Solved!

Not to bring this thread up again but just to end it with some good trustworthy news on this question, if anyone else are to wonder if this can happen, the answer is apparently a most definite no!

Today I've been talking with my local doctor about my earlier concussion many years ago, which also, since she declared it was a mild one I had, it can no longer affect my performance at all. According to her, rotating/shaking your head from side to side, rapidly or not, cannot under any circumstance cause a concussion unless it happened in a car crash with rear end collision. It requires a lot more force than a quick shaking, even if it is followed by a sudden change in rotation!

Just to confirm everything.
Good day to you all!