Magnetic resonance imaging (MRI) of the central nervous system in long-term manganese dioxide (MnO2) exposed workers.

Aim: Changes within the brain detected by MRI after chronic manganese poiso ning raised the question whether morphological changes of the basal ganglia , particularly of the globus pallidus, could be detected after chronic occu pational exposure to manganese dioxide. Method: In a cross-sectional study, healthy workers (48 male and 27 female) at a dry cell battery factory were examined. Actual internal exposure was quantified by the analysis of manga nese in the blood using atomic absorption spectrometry. Chronic exposure wa s defined as a cumulative index (CBI) including duration of exposure, indiv idual workplace factors, and previously measured concentrations of MnO2 in dust samples. A Philips Gyroscan T5-II (0.5 T) was used for the MRI of the brain. The following indicators were taken to ascertain possible manganese- induced changes; Pallidum-Index (PI), width of 3(rd) ventricle and cella me dia index in addition to clinical examinations. Results: No cases of parkin sonism were detected in clinical examinations or by other means. The mean m anganese concentration in blood was 12 mu g/l (range: 3.9-23.3 mu g/l). In comparison to the upper reference value of 10 mu g/l, 42 workers (56%) had a higher body burden. A significant positive correlation between manganese levels in blood and the PI (indicated by T-1-shortening) was observed as we ll as between the CBI and workplace-specific exposure. Brain atrophy was no t detected in any of the observed cases. Conclusions: Long-term exposure to manganese dioxide dust correlates with the Pallidum-Index in MRI scans. Al though the MRI findings have no current clinical relevance for individuals, further studies are necessary to evaluate specificity and potential progno stic value.