Parkinson's disease destroys neurons in the brain that are essential for controlling movement. As a result, people may have shaking, stiffness, and difficulty with walking, balance, and coordination. Symptoms usually begin gradually and get worse over time.
Other disorders can cause symptoms similar to those of Parkinson's disease. When people don't show all of the classic symptoms of Parkinson's disease, or have additional symptoms, they're said to have "parkinsonism." Multiple system atrophy (MSA) is a slowly progressive disorder that affects the nerves in the brain and spinal cord (central nervous system) as well as those that extend from the spinal cord out to the body's organs (autonomic nervous system). Progressive supranuclear palsy (PSP) is a rare, progressive brain disorder that causes problems with control of walking and balance.
A research team led by Dr. David Vaillancourt at the University of Florida examined how these 3 diseases affect brain regions that are critical for movement and balance. The research was funded by NIH's National Institute of Neurological Disorders and Stroke (NINDS). Results were published in Neurology.
The team enrolled 46 patients with Parkinson's disease, 13 with MSA, 19 with PSP, and 34 healthy controls. The participants underwent 2 functional magnetic resonance imaging (fMRI) brain scans spaced a year apart. During the scans, they performed a grip strength exercise that allowed researchers to measure changes in muscle control-related areas of the brain.
The healthy controls showed no changes in brain activity after a year. Participants with Parkinson's showed reduced responses in 2 brain regions called the putamen and the primary motor cortex. Previous research has found reduced activity in the primary motor cortex of Parkinson's patients, but this study demonstrates that this deficit continues to worsen over time. For patients with MSA, activity decreased in the primary motor cortex as well as the supplementary motor area and the superior cerebellum. Individuals with PSP showed a decline in the responses of all 4 regions.
Clinical trials for Parkinson's disease have long relied on observing whether a therapy improves patients' symptoms, but such studies reveal little about how the treatment affects the underlying progressive neurodegeneration. This study suggests measurable targets, called biomarkers, which could be useful for assessing whether a drug slows or even stops the progression of the disease in the brain.
"For decades, the field has been searching for an effective biomarker for Parkinson's disease," says Dr. Debra Babcock, a neuroscientist and neurologist at NINDS. "This study is an example of how brain imaging biomarkers can be used to monitor the progression of Parkinson's disease and other neurological disorders."
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