Review Question - QID 216395

A 67-year-old man presents with a recurrent episode of syncope. He states that this has happened to him multiple times, particularly when he changes body position from sitting to standing, exerts himself, or turns his head quickly. He says that he notes numbness, vertigo, and sometimes even trouble with speaking immediately prior to fainting. The episodes usually last 1-5 minutes. When he wakes up, he is mildly confused but typically returns to baseline within a minute. The patient has a past medical history of diabetes, dyslipidemia, and hypertension. His temperature is 98.5°F (36.9°C), blood pressure is 153/89 mmHg, pulse is 90/min, respirations are 11/min, and oxygen saturation is 97% on room air. The patient's neurological exam is unremarkable. However, when he is asked to stand up and start walking, he experiences the same numbness and tingling and feels like he may faint. Which of the following is the most likely diagnosis?