Subtle Alterations in Postural Behavior May Help Diagnose Parkinson’s Earlier
People with Parkinson’s have postural adjustments even at early stages of the disease when clinical symptoms of postural instability are not evident and despite the use of antiparkinsonian medications, a recent study shows.
Researchers believe these findings suggest that postural behavior may be used as an early indicator to diagnose the disease.
Parkinson’s disease usually is diagnosed based on the presence of classic motor symptoms. But other signs of the disease are present sometimes years before motor symptoms are evident, though still insufficient to make a definite diagnosis.
Identifying patients in this earlier phase would ensure they receive treatment early, before their disease progresses to more advanced stages and significantly affects daily activities.
Generally, Parkinson’s patients with early disease are classified as not having postural instability. But modern technologies are more sensitive to subtle impairments in balance, and potentially may identify changes in postural behavior that take place even in earlier stages of disease.
To clarify the presence of postural changes in early Parkinson’s disease, and whether these changes can be used to diagnose the disease before motor symptoms are evident, researchers at the Western Michigan University and collaborators at the Federal University of Piauí, Brazil, investigated two groups of Parkinson’s patients, and compared them to a group of healthy controls.
Participants included nine patients with early disease — defined as a Hoehn and Yahr Stage rating scale up to 2, which means their balance was not yet affected — and nine patients with mid- to advanced disease (a Hoehn and Yahr Stage of 2.5 or higher, whose balance was already compromised).
These patients were all taking antiparkisonian medication, allowing researchers to account for the effects of medication on balance, which the team believes is a clear limitation of prior studies that lacked a standardization on this parameter. Controls included nine healthy subjects matched by age, who had no history of sensory, muscular, or neurological disorder.
Participants were asked to perform two simple postural tasks: stand quietly on a force platform with arms crossed, with eyes open or closed. Each task took 120 seconds. During that time, the platform collected information regarding participants’ center of pressure, including body sway trajectory (how the center of pressure moved), sway amplitude (how far in each direction it went), sway velocity (how fast it moved), and sway jerkiness (how shakier body sway was).
The team found that most measures were similar across patients and controls when they did the test with their eyes open. But Parkinson’s patients already showed greater sway velocity and jerkiness compared to controls in this task. Late-stage patients also had more overall sway movement and greater sway amplitude.
When the task was done with eyes closed, patients also had higher sway jerkiness — though sway was only laterally shakier — compared to controls, but not higher sway velocity. Those with advanced disease also had greater sway amplitude.
No significant differences were seen between groups of Parkinson’s patients in either task. Also, while controls and early-stage patients swayed more, faster, and shakier when they stood still with their eyes closed, no differences were seen in advanced patients with eyes open and closed.
The findings show that Parkinson’s patients have alterations in postural behavior starting in early stages of disease, and despite the use of dopaminergic medication. “This finding indicates that balance control is affected even before clinical signs surface,” the researchers wrote.
“Therefore, postural markers used in this study are [of] great importance to improve early diagnosis of postural instability in PD [Parkinson’s disease], record progress of balance control, and assess fall risk. They should also be implemented in clinical trials of pharmacotherapy and balance training protocols specific to populations diagnosed with PD,” they concluded.