Dopamine Transporter Density in de novo Parkinson's Disease Does Not Relate to the Development of Levodopa-Induced Dyskinesias.

Background: In Parkinson's disease (PD), the onset of levodopa-induced dyskinesias (LIDs) is difficult to predict. This study examines whether dopamine transporter (DAT)-specific SPECT imaging in de novo PD relates to later development of LIDs.

Methods: 42 de novo unilateral PD participants received DAT-specific SPECT imaging with ¹²³I-FP-CIT at time of diagnosis. At five years post-diagnosis, all PD patients were clinically evaluated and divided into two groups based on whether they had or had not developed LIDs. Fourteen gender- and age-matched healthy volunteers undertook ¹²³I-FP-CIT SPECT imaging and were included as controls. A semi-quantification approach was used for the ¹²³I-FP-CIT data using the occipital cortex as the reference region. We calculated specific binding ratios (SBR) for the caudate and putamen (posterior and anterior putaminal subregions). In parallel, we analysed our ¹²³I-FP-CIT dataset with a voxel-based analysis approach.

Results: PD patients had significantly lower striatal ¹²³I-FP-CIT SBR values in comparison to controls (p<0.001). After five years, dyskinetic patients (N=10) were taking higher daily doses of dopaminergic medication (p<0.001) and had more severe disease (difference in Hoehn & Yahr staging scores p<0.05) as compared to the non-dyskinetic group (N=32). At the time of diagnosis, ¹²³I-FP-CIT SBR values were not statistically different between the two groups for all striatal regions (p>0.05). SPM voxel-based analysis did not show a statistically significant difference between the two groups (p>0.05).

Conclusion: ¹²³I-FP-CIT SPECT imaging, performed at diagnosis in de novo early-stage PD could not differentiate patients who will develop LIDs within five years from those who will not.