Trigeminal neuralgia: An overview from pathophysiology to pharmacological treatments

Different mechanisms guide the antinociceptive effect of bone marrow-mononuclear cells and bone marrow-mesenchymal stem/stromal cells in trigeminal neuralgia

AIMS

Trigeminal neuralgia (TN) is a type of chronic orofacial pain evoked by trivial stimuli that manifests as episodes of excruciating and sudden, recurrent paroxysmal pain. Most patients are refractory to pharmacological therapy used for the treatment of TN. Mononuclear cells (MNC) and mesenchymal stem/stromal cells (MSC) have shown therapeutic potential in painful neuropathies, but their mechanism of action is not fully understood. The present work aimed to investigate the antinociceptive effect and mechanism of action of MNC and MSC in experimental TN.

MATERIALS AND METHODS

Mice submitted to the chronic constriction injury of the infraorbital nerve (CCI-ION) mouse model of TN received a single intravenous injection of saline, MNC, or MSC (1 × 106 cells/mouse). The effect of the treatments on the behavioral signs of painful neuropathy, morphological aspects of the infraorbital nerve, and inflammatory and oxidative stress markers in the infraorbital nerve were assessed.

KEY FINDINGS

MNC and MSC improved behavioral painful neuropathy, activated key cell signaling antioxidant pathways by increasing Nrf2 expression, and reduced the proinflammatory cytokines IL-1β and TNF-α. However, treatment with MSC, but not MNC, was associated with a sustained increase of IL-10 and with the re-establishment of the morphometric pattern of the infraorbital nerve, indicating a difference in the mechanism of action between MNC and MSC. In line with this result, in IL-10 knockout mice, MSC transplantation did not induce an antinociceptive effect.

SIGNIFICANCE

Importantly, these data suggest an IL-10-induced disease-modifying profile related to MSC treatment and reinforce cell therapy's potential in treating trigeminal neuralgia.

Pain Relief-Related Structural Brain Alterations in Trigeminal Neuralgia Induced by Noninvasive Stereotactic Radiosurgery: A Pilot Study

PURPOSE

Trigeminal neuralgia (TN) is a chronic pain disorder defined by unilateral shock-like pain in at least one division of the trigeminal nerve. Although several studies have investigated structural brain plasticity in patients with TN, treatment-induced alterations remain largely uninvestigated.

METHODS AND MATERIALS

Combining T1-weighted magnetic resonance imaging with voxel-based morphometry and multiple-regression analyses, we assessed gray matter maps of patients with TN to investigate changes in gray matter volume (GMV) before and 6 months after stereotactic radiosurgery (SRS).

RESULTS

Comparison of pre- and post-SRS GMV of 25 patients with TN (16 women; mean age 67 years) did not yield any significant clusters, suggesting that the effect of SRS intervention itself on gray matter structure may be negligible. Regarding SRS-induced pain relief, we found a significant GMV increase in the left superior frontal gyrus associated with greater degree of pain relief (P = .024) and a trend toward an increase in GMV in the left dorsolateral prefrontal cortex (P = .097).

CONCLUSIONS

In this pilot study, we observed significant increases in GMV in the left superior frontal gyrus with SRS-induced improvements in pain and a trend toward an increase in GMV in the dorsolateral prefrontal cortex. Future studies are indicated to validate these findings and determine whether SRS-induced decrease in distracting pain events and subsequent increases in GMV result in improved functionality, decreased dependence on "top-down" control, and improved cognitive/executive balance with amelioration of pain events.

Botulinum toxin type A is a potential therapeutic drug for chronic orofacial pain

BACKGROUND

Botulinum toxin type A (BTX-A), produced by the gram-positive anaerobic bacterium Clostridium botulinum, acts by cleaving synaptosome-associated protein-25 (SNAP-25), an essential component of the presynaptic neuronal membrane that is necessary for fusion with the membrane proteins of neurotransmitter-containing vesicles. Recent studies have highlighted the efficacy of BTX-A in treating chronic pain conditions, including lower back pain, chronic neck pain, neuropathic pain, and trigeminal neuralgia, particularly when patients are unresponsive to traditional painkillers. This review focuses on the analgesic effects of BTX-A in various chronic pain conditions, with a particular emphasis on the orofacial region.

HIGHLIGHT

This review focuses on the mechanisms by which BTX-A induces analgesia in patients with inflammatory and temporomandibular joint pain. This review also highlights the fact that BTX-A can effectively manage neuropathic pain and trigeminal neuralgia, which are difficult-to-treat chronic pain conditions. Herein, we present a comprehensive assessment of the central analgesic effects of BTX-A and a discussion of its various applications in clinical dental practice.

CONCLUSION

BTX-A is an approved treatment option for various chronic pain conditions. Although there is evidence of axonal transport of BTX-A from peripheral to central endings in motor neurons, the precise mechanism underlying its pain-modulating effects remains unclear. This review discusses the evidence supporting the effectiveness of BTX-A in controlling chronic pain conditions in the orofacial region. BTX-A is a promising therapeutic agent for treating pain conditions that do not respond to conventional analgesics.

Advanced neuroimaging of the trigeminal nerve and the whole brain in trigeminal neuralgia: a systematic review

ABSTRACT

For trigeminal neuralgia (TN), a major role of imaging is to identify the causes, but recent studies demonstrated structural and microstructural changes in the affected nerve. Moreover, an increasing number of studies have reported central nervous system involvement in TN. In this systematic review, recent quantitative magnetic resonance imaging (MRI) studies of the trigeminal nerve and the brain in patients with TN were compiled, organized, and discussed, particularly emphasizing the possible background mechanisms and the interpretation of the results. A systematic search of quantitative MRI studies of the trigeminal nerve and the brain in patients with TN was conducted using PubMed. We included the studies of the primary TN published during 2013 to 2023, conducted for the assessment of the structural and microstructural analysis of the trigeminal nerve, and the structural, diffusion, and functional MRI analysis of the brain. Quantitative MRI studies of the affected trigeminal nerves and the trigeminal pathway demonstrated structural/microstructural alterations and treatment-related changes, which differentiated responders from nonresponders. Quantitative analysis of the brain revealed changes in the brain areas associated with pain processing/modulation and emotional networks. Studies of the affected nerve demonstrated evidence of demyelination and axonal damage, compatible with pathological findings, and have shown its potential value as a tool to assess treatment outcomes. Quantitative MRI has also revealed the possibility of dynamic microstructural, structural, and functional neuronal plasticity of the brain. Further studies are needed to understand these complex mechanisms of neuronal plasticity and to achieve a consensus on the clinical use of quantitative MRI in TN.

Nanomedicine and voltage-gated sodium channel blockers in pain management: a game changer or a lost cause?

Pain, a complex and debilitating condition affecting millions globally, is a significant concern, especially in the context of post-operative recovery. This comprehensive review explores the complexity of pain and its global impact, emphasizing the modulation of voltage-gated sodium channels (VGSC or NaV channels) as a promising avenue for pain management with the aim of reducing reliance on opioids. The article delves into the role of specific NaV isoforms, particularly NaV 1.7, NaV 1.8, and NaV 1.9, in pain process and discusses the development of sodium channel blockers to target these isoforms precisely. Traditional local anesthetics and selective NaV isoform inhibitors, despite showing varying efficacy in pain management, face challenges in systemic distribution and potential side effects. The review highlights the potential of nanomedicine in improving the delivery of local anesthetics, toxins and selective NaV isoform inhibitors for a targeted and sustained release at the site of pain. This innovative strategy seeks to improve drug bioavailability, minimize systemic exposure, and optimize therapeutic outcomes, holding significant promise for secure pain management and enhancing the quality of life for individuals recovering from surgical procedures or suffering from chronic 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.

An overview of the safety and efficacy of LX-9211 in treating neuropathic pain conditions

INTRODUCTION

LX-9211 is a drug designed to treat neuropathic pain conditions. It functions by inhibiting the adaptor-associated kinase 1 (AAK1) enzyme which promotes clathrin-dependent endocytosis. Preclinical studies have shown that LX-9211 does produce a reduction in nociceptive related behaviors and produces no major adverse effects in rats. Thus, LX-9211 has advanced to clinical trials to assess its safety and efficacy in humans. So far, phase 1 and phase 2 clinical trials involving patients with postherpetic neuralgia and diabetic peripheral neuropathic pain have been conducted with phase 3 trials planned in the future.

AREAS COVERED

This paper highlights preclinical studies involving LX-9211 in rodents. Additionally, phase 1 clinical trials examining the safety of LX-9211 in healthy subjects as well as phase 2 studies looking at the safety and efficacy of LX-9211 compared to placebo in patients with diabetic peripheral neuropathic pain and postherpetic neuralgia are also discussed.

EXPERT OPINION

In phase 1 and phase 2 clinical trials conducted so far, LX-9211 has been shown to produce few adverse effects as well as cause a significantly greater reduction in pain compared to placebo. However, more clinical studies are needed to further assess its effects in humans to ensure its safety.

Factors associated with outcomes following microvascular decompression for the treatment of primary trigeminal neuralgia in adults: a systematic review and meta-analysis

This study aimed to evaluate pain assessment strategies and factors associated with outcomes after microvascular decompression for the treatment of primary trigeminal neuralgia in adults. We conducted a systematic review and meta-analysis of English, Spanish, and French literature. We searched three databases, PubMed, Ovid, and EBSCO, from 2010 to 2022 and selected studies including patients with primary trigeminal neuralgia, clear pain assessment, and pain outcomes. Population means and standard deviations were calculated. Studies that included factors associated with postoperative outcomes were included in the meta-analysis. A total of 995 studies involving 5673 patients with primary trigeminal neuralgia following microvascular decompression were included. Patients with arteries compressing the trigeminal nerve demonstrated optimal outcomes following microvascular decompression (odds ratio [OR]= 0.39; 95% confidence interval [CI] = 0.19-0.80; X2 = 46.31; Dof = 15; I2 = 68%; P = < 0.0001). Conversely, when comparing arterial vs venous compression of the trigeminal nerve (OR = 2.72; 95% CI = 1.16-6.38; X2 = 23.23; Dof = 10; I2 = 57%; P = 0.01), venous compression demonstrated poor outcomes after microvascular decompression. Additionally, when comparing single-vessel vs multiple-vessel compression (OR = 2.72; 95% CI = 1.18-6.25; X2 = 21.17; Dof = 9; I2 = 57%; P = 0.01), patients demonstrated unfavorable outcomes after microvascular decompression. This systematic review and meta-analysis evaluated factors associated with outcomes following microvascular decompression (MVD) for primary trigeminal neuralgia (PTN). Although MVD is an optimal treatment strategy for PTN, a gap exists in interpreting the results when considering the lack of evidence for most pain assessment strategies.

Interdisciplinary strategies for diagnosis and treatment of trigeminal neuralgia

Temporary, sudden, shooting and recurrent unilateral facial pain in the supply area of one or more trigeminal nerve branches characterises trigeminal neuralgia. Innocuous stimuli trigger the pain, e.g. chewing, speaking or brushing teeth. In some patients, paroxysms superimpose on continuous pain. In aetiological terms, idiopathic, classic (due to neurovascular compression) and secondary trigeminal neuralgia (e.g. due to multiple sclerosis, brainstem ischaemia and space-occupying lesions) are defined. Many drugs may be efficacious, with carbamazepine being first-choice therapy. However, non-pharmacological and invasive procedures may also help. To reach the correct diagnosis and determine the best therapeutic measures, adequate pain characterisation and interdisciplinary collaboration are essential. We hereby present our experience of an interdisciplinary approach for the diagnosis and treatment of trigeminal neuralgia.

The efficacy of acupuncture for trigeminal neuralgia: an overview of systematic reviews

Background

Many systematic reviews (SRs) and meta-analysis (MAs) have reported the efficacy of acupuncture treatment for primary trigeminal neuralgia (PTN), but the quality of evidence is unknown and therefore needs to be evaluated comprehensively.

Methods

Eight electronic databases were searched from their inception until January 5, 2024. The methodological quality, reporting quality, and risk of bias of the included SRs were assessed by the assessment of multiple systematic reviews 2 (AMSTAR-2), the Risk of Bias in Systematic Reviews (ROBIS) tool, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The quality of evidence for outcome measures was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE).

Results

We identified 13 SRs/MAs met inclusion criteria. According to the results of the AMSTAR-2, six were rated as critically low quality and seven as low quality. According to ROBIS assessment, 8 SRs/MAs were classified as low risk, and 5 SRs/MAs were found to be high risk. The PRISMA report still has some reporting deficiencies in aspects such as protocol and registration, search strategy, risk of bias, additional analyzes and funding. According to the GRADE system, no high-quality evidence was found, 1 was of moderate quality, 4 were of low quality, and 8 were of critical low quality.

Conclusion

Based on the evidence collected, acupuncture shows promise as a treatment for PTN patients. However, it is important to note that the included SRs/MAs generally have low methodological quality and evidence quality. Therefore, caution must be exercised when interpreting this conclusion. To enhance future research in this area, it is recommended to adequately report methodological details and adhere to guidelines for conducting SRs/MAs.Systematic review registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42024499280.

Exploring biomarkers in trigeminal neuralgia patients operated with microvascular decompression: A comparison with multiple sclerosis patients and non-neurological controls

BACKGROUND

Trigeminal neuralgia (TN) is a severe facial pain condition often associated with a neurovascular conflict. However, neuroinflammation has also been implicated in TN, as it frequently co-occurs with multiple sclerosis (MS).

METHODS

We analysed protein expression levels of TN patients compared to MS patients and controls. Proximity Extension Assay technology was used to analyse the levels of 92 proteins with the Multiplex Neuro-Exploratory panel provided by SciLifeLab, Uppsala, Sweden. Serum and CSF samples were collected from TN patients before (n = 33 and n = 27, respectively) and after (n = 28 and n = 8, respectively) microvascular decompression surgery. Additionally, we included samples from MS patients (n = 20) and controls (n = 20) for comparison.

RESULTS

In both serum and CSF, several proteins were found increased in TN patients compared to either MS patients, controls, or both, including EIF4B, PTPN1, EREG, TBCB, PMVK, FKBP5, CD63, CRADD, BST2, CD302, CRIP2, CCL27, PPP3R1, WWP2, KLB, PLA2G10, TDGF1, SMOC1, RBKS, LTBP3, CLSTN1, NXPH1, SFRP1, HMOX2, and GGT5. The overall expression of the 92 proteins in postoperative TN samples seems to shift towards the levels of MS patients and controls in both serum and CSF, as compared to preoperative samples. Interestingly, there was no difference in protein levels between MS patients and controls.

CONCLUSIONS

We conclude that TN patients showed increased serum and CSF levels of specific proteins and that successful surgery normalizes these protein levels, highlighting its potential as an effective treatment. However, the similarity between MS and controls challenges the idea of shared pathophysiology with TN, suggesting distinct underlying mechanisms in these conditions.

SIGNIFICANCE

This study advances our understanding of trigeminal neuralgia (TN) and its association with multiple sclerosis (MS). By analysing 92 protein biomarkers, we identified distinctive molecular profiles in TN patients, shedding light on potential pathophysiological mechanisms. The observation that successful surgery normalizes many protein levels suggests a promising avenue for TN treatment. Furthermore, the contrasting protein patterns between TN and MS challenge prevailing assumptions of similarity between the two conditions and point to distinct pathophysiological mechanisms.

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.

The Use of Compounds Derived from Cannabis sativa in the Treatment of Epilepsy, Painful Conditions, and Neuropsychiatric and Neurodegenerative Disorders

Neurological disorders present a wide range of symptoms and challenges in diagnosis and treatment. Cannabis sativa, with its diverse chemical composition, offers potential therapeutic benefits due to its anticonvulsive, analgesic, anti-inflammatory, and neuroprotective properties. Beyond cannabinoids, cannabis contains terpenes and polyphenols, which synergistically enhance its pharmacological effects. Various administration routes, including vaporization, oral ingestion, sublingual, and rectal, provide flexibility in treatment delivery. This review shows the therapeutic efficacy of cannabis in managing neurological disorders such as epilepsy, neurodegenerative diseases, neurodevelopmental disorders, psychiatric disorders, and painful pathologies. Drawing from surveys, patient studies, and clinical trials, it highlights the potential of cannabis in alleviating symptoms, slowing disease progression, and improving overall quality of life for patients. Understanding the diverse therapeutic mechanisms of cannabis can open up possibilities for using this plant for individual patient needs.

Deciphering the functional role of insular cortex stratification in trigeminal neuropathic pain

Trigeminal neuropathic pain (TNP) is a major concern in both dentistry and medicine. The progression from normal to chronic TNP through activation of the insular cortex (IC) is thought to involve several neuroplastic changes in multiple brain regions, resulting in distorted pain perception and associated comorbidities. While the functional changes in the insula are recognized contributors to TNP, the intricate mechanisms underlying the involvement of the insula in TNP processing remain subjects of ongoing investigation. Here, we have overviewed the most recent advancements regarding the functional role of IC in regulating TNP alongside insights into the IC's connectivity with other brain regions implicated in trigeminal pain pathways. In addition, the review examines diverse modulation strategies that target the different parts of the IC, thereby suggesting novel diagnostic and therapeutic management of chronic TNP in the future.

History, Rest and Exercise Score (HRE-S) for assessment of disease severity in horses with trigeminal-mediated headshaking

BACKGROUND

In horses with trigeminal-mediated headshaking (TMHS), clinical signs are likely to be expression of neuropathic facial pain. Currently, subjective assessment of disease severity is used as measure of compromise of animal's welfare.

OBJECTIVES

To develop and validate a precise scoring system for TMHS: History, Rest and Exercise Score (HRE-S). The HRE-S consists of three subscores: history score (H-S), resting score (R-S) and exercise score (E-S).

STUDY DESIGN

Retrospective observational study.

METHODS

Seven masked observers with different experience used HRE-S to score 40 video recordings taken during rest and lungeing including five duplicates. Video recordings were taken from nine horses with TMHS and three controls. Inter- and intraobserver reliability and practicability of HRE-S were assessed. For every video recording severity of clinical signs was graded by every observer using an intuitive global-type-scale and interobserver reliability was calculated. Convergent validity was evaluated comparing HRE-S to groups created by an existing score (grade 0-3). Discriminant validity was analysed comparing HRE-S to groups created by intuitive global-type-scale.

RESULTS

Reliability for HRE-S was excellent, irrespective of observers experience: Spearman's Rho = 0.946, p < 0.001 (intraobserver reliability) and intraclass correlation coefficient = 0.98, p < 0.001 (interobserver reliability). Interobserver reliability for intuitive global-type-scale was fair to substantial: Fleiss' κappa = 0.48 (R-S) -0.63 (E-S). Groups created by intuitive global-type-scale had significantly different R-S and E-S (p < 0.05), demonstrating discriminant validity. Convergent validity was proven as horses with grade 3/3 had significantly higher average E-S and total scores compared with an existing score than those with grade 0/3 or 1/3 (p < 0.001).

MAIN LIMITATIONS

Retrospective nature, video recordings, sample size.

CONCLUSIONS

HRE-S is a valid and reliable score evaluating disease severity in TMHS, independent of observers' experience.

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.

Application of the HRE-S to 140 horses with trigeminal-mediated headshaking and the association of clinical signs with diagnosis, therapy, and outcome

Background

Horses with trigeminal-mediated headshaking (TMHS) exhibit different headshaking patterns (HSPs), electric shock-like jerking, signs of nasal irritation, and painful facial expressions. The History Rest and Exercise Score (HRE-S) was developed to objectively clarify the severity of the condition in affected horses. This score considers the history and severity of clinical signs at rest and exercise. This study aimed to assess the frequency of different clinical signs and their individual associations with diagnosis, treatment, and outcome in horses diagnosed with TMHS.The clinical records of horses presented with headshaking (HS) at the Clinic for Horses, University of Veterinary Medicine Hannover, between 2006 and 2021 were assessed retrospectively for clinical signs, diagnosis, and treatment. A total of 140 horses were included in the study. Video recordings were evaluated using the HRE-S and compared to the score described by Talbot. Following discharge, owners were interviewed via telephone about the outcome. Correlations between the presence and severity of clinical signs, diagnosis, and outcome were evaluated.

Results

The following clinical signs were significantly correlated with a higher HRE-S and grade by Talbot: HS at walk (independently of HSP) (52.9%, 74/140), increased total number of demonstrated HSP (independent of the dominant HSP) (more than one HSP per horse in 91.4%, 128/140), signs of nasal irritation (75.9%, 104/137), painful facial expression (67.8%, 80/118), and electric shock-like jerking (77.5%, 107/138). Diagnosis and outcome do not correlate with the presence of the above-mentioned clinical signs.

Conclusion

The HRE-S was confirmed as a valid tool to evaluate disease severity in a cohort of 140 horses with HS. Additionally, clinical signs identified as indicators for higher disease severity may have a stronger negative effect on patient welfare, but they do not correlate with diagnosis or outcome.

Neuronavigation-guided Percutaneous Rhizotomies to Trigeminal Neuralgia: A Systematic Review

OBJECTIVE

Neuronavigation improves intraoperative visualization of the cranial structures, which is valuable in percutaneous surgical treatments for patients with trigeminal neuralgia (TN) who are refractory to pharmacotherapy or reluctant to receive open surgery. The objective of this review was to evaluate the available neuronavigation-guided percutaneous surgical treatment modalities with cannulation of foramen ovale to TN, and their relative benefits and limitations.

METHODS

This review was conducted based on the PRISMA statement. An initial search was performed on electronic databases, followed by manual and reference searches. Study and patient characteristics, rhizotomy procedure and neuronavigation details, and treatment outcomes (initial pain relief and pain recurrence within 2 y, success rate of forman ovale cannulation, and complications) were evaluated. The risk of bias was assessed with a quality assessment based on the ROBINS-I tools.

RESULTS

Ten studies (491 operations, 403 participants) were analyzed. Three percutaneous trigeminal rhizotomy modalities identified were radiofrequency thermocoagulation rhizotomy (RFTR), percutaneous balloon compression, and glycerol rhizotomy. Intraoperative computed tomography and magnetic resonance imaging fusion-based RFTR had the highest initial pain relief rate of 97.0%. The success rate of foramen ovale cannulation ranged from 92.3% to 100% under neuronavigation. Facial hypoesthesia and masticatory muscle weakness were the most reported complications.

DISCUSSION

Neuronavigation-guided percutaneous trigeminal rhizotomies showed possible superior pain relief outcomes to that of conventional rhizotomies in TN, with the benefits of radiation reduction and lower complication development rates. The limitations of neuronavigation remain its high cost and limited availability. Higher-quality prospective studies and randomized clinical trials of neuronavigation-guided percutaneous trigeminal rhizotomy were lacking.

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.

Sex differences in carbamazepine effects in a rat model of trigeminal neuropathic pain

Carbamazepine (CBZ) represents the first-line treatment for trigeminal neuralgia, a condition of facial pain that affects mainly women. The chronic constriction of the infraorbital nerve (CCI-ION) is a widely used model to study this condition, but most studies do not include females. Thus, this study aimed to characterize sensory and affective changes in female rats after CCI-ION and compare the effect of CBZ in both sexes. Mechanical allodynia was assessed 15 days after CCI-ION surgery in rats treated with CBZ (10 and 30 mg/kg, i.p.) or vehicle, together with the open-field test. Independent groups were tested on the Conditioned Place Preference (CPP) paradigm and ultrasonic vocalization (USV) analysis. Blood samples were collected for dosage of the main CBZ metabolite. CBZ at 30 mg/kg impaired locomotion of CCI-ION male and sham and CCI-ION female rats and resulted in significantly higher plasma concentrations of 10-11-EPX-CBZ in the latter. Only male CCI-ION rats showed increased facial grooming which was significantly reduced by CBZ at 10 mg/kg. CBZ at 10 mg/kg significantly reduced mechanical allodynia and induced CPP only in female CCI-ION rats. Also, female CCI-ION showed reduced emission of appetitive USV but did not show anxiety-like behavior. In conclusion, male and female CCI-ION rats presented differences in the expression of the affective-motivational pain component and CBZ was more effective in females than males. Further studies using both sexes in trigeminal neuropathic pain models are warranted for a better understanding of potential differences in the pathophysiological mechanisms and efficacy of pharmacological treatments.

Local Administration of the Phytochemical, Quercetin, Attenuates the Hyperexcitability of Rat Nociceptive Primary Sensory Neurons Following Inflammation Comparable to lidocaine

Although in vivo local injection of quercetin into the peripheral receptive field suppresses the excitability of rat nociceptive trigeminal ganglion (TG) neurons, under inflammatory conditions, the acute effects of quercetin in vivo, particularly on nociceptive TG neurons, remain to be determined. The aim of this study was to examine whether acute local administration of quercetin into inflamed tissue attenuates the excitability of nociceptive TG neurons in response to mechanical stimulation. The mechanical escape threshold was significantly lower in complete Freund's adjuvant (CFA)-inflamed rats compared to before CFA injection. Extracellular single-unit recordings were made from TG neurons of CFA-induced inflammation in anesthetized rats in response to orofacial mechanical stimulation. The mean firing frequency of TG neurons in response to both non-noxious and noxious mechanical stimuli was reversibly inhibited by quercetin in a dose-dependent manner (1-10 mM). The mean firing frequency of inflamed TG neurons in response to mechanical stimuli was reversibly inhibited by the local anesthetic, 1% lidocaine (37 mM). The mean magnitude of inhibition on TG neuronal discharge frequency with 1 mM quercetin was significantly greater than that of 1% lidocaine. These results suggest that local injection of quercetin into inflamed tissue suppresses the excitability of nociceptive primary sensory TG neurons. PERSPECTIVE: Local administration of the phytochemical, quercetin, into inflamed tissues is a more potent local analgesic than voltage-gated sodium channel blockers as it inhibits the generation of both generator potentials and action potentials in nociceptive primary nerve terminals. As such, it contributes to the area of complementary and alternative medicines.

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.

Transplantation of olfactory ensheathing cells can alleviate neuroinflammatory responses in rats with trigeminal neuralgia

Trigeminal neuralgia (TN) is a common form of facial pain, which primarily manifests as severe pain similar to facial acupuncture and electric shock. Olfactory ensheathing cells (OECs) are glial cells with high bioactivity; these cells are essential for the periodic regeneration of the olfactory nerve and have been utilized for the repair of nerve injuries. A member of the P2X receptor family, P2X7R, is an ion channel type receptor that has been confirmed to participate in various pain response processes. In this study, we transplanted OECs into trigeminal nerve-model rats with distal infraorbital nerve ligation to observe the therapeutic effect of transplanted OECs in rats. Additionally, we utilized the P2X7R-specific inhibitor brilliant blue G (BBG) to study the therapeutic mechanisms of cell transplantation. The facial mechanical pain threshold of these rats significantly increased following cell transplantation. The immunohistochemistry, immunoblotting, and RT-qPCR results demonstrated that the levels of P2X7R, (NOD)-like receptor protein-3 (NLRP3), nuclear factor-κB (NF-κB), interleukin (IL)-1β, and IL-18 in the trigeminal ganglion of rats treated with OEC transplantation or BBG treatment were significantly lower than those in the injured group without treatment. Overall, our results demonstrate that OEC transplantation can alleviate TN in rats, and it can reduce the expression of P2X7R related inflammatory factors in TN rats, reducing neuroinflammatory response in TG.

Gut Microbiota Modulation and Its Implications on Neuropathic Pain: A Comprehensive Literature Review

Neuropathic pain (NP) is a chronic pain disorder arising from somatosensory nervous system impairment. Extensive evidence supports the notion that the gut microbiota (GM) is crucial in maintaining human health by performing vital tasks. At the same time, its disruption has been linked to the emergence and advancement of an expanding range of disorders, including NP, in which GM could play a role in its pathophysiology. The crosstalk between the nervous system and GM happens through immune mediators, metabolites, and nervous structures and involves both central and peripheral nervous systems. This literature review aims to thoroughly investigate the function of modulating GM in the treatment of NP. It will achieve this by integrating existing knowledge, identifying underlying mechanisms, and evaluating the possible clinical consequences of exploiting the gut-brain axis. We will cover the main therapeutic applications of the described GM-modulators, such as probiotics, faecal microbiota transplantation, dietary supplements and emotional support, to the main kinds of NP in which any evidence, even if only pre-clinical, has been unravelled in recent years. The explored NP areas include chemotherapy-induced peripheral neuropathy, diabetic neuropathy, trauma-induced neuropathic pain, trigeminal neuralgia, postherpetic neuralgia and low back pain.

Comparison of initial percutaneous balloon compression versus radiofrequency thermocoagulation followed by percutaneous balloon compression in the treatment of trigeminal neuralgia

OBJECTIVES

There are a variety of minimally invasive interventional treatments for trigeminal neuralgia, and the efficacy evaluation is different. The preferred treatment scheme is still controversial. This study aims to investigate the differences in treatment effects between patients with primary trigeminal neuralgia (PTN) treated with percutaneous balloon compression (PBC) for the first intervention and patients with pain recurrence after radiofrequency thermocoagulation (RT) who then received PBC for PTN, and to offer clinicians and patients more scientifically grounded and precise treatment alternatives.

METHODS

We retrospectively analyzed 103 patients with PTN admitted to the Department of Pain Management of the Second Affiliated Hospital of Guangxi Medical University from January 2020 to December 2021, including 49 patients who received PBC for the first time (PBC group) and 54 patients who received PBC for pain recurrence after RT (RT+PBC group). General information, preoperative pain score, intraoperative oval foramen morphology, oval foramen area, balloon volume, duration of compression, and postoperative pain scores and pain recurrence at each time point on day 1 (T1), day 7 (T2), day 14 (T3), 1 month (T4), 3 months (T5), and 1 year (T6) were collected and recorded for both groups. The differences in treatment effect, complications and recurrence between the 2 groups were compared, and the related influencing factors were analyzed.

RESULTS

The differences of general information, preoperative pain scores, foramen ovale morphology, foramen ovale area, T1 to T3 pain scores between the 2 groups were not statistically different (all P>0.05). The balloon filling volume in the PBC group was smaller than that in the RT+PBC group, the pain scores at T4 to T6 and pain recurrence were better than those in the RT+PBC group (all P<0.05). Pain recurrence was positively correlated with pain scores of T2 to T6 (r=0.306, 0.482, 0.831, 0.876, 0.887, respectively; all P<0.01).

CONCLUSIONS

The choice of PBC for the first intervention in PTN patients is superior to the choice of PBC after pain recurrence after RT treatment in terms of treatment outcome and pain recurrence.

Atlas orthogonal chiropractic management of trigeminal neuralgia: A series of case reports

CONTEXT

Trigeminal neuralgia is a debilitating facial pain condition. Upper cervical chiropractic care has been mentioned as a possible solution OBJECTIVE: To determine the effects of Atlas Orthogonal upper cervical chiropractic technique adjustments on trigeminal neuralgia sufferers DESIGN: Case series SETTING: A private chiropractic practice PARTICIPANTS: Five persons with chronic, severe, daily trigeminal neuralgia pain, radiological findings of significant head tilt, pain upon upper cervical palpation, and supine leg length inequality INTERVENTIONS: Up to two consultations and/or Atlas Orthogonal adjustments a week for eight weeks OUTCOME MEASURES: Self-reported reduction in trigeminal neuralgia pain and changes in radiological findings, sensitivity to upper cervical palpation, and leg length inequality RESULTS: Four participants reported reduced trigeminal neuralgia pain, including two with complete cessation of pain. Three participants reduced medication dosages. One reported no change.

A New Landscape of Human Dental Aging: Causes, Consequences, and Intervention Avenues

Aging is accompanied by physical dysfunction and physiologic degeneration that occurs over an individual's lifetime. Human teeth, like many other organs, inevitably undergo chronological aging and age-related changes throughout the lifespan, resulting in a substantial need for preventive, restorative as well as periodontal dental care. This is particularly the case for seniors at 65 years of age and those older but economically disadvantaged. Dental aging not only interferes with normal chewing and digestion, but also affects daily appearance and interpersonal communications. Further dental aging can incur the case of multiple disorders such as oral cancer, encephalitis, and other systemic diseases. In the next decades or even hundreds of years, the proportion of the elderly in the global population will continue to rise, a tendency that attracts increasing attention across multiple scientific and medical disciplines. Dental aging will bring a variety of problems to the elderly themselves and poses serious challenges to the medical profession and social system. A reduced, but functional dentition comprising 20 teeth in occlusion has been proposed as a measurement index of successful dental aging. Healthy dental aging is critical to healthy aging, from both medical and social perspectives. To date, biomedical research on the causes, processes and regulatory mechanisms of dental aging is still in its infancy. In this article, updated insights into typical manifestations, associated pathologies, preventive strategies and molecular changes of dental aging are provided, with future research directions largely projected.

Effectiveness of gamma knife radiosurgery in the management of trigeminal neuralgia associated with multiple sclerosis: a systematic review and meta-analysis

BACKGROUND

Trigeminal neuralgia (TN) is a chronic condition characterized by intense facial pain akin to electric shocks, often associated with the trigeminal nerve. It can be either idiopathic or secondary, with multiple sclerosis (Ms) being a significant contributing factor. Non-responsive patients may opt for minimally invasive procedures, such as gamma knife radiosurgery (GKRS), which offers precise, non-invasive treatment and is frequently chosen as a primary approach. This meta-analysis evaluates the long-term efficacy of GKRS in TN management in Ms patients.

METHODS

We conducted a focused search across various databases. Inclusion criteria encompassed studies with ≥ 30 patients using GKRS for TN in Ms, reporting pertinent clinical outcomes. Primary outcomes assessed GKRS efficacy through Barrow Neurological Institute Pain scores. Secondary outcomes encompassed bothersome numbness, facial numbness, and recurrence. Data analysis employed OpenMeta, random effect models, and odds ratios with 95% confidence intervals. Heterogeneity was assessed using I2 statistics.

RESULTS

Fourteen studies with 752 cases of GKRS for TN were included. Regarding the outcomes, 83% of patients experienced a positive initial pain response, while the overall treatment success rate was 51%. Additionally, 19.6% of patients reported facial numbness, 4.1% experienced bothersome numbness, and 40% faced recurrence. The odds ratio for positive initial pain response was 0.83 (95% CI, 0.76-0.89), while for treatment success, it was 0.51 (95% CI, 0.379-0.639). Facial numbness had an odds ratio of 0.196 (95% CI, 0.130-0.262), bothersome numbness had an odds ratio of 0.041 (95% CI, 0.013-0.069), and recurrence had an odds ratio of 0.403 (95% CI, 0.254-0.551).

CONCLUSIONS

In conclusion, treating trigeminal neuralgia in multiple sclerosis patients remains challenging. GKRS shows promise, but customized treatment approaches tailored to individual patient characteristics are urgently needed to address the unique challenges of this condition.

Unveiling the Pain Relief Potential: Harnessing Analgesic Peptides from Animal Venoms

The concept of pain encompasses a complex interplay of sensory and emotional experiences associated with actual or potential tissue damage. Accurately describing and localizing pain, whether acute or chronic, mild or severe, poses a challenge due to its diverse manifestations. Understanding the underlying origins and mechanisms of these pain variations is crucial for effective management and pharmacological interventions. Derived from a wide spectrum of species, including snakes, arthropods, mollusks, and vertebrates, animal venoms have emerged as abundant repositories of potential biomolecules exhibiting analgesic properties across a broad spectrum of pain models. This review focuses on highlighting the most promising venom-derived toxins investigated as potential prototypes for analgesic drugs. The discussion further encompasses research prospects, challenges in advancing analgesics, and the practical application of venom-derived toxins. As the field continues its evolution, tapping into the latent potential of these natural bioactive compounds holds the key to pioneering approaches in pain management and treatment. Therefore, animal toxins present countless possibilities for treating pain caused by different diseases. The development of new analgesic drugs from toxins is one of the directions that therapy must follow, and it seems to be moving forward by recommending the composition of multimodal therapy to combat pain.

Occipital Nerve Stimulation for Recurrent Trigeminal Neuralgia Without Occipital Pain

OBJECTIVES

Trigeminal neuralgia (TN) is a severe, debilitating pain condition causing physical and emotional distress. Although the management of TN is well codified with medical and then surgical treatments, 15% to 30% of patients will experience intractable pain. Neuromodulation techniques have been scarcely used for refractory TN, with only small case series and short-term follow-up.

MATERIALS AND METHODS

We conducted a retrospective study of patients treated with occipital nerve stimulation (ONS) for medically and surgically resistant TN without painful trigeminal neuropathy. The effectiveness of the ONS was evaluated using the Barrow Neurological Institute (BNI) pain score and the pain relief (0%-100%) at best and at last follow-up.

RESULTS

Seven patients who have refractory TN were included. The mean age at ONS was 49 years. The mean pain duration was 8.6 years. The mean number of medical and surgical treatments before ONS was six and five, respectively. A percutaneous trial was performed in five of seven patients; all responded (pain relief > 40%), and four of five patients experienced pain recurrence after explantation. Eventually, six patients had a permanent ONS implantation. The average BNI pain score before implantation was V. The mean follow-up after implantation was 59 months. All patients reported an improvement after implantation. The average BNI score and mean pain relief at best were IIIa and 86.7%, respectively. At last follow-up, the average BNI score and mean pain relief were IIIa and 58.0%, respectively, with three patients experiencing pain recurrence. Adverse events were reported for four patients who required surgical revision for lead breakage (1), erosion (1), migration (1), or hardware-related discomfort (1). One patient finally underwent explantation because of infection.

CONCLUSIONS

Although ONS is not validated in this indication, these results suggest that it can induce an improvement in TN recurring after several surgical treatments, and the benefit of the stimulation can be sustained in the long term.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT01842763.

Neurological Complications of Local Anesthesia in Dentistry: A Review

Local anesthesia is a technique that temporarily desensitizes a specific body area, typically for a surgical procedure, dental work, or pain management. It is described as a sensation loss in a specific area of the body due to depression of excitation in the nerve endings or due to the inhibition of the conduction process within the peripheral nerves. It allows for safer and more comfortable medical procedures, reducing the need for general anesthesia and facilitating faster recovery. Local anesthesia is generally safe, but like any medical intervention, it carries potential risks and side effects. The complications related to local anesthetics can be assessed in terms of neurological, vascular, local, systemic, and neurological. In this review article, we discussed the neurological complications of local anesthesia related to the ophthalmic nerve, maxillary nerve, mandibular nerve, branches of the trigeminal nerve, and facial nerve. These include diplopia, ptosis, paralysis of the eye, blindness, paresthesia, trismus, soft tissue lesions, edema, hematoma, facial blanching, infection, allergy, overdose, neuralgia, facial palsy, etc.

Case report: use of high-intensity laser therapy for treatment of trigeminal neuralgia

Trigeminal neuralgia represents a form of chronic facial pain that is characterized by its incapacitating nature. The current therapeutic approaches encompass pharmacological agents with carbamazepine or non-pharmacologic options including utilization of percutaneous rhizotomy, Gamma knife radiosurgery or microvascular decompression may be indicated in certain cases. While the interventions may be effective, medications have negative side effects and procedures are invasive which can pose challenges for patients with various comorbidities. High-intensity laser therapy (HILT) has demonstrated safety and efficacy for many types of chronic pain such as musculoskeletal, autoimmune and neuropathic. Herein, we demonstrate the benefits of HILT therapy in the management of trigeminal neuralgia in a 72 year-old patient with a complex history of facial surgery and radiation who had failed pharmacological treatments and denied any invasive procedures.

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.

Posterior Fossa Volume and Dimensions: Relation to Pathophysiology and Surgical Outcomes in Classic Trigeminal Neuralgia

OBJECTIVE

A small posterior fossa (PF) has been hypothesized to explain the increased incidence of trigeminal neuralgia (TN) in females and could make microvascular decompression (MVD) more challenging. The aim of this study was to investigate the association between the PF volume and dimensions in relation to biological sex, type of neurovascular conflict (NVC), and outcome after MVD in classic TN.

METHODS

In this observational study, 84 patients with TN operated on with MVD with a preoperative head computed tomography(CT) scan were included. Eighty-two adults without TN who had undergone head CT for other reasons were included as controls. PF volume and dimensions (x-axis, y-axis, and z-axis) were evaluated on the CT scans. For the patients with TN, Barrow Neurological Institute (BNI) grade was evaluated 6 months after MVD.

RESULTS

There was no difference in PF volume or dimensions between the patients with TN and controls. Women showed a smaller volume and narrower (x-axis) PF than men, but these differences did not manifest when comparing patients with TN and controls within each sex. Patients with an NVC involving the superior cerebellar artery had a narrower (x-axis) and shorter (y-axis) PF than did patients with an NVC resulting from other arteries. PF volume or dimensions were not associated with BNI grade after MVD.

CONCLUSIONS

PF anatomy was related to the NVC type but did not differ between patients with TN and controls and was not related to the surgical outcome after MVD.

Neurovascular Compression-Induced Intracranial Allodynia May Be the True Nature of Migraine Headache: an Interpretative Review

PURPOSE OF REVIEW

Surgical deactivation of migraine trigger sites by extracranial neurovascular decompression has produced encouraging results and challenged previous understanding of primary headaches. However, there is a lack of in-depth discussions on the pathophysiological basis of migraine surgery. This narrative review provides interpretation of relevant literature from the perspective of compressive neuropathic etiology, pathogenesis, and pathophysiology of migraine.

RECENT FINDINGS

Vasodilation, which can be asymptomatic in healthy subjects, may produce compression of cranial nerves in migraineurs at both extracranial and intracranial entrapment-prone sites. This may be predetermined by inherited and acquired anatomical factors and may include double crush-type lesions. Neurovascular compression can lead to sensitization of the trigeminal pathways and resultant cephalic hypersensitivity. While descending (central) trigeminal activation is possible, symptomatic intracranial sensitization can probably only occur in subjects who develop neurovascular entrapment of cranial nerves, which can explain why migraine does not invariably afflict everyone. Nerve compression-induced focal neuroinflammation and sensitization of any cranial nerve may neurogenically spread to other cranial nerves, which can explain the clinical complexity of migraine. Trigger dose-dependent alternating intensity of sensitization and its synchrony with cyclic central neural activities, including asymmetric nasal vasomotor oscillations, may explain the laterality and phasic nature of migraine pain. Intracranial allodynia, i.e., pain sensation upon non-painful stimulation, may better explain migraine pain than merely nociceptive mechanisms, because migraine cannot be associated with considerable intracranial structural changes and consequent painful stimuli. Understanding migraine as an intracranial allodynia could stimulate research aimed at elucidating the possible neuropathic compressive etiology of migraine and other primary headaches.

Microvascular decompression for trigeminal neuralgia: A retrospective analysis of long-term outcomes and prognostic factors

INTRODUCTION

Microvascular decompression is considered to be the most effective and only etiological surgical treatment for classical trigeminal neuralgia, relieving the neurovascular compression found in up to 95% of cases. This study aims to report the long-term outcomes and to identify prognostic factors in a series of patients with trigeminal neuralgia treated by microvascular decompression.

METHODS

A retrospective observational study of 152 consecutive patients operated by microvascular decompression with at least six months of follow-up. The surgical results, including pain relief according to the Barrow Neurological Institute pain scale, complications and the medical treatment during the follow-up period were reviewed. Binary regression analysis was performed to identify factors associated with a good long-term outcome.

RESULTS

A total of 152 patients with a mean age of 60 years and a mean follow-up of 43 months were included. At the final follow-up visit, 83% of the patients had achieved significant relief of the pain and 63% could reduce the absolute drug doses by 50% or more. The most frequent complications were wound infection (4.5%) and CSF fistula (7%). Being over 70 years of age and having paroxysmal pain were associated with a long-term pain relief.

CONCLUSIONS

Our results support the notion that microvascular decompression is an effective and safe therapy in patients with trigeminal neuralgia. A multidisciplinary approach with an early referral to a neurosurgical unit many be beneficial in patients who are refractory to pharmacological treatment.

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Mechanism and clinical use of botulinum neurotoxin in head and facial region

PURPOSE

Botulinum neurotoxin (BoNT) is a biological toxin produced by Clostridium botulinum. BoNT is a potent toxin extensively used in therapeutic interventions. This review provides an updated overview of the mechanisms of action and clinical applications of BoNT in head and facial region.

STUDY SELECTION

MEDLINE/PubMed searches were conducted using the terms "botulinum neurotoxin" and "dentistry" along with a combination of other related terms. In addition, studies were manually selected from reference lists of the selected articles.

RESULTS

The Food and Drug Administration in the United States initially approved BoNT to treat strabismus, blepharospasm, and hemifacial spasms. The use of BoNT in dermatology and cosmetics has been widely established and has created a revolution in these fields. Over the years, its applications in various medical specialties have expanded widely. Owing to its safety, efficacy, and long duration of action, it is well-accepted by patients. BoNT/A and BoNT/B are widely used in clinical practice. Several off-label uses of BoNT in the dental fraternity have yielded promising results. We have elaborated on the speculated mechanism of action, dosage, effective sites of injection, and adverse effects of each therapeutic application. The various clinical indications for BoNT include bruxism, myofascial pain, temporomandibular joint dislocation, hemifacial pain, orofacial dystonia, facial paralysis, chronic migraine, and trigeminal neuralgia.

CONCLUSIONS

BoNT is a safe treatment that can be used effectively, provided that the clinician has adequate knowledge regarding the mechanism, injection techniques, and local and systemic side effects and that it is administered cautiously and purposefully.

GFAP-NpHR mediated optogenetic inhibition of trigeminal nucleus caudalis attenuates hypersensitive behaviors and thalamic discharge attributed to infraorbital nerve constriction injury

The significance of hyperactive astrocytes in neuropathic pain is crucial. However, the association between medullary astrocytes and trigeminal neuralgia (TN)-related pain processing is unclear. Here, we examined how optogenetic inhibition of medullary astrocytes in the trigeminal nucleus caudalis (TNC) regulates pain hypersensitivity in an infraorbital nerve (ION) constricted TN model. We used adult Sprague Dawley rats subjected to infraorbital nerve (ION) constriction to mimic TN symptoms, with naive and sham rats serving as controls. For in vivo optogenetic manipulations, rats stereotaxically received AAV8-GFAP-eNpHR3.0-mCherry or AAV8-GFAP-mCherry at the trigeminal nucleus caudalis (TNC). Open field, von Frey, air puff, and acetone tests measured pain behavioral flexibility. In vivo thalamic recordings were obtained simultaneously with optogenetic manipulation in the TNC. Orofacial hyperalgesia and thalamic hyperexcitability were both accompanied by medullary astrocyte hyperactivity, marked by upregulated GFAP. The yellow laser-driven inhibition of TNC astrocytes markedly improved behavioral responses and regulated thalamic neuronal responses. Halorhodopsin-mediated inhibition in medullary astrocytes may modify the nociceptive input transmitted through the trigeminothalamic tract and pain perception. Taken together, these findings imply that this subpopulation in the TNC and its thalamic connections play a significant role in regulating the trigeminal pain circuitry, which might aid in the identification of new therapeutic measures in TN management.

Analysis of clinical features of oxcarbazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis

Background

Stevens-Johnson syndrome (SJS) is considered a hypersensitivity syndrome affecting the skin and mucous membranes. It has been reported that an anticonvulsant drug, oxcarbazepine, may cause Stevens-Johnson syndrome and toxic epidermal necrolysis (TEN). However, the clinical features of oxcarbazepine-induced Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) remain ambiguous. This article aims to explore the clinical features of SJS/TEN.

Methods

Systematic searches of several Chinese and English databases were conducted for case reports published on PubMed, EMBASE, Web of Science, MEDLINE, CNKI from January 1, 2007 to March 1, 2023.

Results

A total of seventeen patients (10 males and 7 females) were included in this study, including nine adult patients and eight pediatric patients. The results showed that males seem to have a higher prevalence of SJS/TEN than females, and SJS/TEN usually occurs within 2 weeks after administration of oxcarbazepine (OXC). The main clinical manifestations among the included patients were rashes or maculopapules (17 cases, 100%), fever (11 cases, 64.7%), mucosal lesions (15 cases, 88.2%), conjunctivitis with/without ocular discharge (12 cases, 70.6%), and blisters (12 cases, 70.6%). After stopping OXC or switching to other drugs that treat primary disease as well as treatment with IVIG, glucocorticoid, anti-allergy, and fluid replacement, eight of the included patients recovered completely, and another eight of the included patients reported symptomatic improvement, while the prognosis of one of the included patients was not reported.

Conclusion

Diverse clinical signs and symptoms of SJS/TEN might result in misinterpretation and delayed diagnosis. It should be identified and treated immediately to avoid significant consequences and potentially jeopardize patients' lives.

Seizure caused by intraparenchymal hemorrhage from migration of mandibular dental wire through foramen ovale in a child: A case report

The foramen ovale is a structure that allows for the extracranial passage of multiple significant intracranial structures, most notably the mandibular branch of the trigeminal nerve (CN V3). Here we report the case of a 12-year-old male who presented to the emergency department (ED) with a two-day history of nausea and emesis and a one-day history of altered mental status. Prior to presentation, he started speaking only Spanish, which was unusual because he primarily speaks English. He was also showing signs of absence seizures. Computed Tomography (CT) showed his orthodontic wire had migrated and was entering his skull through the foramen ovale, terminating within the inferior temporal lobe. Associated with the wire was an intraparenchymal hemorrhage. Imaging indicated the sparing of the internal carotid artery and its major branches, suggesting the hemorrhage was likely venous in nature. The wire was then safely removed with no complications. Same day and follow-up neurologic exams all demonstrated no deficit in CN V3 or any of the other surrounding structures. To our knowledge, this is the first case described in the literature in which a foreign object penetrated the skull floor through the foramen ovale.

Trigeminal Autonomic Cephalalgias and Neuralgias in Children and Adolescents: a Narrative Review

PURPOSE OF REVIEW

To summarize the available literature as well as the authors' experience on trigeminal autonomic cephalalgias (TACs) and cranial neuralgias in children and adolescents.

RECENT FINDINGS

While TACs and cranial neuralgias are rare in children, several recent case series have been published. TACs in children share most of the clinical features of TACs in adults. However, there are many reported cases with clinical features which overlap more than one diagnosis, suggesting that TACs may be less differentiated in youth. Indomethacin-responsive cases of cluster headache and SUNCT/SUNA have been reported in children, whereas in adults indomethacin is usually reserved for paroxysmal hemicrania and hemicrania continua. Neuralgias appear to be rare in children. Clinical features are often similar to adult cases, though clinicians should maintain a high index of suspicion for underlying causes.

Debilitating trigeminal neuralgia secondary to idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) is characterized by raised intracranial pressure with unknown etiology. The most common neurological manifestations are headache and visual loss. Often, other cranial nerve impairments are also found, most commonly in the VI nerve. Trigeminal neuralgia (TN) is a debilitating condition that is most frequently caused by neurovascular pathology, but TN secondary to IIH is a rare and poorly described topic. Possible explanations of TN in these patients include the distortion of the local anatomy at CN entry zones and fluid displacement causing distortion of the Meckel's cave. In the case below we describe the clinical course of an obese female patient with TN-like pain who underwent a ventriculoperitoneal shunt to treat IIH and experienced complete resolution of both conditions.

Involvement of Oxidative Stress and Nutrition in the Anatomy of Orofacial Pain

Pain is a very important problem of our existence, and the attempt to understand it is one the oldest challenges in the history of medicine. In this review, we summarize what has been known about pain, its pathophysiology, and neuronal transmission. We focus on orofacial pain and its classification and features, knowing that is sometimes purely subjective and not well defined. We consider the physiology of orofacial pain, evaluating the findings on the main neurotransmitters; in particular, we describe the roles of glutamate as approximately 30-80% of total peripheric neurons associated with the trigeminal ganglia are glutamatergic. Moreover, we describe the important role of oxidative stress and its association with inflammation in the etiogenesis and modulation of pain in orofacial regions. We also explore the warning and protective function of orofacial pain and the possible action of antioxidant molecules, such as melatonin, and the potential influence of nutrition and diet on its pathophysiology. Hopefully, this will provide a solid background for future studies that would allow better treatment of noxious stimuli and for opening new avenues in the management of pain.

Trigeminal Lipomatosis: A Rare Cause of Intractable Neuralgia

Lipomatosis of nerve, earlier known as fibrolipomatous hamartoma is a rare condition which predominantly affects peripheral nerves, cranial nerve involvement being extremely uncommon. Preoperative consideration of this entity is of paramount importance as its inadvertent complete surgical resection may inevitably result in significant neurological deficit. We report a case of trigeminal lipomatosis in a young patient with trigeminal neuralgia.

Dolichoectasia of vertebrobasilar artery presenting as facial pain: a case report

Dolichoectasia of the intracranial arteries is a rare condition characterized by elongated and tortuous arteries due to progressive destruction of the vessel walls. Although most patients present with cerebrovascular accidents, our patient presented with intractable facial pain along the distribution of the trigeminal nerve. Clinical examination revealed involvement of the 5th, 7th, and 8th cranial nerves, and subsequent MRI showed dolichoectasia of the left basilar artery. The patient experienced symptomatic relief after a trial of carbamazepine along with botulinum toxin injections.