Athletes at the youth and high school level should not be allowed to
return to play in the same game or practice even if all post-concussion
signs or symptoms clear, because of the risk of second
impact syndrome (SIS), which occurs when an athlete who sustains head
trauma, i.e. a traumatic brain injury - often a concussion or worse
injury, such as a cerebral contusion (bruised brain) - sustains a
second head injury before signs of the initial injury have cleared. It
is preferable for athletes suffering even a mild concussion
not to return to play for at least one week in order to allow time for
evaluating and treating the concussion and for the
brain to heal.