Objective: To determine whether there are longitudinal differences in dopaminergic denervation [as exemplified by signal reduction in 123I-FP-CIT SPECT] in early PD patients versus mid and late onset PD.

Background: The Parkinson’s progression markers initiative (PPMI) study evaluated the 5-year change of clinical, imaging and biochemical parameters in de novo Parkinson’s disease (PD) patients. Recently published PPMI data indicate a significant longitudinal decrease in dopamine transporter binding in all striatal regions assessed [1].

Method: 123I-FP-CIT SPECT imaging was acquired at Parkinson’s Progression Markers Initiative imaging centers as part of the study imaging protocol and sent to the imaging core for processing and 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 363 mid and late onset PD patients (age > 50 years). Statistical analysis has been performed using repeated measures ANOVA.

Results: Early PD patients had significantly higher caudate nucleus (p=0.001) and putamen (p=0.001) binding ratios ipsilaterally to the most affected side as compared to mid and late onset PD.  A similar trend was observed for the contralateral caudate nucleus and putamen but did not reach significance (p=0.21 and p=0.531).  The rate of signal decline was comparable between young onset and mid/late onset PD in all striatal regions with the exception of ipsilateral putamen (less prominent in the late onset group, Time*Group interaction p=0.031). There was no difference regarding caudate / putamen signal ratio both ipsilaterally and contralaterally (p=0.47 and p=0.407 respectively).  Moreover, caudate nucleus and putamen asymmetry (contralateral/ipsilateral ratio) was more pronounced in the young PD group (p=0.001 and p=0.012). Putamen asymmetry decreased over time in both subgroups.

Conclusion: Assessing longitudinal data, the subgroup of early de novo PD patients exhibited less dopaminergic denervation and a greater striatal asymmetry comparing to mid and late onset PD. This result might implicate an earlier clinical diagnosis of PD since first symptom appearance in younger patients. The faster rate of signal decline in ipsilateral putamen of younger PD is not supportive of a milder disease affectation in this subgroup, as previously suggested [2].

References: [1] Simuni T et al. Longitudinal Change of Clinical and Biological Measures in Early Parkinson’s Disease: Parkinson’s Progression Markers Initiative Cohort. Mov Disord. 2018; 33(5):771-782. [2] Pagano G et al. Age at onset and Parkinson disease phenotype. Neurology. 2016; 86(15):1400-1407.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/123i-fp-cit-spect-imaging-in-early-pd-patients-versus-mid-and-late-onset-pd-longitudinal-data-from-the-ppmi-study/