1. What is a headache? Headache is one of the most common symptoms in people’s lives, a manifestation of many diseases and a protective response issued by the body after being stimulated by injury. According to statistics, 80% of people will experience headache in their lifetime. Headache generally refers to pain in the upper part of the skull (i.e., above the eyebrow arch, the upper part of the auricle, and the line of the external occipital ridge), but some facial pain and neck pain are sometimes difficult to distinguish from headache in detail because they are closely related to headache. There are many causes of headache, the degree of headache varies, and the duration of headache varies from long to short, most of them are not serious so-called functional long-term chronic headache, there is no serious organic lesion in the brain of these headache patients, it does not cause serious consequences, but it affects people’s quality of life. 2.How does headache arise? Like other parts of the body, most headaches are caused by pain-causing factors (physical, chemical or biological) acting on the receptors in the pain-sensitive tissues of the head, which are transmitted to the central nervous system through the nociceptive transmission pathway for analysis and integration to produce nociception. Of course, psychogenic (mental) headache is purely a subjective experience of the patient. Various extracranial structures such as scalp, subcutaneous tissues, muscles, periosteum, blood vessels and peripheral nerves are more sensitive to painful stimuli. The intracranial structures sensitive to pain are mainly the dura, blood vessels and cranial nerves. However, the sensitivity of the above structures to pain varies depending on the location of the structure. The skull, brain parenchyma, ventricular canal, and choroid plexus, however, are not sensitive to painful stimuli. The main mechanisms of headache are: ① dilatation of intracranial and external arteries (vascular headache); ② traction or displacement of intracranial pain-sensitive tissues (traction headache); ③ inflammation of intracranial and external pain-sensitive tissues (e.g., meningeal irritation headache); ④ contraction of extracranial muscles (tension or muscle contraction headache); ⑤ direct damage or inflammation of cranial and cervical nerves that conduct pain (neuritis headache); ⑥ (6) Diffusion of pain from five sensory lesions (involvement headache). Pain-causing nerve mediators are involved in the process of headache. In addition, psychological factors can also cause headache and may be associated with a lowering of the threshold of pain tolerance. As with any pain, the severity of headache varies from person to person, and headaches in the same patient can vary depending on the physical and mental status at the time. In addition, the mechanism of headache in some diseases is often not caused by a single factor. For example, hypertensive headache has both vascular headache directly related to blood pressure and muscle contraction headache related to emotional tension, and the headache can be relieved when blood pressure is restored to normal. Understanding these is important for the prevention and treatment of headache. 3. What are the causes of headache? The causes of headache are very complicated. The general cold and fever will cause headache, the things that make people have “headache” will cause headache, the bad sleep will cause headache, the problems of organs on the head, such as glaucoma, otitis media, sinusitis will have headache, and of course, encephalitis, meningitis, brain tumor, brain hemorrhage, etc. can cause headache, and it is more intense. Some headaches can be relieved without treatment. Some headaches can be relieved without treatment, and some headaches that persist for a long time are not serious, but some headaches are often danger signs of serious diseases and may be life-threatening if not treated in time. There are many classifications of headache, and scholars from different countries classify them differently, generally divided into 14 categories, amounting to more than 250 kinds. Primary headache includes tension headache, migraine, cluster headache and cervical migraine, which are the most common ones in clinical practice. Secondary headache has four categories, including headache caused by intracranial lesions: meningoencephalitis, hemorrhagic cerebrovascular disease, ischemic cerebrovascular disease, brain tumor, brain abscess, intracranial hematoma, cyst (arachnoiditis), cerebral parasites, low cranial pressure syndrome, epileptic headache, headache after cranial injury, etc.; headache caused by extracranial head and neck lesions: such as occipital nerve, supraorbital nerve and auriculotemporal neuralgia, as well as head and neck skin, muscle, cranial bone, five senses, etc. headache caused by lesions of the skin, muscles, skull, five senses, etc.; headache caused by systemic diseases: such as infection, poisoning, high fever, hypertension, various hypoxic states (cerebral blood supply deficiency, cardiopulmonary insufficiency, anemia, plateau reaction) and hypoglycemia, etc.; headache caused by neurosis and psychosis, etc.