Differentiation of early-stage parkinsonisms using neuromelanin-sensitive magnetic resonance imaging

Purpose: 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 disorders, for which differential diagnosis is generally difficult.

Methods: Neuromelanin-sensitive MRI at 3 T was performed in 53 patients with early parkinsonism and 22 healthy controls. After an observation period of >1.5 year, the patients were clinically diagnosed with Parkinson's disease (PD; n = 30), multiple system atrophy with predominant parkinsonism (MSA-P; n = 10), or progressive supranuclear palsy syndrome (PSPS; n = 13). The signal intensity of the lateral, central, and medial parts of the SNc and the LC were measured and the contrast ratios (CR) against adjacent white-matter structures was calculated.

Results: The CR of the lateral SNc was lower in the PD and MSA-P groups than in the PSPS and control groups (p = 0.0001-0.05). The CR of the LC was lower in the PD group than in the other groups (p = 0.0001-0.05). Sensitivity and specificity of the CRs for discriminating PD from MSA-P was 60% and 90%, respectively, those for PD/PSPS were 63-88% and 77-92%, respectively, and those for MSA-P/PSPS were 80% and 85%, respectively. These properties were comparable or better to MIBG scintigraphy.

Conclusions: Neuromelanin-sensitive MRI can depict differences in signal intensity of the lateral SNc and the LC among the parkinsonism disorders at their early stages.