A 22-year-old man presents to the emergency department after a head injury sustained during a collegiate football game. He collided helmet-to-helmet with another player and was knocked unconscious for approximately 1 minute. He now complains of a worsening, generalized headache, nausea, and feeling “in a fog.” His past medical history is unremarkable, and he takes no medications. He has no known allergies. He does not smoke, drink alcohol, or use recreational drugs.

He is alert and answers questions appropriately, though slightly slowly. His blood pressure is 125/78 mmHg with a heart rate of 78 bpm, a respiratory rate of 16 breaths per minute, and a temperature of 98.6°F.