Case History: Case T

An 82-year-old woman started having more severe problems with memory. She could no longer remember appointments or balance her checkbook. This became increasingly worse over a 2-year period. Lab tests were normal and CT scan showed only cortical atrophy, as illustrated in the gross coronal section here. She was placed in an assisted living facility for patients with severe memory loss. She died 3 years later. Brain autopsy was performed. What is the most likely diagnosis?