1.Recurring severe facial pain The pain is brief and repetitive, each pain lasts for a few seconds to a few minutes, and the pain attacks vary from several times to dozens of times a day, with sudden onset and sudden cessation, with intervals as normal: individual patients sometimes have persistent pain with paroxysmal aggravation. There is often no warning before the attack, and the pain is sudden and lightning-like, tearing, burning, cutting or stabbing pain. 2. “Trigger point” The patient or the doctor can trigger a lightning or tearing pain in the face by slight pressure on a part of the face, and this trigger point is called “trigger point”. Such actions as talking loudly, eating, washing face, brushing teeth, or even breeze blowing on the face can trigger pain at the trigger point. 3.Intermittent period The pain can be relieved or completely disappeared after a period of pain attack or drug treatment, which is called intermittent period. This intermittent period can last from several months to several years, but most of the patients will have recurrence, and the severe pain in the face will be aggravated after the recurrence, after which the intermittent period will become shorter and shorter, and the attack will become more and more intense, so that it will last all day long.