So what do you look for if you're worried about a concussion?
Critical point number alpha and omega: Just about anything. Or to come at this from another angle, remember what is being injured --- the brain --- and how important that is to any and everything that a person thinks, says, or does. You pretty much want to have what physicians call "a high index of suspicion" for any sign of neurological damage, no matter how small. Because there really isn't any such thing as a "small" brain injury.
In fact, it is probably less critical that you can list the dozen or so symptoms of brain injury, than it is that you simply decide, right here and now, that anything fishy you come across, you will deal with decisively by removing the injured party from further potentially head traumatizing situations. If you do this, and do not allow the athlete to return to activity until he or she is 100% symptom-free for a safe enough period (determined by a doctor), you will have absorbed what you need to save lives. Please read this paragraph again.
In my experience as a sports medicine physician, scary things happen to concussed athletes, not because of subtle nuances that go missed that only superspecialists could have picked-up, but because common sense, obvious symptoms go deliberately overlooked, usually by family, friends, teammates, and coaching/teaching staff. Sometimes the problem is one of education, and that's what I hope articles like this will help to correct: if you didn't know how serious this stuff was, well, now you know.
And what is it you need to look for? Again, read the above: pretty darn much anything out of the ordinary. That wet bag of neurons is the most precious asset any of us will ever possess, more valuable than 2 or 3 mortgages, half a dozen or so new cars, and a lifetime of airline tickets, martial arts gear, and donated internal organs or fluids *combined*, since all those other things depend upon it. If you'd jump on the teeniest irregularity on your monthly credit card statement, the smallest ding in your car door after a valet parks it, the most minute misspelling of your name on a tournament roster, you should damn well be all *over* any irregularity of brain function.
So here's some of what counts as irregularity, from the relatively subtle to the obvious:
First, any deviation from the crisp, I'm-all-there awareness that the athlete normally exhibits. On the mat, this often shows up as a brief disorientation after a throw or a head blow: a slowing down, a not knowing what just happened, a not doing the bow correctly or just wandering off the mat, or missing part of an easy sequence of partnered moves with the next round. On the football field, this would be the player being on the wrong part of the field, or getting up off the ground too slowly. Something just doesn't look right, because it isn't.
Next, any obvious neurological symptoms. Headaches, dizziness, blurred vision, tingling or numbness, weakness are biggies. Nausea and vomiting can accompany head trauma, too. It goes without saying that anyone who gets knocked out --- even for a second or two --- or has a gap in memory is out, out, out; loss of consciousness and amnesia are on the more severe end of concussion spectrum symptoms. (And by the way, you should treat any unconscious athlete as if he or she has a broken neck until proven otherwise: they can't tell you that they heard a snap before the lights went out, and the last thing you want to do is perform resuscitative kappo, or wave smelling salts under their nose to get their head flopping back and forth, severing the spinal cord. Let the paramedics, or doctors, or whatever medical personnel you access bring them back!)
Most important, perhaps, are the more long lasting symptoms after the workout or tournament. Headaches that won't go away, or keep coming back. Difficulty sleeping. Problems concentrating in class or at work. Wanting to sleep all the time. Acting unusually quiet, or irritable, like the athlete's "not feeling well." If I read one more newspaper story about an athlete's teammates or friends who noticed how strangely he was behaving and feeling in the weeks before he got hit again and died, I'm going to scream.
The above is not an all inclusive list. You or your friend are not okay just because you can convince yourselves that your symptoms don't fall under these specs. You should be able to get the gist of things from these examples, not be transformed into a medical doctor with matside experience. There's a difference between feeling that everything is perfectly fine, and that something is not quite right; with ankles, for example, things are probably fine even if they don't seem quite right, but with the brain, everything is wrong, wrong, wrong unless it's perfectly properly fine. You can play with a sprained ankle or even a fractured fibula in your lower leg; getting hit again after a recent concussion can kill you or effectively render you unememployable and a liability to you loved ones for a very long time.
So if you suspect someone has gotten concussed, take them out of the action right now. They will probably be fine if they get immediate medical attention, and this can be as simple as a ten minute mat consultation with a tournament physician. Don't let them get back into things while they have even a hint of symptoms --- this is where most of the real damage occurs, re-injuring an injured brain --- and better still, don't let them back until a doctor says enough symptom-free time has passed to be safe. And please, don't listen to any advice --- even if it comes from a doctor --- that says it's okay to "suck it up" and keep going if you're still seeing "minor" symptoms, like "a little" dizziness, or "a little" nausea, or "a little" headache. That kind of nonsense is actually very unlikely to come from a physician; it usually comes from the injured party him or herself, who will often hide symptoms to avoid jeopardizing continued participation. This kind of attitude has got to stop; athletes must regularly see that it's SOP to get this kind of thing checked out, and thus, to be taken in stride, not huddled away in hushed secret. And if not, the athlete has to be yanked to the doctor. His or her brain and future are worth saving, even if it's not obvious to them at the time.
For Further Reading: http://www.aafp.org/afp/990901ap/887.html and http://www.aafp.org/afp/20010915/1007.html