Manual Dexterity Test May Offer Clues to Earlier Parkinson Diagnosis

Performance on a manual dexterity test can act as an objective behavior marker that can aid in detecting the prodromal stage of patients with Parkinson disease (PD) and also as a way to monitor disease progression, according to a recent study.

Early detection of PD remains a challenge. While subtle motor function abnormalities in the early stage of the disease has been reported, it is unclear whether such clinical signs can be better detected while patients are performing another cognitive task at the same time, and whether they can be useful in predicting patients’ clinical conversion state.

Typically at onset, the clinical motor deficits in PD are unilateral, and this phenomenon can last for several months to years before symptoms become bilateral. Hallmark motor symptoms include bradykinesia, resting tremor and/or rigidity; patients also report problems with dexterity.

In this study, 72 right-handed participants (40 drug-naive patients with idiopathic unilateral PD and 32 age-matched healthy controls) were enrolled. Of the 40, 16 were left-onset (PD-L, 47-71 years of age) and 24 were right-onset (PD-R, 42—73.3 years of age).

All participants performed the Purdue Pegboard test (PPT) either as a single task or during a concurrent mental subtraction-by-3 task (dual-task condition). The test was performed with the dominant right hand (DRH) and the non-dominant left hand (NDLH) in randomized order.

For the single task, participants were told to transfer a series of small metal rods from the outer concave cup located on the same side of the hand used, one at a time into corresponding holes of the board as quickly as possible within 30 seconds. They were able to practice for 10 seconds to make sure they understood the instructions. Each hand was tested 3 times (trial) in a row. The mean number of pegs placed in 3 trials was scored for each hand.

For the dual task, researchers gave simultaneously a verbal cognitive task requiring participants to subtract 3 as quickly and accurately as possible within 30 seconds from a number randomly selected from 280 to 320. The cognitive task condition alone and the dual-task condition were also administered on 3 occasions in a row. For each trial, the cognitive task was administered with different numbers. Participants were instructed to try not to concentrate on 1 task in particular, but to perform both tasks at the same time. Both the number of subtractions and the number of pegs transferred during each test were then recorded. The order of administration of the motor test alone, the cognitive test alone and the dual-test condition was randomized.

Over 4 years after baseline, 25 of the 40 patients with PD were contacted via telephone calls; 2 were excluded. Among the 23 PD patients included in the final analyses, 12 patients (7 PD-L, 5 PD-R) converted from a unilateral to a bilateral affected disease condition. The baseline performance on the PPT based using the asymptomatic hand of patients in the PD-R group who remained unilaterally affected was significantly higher than that of patients who converted to a bilateral affected condition (13.56 ± 1.36 vs 11.20 ± 1.15, P = .007). Furthermore, a positive correlation between baseline PPT performance of the asymptomatic hands correlated with time to convert from unilaterally to bilaterally affected states (r = 0.62, P = .031).

Patients showed a significant reduction in dexterity on the PPT compared with the controls in both single- and dual-task conditions. Yet patients’ performance in the dual-task condition revealed a greater interference effect when patients performed the task with their right hand than with their left hand. PPT also showed discriminative ability for prediagnosing PD.

However, dual-tasking did not have added value in differentiating early patients. The findings suggest that PPT can serve as a useful auxiliary tool in evaluating early PD, and they shed light on the neuroplasticity mechanism of fine motor deficit at this very early stage.

Reference

Xiajuan D, Jia L, Chan P. Impaired fine motor function of the asymptomatic hand in unilateral Parkinson’s disease [published online October 4, 2019 ]. Front Aging Neurosci. doi: 10.3389/fnagi.2019.00266.