Hey Vanilla Bean, second impact syndrome is when one sustains a second head injury while healing from an initial concussion. For reasons still not completely understood, rapid brain swelling(edema) ensues leading to herniation (sliding) of vulnerable parts of the brain into neighboring compartments (not a good thing). The condition is often fatal. Given that you had the time to write this post suggests to me that you shouldn't worry about second impact syndrome. Just go easy on the grog at parties so you don't re-injure! Cheers, Canadoc