There are many causes of left-sided brain pain in the elderly, and the common ones are as follows: 1. Insufficient blood supply to the cerebral arteries, which is a common cause of headache in the elderly, mainly due to atherosclerosis. 2. Hypertensive encephalopathy, a sharp rise in blood pressure can cause headache, nausea, vomiting and other symptoms on one side. 3. Glaucoma is also a common cause of headache in the elderly, which has a rapid onset and severe headache, and can be accompanied by loss of vision. 4. 4. neurological headache, cold, fatigue, staying up late, emotional excitement, viral infection, alcoholism, etc. are common causes of neurological headache. 5. intracranial tumors, left-sided glioma, meningioma and other intracranial occupying lesions can cause left-sided headache. 6. left-sided temporal arteritis, such patients can have left-sided headache, fever, vomiting, weakness, loss of appetite and other symptoms.