Do behavioural and cognitive deficits support FTD and ALS being on a spectrum or FTD-ALS being a unique entity?

The frontotemporal dementias (FTDs) are a group of disorders linked by presentation features combining executive, language and behavioural dysfunction. FTD includes three main clinical syndromes: behavioural variant FTD (bvFTD), semantic dementia and progressive agrammatic/non-fluent aphasia. Over the past two decades there have been significant advancements in our understanding of the biology, genetics and molecular pathology of FTD. One such advancement was the identification of TAR DNA binding protein 43 (TDP-43) in the brains of FTD patients.1 Another was the discovery that FTD can be associated with expansions in the C9ORF72 gene.2 What is intriguing is that both TDP-43 and C9ORF72 mutations are also strongly linked to another neurodegenerative disease, …