Surgery can be used to treat PD, but it is not suitable for everybody. Currently, no operations provide a cure for PD, although they can offer benefits for some people by improving certain symptoms and sometimes reducing the need for medications. However, even following successful surgery, a person with PD is still required to take continuous medication.
People with PD who are likely to benefit from surgery are those who respond well to their PD medication but in whom this response has become unpredictable and/or short lived, or who are troubled by dyskinesias. Surgery has not been shown to improve symptoms that do not respond to dopamine medication- apart from tremor which can be resistant to medication but generally responds well to surgery.
Surgery is advised by doctors only after due consideration and thorough and detailed assessments.
The three areas of the brain currently targeted during PD surgery are:
- Thalamus : can improve tremor
- Globus Pallidus : can improve levodopa-induced dyskinesia, rigidity and sometimes tremor.
- Subthalamic nucleus : can improve slowness and stiffness, and may allow PD medication to be reduced.
New targets that may be helpful for treating people with PD are also being researched.
Types of Surgery :
There are two main forms of surgery used currently in PD;
Deep Brain Stimulation (DBS)
Deep brain stimulation (DBS) is a treatment option for people with advanced Parkinson's disease. It uses one or two surgically implanted medical devices called neurostimulators, similar to cardiac pacemakers, to deliver electrical stimulation to precisely targeted areas on each side of the brain. Stimulation of these areas appears to block the signals that cause the disabling motor symptoms of Parkinson's disease. As a result, many patients achieve greater control over their body movements.
A DBS system includes three components, which are implanted completely inside the body.
Neurostimulator – A pacemaker-like device that is the power source for the system. It contains a small battery and computer chip programmed to send electrical pulses to control Parkinson's disease symptoms.
Lead – An insulated wire with four electrodes. This is implanted in the brain, with its tip positioned within the targeted brain area.
Extension – An insulated wire placed under the scalp that connects to the lead and runs behind the ear, down the neck, and into the chest below the collar-bone where it connects to the neurostimulator.
Once the system is in place, electrical impulses are sent from the neurostimulator up along the extension wire and the lead and into the targeted brain area. These impulses interfere with and block the electrical signals that cause PD symptoms. Stimulation from the neurostimulator is adjustable—without further surgery—if the patient’s condition changes. Such stimulator adjustments are called as "programming."
With the DBS one of two areas may be stimulated: either the subthalamic nucleus (STN) or the internal globus pallidus (GPi). These structures are deep within the brain and involved in motor control. These structures control movement and muscle function. A neurosurgeon determines which structure will be stimulated.
DBS is used for Parkinson's patients who are "levodopa responsive." This means the primary symptoms respond to the drug levodopa. A person's age or pre-existing medical condition does not necessarily exclude him or her from becoming a candidate for DBS. A doctor considers all factors before determining if a patient is a good candidate, and recommends the surgery accordingly.
While DBS can relieve some of the patient’s symptoms considerably it should be noted that it can target only some specific symptoms. It does not eliminate the use of drugs/medication nor does it result in the reversal of the PD symptoms.
Lesioning
This involves destroying/eliminating the specific part of the brain that is causing PD symptoms. The operation is named after the part of the brain that is destroyed i.e., thalamotomy, pallidotomy or subthalamotomy. However this surgery is rarely performed nowadays.