Secondary headache, i.e. functional headache, is caused by other diseases and has the following causes: 1. trauma; 2. cerebrovascular disease, such as cerebral hemorrhage, subarachnoid hemorrhage, massive cerebral infarction, intracranial edema; 3. intracranial tumor, pulling nerves or occupying, increased intracranial pressure; 4. intracranial infection, encephalitis, meningitis; 5. pulmonary disease, hypoxia combined with headache; 6. renal disease, intrarenal electrolyte disorder; 7. glaucoma, rhinitis, sinusitis, otitis media; 8. psychogenic headache, i.e. headache caused by psychiatric disease.