Abstract
The early detection of Parkinson’s disease (PD) still remains a challenge to date. Although studies have previously reported subtle motor function abnormalities in early PD patients, it is unclear whether such clinical signs can be better detected while patients are concurrently performing a cognitive task, and whether they can be useful in predicting patients’ clinical conversion state. Seventy-two right-handed participants (40 drug-naive patients with idiopathic unilateral PD and 32 age-matched healthy controls) were enrolled in this study. All participants were asked to perform the Purdue Pegboard test (PPT) either alone (single-task condition) or during a concurrent mental subtraction-by-3 task (dual-task condition). A 4-year telephone follow-up was later conducted to determine whether PD patients converted to bilateral signs. We found that PD patients showed a significant reduction in dexterity on the PPT compared to 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 revealed reasonable discriminative ability for prediagnosing PD. However, dual-tasking did not have added value in differentiating early patients and controls. At follow-up, the baseline PPT performance of the asymptomatic hands was positively correlated with time to convert from unilaterally to bilaterally affected states (r = 0.62, P = 0.031). Together, these findings suggest that PPT can serve as a useful auxiliary tool in evaluating early PD, and shed light on the neuroplasticity mechanism of fine motor deficit at this very early stage.
Highlights
Parkinson’s disease (PD) is the second most common neurodegenerative disorder, which is characterized pathologically by the progressive loss of dopaminergic neurons in the substantia nigra, and clinically by the presence of cardinal motor symptoms including bradykinesia, resting tremor and/or rigidity
Scores based on activities of daily living, as measured with the Unified Parkinson’s Disease Rating Scales (UPDRS) part II, were inferior in patients with PD-R compared to the PD-L (P = 0.038) group, the level of motor impairment assessed with the UPDRS part III was comparable between the PD-R (6.71 ± 1.76) and PD-L (6.94 ± 3.09) groups, suggesting that patients who were clinically affected on the dominant side had lower level of activities of daily living than those who experienced motor deficits on the non-dominant side
Our study confirms and extends the results of previous reports that manual dexterity functions are impaired in PD patients, that their performance can be distinguished with relatively high sensitivity and specificity compared to matched control participants, and that their performance on Purdue Pegboard test (PPT) is positively correlated with disease severity as measured using the UPDRS III motor scores (Haaxma et al, 2008, 2010)
Summary
Parkinson’s disease (PD) is the second most common neurodegenerative disorder, which is characterized pathologically by the progressive loss of dopaminergic neurons in the substantia nigra, and clinically by the presence of cardinal motor symptoms including bradykinesia, resting tremor and/or rigidity. Postmortem and imaging studies have shown that the asymmetry in clinical motor deficits observed in the early stage of the disease reflect the known asymmetry in pathological progression of loss of dopaminergic neurons in the two hemispheres (Kempster et al, 1989; Morrish et al, 1995; Rinne et al, 2001; Kumakura et al, 2010; Wang et al, 2015). One can assume that the assessment of motor functions on the asymptomatic side of an unilaterally-affected PD patients provides a ‘‘model/proxy’’ of prodromal PD, which can be useful to identify potential biomarkers in the early phase of this neurological condition
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