title: High signal intensity on magnetic resonance imaging as a predictor of neurobehavioral performance of workers exposed to manganese.
abstract: BACKGROUND
  Using previously obtained cross-sectional data from a nationwide survey on workers exposed to manganese (Mn), we assessed the relation of high signal intensity with neurobehavioral effects, and reevaluated the preexisting cross-sectional data to get additional findings on the relation of high signals with other Mn-exposure indices.
  
  
  METHODS
  Subjects were the same as those in the previous study. The exposure status was reassessed based on similar exposure groups. The signal intensity of the globus pallidus (GP) relative to frontal white matter was subjectively evaluated as either with or without increased signals, and the increased signals were further graded into three categories. For quantitative evaluation of signal intensities of the GP we also calculated the pallidal index (PI). Neurobehavioral function was assessed using the World Health Organization Neurobehavioral Core Test Battery. In addition, computerized finger tapping speed was included to assess motor speed.
  
  
  RESULTS
  The mean blood Mn for those with grade III was significantly greater than those without increased signals and those with grade I. Airborne Mn and PI also showed similar findings. PI paralleled subjective MRI gradings. The proportion of workers with increased signals increased with all the Mn-exposure variables, airborne and blood Mn, the duration of work, and cumulative exposure. The PI was significantly associated with a correct score of pursuit aiming II tests and finger tapping of the dominant hand after control of age and educational level among neurobehavioral performances.
  
  
  CONCLUSIONS
  The present findings showed that signal index on T1-weighted MRI showed a dose-response relationship with all the Mn-exposure variables. The two neurobehavioral tests reflecting fine motor function were significantly decreased above 107.1 of PI, the cutoff point between those with and without increased signals. Hence, signal intensity on MRI is an effective predictor of the neurobehavioral performance of Mn exposed workers.
authors.affiliation: Department of Occupational Health and Safety, Inje University, Gimhae, Korea.
authors.forename: Yong Chul
authors.initials: YC
authors.lastname: Shin
authors.forename: Euna
authors.initials: E
authors.lastname: Kim
authors.forename: Hae-Kwan
authors.initials: HK
authors.lastname: Cheong
authors.forename: Sungil
authors.initials: S
authors.lastname: Cho
authors.forename: Joon
authors.initials: J
authors.lastname: Sakong
authors.forename: Kyoo Sang
authors.initials: KS
authors.lastname: Kim
authors.forename: Jung Sun
authors.initials: JS
authors.lastname: Yang
authors.forename: Young-Woo
authors.initials: YW
authors.lastname: Jin
authors.forename: Seong-Kyu
authors.initials: SK
authors.lastname: Kang
authors.forename: Yangho
authors.initials: Y
authors.lastname: Kim
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects*; D001519:Behavior / Q000187:drug effects*; D003430:Cross-Sectional Studies; D004305:Dose-Response Relationship, Drug; D005917:Globus Pallidus / Q000187:drug effects* / Q000473:pathology; D006801:Humans; D007723:Korea; D008279:Magnetic Resonance Imaging; D008297:Male; D008345:Manganese / Q000097:blood; D017895:Manganese Compounds / Q000009:adverse effects*; D020149:Manganese Poisoning / Q000209:etiology / Q000473:pathology / Q000523:psychology; D009048:Motor Skills / Q000187:drug effects; D009483:Neuropsychological Tests; D020258:Neurotoxicity Syndromes / Q000097:blood / Q000209:etiology* / Q000473:pathology / Q000523:psychology; D009784:Occupational Diseases / Q000097:blood / Q000139:chemically induced* / Q000473:pathology / Q000523:psychology; D016273:Occupational Exposure; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted
chemical_list: D000393:Air Pollutants; D017895:Manganese Compounds; D008345:Manganese