Lung cancer brain metastasis always in coma is mainly related to the stimulation or damage of brain tissues and nerves caused by cancer cells, and is also considered to be related to pulmonary encephalopathy and water-electrolyte disorders. Usually, lung cancer brain metastasis patients’ coma is related to the stimulation or damage of brain tissues and nerves caused by cancer cells, which induces insufficient cerebral blood oxygen. Meanwhile, when lung cancer patients combine with pulmonary encephalopathy, they may manifest headache, dizziness, consciousness disorder, large-scale tremor, paroxysmal muscle twitching and so on. In addition to the above factors, some lung cancer brain metastases who are always in coma are related to water-electrolyte disorders of the organism. In addition to coma, they are easy to be accompanied by thirst, nausea and vomiting, chest tightness, mental confusion, convulsions and other symptoms. If no attention is paid or treatment measures are taken, it is easy to jeopardize life. Usually, people with brain metastasis of lung cancer who are always in coma need to do further detailed examination so as to clarify the cause of the disease and then follow the doctor’s instruction for treatment. As a family member, you need to take good care of the patient during the period of coma, such as turning over and buckling the back, cleaning the genital area and oral cavity every day.