Early-occurrence of manual motor blocks in Parkinson's disease: a quantitative assessment

Objectives - Quantitative analysis of internally-cued, repetitive motor per formance in patients with Parkinson's disease (PD). (Material and methods - Computerized quantitative measurements of the frequency, duration and temp oral profile of manual motor blocks (MMBs) during performance of a manual t apping task, in 39 patients with PD, as compared to 17 age-matched healthy controls. Results - Performance of PD patients was markedly abnormal both q uantitatively and qualitatively, as reflected by an increase (7.0% vs 4.6%) in MMBs, and by their occurrence from onset of movement. The phenomenon wa s already observed in the early stages of the disease, and was also correla ted with the occurrence of freezing of gait. A standard levodopa-carbidopa (125-12.5 mg) dose only partially affected this phenomenon. Conclusions - A ugmented motor blocks in internally-cued performance should be recognized a s a frequent, distinct and generalized feature of PD. Whereas the gait diso rder is regarded as characteristic of the advanced stage of PD, our finding s suggest that the basic defect in internal rhythm formation can be detecte d by sensitive measurement tools from the early stages of the disease. In a ddition, the methodology developed in this study to quantitatively measure manual motor blocks may be a useful tool for future development of therapeu tic regimens for this debilitating aspect of motor dysfunction in PD.