The authors explained that this brain scan can identify which Parkinson's patients are at risk of severe disease, thus enabling doctors to better manage and treat their symptoms.
Some specialists already use the DaTscan when confirming a Parkinson's diagnosis after a physical examination.
However, the DaTscan can only help in the diagnosis to a certain extent. It can point towards Parkinsonism, but cannot help the doctor distinguish between many similar disorders, of which classic Parkinson's disease is one.
GE Healthcare announced the availability of DaTscan™ (Ioflupane I 123 Injection) in June 2011.
When using the DaTscan, the patient is injected with a small quantity of a radioactive contrast agent which binds to dopamine transporters in the brain. Then, a scanner is used to measure how much of the contrast agent there is in the brain, and where exactly it is. People with Parkinson's have fewer neurons with dopamine transporters, thus, lower amounts of the radioactive agent appear in their brain scans, compared to "healthy" individuals.
Bernard Ravina, M.D., M.S.C.E., and team set out to determine whether the DaTscan might be used to predict the long-term progression of Parkinson's disease. They looked at the DaTscan images of 491 individuals who had just been diagnosed with Parkinson's - none of them had yet started on standard medications for the disease. All the patients were participants in the Longitudinal and Biomarker Study in PD (LABS-PD), a clinical trial funded in part by the Parkinson's Disease Foundation.
The LABS-PD study had been a long-term one, thus the team were able to compare participants' DaTscan results, which were taken just after diagnosis and then again 22 months later, with information from their yearly health assessments.
The scientists looked out for correlations between patients' initial brain scan results and the severity of their motor and non-motor symptoms five-and-a-half years later.
Below are some of the highlights of their findings:
- Brain scans that showed lower dopamine transporter levels in newly diagnosed Parkinson's disease patients had more severe symptoms at the end of the 5.5 year period. They had more severe symptoms in the following areas:
- motor-related disability
- falling and postural instability
- cognitive impairment
- psychosis (e.g. hallucinations)
- Those with the lowest dopamine transporter levels had a three times greater probability of becoming cognitively impaired. Their risk of developing psychosis was 12.9 times greater than those with the highest dopamine levels.
- Patients with the steepest drops in dopamine levels between their first and second scans had worse motor, behavioral and cognitive outcomes five-and-a-half years later compared with the patients with the smallest reductions. The researchers stressed that the second scan was not as accurate at predicting symptom severity as the first.
How does predicting Parkinson's disease severity help doctors and patients?Parkinson's is a progressive disease; patients' symptoms gradually get worse over time. However, some develop more debilitating symptoms more rapidly than others. At the moment, doctors are unable to predict an individual patient's clinical course, or make a prognosis of a person's disease when they are newly diagnosed.
Being able to make predictions by looking at the data on the initial scan allows the doctor to anticipate, and therefore treat severe symptoms early on. Especially such symptoms as cognitive impairment, psychosis and falling.
If doctors can predict the likely course of a disease, they can design more informative clinical trials, the authors added. Volunteers could be placed into groups according to their predicted disease progression.
Prior studies had tried to see whether the DaTscan might be used for Parkinson's disease diagnosis. This study provides the most compelling evidence yet that this type of brain scan could be used to predict the progression of Parkinson's, both its long-term motor and non-motor progressions.
Dr. Ravina said that these findings need to be confirmed in further studies, because the DaTscan is not always an accurate predictor of Parkinson's, and should be interpreted with correlation to the neurological examination. He added that "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."