If the head is knocked, headache, nausea, vomiting may occur, and there may also be unclear consciousness, limb movement, or even epilepsy or incontinence, depending on what kind of condition occurs after the head is knocked. If the patient has a simple head trauma that does not cause brain tissue damage, he or she will have a mild headache and may be a little dizzy. If a concussion is caused, the patient will experience a brief coma and retrograde amnesia, as well as a slightly more severe headache, nausea, and vomiting. If an intracranial hemorrhage is caused, which is more severe, the patient is also likely to experience severe unconsciousness, hemiparesis, incontinence, and in some cases, seizures as a result. If a skull base fracture occurs, cerebrospinal fluid leakage from the ear or cerebrospinal fluid leakage from the nose may occur.