Could it be the fluid in the cranial cavity of the brain? You'd better go to the hospital for a brain CT.

Because I have seen a movie starring Liu Qingyun, whose name seems to be Detective. He was shot in the head, but miraculously survived with a runny nose for no reason. The doctor told him that the wound between his nasal cavity and his brain could not be completely healed, that is, there was a hole in his brain. . . . Some brain fluid will flow out of this hole.

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