Background: Quantitative evidence of levodopa-induced beneficial effects on parkinsonian rigidity in Parkinson's disease (PD) is lacking. Recent research has demonstrated the velocity-dependent nature of objective rigidity in PD and revealed its neural underpinning.
Objective: The present study aimed to examine the effect of levodopa on objective rigidity in PD.
Methods: Eighteen patients with PD underwent clinical and instrumental evaluations of muscle tone in the OFF and ON states. The clinical assessments focused on rigidity in the most affected upper limb. The biomechanical components of objective rigidity were assessed using robot-assisted wrist extensions at seven angular velocities (5-280°/s). Surface electromyography of the flexor carpi radialis muscle enabled the concurrent evaluation of short- and long-latency stretch reflexes (SLR and LLR).
Results: Levodopa improved the clinical scores of rigidity. Biomechanical measurements showed that levodopa reduced the total and neural components of force but had no effect on viscoelastic components. Levodopa reduced the velocity dependence of the LLRs but did not affect the SLRs. Finally, we found significant clinical-instrumental correlations between levodopa-induced changes and biomechanical and neurophysiological measures of objective rigidity in PD.
期刊介绍:
Movement Disorders publishes a variety of content types including Reviews, Viewpoints, Full Length Articles, Historical Reports, Brief Reports, and Letters. The journal considers original manuscripts on topics related to the diagnosis, therapeutics, pharmacology, biochemistry, physiology, etiology, genetics, and epidemiology of movement disorders. Appropriate topics include Parkinsonism, Chorea, Tremors, Dystonia, Myoclonus, Tics, Tardive Dyskinesia, Spasticity, and Ataxia.