DaTSCAN (123I-FP-CIT SPECT) imaging in early versus mid and late onset Parkinson's disease: Longitudinal data from the PPMI study

Introduction: It has been reported that early onset Parkinson's Disease (PD) patients have a less profound dopaminergic degeneration. The aim of the current study was to determine whether there are longitudinal differences in dopaminergic denervation [signal reduction in 123I-FP-CIT SPECT] in early versus mid and late onset PD. Methods: DaTSCAN (123I-FP-CIT SPECT) imaging was acquired at Parkinson's Progression Markers Initiative (PPMI) imaging centers and sent to the imaging core for calculation of striatal binding ratios. Data from the PPMI database of 58 early de novo PD patients (age <= 50 years) were compared to those of 362 mid and late onset PD patients (age > 50 years). Results: Although raw striatal binding ratios were higher in early onset versus mid/late onset PD, especially on the ipsilateral side, such differences were not observed, and were in fact reversed in the contralateral putamen, after age correction. The rate of signal decline was similar between the two groups. Interestingly, based on both raw and age-adjusted data, caudate nucleus and putamen asymmetry (contralateral/ipsilateral ratio) was more pronounced in early onset PD. Striatal asymmetry also significantly correlated with age at onset as a continuous variable. Conclusion: Early onset PD patients exhibited similar rates of decline of dopaminergic denervation compared to mid/late onset PD. These results are not supportive of a more benign disease in this subgroup. The more pronounced asymmetry in early onset PD may however signify a qualitatively different pattern of neurodegeneration compared to mid/late onset PD.