Objective: to investigate the pattern of substantia nigra – neuromelanin (SN-NM) area loss and contrast ratio (CR) intensity changes in late-stage Parkinson’s disease (LSPD) patients, compared to de novo PD patients and PD patients with a 2-5 year disease duration in order to evaluate NM changes throughout disease progression.

Background: A specific T1-weighted magnetic resonance imaging (MRI) sequence has been shown to detect SN-NM signal changes that accurately discriminate PD patients from controls, even in early disease stages. However it is unclear what happens to these SN changes in later stages of the disease.

Methods: A comparative cross-sectional study was performed, analyzing SN-NM MRI signal in  LSPD defined as Schwab and England ADL Scale < 50 or Hoehn Yahr Stage (HY) >3, comparing them with other disease stages, i.e. de novo, 2-5 year PD and controls. For all the groups SN-NM signal area and CR values for the internal and lateral SN regions were obtained with semi-automated methods.

Results: 13 LSPD, 12 de novo patients with PD, 10 PD patients with a 2-5 year disease duration, and 10 controls were included. NM signal area was significantly decreased in de novo PD patients compared to LSPD ones (P-value = 0.005; sensitivity: 75%; specificity 92% and AUC: 0.86) and in PD patients compared to controls (P-value < 0.002). In the lateral SN region, a decrease in the CR was detected in all the PD groups compared to controls; also, despite not reaching statistical significance, a slight increment was observed comparing LSPD to 2-5 year PD patients. NM signal area had a significant correlation with HY (R= -0.37; P<0.05) and MDS-UPDR part II (R= -0.4; P <0.05) while a weak correlation was found with MDS-UPDRS part III (R= – 0.26; P: 0.1).

Conclusions: SN area evaluated by NM-sensitive MRI may be a promising biomarker of nigral degeneration and disease progression in PD patients. Further longitudinal studies on a larger population and the use of consensus acquisition and analysis protocols are warranted in order to replicate our results and verifying if SN-NM area could be considered as a disease progression imaging biomarker in clinical trials.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/substantia-nigra-area-evaluated-by-neuromelanin-sensitive-mri-as-an-imaging-biomarker-of-disease-progression-in-parkinsons-disease/