Treatment Options for Parkinson's Disease

Surgical Therapy for Parkinson's Disease

Surgical intervention was relatively common for the treatment of Parkinson's disease before the introduction of levodopa. It then fell out of practice but is now being re-evaluated as new surgical techniques become available.

Surgery may be recommended as a treatment for:

  • Young-Onset Parkinson's Disease patients for whom drugs do not adequately control the symptoms and who have no evidence of cognitive impairment or other medical problems
  • Patients of any age with advanced stage Parkinson's disease who are no longer responsive to medication and who suffer from disabling tremors or associated Parkinson's disease symptoms such as motor fluctuations or dyskinesia
  • Parkinson's disease patients of any age who have a significantly impaired quality of life

Surgery for Parkinson's disease is often done under local anesthesia. Surgery is not curative and is intended only to relieve symptoms of Parkinson's disease. Since the symptoms which may warrant surgery are associated with advanced Parkinson's disease, surgical intervention is not considered to be an option for early Parkinson's disease.

Currently, there are four types of surgical procedures that may be considered for Parkinson's disease patients:

  • Pallidotomy
  • Thalamotomy
  • Deep Brain Stimulation (DBS)
  • Fetal Tissue Transplantation

If your doctor recommends surgery for Parkinson's disease, it is important to confirm coverage for these procedures with your health insurance carrier before undergoing surgery.

Pallidotomy

Pallidotomy involves the destruction of part of the globus pallidus (GPi) area of the brain which controls movement. A wire probe is inserted into the GPi and the precise target location is identified by MRI. The probe is heated by radio-waves to a temperature that destroys the tissue around it. Since the reduction and loss of dopamine cause overactivity in the GPi, destruction of part of the tissue restores the balance needed for controlled movement.

Pallidotomy is performed to treat:

  • Peak-dose dyskinesias (uncontrolled movements that occur when levodopa is at its highest concentration in the blood)
  • "Wearing-off" dystonia (muscle spasms at the lowest concentration of levodopa as the medication wears off)
  • Bradykinesia and tremor are sometimes targeted but the surgery is not as effective for these symptoms

Pallidotomy can be performed in one of two ways:

  • Unilateral pallidotomy - a portion of the tissue on only one side of the brain is destroyed (ablated) which improves motor control on the opposite side of the body and has a moderate effect on dyskinesia on the same side as the ablation.

  • Bilateral pallidotomy - tissue is ablated (destroyed) on both sides of the brain.

At this point, results of unilateral pallidotomy are more promising than for bilateral pallidotomy. There is evidence that after pallidotomy, some patients can tolerate a higher dose of levodopa. Pallidotomy is most effective in patients under the age of 70 but may be performed on older patients as well.

There are complications in approximately 10-20% of patients undergoing the pallidotomy procedure. There is a risk that the probe can strike a blood vessel causing a stroke. There is also the risk of damaging other parts of the brain.

Thalamotomy

Thalamotomy is also a destructive (ablative) procedure during which a part of the thalamus is destroyed. The thalamus is the area of the brain that helps process information from the senses and transmits it to other parts of the brain. Thalamotomy is most effective for tremors in younger patients and has some benefit for rigidity and peak-dose dyskinesia. The ablation can be unilateral or bilateral. There are two methods used to perform this procedure:

  • Stereotactic Electrode Heat Coagulation - Using stereotactic techniques, a specific area of the thalamus is located and an electrode (probe) is inserted. The tip of the electrode is heated which destroys the tissue around it. A positive effect on tremors is seen immediately.

  • Gamma Knife Radiosurgery - This is a new method and employs focused radiation. It is used primarily on older patients who cannot tolerate stereotactic surgery. Improvement is usually seen within 1-2 months.

The probe in thalamotomy may damage other major brain centers that are adjacent to the thalamus. Also, thalamotomy can cause worsening gait and speech problems. Patients who exhibit these symptoms prior to surgery are usually excluded from the procedure. Thalamotomy also carries the risk of hemorrhage or stroke.

Deep Brain Stimulation (DBS)

Deep brain stimulation is not a destructive procedure. It does not ablate any tissue. Rather, an electrode is placed in the brain and a battery is inserted into the chest wall with a wire connecting the electrode and the battery. Continuous high-frequency electrical stimulation is delivered to the GPi, the thalamus, or the subthalamic nucleus. High frequency stimulation stops the activity of cells in the target area and helps "reset" the control of movement.

Consideration of which brain structure is targeted for DBS is partially based on the following:

  • GPi - for treatment of bradykinesia, tremors and drug induced dyskinesia. Some patients can reduce the dosage of levodopa following this surgery. This surgery is also effective on patients suffering from dystonia.
  • Subthalamic nucleus - improves most motor features of Parkinson's disease, namely bradykinesia, tremor and rigidity. Some patients can reduce the dosage of levodopa. This is performed primarily on patient with advanced and disabling Parkinson's disease
  • Thalamus - reduces disabling tremor when it is stronger on one side of the body than the other. This procedure is reported to significantly reduce tremor in approximately 2/3 of the patients undergoing the surgery.

Stimulation of the GPi and the subthalamic nucleus are performed primarily for restoration of movement.

The FDA has approved bilateral DBS of the GPi and subthalamic nucleus. A patient who already has undergone pallidotomy or thalamotomy is still considered eligible for DBS.

Possible complications include an electrode or wire leading to the battery becoming infected, or excessive bleeding may occur if a blood vessel is penetrated. Stroke is also recognized as a risk factor of DBS. Hemorrhage or stroke occurs in approximately 1-3% of patients who undergo this surgical procedure.

The advantages of DBS over pallidotomy or thalamotomy include:

  • Brain tissue is not destroyed and can be continuously treated or the current can be turned off if necessary
  • Better control of symptoms because placement of the electrode is more accurate
  • Less risk of stroke or hemorrhage

Fetal Tissue Transplantation

Fetal tissue transplantation is an experimental procedure in which fetal brain cells that are rich in dopamine are implanted in the corpus striatum area of the brain. The corpus striatum is involved in motor control and is easier and safer to locate than the substantia nigra which is smaller and deeper in the brain. This procedure is performed to restore dopamine levels in the brain and thus restore the patient to a less advanced stage of Parkinson's disease.

Several hundred fetal cell transplants have been performed with variable outcomes, ranging from no response to significant improvement. The agreed upon aspects of limited improvement include better motor control during "on" and "off" periods, an increase of "on" time, as well as a reduction of rigidity and bradykinesia. Results have been tracked from 6 months to several years. A reduction in the dose of dopamine may follow the surgery.

Fetal tissue transplantation is usually performed bilaterally, either in stages or simultaneously. Since not all fetal cells take effect with the procedure, an oversupply of fetal cells must be transplanted in order to hopefully reach a critical mass of cells that will restore dopamine production. Benefits from the surgery are usually not seen for several months because the cells need time to propagate.

Trials show that the greatest benefit of fetal cell transplantation is in younger Parkinson's disease patients. Because of the risk of rejection of the foreign fetal cells, the patient may be given immunosuppressive drugs indefinitely. The surgery is still considered experimental and the source of fetal cells is controversial for many doctors and patients.

In some patients, fetal tissue transplantation resulted in disabling dyskinesia. The risk of stroke or hemorrhage is approximately 1-3%.