I have a hard time believing those stories though.
If a sudden blood pressure drop is enough to make someone fall unconscious immediately with blood still flowing to the brain, then a full blood pressure drop with no blood flowing to the brain should have the same effect.
If I had to guess, eye and mouth movements are probably from the nerves going crazy after being severed at the brain stem.
I had heard anecdotes of the head surviving for several seconds before death in that case. The aesthetic is top tier though.
I have a hard time believing those stories though.
If a sudden blood pressure drop is enough to make someone fall unconscious immediately with blood still flowing to the brain, then a full blood pressure drop with no blood flowing to the brain should have the same effect.
If I had to guess, eye and mouth movements are probably from the nerves going crazy after being severed at the brain stem.