Neuromelanin MRI measures correlate with Parkinson’s disease severity

Neuromelanin-sensitive MRI (NM-MRI) can assess catecholaminergic neuron populations affected in Parkinson’s disease, but its relationship to clinical burden is not fully established. Researchers conducted a PRISMA-guided systematic review and random-effects meta-analysis of NM-MRI measures and clinical outcomes. The review included 39 studies involving 1,983 patients; pooled analyses were available for selected associations.

Lower NM-MRI measures correlated with greater motor impairment across 18 studies (pooled r = −0.406), longer disease duration across 14 studies (r = −0.426), higher Hoehn and Yahr stage across 10 studies (r = −0.336), and higher levodopa-equivalent daily dose across six studies (r = −0.337); all associations had P < 0.001. Narrative findings linked substantia nigra measures mainly to motor dysfunction and disease stage, and locus coeruleus measures more to cognitive, affective, autonomic and sleep symptoms.

Four longitudinal studies, with follow-up of approximately 1.5–3 years, reported annual declines of about 5%–19% in selected measures. The findings support NM-MRI as a potential imaging marker of disease burden and a candidate for progression-focused research, including disease-modifying trials. However, longitudinal evidence is based on only four studies, and the review does not establish that NM-MRI is a validated clinical biomarker or that it should guide patient management.