A quantitative study of levodopa-induced dyskinesia in Parkinson's disease.

The present study addressed the question of whether the emergence and severity of levodopa-induced dyskinesia was related to the therapeutic benefits derived from levodopa. Eight PD patients with clinically observed levodopa-induced dyskinesia were studied prior to and for two hours following a single dose of Sinemet (carbidopa/levodopa). Quantitative instrumental procedures were used to assess upper extremity dyskinesia, rigidity and bradykinesia. Results indicated that all patients exhibited significant reduction in their parkinsonism within 45 minutes following treatment. Reduction in bradykinesia, but not rigidity appeared to coincide with the emergence of dyskinesia. There was a significant relationship between severity of dyskinesia and the degree of improvement in movement velocity but not rigidity. Further analyses revealed that this relationship depended largely on the age of the patient. These findings are discussed as they pertain to a unified model of basal ganglia movement disorders which places dyskinesia and bradykinesia at opposite extremes along a continuum.