by and large, the "research world" is only using grades, which are still entirely arbitrary as you can connect any level of importance or weight whatever symptom you'd like, however you'd like, because they have zero impact on predicting outcomes, dictating treatment, or how that concussed individual is going to, or what treatment they will respond to, to simplyl quantify some symptoms that they noted. and they won't even translate to other researchers by their giving of some grade. The breakdown of catagories should be given in the methods for any study and again, leave the need for a meaningless grade out like everyone else.
Not even sure why these guys did use that language in their study other then all they did was look at older data. and obviously some concussions are more severe than others, that wasn't my point. The point was, we don't grade them because what we used to think were important, didn't seem to have much impact on outcomes or predicting them. and as I said previously, I"m sure we may grade them again, once we have something besides arbitrary importance placed on things that may or many not mean anything in the long run.