Li, XR; Long, LL; Qin, WP; Jiang, ML; Jiang, YM; Fu, X
Objective: MRI and MR hydrogen proton spectroscopy ( 1H-MRS) were used to detect the abnormal signal and alteration of metabolites, in order to explore the efficacy of these method in evaluating the damages of central nervous system (CNS) induced by occupational manganese exposure. Methods: Eighteen workers exposed to manganese without any manganism symptoms, 12 workers with slightly chronic manganese poisoning, and 19 healthy workers were scanned using routine MRI sequence and 1H-MRS. The blood manganese concentration was also collected for each subject. On cerebral axial T 1WI, the signal intensities of ipsilateral globus pallidus and frontal white matter were measured in the visually brightest area (try to select the signal homogeneous region), and the globus pallidus index (PI) was then calculated. The 1H-MRS data was calculated to get the values of the peak height of N-acetylaspartate (NAA), choline (Cho), inositol (ml) and creatine (Cr) and the ratios of NAA/Cr, Cho/Cr, and mI/Cr were also calculated. One way ANOVA was used to compare the values of PI, NAA/Cr, Cho/Cr, mI/Cr and MnB among the three groups, and the correlations between PI and the time span of manganese exposure or blood manganese concentration were analyzed by Pearson correlation analysis. Eight workers exposed to manganese were followed up one year, and their PI, NAA/Cr before and after follow-up were compared by t test. Results: Fourteen of 18 cases exposed to manganese without any manganism symptoms showed symmetrically high intensity signal on T 1WI, while the T 2WI were normal. No high signal intensity was observed on T 1WI in any of the healthy workers or manganese poisoning workers. We found that the average PI in manganese exposed group (1.16±0.09) was significantly higher (F = 24.79, P = 0.000) than those of the poisoning (1.05±0.07) and control groups (1.01±0.05). The blood manganese concentration in manganese exposed group, the poisoning group and the control group were (0.051±0.024), (0.047±0.018), (0.043±0.020) μg/ml respectively, which was not significantly different (F = 0.623, P = 0.541) and did not exceed the upper limit of normal reference value (<0.10 μg/ml). There was a significantly correlation between PI and the time span of manganese exposure (r = 0.67, P = 0.002), however, there was no correlation between PI and blood manganese concentration (r = 0.20, P = 0.427). Furthermore, the NAA/Cr ratio decreased variously in the manganese poisoning group (1.22±0.07) which was significantly lower(F =4.120, P=0.023) than those of the poisoning(1.33±0.13)and control groups (1.31±0.13). No statistical significances were found in the ratios of Cho/Cr and ml/Cr among these three groups (P>0.05). No obvious changes of the PI and NAA/Cr were found in the 8 manganese exposed workers after 1 year follow-up. Conclusion: Manganese exposure could lead to the high intensity signal on T 1WI, therefore the increased PI may be the biomarkers of central nerve system damages caused by the occupational manganese exposure. © 2010 by the Chinese Medical Association.