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Deep Brain Stimulation for Parkinsonís: Which Site Is Best?

A new study has shown that deep brain stimulation surgery (DBS) for Parkinson’s disease (PD) of the STN target of the brain may be superior to DBS at the GPi site. This research, published in the January 2013 issue of The Lancet Neurology, helps resolve years of uncertainty about which site in the brain is best. These results will guide doctors in their decisions about surgery for people living with PD.

Deep brain stimulation is a surgical treatment for advanced PD that provides tiny electric currents to structures of the brain in order to block motor symptoms of the disease. It involves the surgical insertion of tiny electrodes to tissues deep in the brain.  The electrodes are connected to an impulse generator (similar to a pacemaker) under a person’s collarbone. 

Since the widespread use of DBS for the treatment of PD, investigators have known that there are two targets within the brain: the subthalamic nucleus (STN) and the globus pallidus interna (GPi). Clinical trials have shown that both targets offer equal reduction in PD symptoms. Individuals who undergo STN stimulation are often able to reduce their medications, an advantage which has resulted in a preference for the STN target at most medical centers. 

A team of researchers led by Rob M.A. de Bie, M.D., at the Academic Medical Center in Amsterdam, Netherlands, conducted a randomized controlled trial of 128 people with advanced PD. The researchers randomly assigned 65 of the people to receive GPi DBS and 63 to receive STN DBS. After 12 months, the researcher made careful measurements of the individuals’ quality of life, cognitive ability and motor function, using a variety of measures. They made a close record of any side effects resulting from the surgery and stimulation.

Results:

  • People in the two surgery groups, STN versus GPi, showed identical quality of life. 
  • There were no significant differences in negative effects on thinking, mood, or behavior (cognitive, mood and behavioral) between the two surgery groups.
  • However, when the ability to perform independent daily tasks was analyzed when people were at the worst point of the day – when their medications were not working – subjects in the STN group did better than those in the GPi group. 
  • People in the STN group were able to reduce their levodopa medication to a greater extent than those in the GPi group.

What Does It Mean?

Since DBS was first shown to effectively treat PD motor symptoms in the 1990s, the medical community has questioned which part of the brain is the best one to perform the task of controlling motor symptoms of PD with the fewest side effects. This new study confirms that DBS at either brain site – the STN or the GPi – will result in nearly equal benefit. 

However, for individuals who experience wearing off spells after undergoing DBS, the STN target seems to be better, because their PD symptoms will be milder, even when they experience their worst times of the day. Their “off” spells will be less severe, and their ability to perform tasks of daily living will be better. In concrete terms, a person with PD unable to shower independently before surgery would be able to walk down a flight of stairs, even at his or her worst, after surgery at the GPi site; but a person who undergoes surgery at the STN would be able to walk down a flight of stairs and go to a movie. 

In addition, the study confirmed the long-standing observation that people who received STN DBS could reduce their daily dose of levodopa medication to a greater extent than those in the GPi group, which may result in a decrease of dyskinesias, drug-induced twisting movements. 

Taken together, the data from this study suggest that the STN should continue to be the preferred target for DBS. It must be emphasized that this study compared populations of people with Parkinson’s disease, and not individuals: results of any procedure vary from person to person.  Medical practice and surgical techniques vary between countries. The findings of this study, particularly the self-reported quality of life scales, will require confirmation in additional studies at different medical centers  before a scientific consensus is reached. This study was conducted over a relatively short period of time (12 months after surgery), so long-term results may vary. Finally, despite the overall advantages of STN detected by this study, there may be selected individuals with PD who might benefit more from surgery at the GPi target. Further research into individual responses to DBS is needed.

Reference: Odekerken VJJ, van Laar T, Staal MJ, Mosch A, Hoffmann CFE, Nijssen PCG, Beute GN, van Vugt JPP, Lenders MWPM, Contarino MF, Mink MSJ, Bour LJ, van den Munckhof P, Schmand BA, de Haan RJ, Schuurman PR, de Bie RMA (2013) Subthalamic nucleus versus globus pallidus bilateral deep brain stimulation for advanced Parkinson's disease (NSTAPS study): a randomised controlled trial. Lancet Neurol 12:37–44. http://dx.doi.org/10.1016/S1474-4422(12)70264-8

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Source Date: Feb 18 2013