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 poisoning raised the question whether morphological changes of the basal ganglia, particularly of the globus pallidus, could be detected after chronic occupational 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 manganese in the blood using atomic absorption spectrometry. Chronic exposure was defined as a cumulative index (CBI) including duration of exposure, individual 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 media index in addition to clinical examinations. Results: No cases of parkinsonism were detected in clinical examinations or by other means. The mean manganese 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 well as between the CBI and workplace-specific exposure. Brain atrophy was not detected in any of the observed cases. Conclusions: Long-term exposure to manganese dioxide dust correlates with the Pallidum-Index in MRI scans. Although the MRI findings have no current clinical relevance for individuals, further studies are necessary to evaluate specificity and potential prognostic value.