When and how should treatment be started in Parkinson disease?

The questions of when and how to start treatment for Parkinson disease (PD) remain extremely challenging. A variety of treatment- and patient-related factors must be taken into account when making these decisions. Ideally, neuroprotective therapy would be started at the time of diagnosis. However, no treatment has been unequivocally shown to modify disease progression, and those that have some evidence for this effect all provide confounding symptomatic benefits, which may also be important to supplement faltering compensatory mechanisms within the basal ganglia. Dopamine agonists are clearly associated with a reduction in the incidence of dyskinesias in the early years, but it is not certain that this translates into long-term benefit. In addition, a number of nonmotor side effects are more frequently associated with dopamine agonists than with levodopa. This review will highlight these and other issues that must be considered when deciding on the early treatment of PD.