Drilling for Answers

In this interactive decision, we’re going to ask you about some experimental treatments for Parkinson’s Disease.

What is Parkinson’s Disease?

Up to 1 million Americans are currently diagnosed with Parkinson’s Disease, a brain disease that gradually worsens over many years and causes tremors, stiffness, slowness of movement, and balance problems. Some people with Parkinson’s Disease also experience changes in memory, concentration, and mood.

The average age at onset of symptoms is 65, but 5% to 10% have onset before the age of 45. The symptoms are caused by the death of cells in the brain that make a chemical called dopamine. Medications that are available to treat Parkinson’s Disease provide more dopamine to the brain or mimic the action of dopamine in the brain. In early stages of Parkinson’s Disease, symptoms generally respond well to medications. Over time, the medications become less effective and may cause more side effects.

What treatments are researchers developing?

One experimental procedure to treat moderate to advanced Parkinson’s Disease is gene transfer, which involves neurosurgery to insert a gene into the brain, to lower the side effects of medications and to increase the effectiveness of medications. Note that no stem cells or fetal cells are used. The patient is sedated but remains awake. The scalp is numbed by injections of local anesthetics (like Novocaine), so the patient should not feel discomfort. The surgeon drills two small holes into the skull and injects a liquid containing the gene on each side of the brain into areas known to be affected in Parkinson’s Disease.

How would gene transfer surgery be tested?

To see if the gene transfer surgery is truly effective, investigators need to compare a group that receives the gene transfer surgery with a group that does not. People would be randomly assigned (e.g., by flipping a coin) to one of the two groups. This kind of study could be done in two ways.

  • An open study could be done, where everyone knows who has and who has not received the gene transfer. One half of the patients would receive their usual medications only. The other half would receive their usual medications plus the gene transfer surgery.

  • A blinded study could be done, where neither the patient nor the evaluating researcher knows who has and who has not received the gene transfer. One half of the patients would receive their usual medications plus gene transfer surgery. The other half of the patients would receive their usual medications plus “sham surgery.” Patients receiving sham surgery have the two small holes drilled into the skull. But the protective coverings in the brain are not disturbed, and there is no insertion of any material into the brain.

    In a blinded study, only the surgeon would know who has received the gene transfer surgery and who has received sham surgery. If the gene transfer surgery is found to be both safe and effective, those in the sham surgery group would have the option of receiving the gene transfer at a later date without cost, using the holes drilled during the sham surgery.

What are the risks of these studies?

For surgery patients in both an open study and a blinded study, the surgery poses potential risks. There is a 1% to 4% risk of bleeding into the brain (usually minor, but there is a less than 1% chance that it could result in death or substantial disability). There is also a 1% to 5% risk of infection developing in the skin or brain, which would be treated with antibiotics. Overall, the risk of bleeding and infection is smaller for sham surgery than for actual gene transfer surgery.

Those subjects receiving the gene transfer surgery would face additional risks, including the possibility of brain tumors, inflammation of the brain, and a worsening of the Parkinson’s Disease. Patients in pilot studies have been followed for only one year, so longer-term effects are not known.

What are the pros and cons of the two kinds of studies?

When deciding whether or not to adopt a new procedure, it’s important to get accurate, unbiased evidence. If we adopt a new procedure that is unsafe or ineffective, people will end up receiving unnecessary surgeries. If we fail to adopt an effective procedure, we miss the opportunity to offer people a treatment that could benefit them.

Most, but not all, researchers in the field believe that the blinded study, using sham surgery, would provide better quality data than the open study. These researchers worry that if people know which procedure they receive, the results of the study may be difficult to interpret because expectations of both the patient and the evaluating researcher can unintentionally bias the results.

However, some people, including some researchers, worry that a study using sham surgery may not be worth the risks and burdens. The patients with Parkinson’s Disease who get the sham surgery undergo a neurosurgical procedure that provides no benefit to them, while being exposed to the risks and burdens of the procedure. There is also the worry that people with moderate to advanced Parkinson’s Disease are vulnerable to exploitation because having a serious, incurable illness may put them in a desperate situation.

Now, you decide!

Go to the next page for a decision scenario.