CTSA News

During her clinical rotations as an occupational therapy student, Brooke Dexheimer, Ph.D., O.T.D., frequently found herself grappling with a troubling question while working with patients recovering from neurological conditions.
 

“These patients have limited visits because of their insurance,” said Dexheimer, now an assistant professor of occupational therapy in the Virginia Commonwealth University College of Health Professions. “It feels like every single minute that we can squeeze out of their rehab needs to be really effective at promoting their recovery. I couldn't help but feel like, ‘Is this the best that we can do?’”
 

That question drove Dexheimer to return to academia to earn her research doctorate and dedicate her career to improving rehabilitation through innovative research. At VCU, where she directs the Novel Environments for Reducing Disability & Dysfunction (NERDD) Lab, her work has taken on an even deeper resonance. Family members of hers have been directly affected by Parkinson's disease.

“For me, it's a passion project that really feels personal,” Dexheimer said. “The more we can learn about this disease, the more it can help down the line in terms of helping preserve people’s quality of life longer and slowing progression.”

The nondominant hand paradox

Supported by a K12 Mentored Career Development Award funded by the National Institutes of Health's National Center for Advancing Translational Sciences and administered through the C. Kenneth and Dianne Wright Center for Clinical and Translational Research, Dexheimer is investigating how hand dominance influences the onset and clinical presentation of Parkinson's disease.

The human brain controls motor function asymmetrically, dividing tasks between a dominant hand that manipulates objects and a nondominant hand that stabilizes them — such as holding a glass steady with one hand while pouring water with the other.

Intuitively, one might assume that motor disruptions like tremors or muscle stiffness would be noticed immediately if they began in a person's primary, dominant hand. However, prior research conducted by VCU neurologist Matthew Barrett, M.D., revealed a surprising pattern.

“Individuals whose motor symptoms related to Parkinson's disease appear initially in their nondominant hand seem to be diagnosed sooner than those who have their symptoms first appear in their dominant hand,” Dexheimer said. “Which feels really counterintuitive, right? Because you'd think if you had some coordination disruption or a tremor appear in your dominant hand, you'd notice that first compared to your nondominant hand.”

During her Ph.D. study, Dexheimer studied the underlying mechanisms related to handedness.

“It made for kind of the perfect intersection of my interest areas in terms of looking at the mechanisms of handedness and why that might contribute to why someone is diagnosed sooner or later,” she said.

Bridging the gap between clinic and home

To investigate this phenomenon, Dexheimer developed a novel, portable two-handed assessment designed to evaluate functional motor performance. Standard clinical tests for Parkinson's often rely on rapid, isolated movements like finger tapping or opening and closing hands.

“Those rapid, nonfunctional movements might miss something,” Dexheimer said. “You might do well at that assessment in the clinic, but when you go home and try to button the buttons on your clothes, or cut up food when cooking, you're having difficulties that are slipping through the cracks.”

The NERDD Lab's assessment pairs two digital tablets with two styluses connected by an elastic band. Participants stabilize one stylus on a tablet screen with one hand while manipulating the second stylus to draw on the adjacent tablet screen. By testing right-handed individuals across three distinct cohorts — those with dominant-side affected Parkinson's, nondominant-side affected Parkinson's, and age-matched healthy controls — the team aims to establish new metrics for subtle bimanual motor deficits.

Team science and translational impact

Dexheimer emphasized that the project relies heavily on interdisciplinary collaboration across VCU. Her primary mentor on the grant is Brian Berman, M.D., director of the Parkinson's and Movement Disorders Center. Her mentorship team also includes Peter Pidcoe, Ph.D., director of VCU's Engineering and Biomechanics Lab, and Dean Krusienski, Ph.D., director of VCU's Advanced Signal Processing in Engineering and Neuroscience Lab, alongside ongoing collaboration with Barrett.

Beyond technical training and statistical support, the K12 award grants Dexheimer protected research time to advance her long-term goal of becoming an independent translational scientist.

“Translational science to me means closing the gap between basic mechanistic research and clinical research that's at the cusp of changing clinical practice,” Dexheimer said.

For the study's clinical participants, the research offers a sense of shared purpose.

“A lot of times when I chat with them during the visit, they talk about how committed they are to participating in research because they really want to see change happen related to Parkinson's disease treatment,” Dexheimer said. “Even if it doesn't affect them in time, they hope that down the line, more individuals diagnosed with Parkinson's can benefit.”

The project described was supported by CTSA award No. K12TR004364 from the National Center for Advancing Translational Sciences. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health.