Ego and body are not the same thing. You can have a functioning living brain and body and have your ego temporarily die. It is probably more of an emotion / feeling than anything. People who experience it for the first time sometimes panic thinking that they are actually dying because they so strongly associate their ego with their physical body / brain. When I had ego death everything including my body separated apart into grains of sand that expanded outwards from their initial solid state until there was nothing. There was nothing left for me to see, only infinite white everywhere. I felt as if I became one with the universe, time and space became meaningless, you and I became meaningless, all was I and therefor nothing was I as I had known myself, there was no more self to know there was only eternity and all within it and even it were only one thing. It is like a drop of rain that is distinctly formed as it falls from the sky and into the ocean, ego death is when your self the raindrop enters into the ocean, it still exists but it loses all form and merges into something much bigger than itself, the only reason this is not a perfect analogy is because with ego death you realize that there is NOTHING except the ocean and you stop thinking of yourself as a droplet of rain but rather as the ocean, and all the other droplets of rain are also not droplets of water they are all the ocean as well there is nothing else.