Since there was no proven biomarker for Parkinson’s disease (PD), clinical diagnosis and surveillance remained difficult. Neuromelanin-magnetic resonance imaging (NM-MRI) is a new biomarker of nigral depigmentation that measures the loss of melanized neurons, although it’s future diagnostic and monitoring effectiveness in multicenter settings is uncertain. For a study, researchers sought to determine and evaluate serial NM-MRI changes in PD and controls, as well as to examine the diagnostic accuracy of NM-MRI in early PD in a multiprotocol scenario.
In the longitudinal case-control 3 T MRI investigation, 148 patients and 97 controls from six clinical institutions were enrolled, with 140 undergoing a second scan 1.5 to 3 years later. Subregional substantia nigra NM-MRI contrast and volume were assessed using an automated template-based technique. The period of prediagnostic depigmentation was estimated using a point estimate.
All NM measures performed well in distinguishing patients from controls, with the receiver operating characteristic indicating an 85% accuracy for ventral NM contrast and an 83% accuracy for volume. The generalizability of an a priori volume limit proved satisfactory (79% accuracy). Serial MRI revealed that patients’ NM loss was accelerated as compared to controls. Ventral NM contrast loss began 5 to 6 years before clinical diagnosis. Ventral nigral depigmentation was more severe on the afflicted side, and nigral NM volume change corresponded with motor severity change. They showed that NM-MRI could give clinically meaningful diagnostic information in early Parkinson’s disease across procedures, platforms, and locations. It offered methodologies and estimated depigmentation rates that showed the potential for detecting preclinical Parkinson’s disease and tracking development in biomarker-enabled clinical trials.