Causes of headaches commonly fall into four categories: Vascular (conditions affecting the blood vessels), tension, inflammatory and those associated with abnormalities of the cranial nerves (the nerves supplying the face, head and neck). There are no nerve endings in the brain itself.
Therefore, a headache is a painful sensation in the muscles, the skin or in some organ around the head or around the brain. The pain can be confined to a small area or cover the entire head. Some headaches are preceded by auras (sensations that things are not quite right). These auras can be visual, associated with smell, or auditory (sounds). Most headaches are benign, that is, they are self–limiting and not likely to be serious. However, some headaches are not, and they require extensive evaluation.