Analysis of 1,821 Alzheimer’s brains has found that 11% of them actually suffered from a variant called hippocampal sparing Alzheimer’s. This subtype has been neither well recognized nor treated appropriately, but is now revealed to be relatively common.
The variant often produces symptoms that are substantially different from the most commonly known form of Alzheimer’s (e.g., frequent and sometimes profane angry outbursts, feelings that their limbs do not belong to them and are controlled by an "alien" unidentifiable force, or visual disturbances in the absence of eye problems), and because their memory is often little affected, they’re often misdiagnosed — often with frontotemporal dementia, or corticobasal syndrome. The problem mostly affects males, and at a much younger age than normal for Alzheimer’s. Correct diagnosis is particularly important because there is evidence that some Alzheimer’s drugs may work better with this variant than they do with the normal form.
The study was presented at the annual meeting of the American Academy of Neurology in Philadelphia, May 2014.