Imaging signatures of molecular pathology in behavioral variant frontotemporal dementia

Abstract

Pathology underlying behavioral variant frontotemporal dementia (bvFTD) is heterogeneous, with the most common pathologies being Pick's disease (PiD), corticobasal degeneration (CBD), and FTLD-TDP type 1. Clinical features are unhelpful in differentiating these pathologies. We aimed to determine whether imaging atrophy patterns differ across these pathologies in bvFTD subjects. We identified 15 bvFTD subjects that had volumetric MRI during life and autopsy: five with PiD, five CBD, and five FTLD-TDP type 1. Voxel-based morphometry was used to assess atrophy patterns in each bvFTD group compared to 20 age- and gender-matched controls. All three pathological groups showed gray matter loss in frontal lobes, although specific patterns of atrophy differed across groups: PiD showed widespread loss in frontal lobes with additional involvement of anterior temporal lobes; CBD showed subtle patterns of loss involving posterior lateral and medial superior frontal lobe; and FTLD-TDP type 1 showed widespread loss in frontal, temporal, and parietal lobes. Greater parietal loss was observed in FTLD-TDP type 1 compared to both other groups, and greater anterior temporal and medial frontal loss was observed in PiD compared to CBD. Imaging patterns of atrophy in bvFTD vary according to pathological diagnosis and may therefore be helpful in predicting these pathologies in bvFTD.

Figure 1

Patterns of grey matter loss observed in bvFTD subjects with PiD, CBD or FTLD-TDP type 1 pathology compared to controls. Results are shown uncorrected for multiple comparisons at p<0.001 on medial and lateral three dimensional renderings of the brain.

Figure 2

Regions of grey matter loss that were different between the bvFTD subjects with PiD, CBD or FTLD-TDP type 1 pathology. The top panel shows regions of greater loss in PiD compared to CBD; the middle panel shows regions of greater loss in FTLD-TDP type 1 compared to CBD; and the bottom panel shows regions of greater loss in FTLD-TDP type 1 compared to PiD. Results are shown uncorrected for multiple comparisons at p<0.001 on medial and lateral three dimensional renderings of the brain.