Study design and Patients
In this retrospective study, we identified all patients who underwent RFT or coblation for treatment of TN between August 2017 and April 2019 in the department of pain management at Xuanwu Hospital of Capital Medical University in China. The study was approved by the ethics committee of Xuanwu Hospital, Capital Medical University. Data collection and analysis was also approved by Institutional Review Board (IRB) of Xuanwu hospital (XW20190125).Written informed consent from patients was exempted due to the retrospective study.
The inclusion criteria were as follows: (1) ITN of maxillary and/or mandibular divisions in accordance with the International Classification of Headache Disorders20, (2) no space occupying lesions, (3) poor effect of drug therapy or side effects were intolerable.
The following patients were excluded: (1) patients with severe systemic diseases who were intolerable to surgery and anesthesia, (2) coagulation dysfunction or local infection in the puncture area before surgery, (3) patients with mental illness, who were unable to express subjective feelings clearly.
Clinical data of patients were extracted from the electronic medical records. All the patients who had undergone RFT or coblation for ITN were followed as the routine practice. The follow-up data were registered in the hospital data system. Each patient was taken physical examination to assess pain, numbness and other complications at discharge (3 days after surgery). Long term follow-up was carried out at 1 month, 3 months, 6 months and 12 months by telephone interview by specially trained investigators on schedule. Although telephone interview carries risks of bias including the characteristics of the respondent and the examiner, it was acceptable for patients who were unable to come to our center for further examination.
Grouping
The patients were grouped according to the procedures they selected after an informed comprehensive discussion with their surgeon: RFT group and coblation group. All procedures were performed in an operating room under fluoroscopic guidance of C-arm.
RFT Group
The patients were lying supine with their head in a reverse occipitomental position and vital signs were monitored routinely. The C-arm was rotated 15 to 25 degrees in the coronal plane and 20 to 30 degrees in the sagittal plane to visualize the foramen ovale (FO). After achieving the optimal visualization of the FO, a 22-G radiofrequency needle (15 cm, with a 5-mm active tip; Cosman TICC5 electrode, Cosman Medical, Burlington, MA, U.S.A.) was advanced to the FO after sterilization and local anesthesia with 0.5% lidocaine using the Hartel anterior approach. When the depth of the needle tip was approximately 3mm into the FO, the proper location of the needle was checked in coaxial and lateral views with the C-arm to make sure the depth of the needle tip did not exceed the clivus. After verification, the position of the needle tip was adjusted according to patients’ reactions to the sensory (50Hz, 1ms) and motor (2Hz, 0.1ms) stimulation test until paresthesia was elicited in the affected area. After positioning was accomplished satisfactorily, patients were administered intravenous anesthesia (propofol 1.5-2 mg/kg). All patients were thermally coagulated with radiofrequency at 70℃ for 180 seconds.
Coblation Group
The procedures before verifying the position of the needle tip were the same as the RFT group. When the needle was located in FO, we connected the anode of the neuro-stimulator (B. Braun Co., Ltd., Melsungen, Germany) to the tail of coblation needle (DXR-G1100-A185; Xi’an Surgical Medical Technology Co., Ltd., Xi’an, China) and the cathode was connected with patient's skin. We turned on the neuro-stimulator and adjusted it to 2 Hz and 0.1 ms, and gradually increased the intensity of the stimulus until it caused reproducible pain at 0.5 mV. When reproducible pain was successfully repeated, intravenous anesthesia was applied (propofol 1.5-2 mg/kg). The ablation energy and the coagulation energy of low-temperature plasma multifunction operating system (SM-D380C; Xi’an Surgical Medical Technology Co., Ltd., Xi’an, China) was level 1 and parameters were unchanged during the operation. The ablation time was 30 seconds, and the ablation was performed again after 30 seconds.
Clinical Materials
Clinical characteristics of patients were collected from electronic medical records, including gender, age, disease duration, affected side (left, right), co-morbidity (diabetes mellitus or not), baseline pain numeric rating scale (NRS) scores (0=no pain, 10=severe pain), pain characteristics (paroxysmal, continuous), pain distribution in anatomic trigeminal nerve dermatome (V2, V3, V2+V3), and history of previous treatment at the affected side (none, MVD, RFT, other).
All patients were followed up by telephone interviews at 1-month, 3-months, 6-months and 12-months by our investigators respectively. Follow-up data included NRS scores of pain intensity, pain relief, the degree of postoperative facial numbness, recovery from postoperative facial numbness and other complications.
Pain intensity was assessed using NRS score (0= no pain, 10= severe pain). Pain relief was considered when the NRS score was less than 4. For facial numbness, the degree of facial numbness was assessed by the Barrow Neurological Institute (BNI) facial hypesthesia scale21: Class I: no facial numbness; Class II: mild facial numbness and not bothersome; Class III: facial numbness and somewhat bothersome; Class IV: facial numbness and very bothersome. With regard to postoperative facial numbness, we observed three outcomes at the endpoint of our study: (1) no numbness: patients without subjective facial numbness; (2) remission: the degree of facial numbness was improved by 1-2 BNI level but still hadn't reached BNI I; (3) no remission: postoperative facial numbness was not changed or even raised some levels. Besides, none of the patients had subjective facial numbness before surgery and all the patients had stopped taking medicines before surgery. Other complications such as oral ulcer, corneal hypoesthesia, masticatory weakness, hypoesthesia of temperature and tinnitus were recorded as well.
Statistical Analysis
Under normal distribution and equality of variances, quantitative data were reported as means ± standard deviation (SD) and were compared using the independent-sample t test or the paired-sample t test. Otherwise, non-normal variables were reported in the median with interquartile range (IQR) and Wilcoxon rank-sum test was used. Categorical data were described by frequencies and proportions and were compared by Pearson’s chi-square test or the Wilcoxon rank-sum test.
Univariate and multivariate ordered logistic regression analysis was used to assess the statistical significance of the potential variables in patients' clinical characteristics, with previous parallel lines test (likelihood ratio test). Each relevant parameter was calculated with an associated confidence interval (CI) and odds ratios (ORs) respectively.
Statistical analyses were performed using SPSS software, version 23.0 (IBM SPSS, New York, NY, USA). The level of significance was set at P < 0.05 (2-tailed).