[MRI of degenerative extrapyramidal syndromes. Parkinson disease, progressive supranuclear palsy and multiple system atrophy].

MR imaging of the brain, particularly with high field MR imagers, may demonstrate signal abnormalities consistent with deposits of iron or other paramagnetic substances in extrapyramidal disorders. The diagnosis of Parkinson's disease and progressive supranuclear palsy can be made on clinical grounds in most of the cases and MR signs are of little help in the diagnosis of these diseases. In patients with parkinsonian disorders poorly responding to therapy, MR imaging may be useful in demonstrating signal abnormalities in the putamen that may help to establish the diagnosis of striatonigral degeneration (component of multiple system atrophy) with a poorer prognosis than Parkinson's disease. Finally, MR imaging may be useful in the exclusion of other disease processes.