A concussion as I understand it refers to impact that causes brain injury and subsequent conussive symptoms. But for a PCS brain, a mild bump to the head that presumably wouldn't cause any considerable physical damage, may result in a return or worsening of symptoms due to the brain's sensitivity. Does this indicate significant new damage, or more that a very small amount of damage added to the original damage that caused the PCS in the first place results in a worsening of symptoms.

And how does this differ from other triggers that don't involve jolting movements, such as light excercise causing diziness? Is this causing damage?