There are many causes of left headache, such as vascular migraine, sinusitis headache, otogenic headache and odontogenic headache. According to the nature of the headache and the form of its onset, there can be the following causes: 1. acute headache, mostly seen in subarachnoid hemorrhage, cerebral infarction, cerebral hemorrhage, encephalitis, meningoencephalitis, epilepsy, hypertensive encephalopathy, etc. 2. subacute headache: mostly seen in intracranial occupying lesions, benign intracranial pressure increase, hypertensive headache, etc. 3. chronic headache: mostly seen in migraine, cluster headache, tension headache, Drug-dependent headache, sinusitis, myoclonic headache, etc.