getting hit in the head dose itause damage even if no effects are fell after around

[thatpiffFirstNameB]

30 minutes? i got slapped in the head a few weeks ago, however i got no Concussion or any other symtops of head injuries and my head was fine after around 30minutes. My question is dose there need to be symptons of head injuries in order for something like getting hit in the head to cause brain damage?