Drug-induced dyskinesia in Parkinson's disease. Should success in clinical management be a function of improvement of motor repertoire rather than amplitude of dyskinesia?

Abstract

BackgroundDyskinesia, a major complication in the treatment of Parkinson's disease (PD), can require prolonged monitoring and complex medical management.DiscussionThe current paper proposes a new way to view the management of dyskinesia in an integrated fashion. We suggest that dyskinesia be considered as a factor in a signal-to-noise ratio (SNR) equation where the signal is the voluntary movement and the noise is PD symptomatology, including dyskinesia. The goal of clinicians should be to ensure a high SNR in order to maintain or enhance the motor repertoire of patients. To understand why such an approach would be beneficial, we first review mechanisms of dyskinesia, as well as their impact on the quality of life of patients and on the health-care system. Theoretical and practical bases for the SNR approach are then discussed.SummaryClinicians should not only consider the level of motor symptomatology when assessing the efficacy of their treatment strategy, but also breadth of the motor repertoire available to patients.

Parkinson's disease patients experiencing peak-dose dyskinesia redistribute involuntary movements throughout their body to improve motor control

“…The fact that patients experiencing more severe dyskinesia were more efficient in transferring energy points to an implicit strategy in their part. Conversely, this phenomenon could also be analogous to re-emerging tremor previously described by others [9] where the command of the intended movement (signal) overcomes the command generating the involuntary movement (noise), hence increasing temporarily the signal-to-noise ratio [10]. However, our data tend to demonstrate that the switch in dyskinesia amplitude distribution occurs prior to the global increase in energy, which makes it less likely that re-emerging dyskinesia shares neurophysiological bases with re-emerging tremor.…”

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“…It is reasonable to believe that more severe tremor amplitudes would increase the time required to perform an activity of daily living by forcing the individual to reduce movement speed in an attempt to improve accuracy. The amplitude threshold at which this occurs could be explained by a signal-to-noise ratio approach, where the signal is the voluntary movement and the noise the involuntary movement 26. Past a certain signal-to-noise ratio, the rate of failure as well as the time required to perform a specific task would increase dramatically.…”