Frontotemporal dementia as a frontostriatal disorder: Neostriatal morphology as a biomarker and structural basis for an endophenotype

Objective: This article reviews the evidence for a re-conceptualisation of a subtype of frontotemporal lobar degeneration (FTLD), frontotemporal dementia (FTD), as a frontostriatal disorder, working towards an endophenotype. Method: We provide an overview of the role of frontostriatal circuits relevant to FTLD and FTD, as a subset of larger-scale distributed brain networks. We discuss the role of a strategic structure in these circuits, the neostriatum. Then we review the relationship of the clinical features of FTLD to frontostriatal circuits, correlating this with neuropsychological and neuropathological data. Conclusion: The unique structure and linkages of the neostriatum make it an ideal structure for in vivo neuroimaging to understand the neuroanatomical basis of FTD. We develop a frontostriatal endophenotypic model for FTD as a platform for further investigation.