Michael Paul Mason is one of an elite group of experts who appear in the wake of tragic accidents and coordinate care that can last a lifetime. On the road with Mason, we encounter survivors of brain injuries as they struggle to map and make sense of the new worlds they inhabit. We meet a snowboarder whose life became permanently surreal after an errant jump; an "ultra-violent" child who has lost the brain's instinctive check on the impulse to strike out at others; a young man who cannot cry; and an Iraq war veteran whose odd maladies suggest that brain injury will be the war's most conspicuous legacy.Underlying each of their stories is an exploration into the brain and its mysteries. When injured, the brain must figure out how to heal itself, reorganizing its physiology in order to do the job, and Mason gives us a series of vivid glimpses into brain science, the last frontier of medicine. We come away in awe of the miracles of the brain's workings and astonished at the fragility of the brain and the sense of self, life, and order that resides there. "Head Cases" echoes both Oliver Sacks and Raymond Carver, and is at once illuminating and deeply affecting.