Presynaptic and postsynaptic striatal dopaminergic function in patients with manganese intoxication: A positron emission tomography study

We performed PET on four patients with chronic industrial Mn intoxication; presynaptic and postsyn aptic dopaminergic function were measured with [F-18]6-fluoro-L-dopa (6FD) and [C-11]raclopride (RAC). All patients had a rigid-akinetic syndrome; they had no sustained benefit from L-dopa. Influx constants (Ki) of 6FD were normal in the caudate and putamen. RAC binding was mildly reduced in the caudate and normal in the putamen. We conclude that nigrostriatal dopaminergic dysfunction is not responsible for the parkinsonism caused by chronic Mn intoxication. The pathology is likely to be downstream of the dopaminergic projection.