The headache lasts for about two weeks after craniotomy. Craniotomy involves cutting the scalp and muscles, causing the nerves above the scalp to be cut, causing pain. In addition, because craniotomy requires pulling the brain tissue, the brain tissue will be irritated, pulled and damaged, which will cause edema and swelling, resulting in increased intracranial pressure, and the increased intracranial pressure will stimulate the nerves above the dura mater and cause headache. In addition, due to the oozing of blood from the surgery, blood seeps into the subarachnoid space, which can also irritate the nerves above the dura mater and cause headaches. The edema in the brain tissue is usually eliminated in about two weeks, and the blood seepage is absorbed in about two weeks, so the headache lasts for about two weeks after surgery. During this process, if the pain is severe, symptomatic treatment such as pain relief can be given.