A 21-year-old man presents 20 minutes after his car hit a tree head-on. The car was traveling at ~40 miles per hour (~64 kilometers per hour) at the time of impact. He was seated in the back seat, wearing only the lap portion of the lap-sash seatbelt. He did not lose consciousness. He cannot feel or move his lower limbs now. His medical, surgical, and family histories are unremarkable. He is not on any medications currently.