A lot of people here are confused. There are
several definitions of "concussion" but the one we are talking about here is the MEDICAL definition.
From the Mayo Clinic:
"A concussion is a traumatic brain injury that alters the way your brain functions..."
(this means that the oft repeated definition of concussion being the mere "
losing consciousness from your brain slamming into your skull" is completely incorrect. That's like listing a hematoma as "when you lose control of your car and hit the window."
"...Although concussions usually are caused by a blow to the head, they can also occur when the head and upper body are violently shaken. These injuries can cause a loss of consciousness, but most concussions do not. Because of this, some people have concussions and don't realize it."
Again, a concussion is NOT the losing of consciousness, in fact
most concussions (as stated above) do not lead to loss of consciousness. Concussions are merely physical brain damage received which is significant enough to alter your function from the damage. Damage resulting NOT NECESSARILY from blows to the head (although that is the most common way). You've all heard of 'correlation does not = causation'. Well, even more obviously, "correlation does not equal definition."
"...every concussion injures your brain to some extent"
This does not mean you have to be hit in the skull to injure your brain/get a concussion.
We already have a neurologist in this thread saying that they aren't the same thing, but everyone wants to kneejerk and pile on to establish the 1st layman's internet definition as the ultimate standard. Clearly, it is not.
Read the whole article, it's interesting and it only takes 20 seconds, if that.
http://www.mayoclinic.org/diseases-conditions/concussion/basics/definition/CON-20019272