A knock to the head can shake the brain even when the skin looks fine. Watch for clues that start right away or build over the next day. Headache is the common first signal. It may throb, feel tight, or grow worse when you move your eyes or stand up. Thinking feels slow. You forget why you walked into a room, lose track of conversations, or give the same answer twice. Stomach trouble shows up next. You may feel queasy, throw up once, or keep vomiting long after the hit. Balance drifts. Walking turns clumsy, like weaving after spinning in... Learn more