Abstract
Neuromelanin (NM) is a dark pigment that mainly exists in neurons of the substantia nigra pars compacta (SNc). In Parkinson disease (PD) patients, NM concentration decreases gradually with degeneration and necrosis of dopamine neurons, suggesting potential use as a PD biomarker. We aimed to evaluate associations between NM concentration in in vivo SN and PD progression and different motor subtypes using NM magnetic resonance imaging (NM-MRI). Fifty-four patients with idiopathic PD were enrolled. Patients were divided into groups by subtypes with different clinical symptoms: tremor dominant (TD) group and postural instability and gait difficulty (PIGD) group. Fifteen healthy age-matched volunteers were enrolled as controls. All subjects underwent clinical assessment and NM-MRI examination. PD patients showed significantly decreased contrast-to-noise ratio (CNR) values in medial and lateral SN (P < 0.05) compared to controls. CNR values in lateral SN region decreased linearly with PD progression (P = 0.001). PIGD patients showed significant decreases in CNR mean values in lateral SN compared to TD patients (P = 0.004). Diagnostic accuracy of using lateral substantia nigra (SN) in TD and PIGD groups was 79% (sensitivity 76.5%, specificity 78.6%). NM concentration in PD patients decreases gradually during disease progression and differs significantly between PD subtypes. NM may be a reliable biomarker for PD severity and subtype identification.
Highlights
Parkinson disease (PD) is a common neurodegenerative disorder, its pathological changes mainly focus on the dopaminergic neurons containing neuromelanin (NM) lost in the subatantia nigra pars compacta (SNc), and both noradrenergic and dopaminergic neurons containing NM lost in the locus coeruleus (Hirsch et al 1988; Gibb 1992; Kastner et al.1992; Zarow et al 2003)
Compared with the tremor dominant (TD) group, the postural instability and gait difficulty (PIGD) group showed a significantly higher H–Y stage and UPDRSIII score (P = 0.008, 0.017), but no significant differences were found between groups in the course of disease, Mini-Mental State Examination (MMSE) scores, MocA scores, and Hamilton Depression Rating Scale (HAMD) scores (P = 0.150, 0.437, 0.639 and 0.768, respectively, Table 1)
We confirmed the correlation between NM and the progression of PD, and found that there was a significant difference in the degree of NM signal attenuation between the subtypes of PD patients: (1) contrast-to-noise ratio (CNR) values were significantly decreased in PD patients in medial and lateral substantia nigra (SN) compared to controls, and decreased linearly with PD
Summary
Parkinson disease (PD) is a common neurodegenerative disorder, its pathological changes mainly focus on the dopaminergic neurons containing neuromelanin (NM) lost in the subatantia nigra pars compacta (SNc), and both noradrenergic and dopaminergic neurons containing NM lost in the locus coeruleus (Hirsch et al 1988; Gibb 1992; Kastner et al.1992; Zarow et al 2003). It has shown that NM is an important factor in promoting dopaminergic neurons degeneration in Parkinson disease The loss of high signal area can be detected by NM-MRI in the early stage of Parkinson’s disease. The difference of NM concentration between different subtypes of PD detected by NM-MRI is helpful to deepen the understanding of the pathogenesis of these two subtypes and improve the efficacy of clinical intervention. It is of great clinical significance for the treatment and prognosis of PD patients to strengthen the research on the neural mechanism of PD subtypes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
