A 58-year-old man with a 12-year history of poorly controlled hypertension and type 2 diabetes presents with acute onset weakness of the right face, arm, and leg occurring 2 hours ago. CT brain shows a small hypodense lesion in the region marked **C** on the axial basal ganglia level image. Neurological examination reveals equal weakness across face, arm, and leg with intact language, normal visual fields, and normal sensation. Which of the following best explains the clinical presentation and guides acute management?