Parkinson’s progression, treatment response may depend on onset side

Differences in typing skills seen in patients by body side first affected

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Rates of Parkinson’s disease progression and treatment response may differ among patients depending on whether the disease primarily affects the dominant or nondominant side of the body, a small study of typing skills in patients new to dopaminergic therapy suggests.

“These findings suggest that the relationship between side of onset and handedness might play a role in understanding disease progression and medication response,” its researchers wrote.

The study, “Exploring asymmetric fine motor impairment trends in early Parkinson’s disease via keystroke typing,” was published in Movement Disorders Clinical Practice.

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Previous research indicates Parkinson’s progression differs by side affected

In its early stages, Parkinson’s usually affects one side of the body more than the other. Depending on which side is affected, Parkinson’s can be classified into dominant-side onset or nondominant-side onset.

Some research has suggested that Parkinson’s may progress differently between these two patient groups, but whether there are meaningful differences in disease progression based on the side of onset is debated. To learn more, scientists evaluated the progression of fine motor skills in patients by onset side.

Their study enrolled 28 people with Parkinson’s disease: 15 with dominant and 13 with nondominant onset. Another 25 age- and sex-matched people without Parkinson’s were included as controls. All of the participants were right-handed.

Fine motor skills were assessed via scores on the nQiMechPD, which digitally marked such skills based on a typing task.

“The nQiMechPD algorithm is well-suited to support research and improve PD [Parkinson’s disease] care, providing detailed insights into asymmetrical fine motor progression,” the researchers wrote.

Participants completed the typing task at a clinic five times over the course of about six months, and the researchers compared changes in nQiMechPD scores over time. These scores were calculated for each hand individually and for both hands collectively.

“Typing involves complex, bimanual processes and cortical and subcortical brain areas,” the researchers wrote, and “it is expected that the left-side keys are most likely to be tapped using the left hand and the right-side keys using the right hand for the majority of individuals.”

Of note, all of the patients started on a first Parkinson’s treatment around the same time they started these typing tasks.

Typing skills improved over time in treated patients with nondominant onset

For patients with nondominant disease onset, the nQiMechPD score for the dominant right hand tended to improve over time, likely owing to the effects of treatment. For those in the dominant-onset group, however, scores for the dominant hand tended to worsen over time despite treatment.

Scores for the left hand did not differ between the patient groups, results showed.

With both hands analyzed together, nQiMechPD scores tended to improve over time in the two groups, but the magnitude of improvement was significantly larger with nondominant onset. This difference “may suggest poorer response to medication in the D-PD [dominant-onset Parkinson’s] group,” the researchers wrote.

Significant differences in “overall progression trends” were evident between these patient groups, “driven by diverging trends in the dominant hand (right),” they added. “Combined with previous work, this suggests PD [Parkinson’s disease] onset side may influence medication response and fine motor impairment progression rate” in early disease stages.

Researchers noted that this was a small study focused only on right-handed people; they highlighted a need for further research in wider populations to verify the results.