What is second impact syndrome (SIS)?

Second impact syndrome (SIS) refers specifically to a critical medical condition that can occur when an individual sustains a second concussion before fully recovering from a prior concussion. This rapid second impact can lead to severe and potentially life-threatening swelling of the brain. The brain, already vulnerable from the first injury, is susceptible to significant damage when subjected to a second trauma. The swelling associated with SIS can lead to catastrophic consequences such as coma or even death if not addressed immediately.

Understanding SIS is crucial for athletes, coaches, and medical professionals to ensure proper assessment and management of concussions, as it highlights the importance of allowing sufficient recovery time after an initial concussion before returning to contact sports or activities. The other options describe various conditions related to injuries or inflammation, but they do not capture the specific and acute nature of the swelling caused by a second concussion as seen in second impact syndrome.