title: T1-weighted MRI shows stage-dependent substantia nigra signal loss in Parkinson's disease.
abstract: Depigmentation of the substantia nigra is a conspicuous pathological feature of Parkinson's disease and related to a loss of neuromelanin. Similar to melanin, neuromelanin has paramagnetic properties resulting in signal increase on specific T1-weighted magnetic resonance imaging. The aim of this study was to assess signal changes in the substantia nigra in patients with Parkinson's disease using an optimized neuromelanin-sensitive T1 scan. Ten patients with Parkinson's disease and 12 matched controls underwent high-resolution T1-weighted magnetic resonance imaging with magnetization transfer effect at 3T. The size and signal intensity of the substantia nigra pars compacta were determined as the number of pixels with signal intensity higher than background signal intensity+3 standard deviations and regional contrast ratio. Patients were subclassified as early stage (n=6) and late stage (n=4) using the Unified Parkinson's Disease Rating Scale and the Hoehn and Yahr Parkinson's disease staging scale. The T1 hyperintense area in the substantia nigra was substantially smaller in patients compared with controls (-60%, P<.01), and contrast was reduced (-3%, P<.05). Size reduction was even more pronounced in more advanced disease (-78%) than in early-stage disease (-47%). We present preliminary findings using a modified T1-weighted magnetic resonance imaging technique showing stage-dependent substantia nigra signal reduction in Parkinson's disease as a putative marker of neuromelanin loss. Our data suggest that reduction in the size of neuromelanin-rich substantia nigra correlates well with postmortem observations of dopaminergic neuron loss. Further validation of our results could potentially lead to development of a new biomarker of disease progression in Parkinson's disease.
authors.affiliation: Radiological & Imaging Sciences, University of Nottingham, and Department of Medical Physics, Queen's Medical Centre, University Hospitals of Nottingham, Nottingham, United Kingdom.
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Schwarz
authors.forename: Timothy
authors.initials: T
authors.lastname: Rittman
authors.forename: Vamsi
authors.initials: V
authors.lastname: Gontu
authors.forename: Paul S
authors.initials: PS
authors.lastname: Morgan
authors.forename: Nin
authors.initials: N
authors.lastname: Bajaj
authors.forename: Dorothee P
authors.initials: DP
authors.lastname: Auer
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008543:Melanins / Q000378:metabolism; D008875:Middle Aged; D010300:Parkinson Disease / Q000473:pathology*; D013378:Substantia Nigra / Q000378:metabolism / Q000473:pathology*
chemical_list: D008543:Melanins; C014121:neuromelanin