What is wrong with the pain in the face that is always unbearable and cannot be touched or scratched, as if it is being tortured? What the hell is the trigeminal nerve, and why does it make people painful and uncomfortable for a good reason? The reason why the face can feel cold, heat, touch, etc., and also chew things and other motor functions, is mainly due to the trigeminal nerve. This is the thickest set of nerves on the face, which innervates the sensation of the face, mouth, nasal cavity and the movement of the chewing muscles, and feeds the sensory signals from the head to the brain. This thick nerve is divided into three branches on the face – the ophthalmic nerve, the maxillary nerve and the mandibular nerve. (See figure below.) Each large branch has its own area of jurisdiction and manages the sensory or motor functions there. Ophthalmic nerve: the smallest of the three branches, it has relatively little power and its area of jurisdiction is the skin of the top of the forehead, upper lid and dorsum of the nose, as well as sensation in the areas of the eyeball, lacrimal gland, conjunctiva and part of the nasal mucosa. Maxillary nerve: Although it also has only sensory functions, it has a larger area of jurisdiction, mainly the mucous membranes of the maxillary teeth, gums, maxillary sinuses, nasal and oral cavities, and the facial skin between the lid fissures, as well as part of the dura mater. This branch mainly perceives sensations such as cold, heat, and touch in this area. Mandibular nerve: It is the boss here and is the thickest one. Although its area of jurisdiction is small, it has a lot of power. It mainly governs the movement of the masticatory muscles, as well as the sensation of the jaw, gums, the anterior 2/3 of the tongue and the mucosa of the floor of the mouth, as well as the auriculotemporal region and the facial skin below the orofacial fissure. It can govern both masticatory activities and sensory functions, and can be said to reign supreme. If your face hurts inexplicably, like pins and needles, and you feel like a pinch, it is most likely that the trigeminal nerve is having a temper tantrum, which is called trigeminal neuralgia. This is trigeminal neuralgia. When different branches of the trigeminal nerve are stimulated to different degrees, there will be different sensations. The main difference is the location of the pain, such as the forehead pain, the corner of the mouth pain, the inability to chew, and so on. Sometimes, when you don’t touch your face, it doesn’t hurt, but when you touch a spot on your face, it starts to hurt, and this spot is called a “trigger point”. Most patients have a trigger point, but some patients do not have a trigger point, and even if they do not touch their face, they still have pain. Trigeminal neuralgia is mainly divided into secondary and primary. If the trigeminal nerve is pressed, or if the blood vessels that supply blood and oxygen to the nerve are pressed, or if there is a mass taking up its place, etc., causing constant irritation of the trigeminal nerve, you will feel pain, which is secondary trigeminal neuralgia. If the face pain is really just inexplicable and no direct cause can be found, it is primary trigeminal neuralgia. In addition to these causes that can directly lead to face pain, there are many other indirect factors that can trigger pain. For example, tooth extraction, washing face with cold water, eating popsicles, etc. In addition, since the trigeminal nerve is a thick nerve drilled from the brain, it has to pass through a barrier, the foramen ovale, from the brain to the face. This is a thin bone seam, some people have osteophytes in the foramen ovale, blocking the already thin seam, or the bone seam has become narrow, or even inflammation, which can invade the trigeminal nerve and cause face pain.