Review Question - QID 212378

A 72-year-old man is brought into the clinic by his daughter for increasing confusion. The daughter states that over the past 2 weeks, she has noticed that the patient “seems to stare off into space.” She reports he has multiple episodes a day during which he will walk into a room and forget why. She is also worried about his balance. She endorses that he has had several falls, the worst being 3 weeks ago when he tripped on the sidewalk getting the mail. The patient denies loss of consciousness, pre-syncope, chest pain, palpitations, urinary incontinence, or bowel incontinence. He complains of headaches but denies dizziness. He reports nausea and a few episodes of non-bloody emesis but denies abdominal pain, constipation, or diarrhea. The patient’s medical history is significant for atrial fibrillation, diabetes, hypertension, hyperlipidemia, and osteoarthritis. He takes aspirin, warfarin, insulin, lisinopril, simvastatin, and ibuprofen. He drinks a half glass of whisky after dinner every night and smokes a cigar on the weekends. Her temperature is 98.7°F (37°C), blood pressure is 138/91 mmHg, pulse is 78/min, respirations are 14/min, and oxygen saturation is 98% on room air. On physical examination, he is oriented to name and place but not to date. He is unable to spell "world" backward. When asked to remember 3 words, he recalls only 2. There are no motor or sensory deficits. Which of the following is the most likely diagnosis?