Ok that makes sense. Just to clarify, the activator might not be particularly useful with c-1, but the risk is low even if it's being used right at the base of the skull/upper neck?

In other words, the activator isn't likely to aggravate any brain swelling even if it's used right up there in that area?

And twisting of the neck type of adjustment might pose a slightly greater risk? And if so, this risk is just a general risk about doing those type of adjustments in the neck, or is it more risky in regards to the concussion specifically?