Asploro Journal of Biomedical and Clinical Case Reports
ISSN: 2582-0370
Article Type: Original Article
DOI: 10.36502/2024/ASJBCCR.6345
Asp Biomed Clin Case Rep. 2024 May 25;7(2):106-18

Abstract

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Establishment of a Clinical Prediction Model Based on the Study of Risk Factors for Pain Recurrence after Percutaneous Radiofrequency Thermocoagulation in Patients with Primary Trigeminal Neuralgia

Xueguang Zhang^1,2, Yuting Huang¹, Wen Shen^1*
¹Department of Pain Management, The Affiliated Hospital of Xuzhou Medical University, China
²Department of Pain Management, West China Hospital, Sichuan University, China

Corresponding Author: Wen Shen
Address: Department of Pain Management, The Affiliated Hospital of Xuzhou Medical University, No.99-9 Huaihai West Road, Xuzhou, Jiangsu 221000, P.R China.
Received date: 01 May 2024; Accepted date: 18 May 2024; Published date: 25 May 2024

Citation: Zhang X, Huang Y, Shen W. Establishment of a Clinical Prediction Model Based on the Study of Risk Factors for Pain Recurrence after Percutaneous Radiofrequency Thermocoagulation in Patients with Primary Trigeminal Neuralgia. Asp Biomed Clin Case Rep. 2024 May 25;7(2):106-18.

Copyright © 2024 Zhang X, Huang Y, Shen W. This is an open-access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Keywords: Primary Trigeminal Neuralgia, Percutaneous Radiofrequency Thermocoagulation, Pain Recurrence, Risk Factor, Prediction Model

Abstract

Objectives: This study aimed to investigate the follow-up outcomes and risk factors associated with pain recurrence after percutaneous radiofrequency thermocoagulation (PRT) among patients with primary trigeminal neuralgia (PTN) and to establish a clinical prediction model based on these risk factors.
Methods: The data of PTN patients who underwent PRT were collected in our study. All subjects were randomly divided at a 7:3 ratio into a training group (T Group) and a test group (C Group) to select risk factors. According to the follow-up results, the patients were divided into a recurrence group (F Group) and a nonrecurrence group (NF Group). Predictive factors were selected through LASSO regression analysis based on T Group. The identified variables were subjected to multivariate logistic regression analysis to construct a nomogram. Receiver operating characteristic (ROC) curves and calibration curves were uesd to evaluate discrimination and calibration ability separately.
Results: A total of 884 patients were initially included, 857 patients achieved satisfactory results, and the pain relief rate at discharge was 96.95%. A total of 529 subjects were included after screening, and the recurrence rate was 27.22% after 1 year. Six non-zero variables were selected through LASSO regression analysis: the disease course, atypical pain, previous surgery, facial numbness before PRT, neurovascular contact (NVC), and operation duration. Six variables were included in the multivariate logistic regression analysis, and the results showed that they were independent risk factors (P<0.05). The predictive model is represented by a nomogram. The area under the curves (AUC) of the ROC curves were 0.868 (0.826~0.909) and 0.874 (0.802~0.950) for T Group and C Group, respectively. The prediction curves for T Group (P=0.784) and C Group (P=0.293) fit the ideal prediction curve, and the Brier scores were 0.120 and 0.099 for T Group and C Group, which indicates that the probability predicted by the model is consistent with the actual occurrence.
Conclusion: The Pain relief rate at discharge was 96.95% for PTN patients after PRT, and the recurrence rate was 27.22% after 1 year. The disease course, atypical pain, previous surgery, facial numbness before PRT, NVC, and operation duration are independent risk factors for the recurrence of pain. A nomogram model for pain recurrence was established, which has good predictive ability.

Introduction

Trigeminal neuralgia (TN) is a chronic neuropathic pain, and performed in the distribution of one or more branches of the trigeminal nerve. Severe pain often appears suddenly and can be induced by unconscious mechanical stimulation or facial movements (e.g., chawing food or washing face). Many patients suffer from severe and recurrent neuralgia for a long period of time, which is often accompanied by emotional abnormalities and psychiatric disorders [1,2]. Compared with healthy people, patients with TN have a greater chance of depression, anxiety, and sleep disturbance [3]. In addition, one previous study showed that more than 50% of TN patients take significant time off from work and experience participation restrictions [4,5]. For more convenient diagnostic grading in practice and research, TN was categorized according to the third edition of the International Classification of Headache Disorders (ICHD-3) into classical TN, idiopathic TN and secondary TN [6]. Primary trigeminal neuralgia (PTN) includes idiopathic TN and classic TN.

Microvascular decompression (MVD) and percutaneous radiofrequency thermocoagulation (PRT) are the main treatment methods for PTN patients when pharmacologic therapy is ineffective. The guidelines suggest that MVD is the most appropriate treatment when imaging reveals significant nerve compression, if preoperative MRI/MRA does not reveal any neurovascular conflict (NVC), no recommendation can be made [7]. PRT is usually favored because of its ability to achieve satisfactory outcomes with low mortality and morbidity [8]. PRT can also be used to treat recurrent TN patients who fail to respond to MVD, PRT, or other surgical treatments [9,10]. In addition, the frequency and severity of adverse effects (e.g., decreased sensation, muscle weakness, and loss of corneal reflexes) are not increased with repeat PRT compared with initial PRT [11,12]. However, many patients also experience recurrent pain after PRT. Previous studies have shown that pain recurrence rates range from 17% at 1 year to 40% at 5 years during long-term follow-up. A large sample report showed that only 41% of TN patients achieved complete pain control after 20 years after PRT [13,14].

Some factors related to recurrent pain in PTN patients after PRT have been identified in the previous literature, with varying screening methods and outcome variable criteria. In our study, a more comprehensive set of relevant variables was used to screen risk factors, and a nomogram was created to build a prediction model based on the screened risk factors. Finally, we can assess the risk of pain recurrence after PRT for more clinical PTN patients.

Methods

Study Design and Patient Sample:

This retrospective study was approved by the Ethics Institutional Review Committee of the Affiliated Hospital of Xuzhou Medical University (XYFY2020-KL161-01). This research was registered at the Chinese Clinical Trial Registry (ChiCTR1900028617). All patients involved in the study were given full explanations of the procedures and purpose. We initially selected 884 PTN patients who underwent PRT from the electronic medical records system from 2010 to 2019, and the last follow-up was completed in 2020. Finally, a total of 529 subjects were included after screening by the admission and exclusion criteria. The first group was divided into a training group (T group, n=373) and a testing group (C group, n=156) according to simple random sampling at a ratio of 7:3 [15]; the second group was divided into a relapse group (F group, n=144) and a nonrelapse group (NF group, n=385) according to whether the results of follow-up were recurrent.

Patients with only single V2, single V3 or combined V2 and V3 PTN involvement who received PRT during hospitalization were included. Patients with secondary TN, chronic craniofacial pain with symptoms similar to those of TN (e.g., comorbid lingual pharyngopharyngeal neuralgia and pterygopalatine neuralgia), and patients with V1 branche were excluded.

Surgical Procedure

All surgical procedures were performed in the CT operating theatre by experienced doctors who have been performing minimally invasive ganglion surgery for many years. First, all patients underwent a CT scan of the skull base to determine whether there were secondary causes (Fig-1). For example, intracranial masses or obvious foramen ovale (FO) variations can occur.

Fig-1: Preoperative 3D CT Reconstruction of the Skull Base

Establishment of a Clinical Prediction Model Based on the Study of Risk Factors for Pain Recurrence after Percutaneous Radiofrequency Thermocoagulation in Patients with Primary Trigeminal Neuralgia

The patient was placed in a supine position, and the CT gantry was then tilted 10-15 degrees to the side of the foot for spiral scanning. According to CT scanning imaging, the best cross section was confirmed, which was parallel to the FO. The point of puncturing was set as 2.0 to 2.5 cm lateral to the angle of the mouth. After local infiltration anesthesia with 1% lidocaine, the same 22-gauge radiofrequency needle with an active tip was inserted into the FO percutaneously (Fig-2). Then, the puncturing direction was adjusted by CT scan to allow the FO to enter according to the patient’s reaction to sensory (50 Hz, 0.2 V) stimulation and motor (2 Hz, 0.2 V) stimulation, and the tip of the needle was approximately 0.5 cm beyond the internal mouth of the FO. The stylet was then removed, and 2% lidocaine (0.5 ml) was injected. PTN patients undergo PRT at different final temperatures to achieve effective pain relief for different durations (ranging from 60 s to 300 s). The total surgical procedure duration ranged from 30 min to 120 min.

Fig-2: Radiofrequency Puncture Needle Tip into the Foramen Ovale

Data Collection and Follow-Up

In the pain management department of the Affiliated Hospital of Xuzhou Medical University, we searched the electronic medical records of all the participants for filtering, including sociodemographic characteristics, current and past medical history, physical examination findings, imaging findings, surgical records, and clinical outcome assessment. Sociodemographic characteristics and medical records were extracted from the electronic medical records. The imaging results were prioritized from the imaging PACS system, and those who could not access them were then referred to the medical records.

The follow-up visits were mainly based on contact telephone numbers combined with the information recorded in the follow-up system, outpatient records and letter follow-ups. The follow-up was completed in December 2020. To assess the clinical outcome of patients 1 year after surgery and to determine whether the criteria for pain recurrence were met.

Clinical Observation and Assessment

The demographic data included name, sex, and age. Disease duration, surgery side, lesion branches, type of pain, previous history of neurosurgery, hypertension, diabetes, and postoperative complications were all recorded. Preoperative and postoperative facial numbness was evaluated by the Barrow Neurological Institute (BNI) facial hypesthesia scale. According to the reference criteria, Class I: no facial numbness; Class II: mild facial numbness and not bothersome; Class III: tolerable facial numbness and feeling bothersome; and Class IV: unbearable facial numbness and very bothersome. All patients underwent MRI/MRA of the TN to assess NVC. Pain intensity was assessed using an 11-point numerical rating scale (NRS). The thermocoagulation duration was defined as the time at which the temperature increases to 60℃ until the end of surgical procedure.

Clinical efficacy was assessed by the BNI scale, which includes the degree of dependence on drugs for pain control. The reference criterias were as follows: Class I: no pain, did not need drugs; Class II: mild pain, did not need drugs; Class III: moderate pain, needed drugs for complete pain control; Class IV: moderate pain, needed drugs but not completely controlled; and Class V: severe pain. We defined BNI Classes I-II as having satisfactory clinical efficacy. Pain recurrence was defined as a change from BNI class I-II to worse BNI class III-V according to the results of the last follow-up [16].

Statistical Analysis

All the statistical analyses were performed with R software (version 4.0.3). Categorical variables are reported as frequencies and proportions, and intergroup comparisons were made with the chi-square test or Fisher’s precision probability test. Continuous variables with a normal distribution are reported as the mean ± standard deviation (x̄ ± s), and intergroup comparisons were made with independent samples t test. Nonnormally distributed continuous variables are reported as the median (M) and interquartile range (IQR), and intergroup comparisons were made with the Mann‒Whitney U test. Least absolute shrinkage and selection operator (LASSO) regression was used to analyze the T group data. Eighteen variables were included in the LASSO regression analysis, and six valid nonzero risk factors were ultimately selected. Then all valid variables were entered into the multivariate logistic regression analysis, the odds ratio (OR) and P value with 95% confidence interval (CI) were considered for variable selection. The rms package was used to construct a nomogram to construct prediction model. We generated a receiver operating characteristic (ROC) curve and calculated the area under the curve (AUC), sensitivity, specificity, positive predictive value, negative predictive value, and Youden index based on the data of C Group for verification of the model. Additionally, calibration curves of the nomogram were plotted. The Brier score was also recorded. In all analyses, P<0.05 was considered to indicate statistical significance.

Results

Characteristics of the Study Patients:

The data of a total of 884 PTN patients were collected initially; 857 patients achieved satisfactory treatment efficacy, and the pain relief rate at discharge was 96.95%. A total of 529 participants (74.82%) were included after screening according to the inclusion criteria. The follow-up results showed that 144 patients experienced recurrence after 1 year of PRT, and the recurrence rate was 27.22%. For internal validation, 373 and 156 participants were divided into the T Group and C Group, respectively. In the T Group, 102 patients (27.61%) experienced pain recurrence, and 41 patients (26.28%) experienced pain recurrence in the C Group. Postoperative complications: 498 patients (93.76%) had facial numbness of BNI Class I-II, 33 patients (6.24%) had facial numbness of BNI Class III-IV, 46 patients (8.70%) had loss of masticatory power, 6 patients (1.13%) had postoperative infection, and 20 patients (3.78%) had decreased corneal reflexes. The data on the characteristics of the participants in the T Group and C Group were similar (P>0.05). Intergroup comparisons were made between the NF group and the F group, and the results showed that disease course, type of pain, previous history of neurosurgery, BNI facial numbness before PRT, type of NVC, PRT temperature, thermocoagulation duration, and BNI facial numbness after PRT were risk factors related to pain recurrence (P<0.05). The detailed characteristics of all patients are listed in Table-1.

Table-1: Participant Characteristics in Different Groups (T Group and C Group/NF Group and F Group)

LASSO Regression Analysis of Pain Recurrence:

Based on the data of T group, 18 variables were included in the LASSO regression analysis. When the best lambda value was 0.047, six non-zero variables were screened as risk factors, including disease course, atypical pain, previous history of neurosurgery, BNI facial numbness pre-PRT, type of NVC, and surgical procedure duration. The results of LASSO regression analysis are shown in Fig-3, and the regression coefficients of each variable are reported in Table-2.

Fig-3: Risk Factor Selection for Pain Recurrence by LASSO Regression Analysis

Table-2: Regression Coefficients of Each Variable in the LASSO Regression Analysis

Independent Risk Factors for Pain Recurrence:

Based on six nonzero variables screened in the LASSO regression analysis, multifactorial logistic regression analysis was used to identify independent risk factors for pain recurrence after PRT. The results suggested that all 6 variables had P values less than 0.05 and OR values greater than 1 (Table-3). Simultaneously, all six nonzero variables were proven to be significant in the construction of the prediction model, and the contributions of the other variables to the prediction model were trivial in this study.

Table-3: Multivariate Logistic Regression Analysis of Pain Recurrence

The Nomogram of the Prediction Model:

Based on the relative weights of the six risk factors, we developed a nomogram for the prediction model. This graphical tool [16,17] is based on proportionally converting each regression coefficient in multivariate logistic regression to a 0 to 100-point scale, and points are added across different risk factors to obtain total points, which are converted to the last predicted probabilities (Fig-4).

Fig-4: Nomogram of Pain Recurrence after PRT

ROC Curves of the Prediction Model:

Based on the T Group and C Group data, ROC curves of the prediction model were performed. We calculated that the AUC of the ROC curve was 0.868 (95% CI: 0.826-0.909) in T Group and 0.874 (95% CI: 0.802-0.950) in C Group (Fig-5), which confirms its good discriminatory ability.

Fig-5: ROC Curve of the Prediction Model

Calibration Curves of the Prediction Model:

We developed nomogram calibration curves of the T Group and C Group separately based on Hosmer-Lemeshow Goodness of Fit tests. The predicted risk of pain occurrence in the nomogram of both curves largely matched the actual risk of pain occurrence, with p values of 0.784 in the T Group and 0.293 in the C Group (P>0.05). The Brier score was 0.120 in the T Group and 0.099 in the C Group. This indicates that the predicted probability of the model output is in good agreement with the true probability and confirms its good calibration ability (Fig-6).

Fig-6: Calibration Curves for the Nomogram

Comparison of the Predictive Ability of the T Group and C Group:

The best cut-off value according to the Youden index was 0.340, which was converted to a total score of 135 for the nomogram. The predictive ability of the T group and C group was compared, as shown in Table-4.

Table-4: Comparison of the Predictive Ability of the T Group And C Group

Discussion

PRT initially provides a high rate of pain relief, but many patients experience pain recurrence during long-term follow-up [18]. A Chinese multicenter retrospective study of 1481 patients with TN who received PRT revealed that 35.18% of patients experienced pain recurrence, with cumulative incidences of 14.7%, 25.4%, 32%, and 45.1% at 1, 3, 5, and 10 years, respectively [13]. Yuan-Zhang et al performed a study to evaluate the efficacy of PRT in 1137 patients with idiopathic TN, and the immediate postoperative pain relief rate was 98.4%. Among all the subjects with V2 lesion branches, the prevalence of pain recurrence was 9%, 11%, 20%, 28%, 40%, and 46% at 1, 3, 5, 7, 9, and 11 years, respectively [19]. In our study, the pain relief rate at discharge was 96.95%, and the prevalence of pain recurrence in PTN patients after PRT was 27.22% at 1 year. These results are similar to those of other previous studies.

We assessed the relationship between the variables and pain recurrence using LASSO regression analysis. It can decrease bias in multiple covariates and avoid overfitting of the prediction model, thus improving discrimination and calibration ability and enhancing the probabilistic power of the model, which is a better alternative to traditional methods [20,21]. The predictive model was constructed by a nomogram. Among all available predictive modeling tools, nomograms have high accuracy and good discriminative ability in estimating risk incidence and can more conveniently guide clinical decisions based on individual characteristics.

In this study, the variables characterizing PTN patients after PRT that were generally associated with pain recurrence included disease duration, atypical pain, history of prior neurosurgery, BNI facial numbness before PRT, type of NVC, and duration of surgery. These three risk factors were consistent with those of previous studies, including the type of NVC, history of previous neurosurgery, and grade of BNI facial numbness before PRT [13].

The correlation between disease duration and the outcome of TN has been less reported in previous studies. The results of our study suggest that disease duration is associated with postoperative recurrence, but the relative weight is not significantly different from other risk factors. Patients with longer disease durations have more complex conditions and may have poorer outcomes in terms of surgical response. In addition, postoperative recurrence in patients with PTN may also lead to prolonged disease duration.

Several studies have shown that atypical pain is a significant risk factor for pain recurrence. Obermann M et al. reported that trigeminal nociceptive processes are affected by prolonged TN duration. According to this theory, central or progressive root damage may be related to the mechanism of atypical pain [22]; therefore, PRT should be contraindicated in PTN patients with atypical features. PRT can only relieve peripheral neuropathic pain and has no therapeutic effect on central pain. It may cause damage to the nervous system and lead to the development of neuropathic pain that is more severe than initial pain [23,24]. Furthermore, patients with PTN and typical pain are more likely to have better long-term outcomes than patients with atypical neuropathic pain.

A history of previous neurosurgery is another risk factor that is significantly and positively associated with pain recurrence. Because of its efficacy and safety, PRT is often used as a common treatment for recurrent TN [25,26]. According to a multivariate analysis, the risk of pain recurrence was 2.808 times greater in patients who underwent repeat PRT and 3.832 times greater in patients who underwent more than two neurosurgical procedures than in those who underwent the first PRT [13]. The results of a previous study also showed that PTN patients without a history of surgery had a significantly greater rate of satisfactory outcomes (OR=1.988), but patients with prior surgical treatment had a significantly greater risk of poorer outcomes (OR=0.240) [8]. One possible explanation is that prior neurosurgery results in neuropathic pain or significant facial numbness. Other types of nerve damage and adhesions between the trigeminal nerve and surrounding tissues can affect the outcome and long-term prognosis of PTN patients after PRT.

High-resolution MRI/MRA can reliably detect NVC in patients with TN, and NVC with neuromorphologic changes significantly increases the risk of painful recurrence. Traditionally, it has been theorized that trigeminal vascular compression is one of the most common etiologies of TN, and therefore, MVD is mandatory when NVC is found to be present in patients with PTN [27]. Miller et al. indicated that asymptomatic patients can also present with trigeminal NVC, while at the same time, some patients with typical TN symptoms do not have evidence of trigeminal NVC [28]. Current evidence suggests that the presence of NVC on the asymptomatic side of TN is associated with a significant increase in the risk of recurrence of pain. TN is associated with any type of NVC on the symptomatic side, but there is strong evidence that idiopathic TN is moderately associated with NVC without morphologic changes, whereas typical TN is strongly associated with NVC with morphologic changes [7].

Since patients with secondary TN were excluded, preoperative dullness of sensation in the anterior region may be a residual adverse effect of previous neurosurgical procedures [22,24]. This finding suggested impaired function of the Aα and Aβ nerve fibers that conduct tactile sensation. A study reported that patients with Class II/III facial numbness prior to PRT had a 2.47/3.29-fold increased risk of recurrence compared to PTN patients without facial numbness. Facial numbness prior to PRT may interfere with sensory testing during the PRT procedure. It affects the accuracy of the puncture and increases the number of punctures, which in turn affects the outcome of the procedure and leads to an increased probability of postoperative recurrence.

Surgical procedure duration is a relatively novel risk factor influencing the incidence of pain recurrence, and no such risk factors have been reported in previous studies. The total duration of the procedure ranged from 30 min to 120 min in this study. The causes of the prolonged procedure time were complex, which might be related to the accuracy of the position of the needle, an anatomical variant of the FO, insensitivity to the sensory stimulation test and patient coordination during the operation (not following the order of the doctor or a wide range of emotionally stressful events may result in adverse reactions). Facial numbness in pre-PRT patients and insensitivity to sensory stimulation are closely related. According to several reports, 2% to 4% of patients have anatomically variant FO [29]. In cases where the FO is difficult to access, those patients require repeated punctures to successfully access the accurate position.

Thermalcoagulation temperatures is one of the most critical factors in PRT treatment. When exceeding a certain temperature, the heat generated by the radiofrequency puncture needle tip selectively destroys the Aδ and C nerve fibers to prevent the induction and exacerbation of pain [19,30]. Previous studies have reported that PRT at higher temperatures (>70℃) results in more pronounced pain relief but causes more severe complications (facial paralysis, blindness, deafness), and PRT at 60 to 70℃results in fewer complications but a greater rate of pain recurrence [21]. The specific criteria for the optimal and most effective temperatures are still highly controversial.

This study has some objective limitations. We selected only internally validated predictive models and not externally validated predictive models. In addition, we may have overlooked several risk factors that are closely related to prognosis, such as trigeminal reflex testing, evoked potentials, pathologic changes in the diseased branch, other nonpharmacologic and nonsurgical supports, and preoperative or postoperative medications (what and how much to use preoperatively).

In this study, a nomogram was used preoperatively to estimate the probability of recurrence in patients. It provides advanced education and communication postoperatively for timely follow-up and early intervention in cases of recurrence. The clinical characteristics of preoperative TN patients were also recorded. Individualized selection of surgical modalities with high remission rates and low recurrence rates is highly beneficial for guiding clinical treatment with scientific data.

Conclusion

According to the results, the disease course, atypical pain, type of previous surgical history, presence of BNI facial numbness pre-PRT, type of NVC, and surgery duration are valuable independent predictors of pain recurrence. We constructed a prediction model of pain recurrence for PTN patients after PRT through THIS risk factor study. To effectively apply the prediction model to other regions and meet the needs of clinical practice for better treatment options, analyses. For internal verification, ROC curve analysis and calibration plot analysis were conducted to identify the prediction model with good performance. We applied a nomogram to estimate the risk incidence rate, which is expected to be useful for clinical evaluation before PRT to help doctors make more beneficial decisions about recurrence-free survival.

Acknowledgments

The authors would like to thank all participants for their involvement.

Funding

This research received no specific grant from any funding agency.

Conflict of Interest

All authors have approved the manuscript for submission and have no conflicts of interest to declare.

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