GRN and frontotemporal dementia: While several segmentation studies have found LGN volume reductions in symptomatic C9orf72 expansion carriers,7,9,26 one study did not corroborate this finding in C9orf72-associated FTD-ALS.8 The LGN relays visual information, and it has been proposed that its atrophy may be related to visual hallucinations that C9orf72 expansion carriers experience.26 The MeD, one of the most affected subregions in symptomatic GRN mutation carriers, has reciprocal connections with the dorsolateral prefrontal cortex,33 which is affected early7 and severely9 in this genetic group.