Quantifying drug-induced changes in parkinsonian rigidity using an instrumental measure of activated stiffness.

We review the literature on quantifying parkinsonian rigidity and present data from 124 subjects to demonstrate the clinical utility of activated stiffness to model rigidity. This method eliminates many of the confounding variables associated with the subjective assessment of rigidity. This 5-min computer-assisted procedure was highly reliable and sensitive to pharmacologic influences that produce and reduce parkinsonian rigidity.