Objective: The aim of this study was to investigate in vivo the progression of neuroinflammation iRBD patients over a 3-year follow-up.

Background: Isolated rapid-eye-movement behaviour disorder (iRBD) is a parasomnia associated with Parkinson’s disease (PD) and other alpha-synucleinopaties that can manifest years before the onset of motor symptoms. Neuroinflammation, in the form of microglia activation, has been detected in the substantia nigra (SN) in iRBD patients using ¹¹[C]-PK11195 (PK) PET.  However, the progression of microglia activation in iRBD has not been investigated yet.

Method: Fifteen patients from our original cohort underwent a repeat PK PET scans 35 ± 4.9 months after their first scan. Parametric images of PK binding potential (BP) were generated with the
simplified tissue reference compartmental model and supervised cluster analysis. 
Based on their inflammation status at baseline, as defined by Z-score, the patients were divided into two groups. Patients who had a Z-score ≥ 2 were labelled as abnormal (N=5), the rest were labelled as normal (N=10).

Results: The normal subgroup showed no significant changes in PK binding from baseline to follow-up. In the abnormal subset, left and right (SN) regions were still significantly increased at follow-up compared to healthy controls (p=0.0095 and p=0.0366). However, PK binding was decreased in the left SN (p=0.0158).

Conclusion: The results suggest that neuroinflammation have remained stable or decreased over a 3 year period, however still increased compared to healthy controls. The clinical relevance of these findings remains to be determined.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/progression-of-neuroinflammation-in-patients-with-isolated-rem-sleep-behavior-disorder-a-11c-pk11195-pet-study/