Quantification of the dopaminergic response in Parkinson's disease

Various investigators have developed complex quantitative procedures for objective assessment of parkinsonian motor impairment, since drawbacks of rating scales are interrater variability, subjective impression, insensitivity to subtle modifications.

To determine whether standardized performance of inserting pegs (i) differentiates between parkinsonian subjects and healthy controls and (ii) reflects quantification of the dopaminergic response with rating scales within a levodopa challenge test design.

We used an easy-to-operate Purdue Pegboard-like apparatus, which measures the total time taken to insert 25 pegs from a rack into a series of appropriate holes by a computer to 100 ms accuracy, and simultaneous rating with part III of the Unified Parkinson's Disease Rating Scale for assessment of motor impairment in 28 idiopathic parkinsonian patients before and during a levodopa challenge test. Additionally we compared data of the instrumental task to age- and sex-matched healthy controls.

We found significant differences between parkinsonian subjects and controls and significant correlations to the rated severity of Parkinson's disease. Within-subject comparisons and correlation analysis demonstrated the ability of this tool to reflect scored motor improvement after intake of levodopa.

Inserting pegs provides an objective quantitative estimation of changes in motor impairment within a typical levodopa challenge test design.