Quantitative regional validation of the visual rating scale for posterior cortical atrophy.

OBJECTIVES: Validate the four-point visual rating scale for posterior cortical atrophy (PCA) on magnetic resonance images (MRI) through quantitative grey matter (GM) volumetry and voxel-based morphometry (VBM) to justify its use in clinical practice.
METHODS: Two hundred twenty-nine patients with probable Alzheimer's disease and 128 with subjective memory complaints underwent 3T MRI. PCA was rated according to the visual rating scale. GM volumes of six posterior structures and the total posterior region were extracted using IBASPM and compared among PCA groups. To determine which anatomical regions contributed most to the visual scores, we used binary logistic regression. VBM compared local GM density among groups.
RESULTS: Patients were categorised according to their PCA scores: PCA-0 (n = 122), PCA-1 (n = 143), PCA-2 (n = 79), and PCA-3 (n = 13). All structures except the posterior cingulate differed significantly among groups. The inferior parietal gyrus volume discriminated the most between rating scale levels. VBM showed that PCA-1 had a lower GM volume than PCA-0 in the parietal region and other brain regions, whereas between PCA-1 and PCA-2/3 GM atrophy was mostly restricted to posterior regions.
CONCLUSIONS: The visual PCA rating scale is quantitatively validated and reliably reflects GM atrophy in parietal regions, making it a valuable tool for the daily radiological assessment of dementia. KEY POINTS: • Visual rating scale reflects grey matter atrophy in posterior brain regions. • Different PCA scores corresponded well to different quantitative degrees of atrophy. • Inferior parietal gyrus volume influenced assessment based on the visual rating scale. • This simple visual rating scale makes it useful for radiological dementia assessment.