Virtual Reality Test Can Detect Subtle Balance Issues in MS Patients

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by David Melamed, PhD |

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A new test involving a virtual reality simulation was able to detect balance issues in patients with multiple sclerosis (MS), potentially allowing doctors to identify whether a patient is at risk of falling despite having no apparent problems with walking, according to new research.

The results of the study, “Can optical flow perturbations detect walking balance impairment in people with multiple sclerosis?,” was published in the journal PLOS One.

One of the known symptoms of MS is problems with balance and walking. However, these issues can be subtle, and are often hard to detect in patients.

According to research studies, MS patients with minimal to no disability are still twice as likely to fall, on average, compared to people without MS, and many of these falls occur during walking. A study estimated that 56% of MS patients fall (defined as falling at least once over a three-month period), and about 37% are frequent fallers (falling at least twice over three months).

The difficulty in predicting a potential fall arises, in part, because some patients do not feel that they are impaired in their ability to walk.

Thus, a team led by researchers at University of North Carolina at Chapel Hill and North Carolina State University, designed a test that could identify the risk of falling in MS patients, even if those patients may not be aware of any walking deficiencies.

The team recruited 14 patients with relapsing-remitting MS (RRMS), under the age of 55 (average of 38.9 years), and who had not experienced an MS relapse within 30 days prior to the test. The patients also had to pass a walking test (they were excluded if they required more than six seconds to complete a 25-foot or 7.62-meter walk test), and had to have symptoms of spasticity under control through medication.

An age-matched cohort of 14 healthy volunteers (control group) was also analyzed for comparison.

To gauge the risk of falling, the researchers utilized a virtual reality (VR) device that simulated the act of walking down a hallway while participants walked on a treadmill. The researchers would then introduce the illusion of side-to-side “wobbles” in the simulation to make participants feel that they were falling, and measured how they responded to the illusion.

The theory behind the use of VR is that MS patients may be compensating for walking deficiencies by relying on their visual abilities. They may have the impression that their walking is normal, but these patients are still at risk for falls.

“When we walk around, our brains use a variety of sensory feedback channels, including force sensors in our feet, to guide our movements and make corrections from one step to the next,” Jason Franz, PhD, the study’s senior investigator, said in a press release.

“But in people with MS, those force sensors can become less reliable, so people need to rely more on other channels, especially vision,” Franz added.

To measure the participants’ responses, the researchers used 3D motion capture cameras to look for any fluctuations in each step (gait variability), differences in overall motion (kinematics), and balance (margin of stability).

Results showed that the measurements taken for standard walking — before the wobbles were introduced — were similar between MS patients and healthy volunteers.

“During normal walking without VR — even with our sophisticated lab equipment including a battery of 3D motion capture cameras — we could not effectively distinguish people with MS from the healthy, age-matched individuals,” said Franz.

However, once participants experienced the falling simulation, there was a clear and statistically significant difference in how MS patients responded — they exhibited a higher variability in step width, position, and stability.

Furthermore, MS patients performed worse than healthy controls on the standing sensory organization test, which assesses a person’s ability to use visual cues and others to maintain postural stability.

“So this perturbed-walking approach could have a lot of important clinical and translational applications,” Franz said.

Based on the results, the team said that its VR simulation technology “revealed differences in walking balance in [MS patients] that went undetected during normal, unperturbed walking. Targeting this difference may be a promising approach to more effectively detect preclinical walking balance deficits” in MS.

Encouraged by the findings, the researchers are now developing the technology to be used as a general diagnostic tool to identify balance impairments. They believe that such a test, potentially portable and inexpensive, could reduce the number of falls and associated injuries among MS patients.

“Our promising results suggest that one can use VR to detect balance problems that usually go undetected until the individual starts experiencing real falls at home or work,” Franz said.

The researchers also intend to develop the technology into a potential tool for physical therapy to help improve balance and reduce the falling risk in MS patients.

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