A 65-year-old man comes to the ·office due to unsteady gait and frequent falls over the past 2 months. His left side feels "weak," which makes it difficult to maintain balance when walking or standing. He has also had headaches and nausea, which are worse in the mornings before he has had coffee. The patient has a history of hypertension and type 2 diabetes mellitus, and he had a myocardial infarction 5 years ago. He takes insulin for diabetes mellitus but does not routinely monitor his blood glucose. The patient is a former smoker and does not use alcohol or illicit drugs. Blood pressure is 130/80 mm Hg and pulse is 76/min. Ambulation results in the patient swaying to the left and using the wall to brace himself. There is increased resistance to passive flexion of the left upper and lower extremity.