Trigeminal neuralgia is a disease with recurrent episodes of severe pain in the distribution of the trigeminal nerve, the cause of which is unknown and can be secondary to other diseases. It is a common painful disease that seriously affects the quality of life of patients. The disease is easy to diagnose but difficult to treat. Patients with severe pain can be treated with oral medications, while patients with severe pain who are not treated with medications can opt for chemical destruction of the meniscal ganglion, radiofrequency thermal coagulation destruction and microballoon compression. Among them, radiofrequency thermocoagulation of the semilunar ganglion is less invasive and has a definite efficacy. However, due to the deep location of the foramen ovale, large anatomical variation, and more important surrounding structures, the traditional blind percutaneous puncture method is difficult to accurately place, with more complications and less effective treatment, making it difficult to popularize this minimally invasive technique. CT guidance can improve the accuracy of puncture, enhance the efficacy and avoid complications.
I. Historical review
In 1968, Letcher and Goldberg demonstrated the effects of radiofrequency current and thermal coagulation on smaller Aδ and C nerve fibers before conducting experiments on α and β nerve fibers. These studies formed the neurophysiological basis for treatment with radiofrequency electrical injury, and the treatment of trigeminal neuralgia with radiofrequency current via percutaneous selective thermal coagulation of the semilunar ganglion began in the early 1970s with satisfactory results. Since the unmyelinated fine fibers that conduct nociception degenerate at 70°C-75°C, the myelinated thick fibers that conduct tactile sensation can tolerate higher temperatures. In this way, the difference in temperature tolerance of different nerve fibers can be exploited to selectively destroy the fine fibers that conduct facial nociception in the semilunar ganglion, while preserving the coarse fibers that conduct touch, which are more resistant to heat.
In recent years, the development of imaging medicine, radiofrequency technology and computer technology has provided conditions for minimally invasive treatment of trigeminal neuralgia under the guidance of imaging intervention, and radiofrequency thermocoagulation destruction has become an important method for the treatment of trigeminal neuralgia. CT-guided radiofrequency thermocoagulation for trigeminal neuralgia has been widely used, and our department treats about 800 patients with this method every year, which has significantly improved the efficacy and safety.
II. Patient selection
1.Patients with trigeminal neuralgia who are not suitable for microvascular decompression treatment in old age and frailty.
2, patients with recurrence after microvascular decompression.
3, Patients who have been taking larger doses of carbamazepine or/and phenytoin sodium for a long time.
4, patients who do not wish to be treated with microvascular decompression
5, younger patients in good general condition who can be treated with microvascular decompression of the trigeminal nerve root.
6, patients with recurrence after controlled coagulation therapy: coagulation therapy may be performed again
7.Patients with recurrence after microvascular decompression therapy: controlled thermal coagulation can be used.
III. Preoperative preparation
1.CT coronal and axial scans of the foramen ovale and posterior cranial fossa to observe the cerebral bridge cerebellar angle site. Diagnose primary trigeminal neuralgia except for secondary pain caused by peri-trigeminal tumor. Enhancement or MRI scan if necessary to exclude intracranial lesions.
2. discontinuation of carbamazepine and phenytoin sodium or dose reduction one day prior to surgery.
3. administration of anxiolytics and antidepressants for those with symptoms of anxiety and depression
4. medical treatment for patients with hypertension or/and coronary artery disease to adjust blood pressure to normal levels.
5. lowering blood glucose to normal for those with a history of diabetes.
6, admission to the ward, routine examination of blood, urine routine, coagulation function, electrocardiogram, blood pressure, blood sugar, liver and kidney function and neurological examination.
7. Explain to the patient and family members the treatment method, expected effect and possible complications, and sign the informed consent form.
IV. Surgical operation methods
1.Puncture access: Mostly the anterolateral access puncture method is used.
2. Preoperative drug administration: Intramuscular injection of atropine 0.3 mg and valium 5 mg half an hour before surgery.
3.Position: The patient was supine on the CT bed, and the ECG, blood pressure and oxygen saturation were monitored continuously.
4.Puncture point: The puncture point was selected at the lateral corner of the affected side of the mouth equivalent to above the maxillary 2nd molar near the lower edge of the zygomatic bone.
5.Puncture oval hole.
Disinfect the face, lay a towel, and connect the relevant electrode for negative electrode. After local anesthesia with 1% lidocaine, puncture with a radiofrequency cannula puncture needle, and enter the needle according to the puncture route and angle selected by CT scan, and under CT monitoring, enter the needle in sections until the puncture reaches the foramen ovale, back aspiration without cerebrospinal fluid or blood outflow, inject 10% Uvexan or Onepac l ml, and scan to confirm the distribution of contrast agent in the semilunar ganglion.
6.Electrical stimulation test.
Apply 50Hz, 0,1~0,3mV current stimulation test, according to the patient’s response, the depth and direction of the puncture needle can be adjusted appropriately to produce numbness and swelling or throbbing pain in the corresponding distribution area of the trigeminal nerve to confirm the accuracy of the puncture site.
7.Continuous radiofrequency thermal coagulation.
Start the radiofrequency current to make generate heat. After the temperature rises to 60°C, the skin of the corresponding area of the face appears obvious redness until 70-80°C, the corresponding area appears numb and the pain disappears. The time and temperature of thermal coagulation can be adjusted according to different pain ranges and pain levels. Commonly used is to first give 60°C thermal coagulation, lasting 60 seconds, and then in with 70-80°C, lasting 60-240 seconds.
8.Pulse radiofrequency thermal coagulation
In recent years the application of pulsed radiofrequency thermal coagulation technology is to give the thermal coagulation temperature does not exceed 42°C, continuous 120 seconds of intermittent pulse frequency heat, compared with the traditional radiofrequency thermal coagulation, the degree of damage to the tissue is less, because the injury temperature is lower, the damage to the motor nerve is lighter, the possibility of complications is low. However, the long-term efficacy of pulsed radiofrequency thermal coagulation technology is still to be evaluated.
9.Postoperative observation index.
Follow-up visits were generally made by telephone and letter on the day, day 7, month 6 and month 12 after the procedure, and the time of puncture treatment operation, pain VAS score, pain relief, quality of life score and complications were recorded respectively. Pain intensity was measured using visual analogue pain score (VAS) for pain, which was recorded by the patient’s oral physician, with VAS values of 0 for no pain and 10 for the most severe pain. VAS values of 1-3 were considered mild pain, 4-6 were considered moderate pain, and 7-10 were considered severe pain.
10.Use of evoked potential monitoring
The key to radiofrequency thermocoagulation is whether the puncture needle can accurately reach the trigeminal meningeal ganglion, and the puncture is often performed from the anterolateral approach. The use of evoked potential to monitor the process of radiofrequency thermal coagulation of the semilunar ganglion can precisely locate and limit the area of destruction and determine the degree of destruction, and improve the effectiveness of radiofrequency treatment.
(5) Close cooperation with radiologists
CT-guided hemilunar ganglion disruption is a painful interventional procedure in which radiologists play an important role, and close cooperation with radiologists should be observed to select appropriate puncture sites and routes. The traditional anterolateral approach entry point is chosen for the body surface puncture point. There are no large vessels or nerves in the area, and to facilitate observation of the needle body position during entry, the shank of the puncture needle should be parallel to the CT frame to facilitate observation of the shank during guidance. The angle and depth of the puncture were measured with a homemade locator, and CT scanning was continuously performed during the needle feeding process to adjust the needle direction and ensure the accurate route of the needle feeding. After entering the foramen ovale, the depth of needle entry is strictly controlled, and the action should be gentle not too violent and too deep.
V. Contraindications
1, uncooperative people, including those with mental disorders.
2. Those who have infected lesions in the skin and deep tissues of the puncture site.
3.Persons with bleeding tendency or those who are undergoing anticoagulation treatment.
4.Persons who are allergic to local anesthetics.
5.Patients with hypovolemia.
6.Severe cardiovascular and cerebrovascular diseases in the unstable stage.
Sixth, complications
1.Facial numbness
Facial sensory loss and numbness are more common after radiofrequency thermocoagulation, and some patients have facial abnormal discomfort, which is a manifestation of tactile nerve fiber injury, but the patient can understand it as a treatment reaction, but must be clearly explained to the patient before surgery. Long-standing facial sensory deficits are approximately 12%. Painful sensory deficits have been reported in the recent literature at a rate of only 0.2% to 5%.
2. Sluggish corneal reflexes or paralytic corneal ulcers
It is a common complication of radiofrequency thermocoagulation, postoperative corneal sensory loss, ipsilateral corneal reflex retardation or paralytic corneal ulcer, mostly due to deep needle entry, which occurs less frequently due to accurate positioning in CT-guided radiofrequency thermocoagulation destruction.
3.Masticatory motor disorder
Masticatory weakness or restricted mouth opening is mostly related to the excessive temperature and duration of radiofrequency thermal coagulation that severely damage the motor fibers of the trigeminal nerve. Generally when the temperature is controlled below 80°C, it is less likely to occur.
4.Visual loss and diplopia
Injury to the optic nerve in the direction of the puncture is inward or deep, resulting in vision loss, and injury to the motoneurone nerve or the talocrural nerve causes diplopia.
5.Other complications
Complications such as salivation at the corners of the mouth, postoperative twitching sensation in the affected area and facial herpes zoster may occur. The incidence of serious complications (permanent brain function loss, numbness, significant sensory abnormalities) can sometimes reach 3%.
The main causes of complications are caused by inaccurate puncture, damage to adjacent tissues by the puncture needle, or damage to adjacent tissues due to improperly positioned puncture needles. These accidents are difficult to avoid during repeated blind punctures. Therefore, improving the accuracy of puncture is the main way to avoid complications. The accuracy of puncture can be ensured by monitoring and guiding the puncture under CT, and the location of the needle tip and the extent of destruction of thermal coagulation can be judged in advance by observing the extent of contrast agent diffusion, which can reduce complications and ensure the efficacy of treatment.
VII. Efficacy of radiofrequency thermocoagulation
A group of 428 patients by radiofrequency temperature-controlled thermal coagulation treatment after the pain completely disappeared in 409 cases, accounting for 95, 56% of the number of treatment, including 5 cases of postoperative pain increased, 2 days to 2 weeks after surgery pain disappeared, due to the cerebral cortex trace reaction. There were 13 cases of pain relief, accounting for 3.04% of the number of patients treated. There were 6 cases with no effect, accounting for 1.40% of the number of patients treated (all of them contained Ⅰ-branch pain). The total effective rate was 98.59%. 265 cases were followed up from 3 months to 2 years, of which 32 cases showed recurrent symptoms, and the recurrence rate was 12.07%. The pain was stopped by re-treatment with radiofrequency.
The recent results of radiofrequency temperature-controlled thermal coagulation therapy were very good, with about 96% to 100% of patients achieving pain disappearance after treatment. The recurrence rate is related to the extent of thermal coagulation. The smaller the area of thermal coagulation (the more it is retained), the higher the recurrence rate. The recurrence rate is 55% in patients with mild sensory loss and 25% in patients with significant postoperative sensory loss.
A multicenter study of radiofrequency temperature-controlled thermocoagulation showed that the immediate pain disappeared up to 80%-100%, with a mean of 94%, and the distant pain disappeared up to 71%-94%, with a recurrence rate of about 29%, which depends on whether there are still vessels compressing the nerve root.