Cerebrovascular Disease USMLE Step 1 Practice Question

A 45-year-old man with a 10-year history of hypertension, diet-controlled, presents to the emergency department with acute onset right-sided weakness and right facial droop. Examination demonstrates dysarthria and a right pronator drift. Vital signs are BP 158/94 mmHg, HR 82, RR 14, temperature 37.2°C, SpO2 99% on room air. Cardiorespiratory examination is unremarkable with no murmurs or arrhythmias. Diffusion-weighted imaging (DWI) shows a 4 mm acute ischemic lesion in the left putamen. Subsequent laboratory workup includes a negative hypercoagulability panel, normal lipid profile (total cholesterol 160 mg/dL), normal HbA1c, normal ECG, and transthoracic echocardiography with normal ejection fraction and no evidence of thrombus or vegetation. Carotid ultrasound shows minimal atherosclerosis (<30% stenosis). Which of the following is the most likely classification of this stroke?