There is marked cerebral atrophy with ex vacuo ventricular dilation. This degree and extent of atrophy, symmetrical and most marked in frontal, temporal, and parietal lobes, is most typical for Alzheimer disease, the most common form of dementia seen in older persons. There is neurologic decline with progressive memory loss with increasing inability to participate in activities of daily living. The course is usually over 5 to 7 years.