Review Question - QID 217110

A 67-year-old man presents to the emergency department 1 hour after sudden-onset weakness and double vision. His medical history is significant for hyperlipidemia and poorly controlled hypertension. His current medications include atorvastatin and amlodipine. His temperature is 98.6°F (37.0°C), blood pressure is 175/95 mmHg, pulse is 90/min, respirations are 16/min. On cranial nerve exam, his left pupil is 6 mm in diameter compared to 3 mm on the right. His left eye is displaced laterally and downward and he also has left-sided ptosis. Strength is 2/5 in the right upper and right lower extremities and 5/5 in the left upper and left lower extremities. He has marked right-sided dysdiadochokinesia. Sensation is intact throughout. Which of the following regions of his brain is most likely affected?