Neuromelanin-sensitive magnetic resonance imaging features of the substantia nigra and locus coeruleus in de novo Parkinson's disease and its phenotypes

Abstract

Background and purpose: Neuromelanin of the brainstem, which is considered a marker of neurodegeneration in Parkinson's disease (PD), can be detected by T1-weighted neuromelanin-sensitive magnetic resonance imaging (NM-MRI). Our aim was to investigate the NM-MRI features of de novo PD and to determine whether these features are associated with motor and non-motor symptoms in de novo PD patients.

Methods: Fifty-one patients with de novo PD (Hoehn and Yahr stage 1-2) and 28 healthy controls were recruited. All subjects underwent clinical and MRI examinations including an NM-MRI sequence. The width and contrast-to-noise ratio (CNR) of the substantia nigra pars compacta (SNc) and the CNR of the locus coeruleus (LC) were measured on NM-MRI images.

Results: Both the width and CNR values of the high intensity signals in the SNc were significantly decreased in the lateral, central and medial SNc parts in de novo PD patients compared to control subjects. The changes in the SNc on NM-MRI were not significantly different between the motor subgroups. The CNR values of the left LC were significantly lower in the PD group than in the control group. Specifically, the subtype of PD patients with depressive symptoms exhibited a significantly lower CNR in the left LC than the control group and PD patients without depressive symptoms.

Conclusions: Substantia nigra pars compacta neuromelanin changes occur across both motor and non-motor (with and without depressive symptoms) subtypes, whilst LC changes are more notable in PD patients with depressive symptoms. Our results may provide new evidence to understand the pathophysiology of non-motor symptoms in PD.

Keywords: MRI; Parkinson's disease; depressive symptoms; neuromelanin; subtype.