title: Correlation of dopaminergic terminal dysfunction and microstructural abnormalities of the basal ganglia and the olfactory tract in Parkinson's disease.
abstract: Signal abnormalities of the substantia nigra and the olfactory tract detected either by diffusion tensor imaging, including measurements of mean diffusivity, a parameter of brain tissue integrity, and fractional anisotropy, a parameter of neuronal fibre integrity, or transcranial sonography, were recently reported in the early stages of Parkinson's disease. In this study, changes in the nigral and olfactory diffusion tensor signal, as well as nigral echogenicity, were correlated with clinical scales of motor disability, odour function and putaminal dopamine storage capacity measured with 6-[(18)F] fluorolevodopa positron emission tomography in early and advanced stages of Parkinson's disease. Diffusion tensor imaging, transcranial sonography and positron emission tomography were performed on 16 patients with Parkinson's disease (mean disease duration 3.7 ± 3.7 years, Hoehn and Yahr stage 1 to 4) and 14 age-matched healthy control subjects. Odour function was measured by the standardized Sniffin' Sticks Test. Mean putaminal 6-[(18)F] fluorolevodopa influx constant, mean nigral echogenicity, mean diffusivity and fractional anisotropy values of the substantia nigra and the olfactory tract were identified by region of interest analysis. When compared with the healthy control group, the Parkinson's disease group showed significant signal changes in the caudate and putamen by 6-[(18)F] fluorolevodopa positron emission tomography, in the substantia nigra by transcranial sonography, mean diffusivity and fractional anisotropy (P < 0.001, P < 0.01, P < 0.05, respectively) and in the olfactory tract by mean diffusivity (P < 0.05). Regional mean diffusivity values of the substantia nigra and the olfactory tract correlated significantly with putaminal 6-[(18)F] fluorolevodopa uptake (r = -0.52, P < 0.05 and r = -0.71, P < 0.01). Significant correlations were also found between nigral mean diffusivity values and the Unified Parkinson's Disease Rating Scale motor score (r = -0.48, P < 0.01) and between mean putaminal 6-[(18)F] fluorolevodopa uptake and the total odour score (r = 0.58; P < 0.05) as well as the Unified Parkinson's Disease Rating Scale motor score (r = -0.53, P < 0.05). This study reports a significant association between increased mean diffusivity signal and decreased 6-[(18)F] fluorolevodopa uptake, indicating that microstructural degradation of the substantia nigra and the olfactory tract parallels progression of putaminal dopaminergic dysfunction in Parkinson's disease. Since increases in nigral mean diffusivity signal also correlated with motor dysfunction, diffusion tensor imaging may serve as a surrogate marker for disease progression in future studies of putative disease modifying therapies.
authors.affiliation: 1 Department of Neurology, Innsbruck Medical University, Anichstrasse 35, A-6020 Innsbruck, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Scherfler
authors.forename: Regina
authors.initials: R
authors.lastname: Esterhammer
authors.forename: Michael
authors.initials: M
authors.lastname: Nocker
authors.forename: Philipp
authors.initials: P
authors.lastname: Mahlknecht
authors.forename: Heike
authors.initials: H
authors.lastname: Stockner
authors.forename: Boris
authors.initials: B
authors.lastname: Warwitz
authors.forename: Sabine
authors.initials: S
authors.lastname: Spielberger
authors.forename: Bernadette
authors.initials: B
authors.lastname: Pinter
authors.forename: Eveline
authors.initials: E
authors.lastname: Donnemiller
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
authors.forename: Irene
authors.initials: I
authors.lastname: Virgolini
authors.forename: Michael
authors.initials: M
authors.lastname: Schocke
authors.forename: Werner
authors.initials: W
authors.lastname: Poewe
authors.forename: Klaus
authors.initials: K
authors.lastname: Seppi
mesh_terms: D000368:Aged; D016880:Anisotropy; D001479:Basal Ganglia / Q000473:pathology* / Q000503:physiopathology; D003342:Corpus Striatum / Q000503:physiopathology; D056324:Diffusion Tensor Imaging / Q000379:methods; D004298:Dopamine / Q000378:metabolism*; D059290:Dopaminergic Neurons / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D009833:Olfactory Pathways / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D049268:Positron-Emission Tomography / Q000379:methods; D011699:Putamen / Q000473:pathology / Q000503:physiopathology; D013378:Substantia Nigra / Q000473:pathology* / Q000503:physiopathology
chemical_list: D004298:Dopamine
keywords: Parkinson’s disease; [18F] DOPA PET; diffusion tensor imaging; midbrain sonography