Neuromelanin-MRI to Quantify and Track Nigral Depigmentation in Parkinson's Disease: A Multicenter Longitudinal Study...

Area of Science:

• Neuroimaging
• Biomarker Discovery
• Clinical Neurology

Background:

• Parkinson's disease (PD) diagnosis lacks reliable biomarkers.
• Neuromelanin-magnetic resonance imaging (NM-MRI) shows potential for detecting nigral depigmentation, an indicator of neuron loss in PD.
• The multicenter diagnostic and tracking performance of NM-MRI is not well-established.

Purpose of the Study:

• To assess the diagnostic accuracy of NM-MRI in early PD across multiple centers and protocols.
• To compare serial NM-MRI changes in PD patients versus controls.
• To estimate the timeline of nigral depigmentation relative to clinical diagnosis.

Main Methods:

• A longitudinal, 3T MRI study included 148 PD patients and 97 controls from six UK centers.
• 140 participants underwent a second scan after 1.5 to 3 years.
• Automated analysis quantified substantia nigra NM-MRI contrast and volume; prediagnostic depigmentation was estimated.

Main Results:

• NM-MRI metrics effectively distinguished PD patients from controls (85% accuracy for ventral NM contrast, 83% for volume).
• Serial MRI revealed accelerated NM loss in PD patients.
• Ventral nigral depigmentation began an estimated 5-6 years before clinical diagnosis and correlated with motor severity.

Conclusions:

• NM-MRI offers clinically valuable diagnostic information for early PD across diverse settings.
• The study provides methods and depigmentation rate estimates for detecting preclinical PD.
• NM-MRI has potential for tracking disease progression in biomarker-enabled clinical trials.