A 58-year-old man describes a temporary weakness in his right hand that occurred 3 days ago while driving his truck. He was unable to move his arm for 30 minutes, but he progressively regained his strength. He also had difficulty speaking around the same time with transient loss of vision. All symptoms are resolved now. His temperature is 98.4⁰ F, heart rate is 71 beats per minute, respiratory rate is 16 breaths per minute, oxygen saturation 97%, and blood pressure is 172/101 mm Hg. His past medical history is significant for diabetes, hypertension and coronary artery disease with stable angina. He has been smoking since he was 15 years-old and he currently smokes one pack of cigarettes a day. His current medications include aspirin, insulin, sublingual nitroglycerin, and metoprolol. On examination, bruits can be auscultated over both carotid arteries. The remainder of his physical examination is unremarkable. Of the following, what is your next step in management of this patient?
