A 58-year-old man with a 15-year history of poorly controlled hypertension presents to the emergency department with acute-onset right hemiplegia and facial droop. Non-contrast CT brain at the level of the basal ganglia is performed. The structure marked **C** in the diagram shows hypodensity consistent with acute ischemic infarction. Which of the following clinical syndromes is most consistent with a lacunar infarct affecting the posterior limb of the structure marked **C**?