Does the side onset of Parkinson's disease influence the time to develop levodopa-induced dyskinesia?

Background: Aberrant plasticity is closely linked to the development of levodopa-induced dyskinesia (LID) in Parkinson'fs disease (PD). Objective: This study investigated whether dominant-side patients with PD exhibit a shorter time to LID development, based on the hypothesis that the dominant hemisphere may have greater plasticity than non-dominant-side patients. Methods: We analyzed data from 387 right-handed patients with PD who exhibited asymmetric motor deficits and received PD medications for.2 years (191 dominant-side and 196 non-dominant-side patients). The influence of side onset on time for LID development was assessed by Kaplan-Meier estimates and time-dependent Cox regression models based on the 5-year time point, after adjusting for age at PD onset, dopamine transporter activity in the posterior putamen, and daily levodopa dose. Results: LID developed in 46 (23.4%) patients with non-dominant-side PD and in 35 (18.1%) patients with dominantside PD. The Kaplan-Meier analyses revealed that non-dominant-side patients developed LID earlier than dominant-side patients (p = 0.027). The time-dependent Cox regression models showed that the risk of LID within 5 years of treatment was significantly higher in non-dominant-side than in dominant-side patients (hazard ratio 1.954; p = 0.034), whereas the risk after 5 years was similar between groups (p = 0.528). Conclusions: The present study demonstrated that LID developed earlier in non-dominant-side than in dominant-side patients with PD. These results suggested a greater potential of synaptic plasticity in the dominant hemisphere that may exert a protective role for the development of LID compared to the non-dominant hemisphere.