Patients with chronic liver disease manifest a high incidence (>75%) o
f pallidal signal hyperintensity on T-1-weighted Magnetic Resonance Im
aging (MRI), the intensity of which correlates with blood manganese le
vels and the presence of extrapyramidal symptoms. A major cause of pal
lidal hyperintensity on T-1-weighted MRI is manganese deposition; chro
nic manganese intoxication in the absence of liver disease results in
pallidal MR signal hyperintensity, in extrapyramidal symptoms and in s
elective effects on the dopaminergic neurotransmitter system in basal
ganglia. Direct measurements in globus pallidus obtained at autopsy fr
om patients with chronic liver disease who died in hepatic coma reveal
2 to 7-fold increases of pallidal manganese and a concomitant loss of
dopamine D-2 binding sites. Liver transplantation results in normaliz
ation of pallidal MR signals and of blood manganese levels. These find
ings suggest that (1) pallidal MR signal hyperintensity in patients wi
th chronic liver disease is the result of manganese deposition and (2)
alterations of dopaminergic function due to the toxic effects of mang
anese may contribute to the extrapyramidal symptoms in these patients.