Impaired finger dexterity in patients with parkinson's disease correlates with discriminative cutaneous sensory dysfunction

To study the influence of discriminative cutaneous sensory dysfunction on impaired finger dexterity in Parkinson's disease (PD), we evaluated 48 right-handed PD patients during a practically defined off-medication period and 24 healthy age-matched controls. With visual deprivation, a finger tapping task (FTT) was performed to assess the speed of simple repetitive finger movements and a coin rotation task (CRT) was used to assess finger dexterity. The tasks were performed with the right hand. We measured the somesthetic temporal discrimination threshold (sTDT) in the right index finger. The mean ± SD FTT score of the patient group was lower than that of the control group (24.0 ± 8.0 vs. 29.8 ± 7.8; P < 0.01). The patient group performed worse on the CRT than the control group (8.5 ± 3.5 vs. 12.6 ± 1.7; P < 0.001). The mean sTDT value of the patient group was longer than that of the control group (124.0 ± 44.8 vs. 78.1 ± 26.2 ms; P < 0.001). The CRT scores correlated with the sTDT values (Pearson's correlation coefficient = -0.43; P < 0.01), but not with the Unified Parkinson's Disease Rating Scale (UPDRS) finger bradykinesia scores or FTT scores. Multiple regression analysis showed that the sTDT values (parameter estimate = -0.03, SE = 0.01; P < 0.01), but not patient age, UPDRS finger bradykinesia score, or FTT score, affected the CRT score. Slowness of simple repetitive finger movements did not have a strong impact on the impaired manual dexterity of PD. Discriminative sensory dysfunction and consequent abnormal sensorimotor integration seem to be involved in the impaired finger dexterity of PD.