, or map out, the route to the correct area of the temporal lobe. After the brain tissue is removed, the dura and bone are fixed back into place, and the scalp is sutured up using stitches or staples.
Other surgical procedures
Another area of surgical intervention is implantation of brain stimulators. Stimulators introduced into the brain are currently being investigated. In general, they can be considered in people where there are no resective surgery options. Deep Brain Stimulation (DBS) is a surgical procedure by which leads that have been implanted into specifically targeted areas in the brain deliver controlled electrical stimulation. This procedure may, in selected people, ameliorate seizures.
Much more widely used are Vagal Nerve Stimulators. These are small devices, similar to a cardiac pacemaker, which are implanted under the skin below the left collarbone. This is connected via a lead to the vagus nerve in the left side of the neck. The VNS stimulates the vagus nerve at intervals to reduce the frequency and intensity of seizures.