The head is rich in pain-sensitive tissues, but there is no pain-sensitive tissue in the brain parenchyma. Therefore, lesions in the brain parenchyma, such as tumors or cerebral infarction, usually do not cause headache, but only when the lesion reaches a certain degree and involves the dura mater or large blood vessels around the dura mater, as well as the nerve root plexus at the base of the skull, it will cause headache. Headache is very common, the scalp, subcutaneous muscles, fascia, and facial organs, eyes, ears, nose, mouth, teeth, dental pulp are very rich in pain-sensitive receptors, there is the distribution of the endings of the trigeminal nerve, when these organs are stimulated to produce headache. So, most headaches actually come from these areas. With intracranial lesions, headaches only occur when the dura mater or the large blood vessels on the surface of the dura mater, as well as the nerve root plexus at the base of the skull, are stimulated.