When the young man is taken in for treatment, he is too confused and restless to tell what happened to him. "I'm worried about cranial injury," the doctor says, but there is no sign of any injury to the skull or scalp. On the neurological exam, the patient's pupils are equal and react to light, but their reaction is a little sluggish. Blood pressure is 142/90 mm Hg, heart rate 58 bpm, and respirations 14 breaths/min. Temperature is 98.6∘F. His hands and fingers are slightly swollen, and his jugular veins are distended. He denies any pain or stiffness and can turn his head easily in response to verbal commands. The ER doctor orders blood analysis and a neurology consult, but before the neurologist arrives, the patient is taken for a CT scan. The patient is extremely cooperative about lying still during the CT. When they finish and bring him out, though, they find it is because he is somnolent and much less responsive. On his way back to the ER, he has an episode of projectile vomiting. When he arrives back in the ER, his BP is 185/60 mm Hg, and his heart rate is 52 bpm. Respiratory rate is 8 breaths/min. The ER doctor says, "That's Cushing reflex! Something's increasing the pressure in his brain!" But what are the possibilities? Let's look at cranial anatomy for some answers. g