Surgery:

Surgical techniques to remove injured brain tissue may be appropriate for many patients with epilepsy. The surgeon's goal is to remove only the damaged tissue in order to prevent seizures and to avoid healthy brain tissue. Surgical techniques for reaching these goals have improved significantly over the past decades due to advances in imaging and monitoring, new surgical techniques, and a better understanding of the brain and epilepsy.

Tests to Determine if Surgery Is Indicated

A number of tests using imaging and electroencephalography (EEG) can determine if surgery is an option:

• MRI of the brain is performed on all patients with epilepsy during the course of their illness. It often may identify an abnormality in brain tissue that is causing poorly controlled seizures.
• Many patients now have long-term EEG monitoring. This may involve wearing an EEG while taking part in everyday life or undergoing video EEG. These tests are done to help locate the exact brain tissue that is triggering the epileptic event
• Advanced imaging techniques can sometimes provide valuable additional information. They include functional magnetic resonance imaging (fMRI), positron emission tomography (PET), or single-photon emission computer tomography (SPECT) scans.

If the imaging tests indicate that more than one site is involved or their results conflict, then more invasive monitoring of the brain may be required, although the newer imaging tests are proving to be very accurate tools. If such tests pinpoint a specific area in the brain as the location for seizures, surgery is possible. MEG, for example, is now approved for imaging parts of the brain involved with motor control, sensation, and language function, and may become important in evaluating patients who are likely candidates for surgery. The doctor will also examine the test results to determine if the offending nerve cells perform vital functions and try to predict surgical outcome in certain cases.

The major areas of the brain have one or more specific functions.

Temporal Lobectomy

The most common surgical procedure for epilepsy is temporal lobectomy, which is performed when epilepsy are beginning in an area of the temporal lobe. (Surgery is not as successful in epilepsies that occur in the frontal lobe.) It involves removing small portions from the hippocampus. The hippocampus is a part of the brain that is involved in memory processing. It is part of the limbic system, which controls emotions.

Candidates. Candidates for this surgery usually have a history of seizures. Anti-epileptic drugs have not helped them. Young children may be more difficult candidates because they often have injured areas outside the temporal lobes. Nevertheless, surgery can be very successful in many children, even if more than one area is involved.

Success Rates. Studies have shown that many patients remain seizure-free after temporal lobectomy. When a well-described area in the temporal lobes is identified as the source of the seizures, around 60% of patients became free of disabling seizures after surgery versus only 8% of patients treated with medications. In general, around 60 - 80% of patients are seizure free 1 - 2 years after surgery.

Patients may still need to take medications after surgery, even if seizures are very infrequent. Cure is not always possible, and some patients may still experience some seizures. Double vision is very common after the operation, but it is typically temporary and resolves within a few months.

Successful temporal lobe surgery improves quality of life and can help relieve depression and anxiety.

Effects on Mental Functioning. Although surgery on the left temporal lobe does not impair intelligence to any significant degree, some studies suggest negative effects of mental functioning and behavior. A risk of impairment of verbal memory is also present.

In general, surgical effects on mental functioning and behavior depend on the extent and location of the surgical area.

Lesionectomy

Lesionectomy is a procedure that removes abnormal tissues in certain conditions, such as:

• Cavernous angiomas (abnormal clusters of blood vessels)
• Low-grade brain tumors
• Cortical dysplasias (these are abnormalities in fetal development in which the normal migration of nerve cells is altered for some reason)

This local surgery, which can cure the patient's epilepsy, has become possible with the advent of advanced imaging techniques such as MRI.

Vagus Nerve Stimulation (VNS)

Electrical stimulation of areas in the brain that affect epilepsy is helping many patients with refractory epilepsy. Vagus nerve stimulation (VNS), an electrical stimulation of the vagus nerve, is now an accepted therapy for severe epilepsy that does not respond to AEDs. The two vagus nerves are the longest nerves in the body. They run along each side of the neck, then down the esophagus to the gastrointestinal tract. They affect swallowing, speech, and many other functions. They also appear to connect to parts of the brain that are involved with seizures. The procedure is as follows:

• A battery-powered device similar to a pacemaker is implanted under the skin in the upper left of the chest.
• A lead is then attached to the left vagus nerve in the lower part of the neck.
• The neurologist programs the device to deliver mild electrical stimulation to the vagus nerve. (Patients may also pass a magnet over the device to give it an extra dose if they sense a seizure coming on. This appears to help about 25 - 30% of patients.)
• The batteries wear out after 3 - 5 years and need to be removed and replaced by a simple surgical procedure.

Candidates. The American Academy of Neurology recommends VNS for:

• Patients who are over 12 years old, and
• Have partial seizures that do not respond to medication, and
• Are not appropriate candidates for surgery

Evidence is accumulating, however, to indicate that VNS is effective and safe for many patients of all ages and for refractory epilepsy of many types.

Success Rates. Studies are reporting that the procedure reduces seizures within 4 months by up to 50% and even more in many patients. Studies report that it has been effective for longer than 7 years.

Complications. Vagus nerve stimulation does not eliminate seizures in most patients and is still somewhat invasive. VNS can cause shortness of breath, hoarseness, sore throat, coughing, ear and throat pain, or nausea and vomiting. These side effects can be reduced or eliminated by reducing the intensity of stimulation. Some studies suggest that the treatment causes adverse changes in breathing during sleep and may cause lung function deterioration in people with existing lung disease. People who have obstructive sleep apnea also should be cautious about this procedure. Turning off the VNS (for example before an MRI or surgery) may increase the risk for status epilepticus. (However, VNS may also be helpful for treating status epilepticus in some patients.)

Experimental Procedures

Deep Brain Stimulation. An investigational neurostimulation approach called deep brain stimulation (DBS) targets the thalamus, the part of the brain that produces most epileptic seizures. Early results have shown some benefit. Researchers are also studying other implanted brain and nerve stimulation devices such as the responsive neurostimulator system (RNS), which detects seizures and stops them by sending electrical stimulation to the brain. A third investigational approach, trigeminal nerve stimulation (TNS), stimulates a nerve involved in inhibiting seizures.

Stereotactic Radio Surgery. Focused beams of radiation are able to destroy lesions deep in the brain without the need for open surgery. Sometimes used for brain tumors, stereotactic radio surgery is also under investigation for temporal lobe epilepsy and for seizures due to cavernous malformations. It may be used for patients when an open surgical approach is not possible because the location of the abnormal area is surrounded by delicate brain tissue.