The reason is that after distant metastasis occurs in other organs and organs after invasion of blood vessels, they first pass through the pulmonary circulation and metastasize to the lungs, and it is difficult to metastasize further to the brain after the filtration effect of the pulmonary circulation, while lung cancer directly enters the arterial system to distribute the whole body when distant metastasis occurs, and vertebral arteries and veins have abundant traffic branches with the brain, which can directly occur intracranial implantation and dissemination.