Effects of dopaminergic medication on objective tasks of deftness, bradykinesia and force control

At least one small report has suggested the possibility that limb kinetic apraxia (a deficit in deftness) was not dopamine responsive and independent of bradykinesia and rigidity in PD. Quencer et al. (Neurology 68:150-151, 2007) observed that speed of finger tapping (bradykinesia) in optimally medicated persons with PD was largely comparable to healthy controls, yet their ability to manipulate and rotate a coin (deftness) was impaired. The authors concluded that deftness was independent of parkinsonian features. In this study, we measured tasks of deftness in a more objective way in both the ON and OFF dopaminergic state. Further, we evaluated whether finger-thumb force control was compromised in persons with PD. Eleven PD fluctuators (mean age 68 ± 9 years) and ten healthy age-matched controls (68 ± 8 years) were included. The bradykinesia items in the UPDRS and performance on the large box and block (LBB) tests were used to measure bradykinesia. A small box and block test (SBB), small coin rotation task (SCR) and small lock rotation task (SLR) were used as measures of deftness. Statistical analyses revealed a significant improvement in performance for the LBB, SBB, SLR and the bradykinesia items of the UPDRS following medication. Furthermore, our PD cohort's scores were comparable to controls on tests of bradykinesia and deftness (SLR, SBB and LBB) in the ON state, but they performed statistically worse than controls in the OFF state. On the other hand, analyses of the force control tasks revealed no significant difference between the groups. In summary, the improvement in deftness and bradykinesia in the ON state among our PD cohorts (and their comparable performance in the ON but not OFF state compared to healthy controls) suggests the possibility of a more uniform response of these motor features to dopaminergic therapy in PD.