Reduced uptake of [¹⁸F]FDOPA PET in asymptomatic welders with occupational manganese exposure

Document Type

Article

Abstract

BACKGROUND: Welding exposes workers to manganese (Mn) fumes, but it is unclear if this exposure damages dopaminergic neurons in the basal ganglia and predisposes individuals to develop parkinsonism. PET imaging with 6-[(18)F]fluoro-l-dopa (FDOPA) is a noninvasive measure of nigrostriatal dopaminergic neuron integrity. The purpose of this study is to determine whether welding exposure is associated with damage to nigrostriatal neurons in asymptomatic workers. METHODS: We imaged 20 asymptomatic welders exposed to Mn fumes, 20 subjects with idiopathic Parkinson disease (IPD), and 20 normal controls using FDOPA PET. All subjects were examined by a movement disorders specialist. Basal ganglia volumes of interest were identified for each subject. The specific uptake of FDOPA, K(i), was generated for each region using graphical analysis method. RESULTS: Repeated measures general linear model (GLM) analysis demonstrated a strong interaction between diagnostic group and region (F(4,112) = 15.36, p < 0.001). Caudate K(i)s were lower in asymptomatic welders (0.0098 + 0.0013 minutes(-1)) compared to control subjects (0.0111 + 0.0012 minutes(-1), p = 0.002). The regional pattern of uptake in welders was most affected in the caudate > anterior putamen > posterior putamen. This uptake pattern was anatomically reversed from the pattern found in subjects with IPD. CONCLUSIONS: Active, asymptomatic welders with Mn exposure demonstrate reduced FDOPA PET uptake indicating dysfunction in the nigrostriatal dopamine system. The caudate K(i) reduction in welders may represent an early (asymptomatic) marker of Mn neurotoxicity and appears to be distinct from the pattern of dysfunction found in symptomatic IPD.

Medical Subject Headings

Adult; Aged; Corpus Striatum (diagnostic imaging, metabolism); Dihydroxyphenylalanine (analogs & derivatives, pharmacokinetics); Female; Fluorine Radioisotopes; Humans; Linear Models; Male; Manganese Poisoning (diagnostic imaging); Middle Aged; Occupational Exposure; Parkinson Disease (diagnostic imaging, metabolism); Positron-Emission Tomography; Putamen (diagnostic imaging, metabolism); Substantia Nigra (diagnostic imaging, metabolism); Welding

Publication Date

4-12-2011

Publication Title

Neurology

E-ISSN

1526-632X

Volume

76

Issue

15

First Page

1296

Last Page

301

PubMed ID

21471467

Digital Object Identifier (DOI)

10.1212/WNL.0b013e3182152830

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