Sudden headache and nausea need to be considered: i. Cerebral hemorrhage or subarachnoid hemorrhage, which needs to be ruled out. The headache is more severe accompanied by nausea and vomiting, and cerebral hemorrhage has symptoms such as weakness of upper and lower limbs and slurred speech. Second, migraine, manifested as severe vascular pulsating headache in unilateral head, may or may not be accompanied by blurred vision before headache, often accompanied by nausea and vomiting, with family history and recurrent attacks. Third, tension headache manifests as a dull pain in the whole brain, and in severe cases, there can also be nausea and vomiting without episodes of blurred vision. Fourth, other common diseases such as fever can also cause headache and nausea. V. Other diseases that cause increased pressure in the skull and brain, such as intracranial infection, also need to be considered.