P2-287: The diagnostic utility of regional atrophy in frontotemporal degeneration

The neuropathology of frontotemporal degeneration (FTD) is centered on changes to frontal and temporal lobes. Neuroimaging findings during life, when present, are focused in frontal and temporal regions but are not required within the core consensus clinical criteria for FTD. We investigated the potential diagnostic utility of atrophy in frontotemporal regions as detected on magnetic resonance imaging (MRI). We conducted a prospective cohort study on a sample consisting of MRI data from 21 subjects with FTD and 21 age–matched controls to compare frontotemporal volumes delineated with reproducible semi–automatic brain region extraction methods. We used logistic regression to identify those regions most helpful for distinguishing FTD from controls. Linear regression tested the correlation of duration of illness to atrophy severity. Most of the frontal and temporal volumes of interest (VOIs) were significantly smaller in the FTD group than controls (p values ranging from .00001 to .035), but atrophy focused in the left anterior cingulate and medial Brodmann area 10 (medial middle frontal VOI), as well as right anterior temporal parenchyma, can distinguish 90% of the subjects with FTD from controls. The grey matter of the left medial middle frontal and the white matter of the right anterior temporal VOI accounted for the reduced volumes in these VOIs. Further logistic regression revealed that while no VOIs distinguished between the language variant of FTD and controls, the left medial middle frontal, right anterior temporal, and right superior parietal VOIs could be used to separate behavioral FTD and controls with 88% accuracy. Relative absence of atrophy in the right superior parietal area ruled out global atrophy in two subjects who would otherwise have been misclassified as controls. Among the 13 subjects with behavioral FTD, duration of illness was significantly associated with atrophy in the left orbitofrontal VOI. Atrophy on structural MRI due to FTD involves both grey and white matter compartments. Global atrophy is not supportive of the diagnosis of FTD.