Objective: The purpose of this study was to investigate whether the signal intensity of the substantia nigra pars compacta (SNc) and locus coeruleus (LC) on neuromelanin-sensitive magnetic resonance imaging (MRI) can discriminate early-stage parkinsonism and whether volume loss increases in parallel with disease severity and duration.

Background: Neuromelanin is a byproduct of dopamine and noradrenaline metabolism and is thought to protect neurons from oxidative stress mediated by free metals or free radicals and has paramagnetic properties resulting in high signal on specific T1-weighted MRI that allows its identification in vivo. Neuromelanin-sensitive MRI is able to visualize changes associated with neuronal loss in the SNc and LC in patients with Parkinson’s disease (PD) and recent studies have described a reduction in MRI neuromelanin- generated signal in the SN and LC in patients with PD.

Methods: 31 PD patients and 9 healthy controls (HC) underwent high-resolution T1-weighted MRI with magnetization transfer effect at 3T. All patients were evaluated and scanned in ‘OFF’ phase. Disease severity was evaluated by Hoen and Yahr (H&Y), motor evaluation was performed using the Unified Parkinson’s disease Rating Scale (UPDRS III), cognitive evaluation by Addenbrooke’s cognitive examination (ACE-R) and Montreal Cognitive Assessment (MoCA). We have also rated depression, anxiety, and sleep disorders.

Results: The T1 hyperintense area in the SNc was substantially smaller in PD patients than in HC (p: 0.0001). No significant differences were found for the T1 hyperintense area in the LC (p:0.321). Spearman’s test showed significant correlations between SNc area and disease duration (r: 0.432, p: 0.015), H&Y (r: 0.486, p: 0.006), UPDRS III (r: 0.500, p: 0.004), and the subitems bradykinesia (r: 0.507, p: 0.004) and rigidity (r: 0.422, p: 0.018). Significant correlations were also observed between SNc area of the most affected side and disease duration (r: 0.432, p: 0.14), UPDRS III (r. 0.437, p: 0.014) H&Y (r: 0.486, p: 0.006). No significant correlations were found for LC area.

Conclusions: MRI neuromelanin-sensitive images were able to detect significant changes in the SN area in PD patients. Our findings suggest that neuromelanin decrease is directly related with disease severity and duration. Neuromelanin MRI may be considered a biomarker of nigral degeneration in patients with PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neuromelanin-in-parkinsons-disease-a-3-t-mri-study/