Review Question - QID 216686

A 51-year-old man presents to the emergency department with left arm weakness. He says that he has also been having a progressively worsening headache for the last 2 weeks. Earlier this week, he initially had clumsiness of the left hand that progressed to being unable to elevate his arm. His friends and partner have noted changes in his personality, characterizing him as now being easily irritable and prone to making hurtful statements. His past medical history is significant for HIV and his last CD4 count was 92 cells/mm3. He admits that he has only been taking one of his antiretroviral medications. His temperature is 98.6°F (37.0°C), blood pressure is 122/90 mmHg, pulse is 100/min, and respirations are 18/min. An MRI of the brain with gadolinium is shown in Figure A. Which of the following is the most appropriate next step in management?