Question: what are the causes of headaches

Reference:
 Headaches - danger signs Migraine headache - danger signs Tension headache - danger signs Cluster headache - danger signs Vascular headache - danger signs Summary A headache is a pain or discomfort in the head, scalp, or neck. Common types of headaches include tension headaches, migraine or cluster headaches, sinus headaches, and headaches that begin in your neck. You may have a mild headache with a cold, the flu, or other viral illnesses when you also have a low fever. Most people with headaches feel better by making lifestyle changes, such as learning ways to relax. Taking certain medicines, such as pain medicine, may also help. Emergency Causes of Headaches Problems with blood vessels and bleeding in the brain can cause a headache. These problems include: Abnormal connection between the arteries and veins in the brain that usually forms before birth. This problem is called an arteriovenous malformation, or AVM. Blood flow to part of the brain stops. This is called a stroke. Weakening of the wall of a blood vessel that can break open and bleed into the brain. This is known as a brain aneurysm. Bleeding in the brain. This is called an intracerebral hematoma. Bleeding around the brain. This can be a subarachnoid hemorrhage, a subdural hematoma, or an epidural hematoma. Other causes of headaches that should be checked by a health care provider right away include: Acute hydrocephalus, which results from an interruption of cerebrospinal fluid flow. Blood pressure that is very high. Brain tumor. Brain swelling (brain edema) from altitude sickness, carbon monoxide poisoning, or acute brain injury. Buildup of pressure inside the skull that appears to be, but is not, a tumor (pseudotumor cerebri). Infection in the brain or the tissue that surrounds the brain, as well as a brain abscess. Swollen, inflamed artery that supplies blood to part of the head, temple, and neck area (temporal arteritis). When to Call the Doctor If you cannot see your provider right away, go to the emergency room or call 911 if: This is the first severe headache you have ever had in your life and it interferes with your daily activities. You develop a headache right after activities such as weightlifting, aerobics, jogging, or sex. Your headache comes on suddenly and is explosive or violent. Your headache is "the worst ever," even if you regularly get headaches. You also have slurred speech, a change in vision, problems moving your arms or legs, loss of balance, confusion, or memory loss with your headache. Your headache gets worse over 24 hours. You also have fever, stiff neck, nausea, and vomiting with your headache. Your headache occurs with a head injury. Your headache is severe and just in one eye, with redness in that eye. You just started getting headaches, especially if your are older than 50. You have headaches along with vision problems and pain while chewing, or weight loss. You have a history of cancer and develop a new headache. Your immune system is weakened by disease (such as HIV infection) or by medicines (such as chemotherapy drugs and steroids). See your provider soon if: Your headaches wake you up from sleep. A headache lasts more than a few days. Headaches are worse in the morning. You have a history of headaches but they have changed in pattern or intensity . You have headaches often and there is no known cause. Review Date 11/22/2017 Updated by: Luc Jasmin, MD, PhD, FRCS (C), FACS, Department of Surgery at Providence Medical Center, Medford OR; Department of Surgery at Ashland Community Hospital, Ashland OR; Department of Maxillofacial Surgery at UCSF, San Francisco CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. 

Answer: Some headaches can be dangerous, if they are related to problems with blood vessels and bleeding in the brain. These types of headaches may be caused by abnormal connection between the arteries and veins in the brain that usually forms before birth. Other possible causes include a stroke, a brain aneurysm, high blood pressure, or carbon monoxide poisoning.