C9orf72 and frontotemporal dementia: As in our bvFTD cohort (and with similar limitations noted above and in the “Limitations” section), given the high prevalence of C9orf72 carriers among ALS‐FTD patients [15, 16], it is possible that the pronounced thalamic atrophy observed in our cohort of unknown genetic status may in part be driven by the presence of C9orf72 cases.