A 28-year-old man is brought to the emergency department 20 minutes after a motor vehicle collision. On examination, he is drowsy, opens eyes to pain, and localizes to pain. His pupils are equal and reactive. CT head shows a 12 mm acute subdural hematoma with 4 mm midline shift. His GCS is 12 (E3V4M5). Vital signs are stable. What is the most appropriate next step in management?