C9orf72 and frontotemporal dementia: Imaging-genetic studies in FTD patients with C9orf72 expansions have revealed a distributed symmetric pattern of brain atrophy in the frontal lobe (medial, dorsolateral, and orbitofrontal FTD patients with the C9orf72 expansion may have a more rapid cognitive decline related to cortical atrophy compared with other forms of FTLD-TDP (56, 57), and most C9orf72 expansion carriers with Parkinson-like symptoms respond poorly to levodopa usage (13).