Because patients with DLB (whose most common pattern of brain atrophy is hippocampal sparing19) and patients with AD with less hippocampal atrophy respond well to cholinesterase inhibitors,52,53 we suggest that the interplay between pattern of atrophy and the cholinergic system may be an explanation for good response to cholinergic treatment in DLB and hippocampal-sparing AD. This evidence concerns the gene BCHE and Lewy body dementia.