Trigeminal neuralgia is known as the “king of pain” because of its severe pain and difficulty in eradicating it. From September 2004 to February 2005, 29 cases of primary trigeminal neuralgia were treated by radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion using the “quadruple localization method” to ensure the accuracy of the puncture needle in place. I. Data and methods (a) General data: There were 29 patients in this group, including 17 males and 12 females. The age ranged from 32 to 71 years old, with an average of 57.1 years old. There were 22 cases on the right side and 7 cases on the left side. There were 5 cases of branch II pain, 3 cases of branch III pain, 19 cases of branch II+III pain, and 2 cases of branch I+II+III pain, with the duration of disease ranging from 6 months to 23 years, with an average of 5 years and 2 months. One of the patients had undergone radiofrequency of the semilunar ganglion twice, and the other patient had undergone trigeminal sensory posterior rhizotomy. (B) Methods: All patients were treated with medication, nerve branch block or radiofrequency first, and then radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion was performed when the pain could not be effectively controlled by the above treatments. A 9600 C-arm X-ray machine from GE of the United States was used to localize the foramen ovale, and a LNG30-1 radiofrequency instrument from ELEKA of Sweden was used for treatment. The operation steps of radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion by quadruple localization method: (1) Quadruple localization: ①Symptoms and signs localization: pain and trigger point located above the eye fissure is trigeminal nerve branch I pain, located between the eye fissure and the mouth fissure is branch II pain, located below the mouth fissure is branch III pain. ②Anatomical localization: both the puncture point and the puncture direction were localized using Song’s modified anterior approach [1] (see Figure 1). ③X-ray localization: a. Oval foramen localization with a C-arm X-ray machine (generally, the affected oval foramen can be clearly revealed by rotating the X-ray generator about 30o toward the cephalic end and about 20o toward the healthy side) (see Figure 2); b. Puncture: disinfection, sheeting, and puncture under orthogonal X-ray fluoroscopy; if the localization and orientation are accurate and the operation is skilled, the hole can often be directly entered, and there is a sense of falling and the tip of the needle being sucked when puncturing the oval foramen, At the same time, the patient has severe electric shock-like pain in the corresponding area of the face (see Figure 3). c. Adjust the depth of the puncture needle under lateral X-ray fluoroscopy, the front end of the needle tip does not pass through the skull base plate in patients with branch III trigeminal neuralgia, i.e., the needle tip does not enter the skull; the front end of the needle tip passes through the skull base plate and enters the skull 0.5-1 cm in patients with branches I and II trigeminal neuralgia (see Figure 4). If the needle tip is correctly positioned, the lesion should be painful; if the needle tip is correctly positioned, the trigeminal neuralgia of branches Ⅰ and Ⅱ should be sore, numb and swollen, and the trigeminal neuralgia of branch Ⅲ should be occlusal muscle spasm. (2) Anesthesia: intravenous isoproterenol (1.5-2 mg/kg) is pushed to make the patient lose consciousness and then start RF destruction. (3) Temperature-controlled thermocoagulation: radiofrequency destruction, the temperature was set to 70oC, 80oC and 85oC for three times, and the duration was 60s. After the patient’s consciousness was restored, the facial skin and tongue tip were needled to test the nociceptive and tactile changes in the innervated area of the lesion until the nociceptive sensation disappeared and the tactile sensation was dulled; if the nociceptive sensation still existed, the puncture needle position was adjusted and then radiofrequency thermocoagulation was performed as appropriate. II. Results (1) Efficacy: In this group of 29 patients, radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion was performed after quadruple localization, and all of them were successfully punctured, with a success rate of 100%, and the puncture time ranged from 5 to 23 min, with an average of 15 min; all of the postoperative pain disappeared completely, with an immediate postoperative pain disappearance rate of 100% and no recurrence in 1 to 5 months of follow-up. (2) Complications: one case of keratitis, a patient with trigeminal neuralgia combined with branch I, with an incidence of 3.4%, recovered to normal after 6 days of symptomatic treatment. III. Discussion Radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion as the main method for the treatment of primary trigeminal neuralgia can be divided into several methods: blind exploration method [2], X-ray localization method [3], CT localization method [4] and open MRI localization method [5]. We believe that the blind exploration method is more blind and easy to damage the structures around the foramen ovale; the simple X-ray localization method has better safety and efficacy than the blind exploration method; while the CT and open MRI localization methods are costly and difficult to be widely used. The success rate of puncture, immediate postoperative pain disappearance rate, and recurrence rate were better than those of blind exploration [2], X-ray localization [3], CT localization [4], and open MRI localization [5]; the complication rate was lower than those of blind exploration, X-ray localization, and CT localization, and higher than those of open MRI localization. There are two traditional methods of anesthesia for radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion: one is to inject local anesthetic after the puncture is in place; the other is to gradually increase the radiofrequency temperature from low to high without injecting local anesthetic after the puncture is in place. The disadvantages of the former method are: (1) there is a possibility that the local anesthetic may accidentally enter the cerebrospinal fluid and blood; (2) the localization of the branch of trigeminal neuralgia by local anesthetic test is not accurate; (3) when it is necessary to adjust the position of the puncture needle, it is necessary to wait until the effect of the first local anesthetic wears off, which prolongs the operation time. The disadvantage of the latter is that patients suffer a lot of pain, especially for patients with combined hypertension and coronary artery disease, who are more prone to cardiovascular accidents. Keratitis is a common complication of radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion and is due to injury to the Ⅰ branch of the trigeminal nerve, resulting in diminished or absent corneal reflexes and decreased resistance [6]. Prevention is the key, and the key to the treatment of branch II and/or III trigeminal neuralgia is to carefully perform all localization checks before RF, and the location of the puncture needle should not be too deep; while for branch I trigeminal neuralgia, medication and supraorbital nerve block or RF are feasible, and deep RF of the semilunar ganglion should be performed with caution. In case of keratitis, symptomatic treatment is available. In conclusion, we believe that the treatment of primary trigeminal neuralgia by radiofrequency temperature-controlled thermocoagulation of the semilunar ganglion under general anesthesia with isoproterenol is safe, accurate, effective, and easy to be popularized.