And just to make this clear for anyone reading: Just because you may be wearing a helmet isn't a guarantee of a a future concussion nor prevention of a concussion in the first place.

Cycling helmets are designed to prevent skull fractures from falls/drops. They are not designed for and cannot prevent a large enough force from allowing the brain to smack the inside of the skull if it overcomes the suspension of cerebrospinal fluid that surrounds it. The impact can be linear or rotational as well; doesn't have to be a direct deceleration impact.

-Kurt