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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-[18F]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, Ki, 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 (F4,112 = 15.36, p < 0.001). Caudate Kis 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 Ki 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.
Footnotes
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Study funding: Supported by the Michael J. Fox Foundation, the NIH (R01 ES013743, K24 ES017765, KL2 RR024994, P42ES04696, 5T32NS007205-27, RO1 NS41509, RO1 NS058714), the Clinical Science Translational Award NCRR UL1 RR024992, the Neuroscience Blueprint grant NS057105, the American Parkinson Disease Association (APDA) Advanced Research Center at Washington University, the Greater St. Louis Chapter of the APDA, the McDonnell Center for Higher Brain Function, and the Barnes-Jewish Hospital Foundation (Elliot Stein Family Fund and Jack Buck Fund for PD Research).
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Editorial, page 1286
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- AIR
- Automated Image Registration
- ANCOVA
- analysis of covariance
- ANOVA
- analysis of variance
- FDOPA
- 6-[18F]fluoro-l-dopa
- GLM
- general linear model
- GM
- gray matter
- GP
- globus pallidus
- IPD
- idiopathic Parkinson disease
- MPRAGE
- magnetization-prepared rapid gradient echo
- MR
- magnetic resonance
- PI
- pallidal index
- UPDRS3
- Unified Parkinson's Disease Rating Scale motor subsection 3
- VOI
- volume of interest
- WM
- white matter.
- Received July 20, 2010.
- Accepted October 21, 2010.
- Copyright © 2011 by AAN Enterprises, Inc.
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