frontotemporal lobe dementia symptomsfrontal lobe function dementiatemporal lobe atrophy dementiafrontotemporal lobe dementia stagesfrontal lobe dementia deathfrontotemporal lobefronto temporal lobe dementiaprefrontal lobe dementiafrontal lobe deteriorationtemporal lobe dementiafrontotemporal lobe degenerationfrontal lobe dementia treatment