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Brain Scan May Predict Course of Parkinsonís Disease
- Oct 03 2012
A special type of brain scan could allow doctors to predict the course of Parkinson’s disease (PD) in people newly diagnosed, according to a study published in the September 15 issue of the journal Movement Disorders. Identifying people at risk for severe disease might enable better management and treatment of their symptoms.
Some doctors already use a similar type of brain scan, called dopamine transporter imaging or DaTscan, to help confirm a diagnosis of PD first made by physical examination. DaTscan cannot diagnose Parkinson’s disease exactly. It can be used to diagnose Parkinsonism, but cannot distinguish between several similar disorders, including classic Parkinson’s disease. To use it, doctors inject people with a small amount of a radioactive contrast agent that binds to dopamine transporters in the brain. Then, doctors use a scanner to measure the amount and location of the contrast agent in the brain. Because people with PD have fewer neurons with dopamine transporters, their brains typically show lower amounts of the agent than do the brains of people without PD.
Researchers led by Bernard Ravina, M.D., formerly of the University of Rochester and now of Biogen Idec, a biotechnology company in Cambridge, MA, wondered if DaTscan could be used for a different purpose: to predict long-term progression of Parkinson’s disease. Dr. Ravina and his colleagues examined the DaTscan images of 491 people who were newly diagnosed with PD and had not yet begun standard PD medications. These people were volunteers in the Longitudinal and Biomarker Study in PD (LABS-PD), a clinical trial funded in part by the Parkinson’s Disease Foundation.
Because the LABS-PD study has been going on for several years, Dr. Ravina could compare volunteers’ DaTscan results (performed shortly after diagnosis and 22 months later) with data from their annual health assessments. He and his coworkers examined correlations between people’s initial DaTscan results and the severity of their motor and non-motor symptoms five and a half years later.
- People with newly diagnosed Parkinson’s disease who had lower dopamine transporter levels by brain scan had more severe Parkinson’s disease five and a half years later, including greater motor-related disability, falling and postural instability, cognitive impairment, symptoms of psychosis (such as hallucinations) and depression.
- People with the lowest levels of dopamine transporters in their brains were three times more likely to experience cognitive impairment and 12.9 times more likely to develop psychosis than those with the highest levels of dopamine transporters.
- People with large decreases in dopamine transporter levels between their initial and 22-month DaTscans had worse motor, cognitive, and behavioral outcomes at five and a half years than those with small decreases. However, the follow-up scan at 22 months was not as strong in predicting PD severity as the initial scan.
What Does It Mean?
Some people with PD develop more debilitating symptoms than others, but doctors can’t currently predict the clinical course, or prognosis, of a person’s disease at the time of diagnosis. Being able to do so may help doctors better anticipate and treat severe symptoms such as falling, cognitive impairment and psychosis. In addition, such knowledge could help doctors design more informative clinical trials. For example, in some clinical trials, it might be useful to assign study volunteers into groups of people with similar predicted disease progression.
Although previous studies have investigated DaTscan for PD diagnosis, this study provides the best evidence to date that DaTscan could be used to predict long-term motor and non-motor progression of PD. People with lower levels of dopamine transporters in the brain shortly after PD diagnosis, as determined by DaTscan, had a higher risk of a more rapid progression five years later.
Before doctors can begin using DaTscan to establish prognosis, however, these findings must be confirmed in additional studies. Confirmation is required because the DaTscan does not always predict the PD accurately and should be interpreted with correlation to the neurological examination. Even if these results hold true, it’s important to remember that predictions are only predictions, and not facts. Although DaTscan results may indicate that a person has an increased risk for severe PD, the person may never experience these adverse outcomes.
Reference: Ravina, B., Marek, K., Eberly, S., et al. (2012). Dopamine transporter imaging is associated with long-term outcomes in Parkinson’s disease. Movement Disorders, 27(11), 1392–1397. doi:10.1002/mds.25157
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Source Date: Oct 11 2012