There is such a thing as “internal decapitation” where your head separates from the spinal column but the flesh is fully intact.
One of my coworkers had this happen to her when she fell out of a moving truck. It didn’t kill or paralyze her but it could have if it hadn’t been caught. She was very, very lucky.
THAT’S the term. However, in this case, supposedly the head came rolling along after.