MAGNETIC-RESONANCE-IMAGING IN PROGRESSIVE SUPRANUCLEAR PALSY AND OTHER PARKINSONIAN DISORDERS

High field intensity MRI may demonstrate signal abnormalities consiste nt with deposits of iron or other paramagnetic substances in several e xtrapyramidal disorders. Hallervorden-Spatz disease was the only disor der widely known to have iron deposits in the pallidum, that are now e asily demonstrated in vivo by MRT. However, lower field intensity MRI may also demonstrate characteristic findings. In progressive supranucl ear palsy, definite atrophy of the midbrain and of the region around t he third ventricle is seen in slightly more than half of the cases. Mi nimal signal abnormalities are sometimes seen in the periaqueductal re gion, but MRI studies remain of little help in establishing the diagno sis of the disease. Asymmetric atrophy in the parietal regions is seen in corticobasal degeneration, as expected from pathological studies. Minimal alterations may be seen in the substantia nigra in Parkinson's disease. The most interesting MRI findings are observed in multiple s ystem atrophies. Variable abnormal signal intensities, depending on th e field intensity, are visible in the putamen in striatonigral degener ation and in Shy-Drager syndrome; in this latter condition the abnorma lities are due to its striatonigral degeneration component. Atrophy of the pens, middle cerebellar peduncles, and cerebellum, and signal abn ormalities in a characteristic distribution are visible in olivopontoc erebellar atrophy. A combination of these posterior fossa abnormalitie s and putaminal alterations may confirm the involvement of the cerebel lar and extrapyramidal systems in multiple system atrophies.