Surgical Treatment of Parkinson's Disease

Surgery can be very effective for Parkinson's disease. It is currently utilized in the later stages of disease. There is an active, state-of-the-art surgical program for Parkinson's disease at the Sacramento Kaiser Permanente facility

Appropriate patients for surgery include those with

• Severe motor fluctuations or dyskinesias despite optimal medical management
• Typical (as opposed to atypical) Parkinson's disease
• Good levodopa response
• No significant dementia
• No severe brain atrophy

There are several potential surgical targets including the globus pallidus interna (GPi), and the subthalamic nucleus (STN) and, for tremor only, the ventromedial thalamus.

Pallidotomy

Loss of dopamine leads to overactivity in the GPi part of the brain. Destroying part of the GPi may help to restore the balance that normal movement requires. Pallidotomy is most useful for the treatment of peak-dose dyskinesias and for dystonia that occurs at the end of a dose. It may also improve bradykinesia and tremor. By eliminating peak-dose dyskinesia, pallidotomy may allow an increase in levodopa dose, resulting in more effective symptom management. Results from bilateral pallidotomy have not been good. Risks include bleeding, visual filed loss, memory changes, infection, and stroke.

Deep Brain Stimulation (DBS)

Deep brain stimulation (DBS) uses an implanted electrode to deliver continuous high-frequency electrical stimulation to either the thalamus, globus pallidus (GPi), or the subthalamic nucleus (STN). High frequency stimulation of cells in these areas actually shuts them down, helping to rebalance control messages throughout the movement control centers in the brain.

DBS of the thalamus is primarily used to treat disabling tremor, especially tremor that affects one side of the body substantially more than the other. Studies have shown that DBS may significantly reduce tremor in about two thirds of patients with Parkinson's disease. Tremor may not be eliminated, and may continue to cause some impairment.

DBS of the globus pallidus is useful in treatment of dyskinesias as well as tremor, and may improve other symptoms, as well.

DBS of the subthalamic nucleus may have an effect on most of the main motor features of PD, including bradykinesia, tremor, and rigidity.

DBS of the STN may allow a reduction in levodopa dose, which may improve dyskinesias as well. Because it relies on continuous stimulation, DBS requires placement of an electrode in the brain, connected by a wire to a battery source. Electrode placement is performed under local anesthesia. The wire is implanted under the scalp and neck, and the battery is implanted in the chest wall just below the collar bone. A series of stimulation adjustments are required in the weeks following implantation. Battery replacement, required every 3-5 years, requires only an incision in the chest, and is performed as an outpatient procedure.

In the United States, the Food and Drug Administration has approved bilateral (both-sided) deep brain stimulation of the STN or GPi (using a system from Medtronic®) for treatment of Parkinson's disease. The side controlling the most severely affected limbs is usually the one chosen for a unilateral implant. Unilateral DBS may be performed on a person who has already had pallidotomy or thalamotomy on the opposite side.

Thalamotomy

Thalamotomy is effective for the treatment of tremor, but is generally not beneficial for rigidity, bradykinesia, or dyskinesias. Nonetheless, it can be an effective treatment, especially for tremor, in patients without pre-existing gait and speech problems. It may be used as an alternative to thalamic DBS in selected patients who refuse or are poor candidates for DBS.

What factors predict whether a patient will obtain benefit from surgery?

For both pallidotomy and deep brain stimulation, improvement after surgery correlates with preoperative levodopa responsiveness and younger age. Patients with dementia or atypical parkinsonism do not typically benefit from surgical treatments.

What are the risks of pallidotomy or DBS surgery?

The most serious potential risk of the surgical procedures is a cerebral hemorrhage (bleeding in the brain) , producing a stroke. This risk varies from patient to patient, depending on the amount of brain atrophy and the general medical condition, but the average risk is about 2%. If stroke occurs, it usually occurs during or within a few hours of, surgery. The effects of stroke can range from mild weakness that recovers in a few weeks or months to severe, permanent weakness, intellectual impairment, or death.

For DBS some additional risks apply. The second most serious risk is infection, which occurs in about 4% of patients. If an infection occurs, it is usually not life threatening, but it may require removal of the entire DBS system. In most cases, a new DBS system can be re-implanted when the infection is eradicated. Finally, in 10-20% of patients, hardware may break or erode through the skin with normal usage, requiring it to be replaced. In the first few days after surgery, it is normal to have some temporary swelling of the brain tissue around the electrode. This may produce no symptoms, but it can produce mild disorientation, sleepiness, or personality change that lasts for up to 1-2 weeks.