The Molecular Basis and Pathophysiology of Trigeminal Neuralgia

Involvement of the cingulate cortex and insula in patients with trigeminal neuralgia: A clinical and volumetric study

AIM

Advanced neuroimaging strategies may provide new insights into the underlying mechanisms of trigeminal neuralgia (TN). The objective of this study is to measure central pain centers in patients with long-standing trigeminal neuralgia and compare them to those of normal individuals. The findings of this study could improve the understanding of central region changes related to pain and improve the diagnosis and management of chronic trigeminal pain.

MATERIAL AND METHODS

We examined radiologic data from 20 patients with trigeminal neuralgia and 28 healthy controls who underwent 3D iso T1-weighted brain MRI at our university hospital between 2018 and 2023. Patients with a minimum pain duration of 5 years were included and compared with healthy controls. Additionally, patients were categorized into groups based on the presence of vascular compression. The pain-related subcortical structures, such as the cingulate cortex and insula, were analyzed volumetrically using volBrain software. The results were evaluated statistically.

RESULTS

Significant differences were observed in the measurement of the posterior insula (p = 0.014) when comparing patients with trigeminal neuralgia and healthy subjects. Additionally, group comparisons based on the presence of vascular compression revealed significant differences in the Middle Cingulate Cortex (0.036) and Posterior Cingulate Cortex (0.031) between groups, which may be related to the etiological factor.

CONCLUSION

Understanding changes in central regions related to pain can aid in the diagnosis and management of chronic trigeminal pain.

An update on pharmacotherapy for trigeminal neuralgia

INTRODUCTION

Trigeminal neuralgia is a rare condition that can be effectively treated by carbamazepine or oxcarbazepine but these older drugs are associated with dose-dependent and potentially treatment-limiting adverse effects. Third-generation anticonvulsants, new calcitonin gene-related peptide blockers for migraine, and older drugs such as ketamine and cannabinoids may be promising adjuvants or monotherapeutic options.

AREAS COVERED

The new drugs, their presumed mechanisms of action, safety and efficacy are discussed herein. There is a paucity of robust clinical evidence in support of these drugs for trigeminal neuralgia. New migraine agents are considered as well although migraines and trigeminal neuralgia are distinct, albeit similar, conditions. No new drugs have been released to market in recent years with the specific indication of trigeminal neuralgia.

EXPERT OPINION

In real-world clinical practice, about half of trigeminal neuralgia patients take more than one agent for prevention and combination therapy may be the optimal approach. Combination therapy might allow for lower doses of carbamazepine or oxcarbazepine, thus reducing the number and severity of potential adverse events but the potential for pharmacokinetic drug-drug interactions must be considered. Drug therapy for trigeminal neuralgia involves acute or abortive treatments, often administered in hospital versus long-term preventive therapy, usually involving oral agents.

OTULIN's influence on neuroinflammation and pain modulation in trigeminal neuralgia

INTRODUCTION

Trigeminal neuralgia (TN), marked by chronic pain from neural damage, is closely associated with inflammation. The role of OTULIN, a key regulator in inflammation and autophagy, is not fully understood in TN. The regulatory mechanism of OTULIN, a key protein involved in modulating inflammatory responses and autophagy processes, remains incompletely elucidated, particularly in the context of TN and neuroinflammation.

METHODS

An infraorbital nerve ligation-induced rat model of TN was used. OTULIN's expression was modulated using adenovirus vectors and short hairpin RNA. The impact on pain and inflammatory responses was assessed via quantitative real-time polymerase chain reaction, western blot, immunofluorescence, and transcriptomic analysis.

RESULTS

Enhanced OTULIN expression significantly increased head withdrawal thresholds and reduced pain sensitivity and neuroinflammatory markers in the model. Conversely, silencing OTULIN exacerbated pain and inflammation. Transcriptomic data revealed OTULINs influence on both inflammatory and autophagy pathways, specifically in suppressing NLR family pyrin domain containing 3 (NLRP3) inflammasome and promoting autophagy. In vitro experiments demonstrated OTULIN's inhibition of inflammatory markers in microglia and neurons.

CONCLUSION

OTULIN is crucial in modulating TN, reducing neuropathic pain and neuroinflammation by activating the autophagy pathway and inhibiting the NLRP3 inflammasome.

Multi-metric predictors of radiofrequency-treated trigeminal neuralgias

Evaluation of neurovascular compression-related trigeminal neuralgia (NVC-TN) and its resolution through microvascular decompression are demonstrable by MRI and intraoperatively [Leal et al. (Atrophic changes in the trigeminal nerves of patients with trigeminal neuralgia due to neurovascular compression and their association with the severity of compression and clinical outcomes: Clinical article. J Neurosurg. 2014;120(6):1484-1495)]. Non-NVC-TNs treated by radiofrequency (RF) lack such detectable features. Multimodal integration of pre-surgical diffusion tensor imaging (DTI) and volumetry (VOL) with intraoperative neurophysiology (ION) could improve understanding and performance of RF among non-NVC-TN. We hypothesized that DTI disturbances' localization (central relay versus peripherally) rather than their values bares the most significant predictive value upon outcome and that ION could quantitatively both localize and assist RF of affected branches. The first pre-surgical step evaluated the differences between affected and non-affected sides (by DTI and VOL). Four TN's segments were studied, from peripheral to central relay: Meckel's cave-trigeminal ganglion (MC-TGN), cisternal portion, root entry zone (REZ) and spinal tract [Lin et al. (Flatness of the Meckel cave may cause primary trigeminal neuralgia: A radiomics-based study. J Headache Pain. 2021;22(1):104)]. In the second intraoperative step, we used both ION and patient's testimonies to confirm the localization of the affected branch, evolving hypoesthesia, pain reduction and monitoring of adverse effects [Sindou (Neurophysiological navigation in the trigeminal nerve: Use of masticatory responses and facial motor responses evoked by electrical stimulation of the trigeminal rootlets for RF-thermorhizotomy guidance. Stereotact Funct Neurosurg. 1999;73(1-4):117-121); Sindou and Tatli (Traitement de la névralgie trigéminale par thermorhizotomie. Neurochirurgie. 2009;55(2):203-210)]. Last and postoperatively, each data set's features and correlation with short-term (3 months) and long-term outcomes (23.5 ± 6.7 months) were independently analysed and blind to each other. Finally, we designed a multimodal predictive model. Sixteen non-NVC-TN patients (mean 53.6 ± SD years old) with mean duration of 6.56 ± 4.1 years (75% right TN; 43.8% V3) were included. After 23.5 ± 6.7 months, 14/16 were good responders. Age, gender, TN duration and side/branch did not correlate with outcomes. Affected sides showed significant DTI disturbances in both peripheral (MC-TGNs) and central-relay (REZ) segments. However, worse outcome correlated only with REZ-located DTI disturbances (P = 0.04; r = 0.53). Concerning volumetry, affected MC-TGNs were abnormally flatter: lower volumes and surface area correlated with worse outcomes (both P = 0.033; r = 0.55 and 0.77, respectively). Intraoperatively, ION could not differ the affected from non-affected branch. However, the magnitude of ION's amplitude reduction (ION-Δ-Amplitude) had the most significant correlation with outcomes (r = 0.86; P < 0.00006). It was higher among responders [68.4% (50-82%)], and a <40% reduction characterized non-responders [36.7% (0-40%)]. Multiple regression showed that ION-Δ-Amplitude, centrally located only REZ DTI integrity and MC-TGN flatness explain 82.2% of the variance of post-RF visual analogue score. Integration of pre-surgical DTI-VOL with ION-Δ-Amplitude suggests a multi-metric predictive model of post-RF outcome in non-NVC-TN. In multiple regression, central-relay REZ DTI disturbances and insufficiently reduced excitability (<40%) predicted worse outcome. Quantitative fine-tuned ION tools should be sought for peri-operative evaluation of the affected branches.

The Challenges in Clinical Diagnosis of Trigeminal Neuralgia: A Review

The lack of established laboratory tests or biomarkers for trigeminal neuralgia (TN) makes diagnosing this relatively rare condition extremely challenging. Trigeminal nerve compression observable on magnetic resonance imaging may indicate TN, but many patients do not have visible lesions or compression. In particular, TN may be confused with migraine, cluster headache, temporomandibular disorder, and other types of headache. An accurate diagnosis is imperative for proper treatment since these conditions do not respond to the same treatment. Many symptoms of these headaches can be vague or overlap, and clinicians depend in large measure on the subjective reports of their patients. Nevertheless, it is imperative to diagnose TN better, which can cause excruciating pain, reduce the quality of life, and even result in disability. It is possible that TN is underestimated.

Trigeminal neuralgia

Trigeminal neuralgia (TN) is a facial pain disorder characterized by intense and paroxysmal pain that profoundly affects quality of life and presents complex challenges in diagnosis and treatment. TN can be categorized as classical, secondary and idiopathic. Epidemiological studies show variable incidence rates and an increased prevalence in women and in the elderly, with familial cases suggesting genetic factors. The pathophysiology of TN is multifactorial and involves genetic predisposition, anatomical changes, and neurophysiological factors, leading to hyperexcitable neuronal states, central sensitization and widespread neural plasticity changes. Neurovascular compression of the trigeminal root, which undergoes major morphological changes, and focal demyelination of primary trigeminal afferents are key aetiological factors in TN. Structural and functional brain imaging studies in patients with TN demonstrated abnormalities in brain regions responsible for pain modulation and emotional processing of pain. Treatment of TN involves a multifaceted approach that considers patient-specific factors, including the type of TN, with initial pharmacotherapy followed by surgical options if necessary. First-line pharmacological treatments include carbamazepine and oxcarbazepine. Surgical interventions, including microvascular decompression and percutaneous neuroablative procedures, can be considered at an early stage if pharmacotherapy is not sufficient for pain control or has intolerable adverse effects or contraindications.

Trigeminal and Glossopharyngeal Neuralgia

Trigeminal neuralgia and glossopharyngeal neuralgia are craniofacial pain syndromes characterized by recurrent brief shock-like pains in the distributions of their respective cranial nerves. In this article, the authors aim to summarize each condition's characteristics, pathophysiology, and current pharmacotherapeutic and surgical interventions available for managing and treating these conditions.

Cranial Neuralgias

OBJECTIVE

The cranial neuralgias are relatively rare, but recognizing these syndromes and distinguishing among them is critical to reducing unnecessary pain and disability for affected patients. Despite their distinctive features, cranial neuralgias may go undiagnosed or misdiagnosed for several years. A notable proportion of cranial neuralgia presentations are due to secondary causes and require targeted treatment. The purpose of this article is to review the diagnosis and management of cranial neuralgias encountered in clinical practice.

LATEST DEVELOPMENTS

In 2020, the International Classification of Orofacial Pain was released for the first time. Modeled after the International Classification of Headache Disorders, it includes updated terminology for cranial neuralgias. The underlying pathophysiology of the cranial neuralgias is currently believed to be rooted in both peripheral and central nociceptive systems. In addition, a growing number of familial cases are being identified. Recent therapeutic advancements include a better understanding of how to utilize older therapies and procedures more effectively as well as the development of newer approaches.

ESSENTIAL POINTS

Cranial neuralgia syndromes are rare but important to recognize due to their debilitating nature and greater likelihood of having potentially treatable underlying causes. While management options have remained somewhat limited, scientific inquiry is continually advancing the understanding of these syndromes and how best to address them.

Frame navigation guided percutaneous balloon compression for intractable trigeminal neuralgia secondary to multiple sclerosis

Background

Patients with multiple sclerosis (MS) are more likely to develop trigeminal neuralgia (TN) compared to the regular population, due to scarring of the nerve and development of a demyelination plaque. Despite treatment, approximately 10% of MS patients treated for TN experience symptom recurrence, including the development of MS-like symptoms such as optic neuritis and bilateral facial pain.

Methods

A computed tomography (CT) scan was performed preoperatively on two patients diagnosed with multiple sclerosis (MS) who experienced secondary trigeminal neuralgia (TN). A precise reference frame was strapped firmly to the patient's forehead during the intraoperative procedure. Preliminary CT images were registered using the navigation system and the bony landmarks were set.

Case description

Two patients diagnosed with multiple sclerosis (MS) who experienced refractory trigeminal neuralgia (TN) underwent percutaneous balloon compression. Initial conservative treatment and one dosage of Gamma Knife Radiosurgery (GKR) resulted in symptom control for a few weeks. Both patients had an acute recurrence of pain; thus, percutaneous retrogasserian balloon compression was performed. During follow-up, the patients reported a 70% decrease in pain after the procedure, with minimal recurrence of shooting episodes.

Conclusion

Management of trigeminal neuralgia secondary to drug-resistant multiple sclerosis presents a persistent challenge. The percutaneous technique for retrogasserian balloon compression may offer a solution for some patients, but it presents unique challenges for neurosurgeons. Given the complexity of the pathogenesis, target identification, and the potential absence of neurovascular conflict, microvascular decompression remains a debated approach for this patient population. While stereotactic radiosurgery may be a promising alternative.

Altered trends of local brain function in classical trigeminal neuralgia patients after a single trigger pain

OBJECTIVE

To investigate the altered trends of regional homogeneity (ReHo) based on time and frequency, and clarify the time-frequency characteristics of ReHo in 48 classical trigeminal neuralgia (CTN) patients after a single pain stimulate.

METHODS

All patients underwent three times resting-state functional MRI (before stimulation (baseline), after stimulation within 5 s (triggering-5 s), and in the 30th min of stimulation (triggering-30 min)). The spontaneous brain activity was investigated by static ReHo (sReHo) in five different frequency bands and dynamic ReHo (dReHo) methods.

RESULTS

In the five frequency bands, the number of brain regions which the sReHo value changed in classical frequency band were most, followed by slow 4 frequency band. The left superior occipital gyrus was only found in slow 2 frequency band and the left superior parietal gyrus was only found in slow 3 frequency band. The dReHo values were changed in midbrain, left thalamus, right putamen, and anterior cingulate cortex, which were all different from the brain regions that the sReHo value altered. There were four altered trends of the sReHo and dReHo, which dominated by decreased at triggering-5 s and increased at triggering-30 min.

CONCLUSIONS

The duration of brain function changed was more than 30 min after a single pain stimulate, although the pain of CTN was transient. The localized functional homogeneity has time-frequency characteristic in CTN patients after a single pain stimulate, and the changed brain regions of the sReHo in five frequency bands and dReHo complemented to each other. Which provided a certain theoretical basis for exploring the pathophysiology of CTN.

Safety and efficacy of carbamazepine in the treatment of trigeminal neuralgia: A metanalysis in biomedicine

Trigeminal neuralgia is a debilitating condition characterized by severe facial pain. Carbamazepine has been widely used as a first-line treatment option for trigeminal neuralgia, but there is a need to evaluate its safety and efficacy based on existing evidence. This meta-analysis aims to systematically assess the available literature and provide a comprehensive evaluation of the safety and efficacy of carbamazepine in the treatment of trigeminal neuralgia. A thorough search of electronic databases yielded a total of 15 relevant studies that met the inclusion criteria. The pooled analysis of these studies revealed that carbamazepine demonstrated significant efficacy in reducing pain intensity and frequency in patients with trigeminal neuralgia. Moreover, the drug was generally well-tolerated, with the most common adverse events being mild and transient. Subgroup analyses based on different dosages and treatment durations further supported the overall findings. However, caution should be exercised in patients with certain comorbidities or specific populations, as some rare but severe adverse events were reported. In conclusion, this meta-analysis provides strong evidence supporting the safety and efficacy of carbamazepine as a valuable therapeutic option for the management of trigeminal neuralgia. These results can guide clinicians in making informed decisions regarding the use of carbamazepine and contribute to optimizing treatment strategies for patients with trigeminal neuralgia. Further research is warranted to explore long-term safety and efficacy outcomes, as well as to compare carbamazepine with alternative treatment modalities.

Optogenetic Approach in Trigeminal Neuralgia and Potential Concerns: Preclinical Insights

The integration of optogenetics in the trigeminal pain circuitry broadens and reinforces existing pain investigations. Similar to research on spinal neuropathic pain, the exploration of the underlying determinants of orofacial pain is expanding. Optogenetics facilitates more direct, specific, and subtle investigations of the neuronal circuits involved in orofacial pain. One of the most significant concerns of both dentistry and medicine is trigeminal neuralgia (TN) management due to its substantial impact on a patient's quality of life. Our objective is to gather insights from preclinical studies conducted in TN employing an optogenetic paradigm, thereby extending the prospects for in-depth neurobiological research. This review highlights optogenetic research in trigeminal pain circuitry involving TN. We outline the central and peripheral regions associated with pain-that have been investigated using optogenetics in the trigeminal pain circuitry. The study further reports its scope and limitations as well as its potential for future applications from bench to bedside.

In situ tissue profile of rat trigeminal nerve in trigeminal neuralgia using spatial transcriptome sequencing

BACKGROUND

Trigeminal neuralgia (TN) is the most common neuropathic disorder in the maxillofacial region. The etiology and pathogenesis of TN have not been clearly determined to date, although there are many hypotheses.

OBJECTIVE

The goal of this study was to investigate the interactions between different types of cells in TN, particularly the impact and intrinsic mechanism of demyelination on the trigeminal ganglion, and to identify new important target genes and regulatory pathways in TN.

METHODS

TN rat models were prepared by trigeminal root compression, and trigeminal nerve tissues were isolated for spatial transcriptome sequencing. The gene expression matrix was reduced dimensionally by PCA and presented by UMAP. Gene function annotation was analyzed by Metascape. The progression of certain clusters and the developmental pseudotime were analyzed using the Monocle package. Modules of the gene coexpression network between different groups were analyzed based on weighted gene coexpression network analysis and assigned AddModuleScore values. The intercellular communication of genes in these networks via ligand-receptor interactions was analyzed using CellPhoneDB analysis.

RESULTS

The results suggested that the trigeminal ganglion could affect Schwann cell demyelination and remyelination responses through many ligand-receptor interactions, while the effect of Schwann cells on the trigeminal ganglion was much weaker. Additionally, ferroptosis may be involved in the demyelination of Schwann cells.

CONCLUSIONS

This study provides spatial transcriptomics sequencing data on TN, reveals new markers, and redefines the relationship between the ganglion and myelin sheath, providing a theoretical basis and supporting data for future mechanistic research and drug development.

Radiomics nomogram based on MRI water imaging identifying symptomatic nerves of patients with primary trigeminal neuralgia: A preliminary study

The study proposes a combined nomogram based on radiomics features from magnetic resonance neurohydrography and clinical features to identify symptomatic nerves in patients with primary trigeminal neuralgia. We retrospectively analyzed 140 patients with clinically confirmed trigeminal neuralgia. Out of these, 24 patients constituted the external validation set, while the remaining 116 patients contributed a total of 231 nerves, comprising 118 symptomatic nerves, and 113 normal nerves. Radiomics features were extracted from the MRI water imaging (t2-mix3d-tra-spair). Radiomics feature selection was performed using L1 regularization-based regression, while clinical feature selection utilized univariate analysis and multivariate logistic regression. Subsequently, radiomics, clinical, and combined models were developed by using multivariate logistic regression, and a nomogram of the combined model was drawn. The performance of nomogram in discriminating symptomatic nerves was assessed through the area under the curve (AUC) of receiver operating characteristics, accuracy, and calibration curves. Clinical applications of the nomogram were further evaluated using decision curve analysis. Five clinical factors and 13 radiomics signatures were ultimately selected to establish predictive models. The AUCs in the training and validation cohorts were 0.77 (0.70-0.84) and 0.82 (0.72-0.92) with the radiomics model, 0.69 (0.61-0.77) and 0.66 (0.53-0.79) with the clinical model, 0.80 (0.74-0.87), and 0.85 (0.76-0.94) with the combined model, respectively. In the external validation set, the AUCs for the clinical, radiomics, and combined models were 0.70 (0.60-0.79), 0.78 (0.65-0.91), and 0.81 (0.70-0.93), respectively. The calibration curve demonstrated that the nomogram exhibited good predictive ability. Moreover, The decision curve analysis curve indicated shows that the combined model holds high clinical application value. The integrated model, combines radiomics features from magnetic resonance neurohydrography with clinical factors, proves to be effective in identify symptomatic nerves in trigeminal neuralgia. The diagnostic efficacy of the combined model was notably superior to that of the model constructed solely from conventional clinical features.

Conservative Management of Trigeminal Neuralgia and Degenerative Cervical Myelopathy: A Case Report

It is hypothesized that degenerative cervical myelopathy (DCM) may induce or exacerbate trigeminal neuralgia (TN) through mechanisms such as direct compression of the spinal trigeminal tract, inflammation, or vascular issues, leading to ischemia within cervical segments C3-C4, where the spinal trigeminal nucleus extends. Here, we report the potential therapeutic impact of chiropractic treatment in a 55-year-old female with TN resistance to medical therapy and DCM. The patient received targeted chiropractic care, consisting of high-velocity, low-amplitude (HVLA) spinal manipulation of the C3-C7 and T1-T4 vertebral segments to address joint dysfunction, coupled with intermittent mechanical cervical traction for 20-minute sessions, and focused radial shockwave therapy aimed at myofascial trigger points within the trapezius and levator scapulae muscles. After initiating the chiropractic care plan, the patient experienced a significant reduction in the frequency and severity of TN pain, which persisted throughout the treatment period. Notably, this alleviation in symptoms was maintained at the six-month follow-up, suggesting a sustained therapeutic effect rather than a transient improvement. The lasting nature of the pain reduction provides a compelling argument for the long-term benefits of chiropractic intervention in the management of TN, particularly in cases with concurrent DCM.

Headache and Other Pain Syndromes in Multiple Sclerosis: A Narrative Review

Multiple sclerosis is a chronic and progressive neurological disease, with an important socio-economic burden. Over time, an increased incidence of headaches like migraines and tension headaches has been observed among these patients. Headaches have not been considered as multiple sclerosis-related symptoms, even representing a red flag for multiple sclerosis diagnosis. It is uncertain whether the headache-multiple sclerosis association could be explained by the presence of common triggers or a common physiopathological mechanism (involvement of tertiary B-cell follicles). An important differential diagnosis is between multiple sclerosis attacks and migraines with aura, which can also be associated with neurological deficits. Another important aspect is the occurrence or exacerbation of the cephalalgic syndrome after the initiation of therapy for multiple sclerosis (DMTs), or the improvement of headache after the initiation of certain DMT drugs. In addition to headaches, individuals diagnosed with multiple sclerosis often report experiencing diverse pain syndromes, contributing to an additional decline in their overall quality of life. These syndromes are frequently neglected, the focus being on slowing down the progression of neurological deficits. This review aims to evaluate the characteristics of multiple-sclerosis-related headaches (frequency, possible correlation with attacks, and disease-modifying therapies) and the key distinctions in imaging characteristics between demyelinating lesions in multiple sclerosis and those observed in cases of primary headaches.

The Therapeutic Effect of Botulinum Toxin Type A on Trigeminal Neuralgia: Are There Any Differences between Type 1 versus Type 2 Trigeminal Neuralgia?

BACKGROUND

Botulinum toxin type A is an effective treatment for trigeminal neuralgia. Moreover, its efficacy in type 2 trigeminal neuralgia and comparative studies between type 1 and type 2 trigeminal neuralgia (TN) still need to be improved.

METHODS

We treated 40 TN patients with onabotulinumtoxinA; 18 had type 1 TN, and 22 had type 2 TN. We compared the baseline pain score with the Visual Analogue Scale (VAS) and paroxysm frequency (number per week) at the baseline with those obtained at 1-month and 3-month follow-ups. Nonetheless, we compared the baseline Penn Facial Pain Scale with the scores obtained at the 1-month follow-up.

RESULTS

BoNT/A effectively reduced pain intensity and frequency at the 1-month and 3-month follow-ups. Moreover, the type 1 TN and type 2 TN groups had baseline pain scores of 7.8 ± 1.65 and 8.4 ± 1.1, respectively. Pain significantly improved (p < 0.001) in both groups to 3.1 ± 2.3 (type 1 TN) and 3.5 ± 2.3 (type 2 TN) at the 1-month follow-up and to 3.2 ± 2.5 (type 1 TN) and 3.6 ± 2.5 (type 2 TN) at the 3-month follow-up. There was no difference between the two groups (p 0.345). The baseline paroxysm frequencies (number per week) were 86.7 ± 69.3 and 88.9 ± 62.2 for the type 1 and type 2 TN groups, respectively; they were significantly reduced in both groups at the 1-month and 3-month follow-ups without significant differences between the two groups (p 0.902). The Pain Facial Pain Scale improved at the 1-month follow-up, and no significant differences were found between the two groups. There was a strong correlation between background pain and paroxysm pain intensity (r 0.8, p < 0.001).

CONCLUSIONS

Botulinum toxin type A effectively reduced the pain, paroxysm frequency, and PFPS scores of type 1 and type 2 trigeminal neuralgia patients without statistically significant differences. Facial asymmetry was the only adverse event.

Attenuates reactive oxygen species: induced pyroptosis via activation of the Nrf2/HO-1 signal pathway in models of trigeminal neuralgia

In this study, we examined the impact of demyelinating and neuroinflammation on trigeminal neuralgia (TN) by utilizing models of chronic constriction injury to the infraorbital nerve (CCI). The CCI rats were treated with either VX-765 (an inhibitor of caspase-1) or a control solution of PBS/DMSO to observe the effects on neurobehavioral and neuropathological outcomes. The histochemical changes, pyroptosis-related proteins were assessed using immunohistochemistry, Elisa, and western blotting. RSC96 cells were pretreated with belnacasan (VX-765, an inhibitor of caspase-1), Gasdermin D(GSDMD)-targeting siRNAs, cobalt protoporphyrin (CoPP) or zinc protoporphyrin (Znpp) before being exposed to H2O2. Following these treatments, the Reactive oxygen species (ROS) level, cell viability, percentage of pyroptosis, pyroptosis-related proteins, nuclear factor erythroid 2-related factor 2 (Nrf2) and HO-1 level was measured. The scanning electron microscopy revealed increased ball-like bulge and membrane pore formation in the CCI group. In the CCI and CCI+ Vehicle groups, we found ROS level and expression of pyroptosis-related proteins increased. While, treatment with VX-765resulted in a decreased expression of GSDMD, IL-1, IL-18, and caspase-1 decreased. In the in-vitro study, RSC96 cells showed mild pyroptosis and overall mild edema after being exposed to H2O2. The ROS level, percentage of pyroptosis, pyroptosis-related proteins, Nrf2 and HO-1 level increased significantly in the H2O2 group. While, the percentage of pyroptosis and pyroptosis-related proteins decreased significantly in the H2O2 + VX-765 group, H2O2 + siRNA group, and H2O2 + VX-765 + siRNA group. After treatment with HO-1-inhibitor Znpp and HO-1-activator Copp, the percentage of pyroptosis and pyroptosis-related proteins increased and decreased significantly respectively. In conclusions, the pyroptosis of Schwann cell in the CCI model generated the demyelination of TN nerve. The ROS is an upstream event of NLRP3 inflammasome activation which induced eventual pyroptosis. The Nrf2/HO-1 signaling pathway could protect the H2O2-induced pyroptosis in RSC96 cells.

Online dynamic nomogram for predicting pain recurrence after microvascular decompression in trigeminal neuralgia

Trigeminal neuralgia (TN) is one of the most common causes of facial pain. Microvascular decompression (MVD) is the first-choice surgical treatment. The present study aimed to develop a novel practical assessment system based on preoperative clinical and imaging factors for clinicians to predict the likelihood of pain recurrence following MVD in TN. A total of 56 patients with primary unilateral TN who underwent MVD were retrospectively analyzed. Patients were followed up to observe pain recurrence 1 year after MVD. An online dynamic nomogram was constructed for predicting the probability of pain recurrence after MVD in patients with TN based on multivariate logistic model. The concordance index (C-index) and receiver operating characteristic (ROC) were used to measure model discrimination. Bootstrap resampling was used for internal validation of the model and calibration curve was constructed. Decision curve analysis (DCA) was used to assess clinical applicability. Factors such as numeric rating scale (to score pain degree of patients with TN), response to neuroanalgesic drugs and neurovascular contact on magnetic resonance imaging were independent risk factors affecting the pain recurrence rate (all P<0.05). C-index was 0.973 (95%CI, 0.938-1.000) and the area under the ROC was 0.973 (95%CI, 0.938-1.000). Calibration curve with a 1,000 bootstrap resampling showed a good fit between dynamic nomogram prediction and actual observations. The DCA showed that at a threshold probability between 0 and 100%, this model can achieve a greater net benefit than if all patients had surgery or none had surgery. In conclusion, this online dynamic nomogram reliably predicted risk of pain recurrence in patients with TN following MVD.

Amelioration of nerve demyelination by hydrogen-producing silicon-based agent in neuropathic pain rats

Trigeminal neuralgia (TN) is a complex orofacial neuropathic pain. The crippling condition's underlying mechanism is still not completely understood. The main cause of lightning-like pain in patients with TN may be chronic inflammation that causes nerve demyelination. Nano-silicon (Si) can safely and continuously produce hydrogen in the alkaline environment of the intestine to exert systemic anti-inflammatory effects. Hydrogen has a promising anti-neuroinflammatory impact. The study aimed to determine how intra-intestinal application of a hydrogen-producing Si-based agent affected the demyelination of the trigeminal ganglion in TN rats. We discovered that increased expression of the NLRP3 inflammasome and inflammatory cell infiltration occurred concurrently with demyelination of the trigeminal ganglion in TN rats. We could determine that the neural effect of the hydrogen-producing Si-based agent was connected to the inhibition of microglial pyroptosis by using transmission electron microscopy. The results demonstrated that the Si-based agent reduced the infiltration of inflammatory cells and the degree of neural demyelination. In a subsequent study, it was discovered that hydrogen produced by a Si-based agent regulates the pyroptosis of microglia may through the NLRP3-caspase-1-GSDMD pathway, preventing the development of chronic neuroinflammation and consequently lowering the incidence of nerve demyelination. This study offers a novel strategy for elucidating the pathogenesis of TN and developing potential therapeutic drugs.

Orofacial Pain: Molecular Mechanisms, Diagnosis, and Treatment 2021

The Special Issue “Orofacial Pain: Molecular Mechanisms, Diagnosis, and Treatment 2021” contains 6 articles published by 41 authors from different countries focusing on nucleus accumbens core GABAergic neurons, receptor-interacting serine/threonine-protein kinase 1, pannexin 1-mediated ATP signaling, ultra-low-frequency transcutaneous electrical nerve stimulation, and triamcinolone acetonide. The content covers several pain models, including neuropathic pain caused by peripheral nerve constriction or malpositioned dental implants, tongue cancer, myogenous temporomandibular dysfunction, and oral ulcerative mucositis. In addition, a review paper on trigeminal neuralgia is included.