MR imaging of brainstem atrophy in progressive supranuclear palsy

Background: To enhance the sensitivity and specificity of the clinical diagnosis of progressive supranuclear palsy (PSP), neuroradiological parameters established in pathologically proven cases are needed. Methods: We examined brainstem atrophy in five pathologically confirmed PSP patients (three men, mean age at death 77 years, range 64-84 years). Time interval between symptom onset and MRI ranged from 1 to 5 years, and between MRI and death from 33 to 52 months. Only one patient had clinical diagnosis of PSP at the time of MRI. Control group consisted of 19 age- and gendermatched healthy subjects. Seventeen morphometric parameters of the midbrain and pons were measured on T1-weighted midsagittal and T2-weighted axial MRI scans with Image Analyzer. Measurements of superior cerebellar peduncle (SCP) width were performed on PSP autopsy specimens. Results: Mean SCP width on MRI in PSP (2.7 ± 0.8 mm, 95%CI: 2.1-3.3) was smaller than in controls (3.7 ± 0.5 mm, 95%CI: 3.5-3.9). Mean SCP width at autopsy was 8% smaller than mean SCP width on MRI. Midsagittal midbrain area in PSP (99.1 ± 6.9 mm², 95%CI: 90.5-107.6) was smaller than in controls (141.0 ± 18.1 mm², 95%CI: 132.2-149.7). Midbrain/pons area ratio in PSP was 1:5 and in controls was 1:4 (p < 0.01). Repeat MRI 17 months later in one PSP case revealed 30% decrease of SCP width. Conclusions: MR imaging with quantitative analysis may be useful in the diagnosis of early PSP and in monitoring disease course.