Shape analysis of the neostriatum in frontotemporal lobar degeneration, Alzheimer's disease, and controls

Background and purpose: Frontostriatal circuit mediated cognitive dysfunction has been implicated in frontotemporal lobar degeneration (FTLD), but not Alzheimer's disease, or healthy aging. We measured the neostriatum (caudate nucleus and putamen) volume in FTLD (n=34), in comparison with controls (n=27) and Alzheimer's disease (AD, n=19) subjects. Methods: Diagnoses were based on international consensus criteria. Manual bilateral segmentation of the caudate nucleus and putamen was conducted blind to diagnosis by a single analyst, on MRI scans using a standardized protocol. Intra-cranial volume was calculated via a stereological point counting technique and was used for scaling the shape analysis. The manual segmentation binaries were analyzed using UNC Shape Analysis tools (University of North Carolina) to perform comparisons among FTLD, AD, and controls for global shape, local p-value significance maps, and mean magnitude of shape displacement. Results: Shape analysis revealed that there was significant shape difference between FTLD, AD, and controls, consistent with the predicted frontostriatal dysfunction and of significant magnitude, as measured by displacement maps. There was a lateralized difference in shape for the left caudate for FTLD compared to AD; non-specific global atrophy in AD compared to controls; while FTLD showed a more specific pattern in regions relaying fronto- and corticostriatal circuits. Conclusions: Shape analysis shows regional specificity of atrophy, manifest as shape deflation, with implications for frontostriatal and corticostriatal motoric circuits, in FTLD, AD, and controls.