Swinging One Arm Less Than Other is Early Sign of Parkinson’s Disease
Early detection can allow treatments to slow the disease progression, maybe save lives
13, 2011 - People with Parkinson's disease swing their arms asymmetrically - one arm swings less than the other - when walking. This
unusual movement is easily detected early when drugs and other interventions may help slow the disease, according to Penn State researchers.
"Scientists have known for some time that people with Parkinson's disease exhibit reduced arm swing during the later
stages of the disease, but no one had come up with an easy way to measure this," said Stephen Piazza, associate professor of kinesiology.
"We found that not only do people with the disease exhibit reduced arm swing, but they also exhibit asymmetric arm swing,
and this asymmetric arm swing can easily be detected early in the disease's progression."
No cure for Parkinson's disease exists, but according to Piazza, if taken early, certain drugs can improve some of the
disease's symptoms and even reduce the likelihood of death, making early diagnosis important. Some people also believe that changes in
nutrition and other lifestyle factors can modify the progression of the disease.
This study used inexpensive accelerometers on the arms of Parkinson's disease patients to measure arm swing. The
researchers attached them to the arms of eight Parkinson's disease patients who were in the early stages of the disease - within three years
of clinical diagnosis.
They also attached the accelerometers to the arms of eight age- and sex-matched people who did not have the disease. The
team asked the subjects to walk continuously for about eight minutes at a comfortable pace. The researchers downloaded the acceleration data
and used software they developed - that will be available free to interested doctors - to analyze it. They published their results in the
current issue of Gait & Posture.
The scientists found significantly higher acceleration asymmetry, lower cross-correlation between the arms and reduced
synchronization of the arms in the early Parkinson's disease patients. According to Joseph Cusumano, professor of engineering science and
mechanics, the lower cross-correlation and reduced synchronization suggest that the arm movements are poorly coordinated.
"In other words, if I measure the location of your right arm, it is difficult to use that measurement to predict the
location of your left arm," he said. "It is well known that Parkinson's disease has an impact on how people move -- neurologists have been
using this fact as the basis for clinical examinations for a very, very long time -- but here we are for the first time precisely quantifying
how the disease not only affects the relative amount of limb movements, but also how well coordinated in time these movements are."
To diagnose patients with Parkinson's disease early, some doctors and scientists have proposed the use of a smell test,
because people with the disease lose their ability to distinguish odors, according to Xuemei Huang, movement disorders physician, Penn State
Milton S. Hershey Medical Center. "But conditions other than Parkinson's disease also can affect a person's ability to smell," she said.
The Penn State team's method of evaluating arm swing can be applied quickly and inexpensively by primary care physicians
in their own offices when the smell test is inconclusive and before the application of an expensive brain scan.
"Measuring arm swing asymmetry and coordination with our method may be the cheapest and most effective way to detect
Parkinson's disease early in patients' lives when it still is possible to treat the symptoms of the disease and to improve longevity," said
The scientists plan to further investigate whether the arm swing evaluation in combination with a smell test can enhance
early diagnosis even more. They also plan to further develop their technique so that the accelerometers give immediate readings, which, they
said, would save the extra step of downloading the data to a computer and analyzing it, thereby making the arm swing assessments of
Parkinson's disease even easier.
Penn State graduate students Joseph Mahoney, Mechelle Lewis and Guangwei Du also worked on this project.
About Parkinson’s Disease
Parkinson's disease is a disorder
that affects nerve cells, or neurons, in a part of the brain that controls muscle movement. In Parkinson's, neurons that make a
chemical called dopamine die or do not work properly. Dopamine normally sends signals that help coordinate your movements. No one
knows what damages these cells. Symptoms of Parkinson's disease may include
● Trembling of hands, arms,
legs, jaw and face
● Stiffness of the arms, legs
● Slowness of movement
● Poor balance and
As symptoms get worse, people
with the disease may have trouble walking, talking or doing simple tasks. They may also have problems such as depression, sleep
problems or trouble chewing, swallowing or speaking.
Parkinson's usually begins around
age 60, but it can start earlier.
It is more common in men than in
women. There is no cure for Parkinson's disease. A variety of medicines sometimes help symptoms dramatically.