T1-weighted hyperintensity in basal ganglia at brain magnetic resonance imaging: are different pathologies sharing a common mechanism?

Basal ganglia bilateral symmetric hyperintensity in T1-weighted sequences at magnetic resonance imaging (MRI) is recognized to be due to the presence of manganese deposits. This abnormal finding has been reported in occupational exposures, liver cirrhosis and total parenteral nutrition with unbalanced solutions. However, the same imaging is often observed "by chance" in brain MRIs of patients not belonging to these groups. In order to better understand which are the clinical conditions coexisting with such findings, we decided to study systematically patients which showed this kind of imaging, focusing on their manganese and iron status, as it is known that these two metals have similar properties and that iron-deficiency can competitively increase manganese absorption. The 20 patients studied underwent clinical evaluation and the following laboratory tests: whole blood iron and manganese, hemoglobin, plasma iron, transferrin and ferritin. The neuroradiologic evaluation was integrated by pallidal index calculation, in order to provide a semi-quantitative esteem of the hyperintensity. The patients could be classified into four subgroups: Parkinsonism, anemia, cirrhosis, central nervous system tumors. In 18 out of 20 cases, we found abnormalities in iron and/or manganese-related values. Particularly, iron-deficiency seems to be frequent among patients showing brain MRI abnormalities compatible with manganese deposits in basal ganglia. This observation suggests that iron-deficiency could be an important risk factor for manganese-induced neurotoxicity and should, therefore, be accurately considered and treated.