Brain metastasis drowsiness may be due to tumor cells proliferation in the brain caused by brain hypoxia and ischemia or brainstem upstream activation system is damaged leading to the appearance of drowsiness. The occurrence of brain metastasis means that the malignant tumor has reached an advanced stage, and its proliferation in the brain needs a large amount of nutrients, and the supply of nutrients is mainly through the delivery of blood through blood vessels, therefore, it will lead to the lack of blood supply to the normal brain tissue parts, which will ultimately cause the obstruction of the normal tissue operation, and the appearance of dizziness, lethargy and other symptoms. In addition, brain metastasis will cause brain hernia, hydrocephalus, cerebral edema, etc., leading to the damage of brainstem upstream activation system, resulting in the emergence of drowsiness, coma and other consciousness disorders. Tumor patients with the above conditions, please seek timely medical treatment for reasonable and standardized diagnosis and treatment.