High signal intensity on magnetic resonance imaging as a predictor of neurobehavioral performance of workers exposed to manganese.
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.
Shin
Yong Chul
YC
Department of Occupational Health and Safety, Inje University, Gimhae, Korea.
Kim
Euna
E
Cheong
Hae-Kwan
HK
Cho
Sungil
S
Sakong
Joon
J
Kim
Kyoo Sang
KS
Yang
Jung Sun
JS
Jin
Young-Woo
YW
Kang
Seong-Kyu
SK
Kim
Yangho
Y
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
D000393:Air Pollutants; D017895:Manganese Compounds; D008345:Manganese