Effects of levodopa on finger and orofacial movements in Parkinson's disease

1. The objective of this study is to compare the efficacy of levodopa on finger and orofacial movements in Parkinson's disease. The sensitivity of the orofacial and finger systems to levodopa would suggest the involvement of dopaminergic lesions. 2. The production of isometric force was estimated in both conditions, without and with levodopa, in 14 patients with idiopathic Parkinson's disease (mean duration of symptoms: 9 +/- 3 years). 3. Forces generated by the upper and lower lips, tongue, right and left forefingers in the presence of visual feedback were measured by means of force transducers. 4. The target force levels used in the present study included 0.25, 0.5, 1 and 2 newtons corresponding to fine forces presumably involved in speech production. Moreover, motor disability of patients was assessed in each condition, using the motor examination of the Unified Parkinson's disease rating scale and a hand-tapping test. 5. Fourteen control subjects also participated in this study. 6. The beneficial effect of levodopa on finger movements was observed as indicated by an improvement in motor scores and production of forces. In contrast, the production of orofacial forces was either not improved, or aggravated by levodopa. 7. These results suggest that cerebral non dopaminergic lesions participate to the impairments of parkinsonian speech.