Headache, it is a difficult topic with great erudition; it is also a headache-inducing symptom that seems simple, but the mechanism behind it is very complex. It can’t be helped, because it is so common and is encountered almost every day in the emergency room. Without understanding the situation, sometimes patients and family members are very nervous about a headache that is nothing, and they call 120 to the emergency room in a hurry, and they are afraid; or sometimes it is a life-threatening disease, but patients and family members think it is a common symptom and it is not a big deal, so they miss the best time to see the doctor, causing irreversible consequences. Therefore, the purpose of introducing headache here is at least to let people know what needs to be dealt with urgently and sent to hospital immediately, and what can be taken easy, and to understand a little bit about prevention and treatment, so that they can better choose treatment and prevention programs. First, let’s define headache as a headache in the upper part of the skull (above the line between the arch of the eyebrows, the upper part of the auricle and the external occipital ridge). The mechanism of headache is caused by stimulation of pain-sensitive structures in the head. Interestingly, the vast majority of brain tissue does not have nociceptive receptors of its own. There are many structures that cause headache, including the skin, subcutaneous tissue, subscalp muscles, extracranial arteries, and intracranial periosteum; the eyes, ears, nose, and sinuses. Inside the skull, there are venous sinuses and several nearby branches, the dura mater and aorta at the base of the brain, the middle meningeal artery, the superficial temporal artery, the trigeminal nerve and other cerebral nerves. Headache is a super common symptom, about 90% of people will have at least 1 headache in a year. 3% of emergency patients complain of headache as a symptom. From the perspective of etiology, they can be classified into primary headaches, which are headaches without other diseases, and secondary headaches, which often have a clear etiology leading to headaches such as subarachnoid hemorrhage, meningitis, temporal arteritis, etc. Overall, there are two types of headaches, safe headaches and dangerous headaches. Of course, the former is the main one, more than 90% of them are relatively safe headaches, at least they do not cause life threatening, at most they bring temporary discomfort and affect work and life. The latter is rare, but the mind should be alerted to the fact that sometimes, missing a day can miss a valuable opportunity to save the day and cause the patient permanent and severe dysfunction or even death. The most common primary headaches are migraines and tension headaches, both of which are recurrent but cause only temporary discomfort and generally have no serious consequences. What kinds of headaches have serious consequences? Often some types of secondary headaches: mainly subarachnoid hemorrhage, acute meningitis, acute encephalitis, other intracranial hemorrhage such as cerebral hemorrhage, subdural hematoma, epidural hematoma, cerebral venous sinus thrombosis, cerebral artery entrapment, temporal arteritis, etc. These require a series of evaluations including imaging tests such as head CT quickly to determine the cause of the headache and choose the appropriate treatment. How can we promptly identify patients with these potentially risky headaches? Table 1 helps to identify them, and the following signs should be promptly seen in the hospital to improve the relevant tests. I once met a patient who had fever with severe headache as the main symptom, thought he had a cold, and after taking oral antibiotics for 3 days, his symptoms were reduced and he thought he was fine, so he stopped taking antibiotics. Bacterial meningitis, if not treated in time, may leave sequelae such as limb paralysis, mental retardation, epilepsy, hydrocephalus, and even risk of death. It is still very scary. As you can see, some headaches should not be taken care of. Since tension headache and migraine are the two most common types of primary headache, the following is a brief introduction to these two diseases. Tension headache is the most prevalent headache, with a global prevalence of 38%, accounting for 70-80% of headache sufferers. The pathogenesis is not yet clear. The site of pain is usually bilateral, more often in the occipital, temporal or frontal regions, or often in the entire head. The headache is usually mild to moderate and does not interfere with daily activities. The pain sensation is mostly pressure, tightness, swelling, dull pain, or soreness, and may even be expressed as a feeling of going to explode. There is no persistent throbbing sensation, usually not accompanied by nausea and vomiting, not accompanied by photophobia and phonophobia, and daily physical activities do not cause the pain to worsen, but stress and mental tension often aggravate the condition. (The part in parentheses emphasizes the difference from migraine.) Some patients describe seemingly having a band tightly around their head (Figure 2), and others may have the sensation of wearing a tight band. Treatment is mainly non-pharmacological, pharmacological during acute attacks and prophylactic medication. Non-pharmacological treatments include relaxation training, cognitive behavioral therapy, and acupuncture. Some over-the-counter pain medications are commonly used for acute attacks, such as Fenbid, Disulfiram, Aspirin, Tylenol, etc. The most commonly used medication for preventive treatment is amitriptyline. Migraine is second only to tension headache in terms of prevalence, but it is often moderate to severe and is more severe than tension headache, so it is the most common headache encountered in outpatient clinics and emergency departments. It is often recurrent, mostly pulsating, consistent with the pulse rate, often unilateral in distribution, accompanied by nausea, vomiting, photophobia and phonophobia, and aggravated by physical activity. A few patients have visual, sensory and motor aura before the headache attack, with visual aura being the most common, which can be dark spots, flashes and black (Figure 3). The symptoms tend to last for 4-72 hours and can be related to the menstrual cycle in women. 85% of patients complain of triggers and common triggers include: weather changes, stress, depression, anxiety, sleep disturbance, overwork, light stimulation, noise, alcohol, chocolate cheese, coffee, tea, etc. Therefore, attention to avoidance of triggers can reduce headache attacks. Treatment is divided into two aspects: treatment during the attack period and preventive medication. Some pain-relieving drugs such as Tylenol, Disulfiram and Fenpropathrin can be applied during the attack period, while the severe headache can be treated with Triptorelin drugs. If the patient has frequent headache attacks with heavy symptoms, which seriously interfere with work and life, preventive medication can be given to reduce the frequency of attacks and alleviate the symptoms during the attacks. Commonly used preventive medications are beta-blockers (such as metoprolol and ponerol), calcium channel antagonists (flunarizine), antiepileptics (sodium valproate and topiramate) and antidepressants (amitriptyline and venlafaxine). Headache is really a difficult topic, I didn’t expect to spend so much time and effort and still write poorly, so forgive me.