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Subtle Alterations in Postural Behavior May Help Diagnose Parkinson’s Earlier

Postural behavior

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.

The study, “Postural Behavior in Medicated Parkinson Disease Patients: A Preliminary Study Searching for Indicators to Track Progress,” was published in the Journal of Central Nervous System 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.

The post Subtle Alterations in Postural Behavior May Help Diagnose Parkinson’s Earlier appeared first on Parkinson’s News Today.

Freedom of Movement May Be Misinterpreted as Balance Instability, Parkinson’s Study Suggests

balance instability

Antiparkinsonian medicines may allow patients with mild to moderate Parkinson’s disease to experience freedom of movement, which could be confused with balance issues if measured by traditional postural stability testing, researchers suggest.

Their findings were published in the study, “The influence of dopaminergic medication on balance automaticity in Parkinson’s disease,” in the journal Gait & Posture.

Dopaminergic medications can help control Parkinson’s motor symptoms, but as the disease progresses, patients typically need to gradually increase the treatment dose for maximum benefit. Even after increasing the dose, they might sometimes experience a reappearance or worsening of symptoms (off periods) due to the diminishing effects of the therapy.

It is known that Parkinson’s patients have difficulty performing learned motor skills automatically, a phenomenon referred to as decreased motor automaticity. Automaticity is the ability to perform movements without having to pay attention to the details of the movement, particularly for actions that require low levels of precision or for movements that are frequently made.

Studies also report that the ability to perform two or more tasks at the same time, called dual-tasking, is impaired in Parkinson’s disease.

“Dual-tasking involves performing a primary motor task (e.g., standing) and a secondary task (e.g., conversing) simultaneously and is the primary means of assessing the automaticity of a given motor task,” the researchers wrote.

In theory, if a primary task is automatic, performing another task simultaneously should not interfere with the first one.

Although dopaminergic medication seems to improve dynamic balance (the ability to maintain postural stability while in motion), there is still little evidence on how it influences standing balance (the ability to maintain the body in a fixed posture).

University of Houston researchers set out to evaluate how dopaminergic medication influenced long-duration standing balance with the eyes open or closed while dual-tasking in Parkinson’s disease.

They recruited 16 Parkinson’s patients with mild to moderate disease (four women and 12 men, with a mean age of 67.1 years) for the study.

Before dual-task testing, the participants underwent a minimum 12-hour overnight medication withdrawal, so that researchers could assess patients’ status in an off state.

Single- and dual-task tests were conducted. For dual-task testing, patients had to stand in silence (primary task), both with their eyes open and then with them closed, while listening on headphones to a pre-recorded unfamiliar speech and mentally counting the number of times a specific word occurred (secondary task). This is known as phoneme monitoring. They also had to listen to the details of the story so that they could answer a few questions about it at the end of the testing session.

Under the protocol, participants were asked to perform the following tasks in random order: 1) phoneme monitoring while seated comfortably in a quiet room, 2) single-task standing eyes open, 3) single-task standing eyes closed, 4) dual-task standing eyes open, and 5) dual-task standing eyes closed.

“After the [off] trials were completed, the subjects took their dopaminergic medication as prescribed for their first/morning dose and waited until they achieved a stable ‘on’ feeling (minimum of 45 [minutes]) before commencing the on-medication testing,” the researchers said.

Every trial session was performed once for three minutes, and participants were given at least a minute between sessions to sit down and rest.

Data on motor variables of interest were obtained by the NeuroCom Balance Master, a system that uses a fixed force plate to measure the vertical forces exerted through the patient’s feet to measure the center of gravity position and postural control.

Results revealed that antiparkinsonian medicines significantly increased center of pressure movement. The center of pressure is a point, inside or outside the body, where the resulting vector of all forces (including gravity) acting on the body is considered to act.

Patients’ performance in the secondary task was reduced after they took the medications.

Additionally, having the eyes closed or open significantly increased the patients’ back and forth plus lateral sway velocities and the integrated time to boundary.

In biomechanics, time to boundary estimates the time required for the center of pressure to reach the boundary of the base of support if it were to continue its instantaneous trajectory and velocity. Higher integrated time indicates poorer balance.

Postural sway was also increased during the on state. Scientists often interpret increases in sway velocity and integrated time to boundary as indications of impaired balance; however, the researchers suggest that their findings could indicate an increase in freedom of movement rather than compromised stability.

Importantly, medication did not improve balance automaticity.

“The data did not support a medication-induced improvement in automaticity, as measured by significant medication by task interactions. An alternate interpretation for medication-induced balance changes in PD [Parkinson’s disease] includes an increase in maneuverability without sacrificing stability after taking dopaminergic medication,” the researchers concluded.

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