Magnetic resonance correlation of iron content with neuromelanin in the substantia nigra of early-stage Parkinson's disease.

BACKGROUND AND PURPOSE: Magnetic resonance (MR) studies have demonstrated a significant reduction of neuromelanin in the substantia nigra (SN) of Parkinson's disease (PD) patients with high accuracy for differential diagnosis compared to non-PD controls and essential tremor. However, studies state that not knowing how paramagnetic effects of iron influence neuromelanin signal is a limitation. In this study a neuromelanin-sensitive MR sequence was combined with T2* relaxometry iron quantification analysis to study the SN of early-stage PD patients to investigate the correlation between these parameters. METHODS: The inclusion criteria were untreated de novo PD patients and a 2-5 year disease duration (early PD); in addition, age-matched controls were enrolled. These were studied at 3.0 T with a high-resolution T1-weighted MR sequence to visualize neuromelanin and a relaxometry sequence for iron quantification. The primary outcome was the correlation of the width of the neuromelanin high signal region and the T2* values in the lateral, central and medial segments of the SN. RESULTS: Very weak correlations of T2* values with neuromelanin width, positive for global and negative for the medial and lateral SN segments, were found in both PD groups and control subjects. The SN neuromelanin width was markedly reduced in the de novo and early PD groups compared with controls in all SN segments, but no significant difference in T2* values was found between the groups. CONCLUSIONS: The SN neuromelanin signal does not have a significant correlation with iron content in PD patients or controls. The neuromelanin MR signal reduction in PD does not seem to be significantly influenced by paramagnetic iron effects.

Substantia nigra neuromelanin magnetic resonance imaging in de novo Parkinson's disease patients.

BACKGROUND: Depigmentation of the substantia nigra (SN) and locus coeruleus (LC) is a conspicuous pathological feature of Parkinson's disease (PD) and is related to the loss of neuromelanin, whose paramagnetic properties result in high signal on specific T1-weighted magnetic resonance imaging (MRI). Recent studies have suggested that neuromelanin decrease in the SN and LC of PD patients may emerge as a possible diagnostic biomarker. The SN neuromelanin signal in de novo and early stage PD patients was studied to assess its diagnostic accuracy. This is the first study based on a semi-automated MRI analysis of the neuromelanin signal in de novo PD patients. METHODS: The inclusion criteria were untreated de novo PD and a 2-5 year disease duration; in addition, age matched healthy controls were enrolled. These were studied with a high-resolution T1-weighted MRI sequence at 3 T to visualize neuromelanin. The primary outcome was SN high signal area, length and neuromelanin/midbrain ratio obtained with semi-automated methods. RESULTS: A total of 12 de novo PD patients and 10 PD patients with a 2-5 year disease duration were evaluated. The area, length of the SN T1 high signal and the SN neuromelanin/midbrain ratio were markedly decreased in the PD groups compared with age-matched controls, with a substantial overlap between the two PD groups. CONCLUSIONS: Neuromelanin-sensitive MRI techniques can discriminate PD patients from healthy individuals with high sensitivity and specificity. Our findings are consistent with recent findings showing that PD neuromelanin changes remain stable during the course of the disease.