Sudden onset of dizziness and headache may be caused by the following: 1. Spontaneous subarachnoid hemorrhage, a very serious central nervous system disease, mostly seen in ruptured aneurysms or arteriovenous malformations, patients may have sudden onset of severe dizziness and headache, accompanied by jet vomiting and other cranial hypertension, requiring urgent surgical treatment. 2. Brain hemorrhage, brain stem or cerebellar hemorrhage is also a common disease causing sudden onset of dizziness and headache, mostly seen in patients with hypertension. 3. 3. Cerebral tethering, patients with large cerebral tethering have sudden onset and are often first manifested by sudden dizziness, headache, hemiparesis and impaired consciousness. 4. Vascular headache, vascular headache induced by exertion, alcoholism, emotional excitement, etc., is also a common disease causing sudden dizziness and headache. 5. Fever, patients with fever whose body temperature exceeds 37.5℃ may also feel dizziness, headache and general weakness. , headache, general weakness and other symptoms, mostly seen in patients with colds and pneumonia.