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Epilepsy Surgery

Dartmouth-Hitchcock Medical Center (DHMC) has developed and maintained a leading epilepsy center with experienced staff and state-of-the-art monitoring equipment.

The center is directed by expert epilepsy specialists. Each patient who enters the program receives personal care during diagnosis and treatment.

Many patients are referred to the Dartmouth Epilepsy Center by another physician, usually a neurologist. An evaluation is done by an epilepsy specialist at the Hitchcock Clinic (Section of Neurology and Neurosurgery) before admission to the hospital. The Dartmouth Epilepsy Center physicians work closely with the patient's own physician. Some patients are treated successfully as outpatients. Others need to be admitted to the hospital for further evaluation and treatment.

Epilepsy Surgery

Dr. David Roberts at DHMC is considered one of the world's experts on epilepsy surgery. He has published and lectured extensively on this subject. There are many different types of surgery for medically intractable epilepsy. The goal of epilepsy surgery is to not only reduce the incidence of seizures, but also to cure them in many patients. In those patients who are not eligible for resection of their seizure focus two options remain, Sub-pial Transection or Vagal Nerve Stimulation.

These procedures are currently being investigated for their potential efficacy as treatment options for medically intractable seizure disorders.

Lobectomy

If seizures cannot be controlled in other ways, the part of the brain where the seizures begin is removed. This is called a lobectomy. Seizures may begin in various lobes such as:

  • Frontal lobe
  • Occipital lobe
  • Parietal lobe
  • Temporal lobe

The most common form of epilepsy surgery is known as a temporal lobectomy. Almost 70% of partial seizures in adults begin in the temporal lobes. The temporal lobes are found on both sides of the head just above and in front of the ears. Seizures that begin in other regions of the brain can also be treated surgically. Dr. Roberts utilizes a frameless based stereotactic operating microscope system to optimally resect the seizure focus and minimize potential complications. Although epilepsy surgery is considered relatively safe, certain risks do remain. The neurologist and neurosurgeon will explain the risks of each surgery. Some risks include:

  • Bleeding at the surgical site.
  • Infection at the surgical site.
  • The risk of anesthesia.
  • A small loss of vision opposite the side of surgery.
  • Having a hard time remembering or speaking certain words.

Other Resective Surgery

Other types of surgery may be done such as removal of tumors, abnormal collections of blood vessels, and congenital lesions, all of which can cause seizures. During resective surgery, the lesion as well as the tissue around it is removed if monitoring has shown that seizures begin in that area. Risks are similar to the lobectomy procedure.

Corpus Callosotomy

Another major type of epilepsy surgery is dividing the corpus callosum. This stops the spread of seizures from one side of the brain to the other and is only done when the origin of a seizure cannot be found.

During the operation, the nerve fibers that connect one side of the brain to the other, called the corpus callosum, are cut. No tissue is removed. This procedure is most helpful for generalized tonic clonic or grand mal seizures and drop attacks. Seizures are not usually stopped entirely by this procedure; however, the effects of the seizure are usually less severe. Often patients may have seizures on only one side of the body instead of both sides, after surgery.

A corpus callosum section is sometimes done in two stages. In the first, the front part of the corpus callosum may be cut two-thirds of the way. If this controls the seizures, then no further surgery will be needed. If this does not reduce the frequency of seizures and/or their intensity, then a complete division of the corpus callosum may be offered.

Hemispherectomy

In some cases, a patient may have congenital brain damage on only one side of the brain that, in turn, causes seizures and paralysis on the other side of the body. If so, a procedure known as a hemispherectomy can be carried out. This entails removing all or almost all of the damaged side of the brain. After this surgery, the function of the rest of the brain may improve and take over some of the functions of the part that was removed. However, any weakness on the side opposite the surgery remains.

Vagus Nerve Stimulation (VNS)

Approved in 1997 after fifteen years of research and clinical studies, VNS is an implantable medical device and has become an effective treatment in reducing the frequency of seizures in candidate patients over the age of twelve with partial onset seizures. The system consists of a battery powered pacemaker-like generator and nerve stimulation lead. The VNS generator and lead are implanted in the chest and neck in an relatively simple operative procedure.

Surgery for Monitoring Purposes

Depth and Subdural Strip Electrodes
These are placed by the surgeon in the operating room. The patient is awake but given sedation and local anesthesia. After returning to the room, the patient is monitored constantly on a video/EEG machine, and is also watched closely by nursing staff. This monitoring takes place for 5-10 days or until enough seizure information is obtained. These electrodes can be removed at the bedside, therefore a second surgery to remove them is not required.

Grid and Subdural Strip Electrodes
The second type of electrode placement involves surgical placement of one or several "sheets" (or grids) of electrodes over the surface of the brain. This is done under general anesthesia. Grid electrodes allow more coverage of the surface of the brain. A small piece of bone must be removed to place the electrode. When the video/EEG monitoring is finished the bone "flap" will be replaced in the operating room. The electrodes are placed about one week before the final surgery to remove the abnormal brain tissue. If there is not enough information in one week, the final surgery will be scheduled later in the second week.

In some cases, functional mapping is done. This test "maps out" vital functions in the brain such as speech, the ability to move arms, legs and face, and the ability to feel. Functional mapping is done before any surgery close to those areas of the brain so that those functions will not be lost.

During the Phase III admission, the patient must stay in bed or on occasion in the recliner chair for safety during the monitoring. At times, light cloth restraints may be used to protect the patient from injury during a seizure. The patient is not allowed to use the bathroom because he or she might have a seizure while alone. Instead, bed pans, urinals, and bedside commodes are used.

Sometimes, after all three phases of testing are finished, a single location of seizure origin cannot be found because the patient has two or more separate regions of seizure origin or the surgically placed electrodes may not have been near enough to the region of seizure origin to record it. If so, a second phase III study might be suggested or a corpus callosotomy may be considered.

Success Rates and Complications

If the exact location of seizure origin can be known, the chance of cure improves a great deal. Epilepsy surgery is elective and is not a guarantee of a cure. Success rates for becoming seizure free following temporal lobectomies, however, are currently averaging over 90%.

Complications of epilepsy surgery are rare occuring in less than 5% of patients. The type of complications include wound infection, brain infection, leakage of spinal fluid from the incision, and weakness on the side opposite the surgery.

Follow-up Care After Surgery

After surgery, the patient will be followed very closely by the medical and surgical team. It is important for the patient to tell the physician or nurse if there is any problem functioning in everyday life or trouble coping with a life without epilepsy. These are very important concerns and the epilepsy treatment team can be of help.

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