Definition and Overview
A pallidotomy, also called globus pallidus lesion surgery, is a neurosurgical procedure used in the treatment and management of Parkinson’s disease. It works by destroying a part of the globus pallidus, a part of the brain’s basal nuclei that becomes overactive in patients with Parkinson’s, to permanently control its activity level.
While surgery is not considered the primary treatment option for Parkinson’s, it becomes necessary when medication alone can no longer control the symptoms of the disease.
Who Should Undergo and Expected Results
Pallidotomy is one of the two surgical procedures that can be used in the treatment and management of Parkinson’s disease and its many symptoms. The other procedure is called a thalamotomy, which destroys a part of the thalamus to control muscle tremors. However, a pallidotomy is considered more effective as it can control not just tremors but also several other symptoms related to the disease.
Parkinson’s disease causes symptoms that affect body movements due to the degeneration of the substantia nigra. The substantia nigra is responsible for producing dopamine, which is necessary for the proper functioning of the globus pallidus internus. When the substantia nigra deteriorates, the body does not get enough dopamine. This then causes the globus pallidus to become overactive, and the following symptoms occur:
- Balance problems
- Speech problems
Despite its benefits, a pallidotomy is not a cure for Parkinson’s disease and does not eliminate the need for medications. In fact, there is evidence that shows a pallidotomy can make medications more effective, even among patients suffering from advanced stages of Parkinson’s.
Although there is no guarantee of a major turnaround in the patient’s condition, some improvements may be expected.
Since pallidotomy is not a primary treatment procedure for the disease, it only becomes necessary when:
- The above symptoms become more severe and cause major disability in the patient
- If the patient’s condition no longer respond to medications
- If long-term use of medication is causing some side effects, such as dyskinesias and on-off responses
The benefits of a pallidotomy are expected to last for a long time but may still fade gradually.
How Does The Procedure Work?
Prior to undergoing a pallidotomy, a person suffering from Parkinson’s first undergoes an MRI scan. This helps identify the exact location of the globus pallidus and the area in which a lesion can be made. The surgeon incorporates this into the treatment plan prior to starting the procedure.
On the day of the surgery, the patient is kept awake but is given a local anesthetic to numb the scalp area where the surgery will be performed. Since the brain has no pain receptors, general anaesthesia is unnecessary. Patients are also kept awake on purpose so that the surgeon can watch out for any sensory changes that may occur during the surgery.
The surgery begins by drilling a burr hole into the top of the skull from where the globus pallidus can be accessed. The surgeon then inserts a hollow microelectrode probe into the hole. The probe helps to precisely locate the globus pallidus and target the right tissues to be destroyed. If necessary, the surgeon may inject some contrast dye through the probe to make it easier for him to detect the correct part of the brain the surgery has to be performed on.
When the correct tissues have been targeted, the tip of the microelectrode probe is heated to around 80 degrees Celsius (or 176 degrees Fahrenheit) for a period of just 60 seconds. This brief process can already adequately destroy a small section of the brain cells in the globus pallidus. Once the targeted tissue is destroyed, the probe is removed and the scalp wound is closed with stitches.
A pallidotomy is also called a globus pallidus lesion surgery specifically because a lesion is created on the globus pallidus.
After the surgery, the patient is required to stay in the hospital for at least two more days while the entire recovery period may take up to 6 weeks.
Possible Risks and Complications
Although a globus pallidus lesion surgery used to be associated with several major risks, it is now significantly safer due to advances in precision technology that allow surgeons to accurately target the correct tissues in the globus pallidus. This helps reduce the risk of complications, which may include:
- Intracranial bleeding, which may lead to a stroke
- Cognitive impairment, or negative effects on the person’s thought and memory functions
- Impaired language learning
- Impaired visuospatial constructional ability
These risks may cause more severe symptoms, such as:
- Slurred speech
Due to the complexity of these potential risks, most Parkinson’s patients are instead given deep brain stimulation surgery as an alternative. This procedure is safer and has a lower risk of complications. However, it is not always appropriate in some cases of Parkinson’s.
Baron MS, Vitek JL, Bakay RAE, et al. (1996) Treatment of advanced Parkinson's disease by internal globus pallidotomy
Lang A, Lozano A, Montgomery E, et al. (1995) Effect of GPi pallidotomy on motor function in Parkinson's disease. Lancet 346:1383–1387.