There are many reasons for sudden onset of headache, including head and neck diseases, primary headache, other diseases, etc. It is recommended that the corresponding groups of people should consult the doctor in time to clarify the causes. 1. Head and neck diseases, such as head and neck trauma, headache can appear after the trauma, accompanied by nausea and vomiting and other manifestations; cerebrovascular diseases, such as subarachnoid hemorrhage, cerebral hemorrhage, ischemic stroke and so on. 2. Primary headache: such as tension headache, trigeminal autonomic headache, acute attack of migraine, etc., or sudden onset of headache. 3. Other diseases: for example, sudden rise in blood pressure can lead to severe sudden headache, in addition to consciousness disorder, limb movement disorder and other manifestations; acute glaucoma, due to the sudden rise in intraocular pressure, can also lead to sudden headache.