For those unfamiliar with the medico-legal definitions, brain death is a diagnosis that is made after severe brain damage from a variety of insults. It is a very specific diagnosis that is based on a host of physical examination techniques and sometimes corroborating diagnostic studies, and it means that there is evidence of irreversible cessation of ALL brain function that has been caused by total lack of blood flow to the brain. A patient who is declared brain dead is legally dead. I have diagnosed brain death dozens of times. The medical mantra is that, properly diagnosed brain death always means that there is NO brain function and that "real death" (that is, cessation of heartbeat) will inevitably ensue in coming weeks or months as the body cannot continue to function without brain function. But isn't this interesting! That we need to reassure people that "real death" will inevitably ensue seems to reveal that we recognize that brain death is not real death, but that it will, after time lead to real death! (Of course, all paths lead to real death, eventually.). Clearly this landscape is fertile ground for cognitive dissonance. Let's explore why.
When I tell a family that their relative is brain dead, and thus legally dead, I expect incredulity. Why? BECAUSE THEY'RE WATCHING THE MONITOR! They know there's a heartbeat. They know there's a blood pressure. They know that the air is going in and out and the blood is going round and round. And they know the patient is warm. They know s/he's alive in the traditional, intuitive, folkloric sense. And I'm gonna have to explain why I've just diagnosed him/her as dead. I'm going to have to tiptoe around and hem and haw and beat around the bush and use analogies, etc. Because brain death is not intuitive like real death. It's counterintuitive. Because it's a legalistic invention created to serve other purposes.