The most serious case of lung cancer is the appearance of extrathoracic metastasis, that is, distant metastasis, which is seen in small cell lung cancer and is easy to appear in the late stage of lung cancer. It can metastasize to the central nervous system, and patients will show signs of increased intracranial pressure, such as headache, nausea, vomiting, and in severe cases, seizures, hemiparesis, unsteady walking, disorientation and speech disorders, as well as changes in mental and psychiatric status such as drowsiness and coma.