Q. A 65-year-old woman is brought to the clinic by her daughter because of increased forgetfulness and having difficulties walking for the past 5 months. She has had frequent episodes of urinary incontinence during this period. She has a history of hypertension that is treated with lisinopril. She does not smoke or drink alcohol. Her mother died of brain cancer at the age of 62. Her temperature is 37°C, BP is 148/83. On the mental-state examination test, she recalls 1 out of three words immediately and does not recall any word after 5 minutes. Additionally, she has a broad-based gate with short steps. What is the most likely mechanism of these symptoms?