What are post-concussion syndrome and Second Impact Syndrome?

Post-Concussion Syndrome refers to a prolonged persistence of concussion symptoms in which a person is still experiencing symptoms of a concussion one or two months after the causal event. Second-impact syndrome refers to a second concussion after returning to activities too soon after suffering the original concussion. SIS is a major concern for young athletes who suffer concussions during recreational sports, as a second concussion can cause brain swelling and may be fatal.