A 76-year-old man is admitted to the hospital for evaluation of progressive memory loss and disorientation. The pupils are small but react normally to light. Muscle tone is normal. A lumbar puncture returns clear, colorless CSF under normal pressure. An electroencephalogram shows diffuse slowing. A CT scan of the brain reveals moderate atrophy. Which of the following is the most likely diagnosis?
Alzheimer disease Creutzfeldt-Jakob disease Glioblastoma multiforme Huntington disease