C9orf72 and frontotemporal dementia: This result was confirmed by a recent large study on genetic FTD,33 which reported 5–8% smaller volumes of the superior cerebellar peduncle, midbrain and pons in GRN mutation carriers, 9% smaller midbrain volumes in MAPT mutation carriers, but no difference in C9orf72 expansion carriers, nor in any presymptomatic carriers.