Review Question - QID 214258

A 68-year-old man is brought to his physician by his wife due to issues with his memory. His wife reports that she has noticed him having issues with his memory for the past year. He appears more fatigued and has had difficulty with walking. She denies him having episodes of urinary incontinence or recent falls. He can no longer cook for himself as he has forgotten to turn off the stove multiple times. He also has impaired short-term memory, such that he forgets family members are going to visit him even though he was told so earlier in the day. He has a medical history of hypertension and hyperlipidemia and currently takes lisinopril and simvastatin. His father had Alzheimer dementia, and his mother was otherwise healthy. On physical examination, the patient is alert to self and place but does not know the year. He has 0/3 in delayed recall. He has decreased vibration and proprioception sense in his bilateral lower extremities, as well as 3+ patellar reflexes. His gait is mildly unstable, and when his eyes are closed he has issues with balance. Which of the following is the most likely the diagnosis?