The causes of headache can be roughly divided into two categories: secondary and primary. Secondary headache means that this kind of headache has a clear cause, which is secondary to other diseases, such as head trauma, meningitis, cerebral hemorrhage, brain tumors, temporal arteritis, cerebral vein thrombosis, and low intracranial pressure headache. These head diseases may cause headache. Some systemic diseases can also cause headache, such as hepatic encephalopathy, renal encephalopathy, respiratory failure, rheumatic immune diseases. Another major category is primary headache, which means that the cause of headache is not yet clear and the pathogenesis is not yet clear, including migraine, cluster headache, tension headache, and other headaches of unknown causes.
