Once encountered such a thing: Zhang was young and exuberant, once for a small matter and neighbors Wang Mou fight, Wang Mou hit his head with a stick, immediately, swelling a large lump. Zhang took Wang to court, claiming that the headache and dizziness was unbearable, and must have been beaten by Wang into a “concussion”, which would certainly leave many sequelae, demanding compensation. The forensic pathologist asked Zhang in detail whether there was a coma at the time, the witness said no; the judge also asked about the situation at the time of the brawl, Zhang answered, memory is very clear. So the forensic physician identified as a scalp hematoma. Zhang shouted injustice, angrily asked the forensic pathologist, I have such a strong headache and dizziness, but still can not be designated as “concussion”? So, what exactly is a concussion? What is the basis of diagnosis? Concussion is produced by an external blow to the head, the patient immediately becomes unconscious, manifesting as confusion or complete coma, which can last from a few seconds to a few minutes, generally not more than half an hour. Upon awakening, the patient cannot immediately recall what happened at the time of the injury or even some time before the injury; this memory deficit is called retrograde amnesia. During the period of impaired consciousness, the patient may have pale skin, sweating, decreased blood pressure, bradycardia, shallow and slow breathing, and decreased muscle tone, but soon normalizes with recovery of consciousness. Thereafter, the patient may have headache, dizziness, nausea, vomiting and other symptoms, which usually improve on their own within a short period of time. Therefore, simple headache and dizziness after trauma cannot be designated as concussion. The diagnosis of concussion should be based on the following two items; (i) impairment of consciousness immediately after trauma; (ii) retrograde amnesia after recovery of consciousness.