C9orf72 and frontotemporal dementia: Overall, the presence of C9orf72 expansions is typically associated with greater thalamic and cerebellar atrophy across the ALS–FTD spectrum [19,45,55,56,57], leading to the suggestion that, despite not being unique to the genetic cases, abnormalities in these structures, most notably the thalamus [58], could be a signature of C9orf72 expansions [57].