Big symptoms (if you're looking at the brain, that is) include brain shrinkage (some of which is normal as part of the aging process). The folds of the brain in a normal brain are much less pronounced than one afflicted with the disease, these folds are known as intraparietal sulci, and they widen dramatically as the disease progresses.
The hippocampus and amygdala are two major structures that help with memory, and these are also areas heavily damaged by the disease.
The parietal regions are often the most affected, leaving the frontal area less atrophied than usual.
The lateral ventricles also are enlarged.
The atrophy of unhealthy brain tissue causes blood to limited, which, of course, can be a bad thing, accelerating the disease and eventual death.