MR Imaging of the Superior Profile of the Midbrain: Differential Diagnosis between Progressive Supranuclear Palsy and Parkinson

BACKGROUND AND PURPOSE: Quantitative evaluation of midbrain atrophy may be useful in differentiating progressive supranulear palsy (PSP) from Parkinson disease (PD); however, this finding is not specific of PSP, and quantitative measurements are not always practical. We determined whether an abnormal superior midbrain profile (flat or concave aspect) is a more practical diagnostic parameter for PSP. METHODS: MR imaging studies of 25 patients with PSP and 27 with PD were reviewed by means of five parameters: midbrain superior profile on midsagittal T1-weighted images, midbrain atrophy, tegmental abnormal T2 hyperintensity, abnormal T2 putaminal hypointen-sity or hyperintensity on axial proton density–weighted images. We also measured the antero-posterior diameter of the midbrain on axial T2-weighted sections at the level of the superior colliculus. RESULTS: The finding of an abnormal superior profile of the midbrain had 68 % sensitivity and 88.8 % specificity. Midbrain atrophy had 68 % sensitivity and 77.7 % specificity. Tegmental T2 hyperintensity had 100 % specificity but poor sensitivity (28%). Only 14.8 % of patients with PD and 24 % of those with PSP had abnormal putaminal T2 hypointensity; none had proton