They didn't find a cause with Terri.
AND if pressure were applied to her neck arteries long enough that would account for her the brain damage and cardiac arrest.
There wouldn't necessarily be any outward sign of this.
Of course, she could have been burked but if that were the case then I think there would possibly be outward signs.
First, an identifiable reason. Second, these sorts of things can happen suddenly, even in otherwise healthy young people. It is rare, but not all that uncommon.
There was a thread last night where a woman posted about her teenage son who died of a spontaneous cardiac arrest due to an electrolyte imbalance. It happens.