As well as contact injuries, the brain is vulnerable to its own internal storms. Strokes and seizures are peculiarly human frailties. Most other mammals never suffer strokes, and for those that do it is a rare event. But for humans, it is the second most common cause of death globally, according to the World Health Organization. Why this should be is something of a mystery. As Daniel Lieberman observes in The Story of the Human Body, we have an excellent blood supply to the brain to minimize the risk of stroke and yet we get strokes.
