Update on neuropathic pain treatment for trigeminal neuralgia. The pharmacological and surgical options

Neuralgia-inducing cavitational osteonecrosis - A systematic review

OBJECTIVE

To assess the aetiologic factors, proposed diagnostic means and treatment strategies for neuralgia-inducing cavitational osteonecrosis.

METHODS

A search of the literature published up to June 2020 was conducted using Medline, the Cochrane Library, PsycINFO, CINAHL and Web of Science. The scientific quality of the evidence was rated according to NIH Quality Assessment Tools.

RESULTS

4,051 articles were found, 59 were reviewed in full text, and 29 studies were included. With the exception of hereditary coagulopathies, which were identified as potential risk factors in five studies, suggestions concerning the aetiology varied widely. No gold standard diagnostic mean could be identified. Treatment was most often performed by surgical curettage of the affected bone. Surgical treatment outcomes were equally varied: significant facial pain remission was reported in 66%-100% for periods varying between 2 months to 18 years, whereas no or little relief and recurrences were reported in up to ⅓ of cases. All studies were observational in their design. All investigations were rated as poor quality because of high risk of bias and non-transparent reporting.

CONCLUSIONS

Evidence concerning the aetiology, diagnosis and treatment of NICO is poor. Prospective diagnostic and therapeutic studies are needed before the usefulness of invasive therapeutic procedures can be evaluated.

A COVID-19 Drug Repurposing Strategy through Quantitative Homological Similarities Using a Topological Data Analysis-Based Framework

Since its emergence in March 2020, the SARS-CoV-2 global pandemic has produced more than 116 million cases and 2.5 million deaths worldwide. Despite the enormous efforts carried out by the scientific community, no effective treatments have been developed to date. We applied a novel computational pipeline aimed to accelerate the process of identifying drug repurposing candidates which allows us to compare three-dimensional protein structures. Its use in conjunction with two in silico validation strategies (molecular docking and transcriptomic analyses) allowed us to identify a set of potential drug repurposing candidates targeting three viral proteins (3CL viral protease, NSP15 endoribonuclease, and NSP12 RNA-dependent RNA polymerase), which included rutin, dexamethasone, and vemurafenib. This is the first time that a topological data analysis (TDA)-based strategy has been used to compare a massive number of protein structures with the final objective of performing drug repurposing to treat SARS-CoV-2 infection.

Effects of Preoperative Carbamazepine Treatment on Microvascular Decompression for Classical Trigeminal Neuralgia

BACKGROUND

Carbamazepine (CBZ) is the first-line therapy for trigeminal neuralgia (TN), and microvascular decompression (MVD) is considered to be an effective surgical treatment for TN. However, the effect of preoperative CBZ treatment on MVD outcome is not clear.

METHODS

From 2013 to 2019, 63 patients with classical TN underwent MVD at the First Affiliated Hospital of Zhengzhou University, China. Data were collected through telephone follow-up and electronic medical records in April 2020. Short-term surgical outcome and long-term follow-up data were estimated by univariate and multivariate analysis.

RESULTS

Multivariate analysis indicated that preoperative CBZ treatment was not a significant predictor for short-term outcomes of MVD (P > 0.05). Multivariate analysis for the long-term outcome of MVD indicated that preoperative CBZ treatment could predict postoperative recurrence of TN (P < 0.05).

CONCLUSIONS

For patients with classical TN, a longer preoperative medication history of CBZ treatment had no significant effect on short-term outcome of MVD, but CBZ treatment was associated with a poor long-term outcome following MVD.

Trigeminal neuralgia: An overview from pathophysiology to pharmacological treatments

The trigeminal nerve (V) is the fifth and largest of all cranial nerves, and it is responsible for detecting sensory stimuli that arise from the craniofacial area. The nerve is divided into three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3); their cell bodies are located in the trigeminal ganglia and they make connections with second-order neurons in the trigeminal brainstem sensory nuclear complex. Ascending projections via the trigeminothalamic tract transmit information to the thalamus and other brain regions responsible for interpreting sensory information. One of the most common forms of craniofacial pain is trigeminal neuralgia. Trigeminal neuralgia is characterized by sudden, brief, and excruciating facial pain attacks in one or more of the V branches, leading to a severe reduction in the quality of life of affected patients. Trigeminal neuralgia etiology can be classified into idiopathic, classic, and secondary. Classic trigeminal neuralgia is associated with neurovascular compression in the trigeminal root entry zone, which can lead to demyelination and a dysregulation of voltage-gated sodium channel expression in the membrane. These alterations may be responsible for pain attacks in trigeminal neuralgia patients. The antiepileptic drugs carbamazepine and oxcarbazepine are the first-line pharmacological treatment for trigeminal neuralgia. Their mechanism of action is a modulation of voltage-gated sodium channels, leading to a decrease in neuronal activity. Although carbamazepine and oxcarbazepine are the first-line treatment, other drugs may be useful for pain control in trigeminal neuralgia. Among them, the anticonvulsants gabapentin, pregabalin, lamotrigine and phenytoin, baclofen, and botulinum toxin type A can be coadministered with carbamazepine or oxcarbazepine for a synergistic approach. New pharmacological alternatives are being explored such as the active metabolite of oxcarbazepine, eslicarbazepine, and the new Nav1.7 blocker vixotrigine. The pharmacological profiles of these drugs are addressed in this review.

Stem Cells from Human Exfoliated Deciduous Teeth Attenuate Trigeminal Neuralgia in Rats

Trigeminal neuralgia is an incurable progressive nervous system disease that can last for several months or years. Stem cells from human exfoliated deciduous teeth (SHED) are a candidate source for cell-based therapy. Owing to their neuroprotective and immunomodulatory effects, these neural crest cells have potential roles in mediating chronic pain. In this study, we established a rat model of chronic constriction injury of the infraorbital nerve (CCI-ION) to evaluate the analgesic effect of SHED in neuropathic pain. The effects of local SHED transplantation on inflammatory cell infiltration in the trigeminal nerve were investigated based on hematoxylin and eosin staining. The levels of proinflammatory factors in the injured nerve and transient receptor potential vanilloid type 1 (TRPV1) expression in the trigeminal nerve and ganglion were quantified. The data showed that systemic or local injection of SHED attenuated the sensitivity of rats to mechanical stimuli after nerve injury, and this effect lasted throughout the observation period of 8 weeks. PKH26-labeled SHED were distributed to the ipsilateral trigeminal ganglions 24 and 72 hours after local injection. SHED transplantation at the lesion site led to reduced inflammatory cell infiltration and proinflammatory cytokine levels in the injured nerve and inhibited CCI-ION-induced upregulation of TRPV1 expression in the trigeminal nerve and ganglion in the early phase. Therefore, these results provide preclinical evidence that supports the use of SHED in the treatment of trigeminal neuralgia and potentially other chronic pain conditions.

CXCL10 and CXCR3 in the Trigeminal Ganglion Contribute to Trigeminal Neuropathic Pain in Mice

Purpose

Trigeminal neuropathic pain is very common clinically, but effective treatments are lacking. Chemokines and their receptors have been implicated in the pathogenesis of chronic pain. This study explored the role of the chemokine CXCL10 and its receptor, CXCR3, in trigeminal neuropathic pain in mice.

Materials and Methods

Trigeminal neuropathic pain was established by partial infraorbital nerve ligation (pIONL) in wild-type and Cxcr3^−/− mice. Facial mechanical allodynia was evaluated by behavioral testing. A lentivirus containing Cxcr3 shRNA (LV-Cxcr3 shRNA) was microinjected into the trigeminal ganglion (TG) to knock down Cxcr3 expression. Quantitative polymerase chain reaction assays and immunofluorescence staining were used to examine Cxcl10/Cxcr3 mRNA expression and protein distribution. Western blotting was performed to examine activation of extracellular signal-regulated kinase (ERK) and AKT in the TG. Intra-TG injection of an AKT inhibitor was performed to examine the role of AKT in trigeminal neuropathic pain.

Results

pIONL induced persistent trigeminal neuropathic pain, which was alleviated in Cxcr3^−/− mice. Intra-TG injection of LV-Cxcr3 shRNA attenuated pIONL-induced mechanical allodynia. Furthermore, pIONL increased the expression of CXCR3 and its major ligand, CXCL10, in TG neurons. Intra-TG injection of CXCL10 induced pain hypersensitivity in wild-type mice but not in Cxcr3^−/− mice. CXCL10 also induced activation of ERK and AKT in the TG of wild-type mice. Finally, pIONL-induced activation of ERK and AKT was reduced in Cxcr3^−/− mice. Intra-TG injection of the AKT inhibitor alleviated pIONL-induced mechanical allodynia in WT mice but not in Cxcr3^−/− mice.

Conclusion

CXCL10 acts on CXCR3 to induce ERK and AKT activation in TG neurons and contributes to the maintenance of trigeminal neuropathic pain.

Invasive and Non-Invasive Electrical Neuromodulation in Trigeminal Nerve Neuralgia: A Systematic Review and Meta-Analysis

BACKGROUND

Trigeminal neuralgia is a chronic disease characterized by intense facial pain that is caused by trigeminal nerve affectation. It usually affects adults from 50 years of age, and is more frequent in women. Additionally, it presents serious psychological effects that often lead to depression, which is why it is considered highly disabling. The therapeutic approach is based on the modification of nerve activity through electrical, surgical or chemical stimulation in specific regions of the nervous system.

OBJECTIVE

To perform a meta-analysis of the scientific literature related to invasive and non-invasive electrical neuromodulation of trigeminal neuralgia, in order to assess their effects over pain and adverse effects.

METHODS

A literature search was conducted in 4 databases, followed by a manual search of articles on invasive or non-invasive electrical neuromodulation to control the pain of trigeminal neuralgia, including the last 15 years.

RESULTS

Regarding non-invasive methods, clinical trials did not present enough results in order to perform a meta-analysis. Regarding invasive methods, clinical trials meta-analysis showed no statistical differences between different treatment methods. In all cases, improvements in patients' pain were reported, although results regarding adverse effects were variable.

CONCLUSION

In the treatment of trigeminal neuralgia, the continuous radiofrequency provides better short and medium-term results, but pulsed radiofrequency shows less adverse effects after treatment, and has better results in the long-term.

Beyond Amitriptyline: A Pediatric and Adolescent Oriented Narrative Review of the Analgesic Properties of Psychotropic Medications for the Treatment of Complex Pain and Headache Disorders

Children and adolescents with recurrent or chronic pain and headache are a complex and heterogenous population. Patients are best served by multi-specialty, multidisciplinary teams to assess and create tailored, individualized pain treatment and rehabilitation plans. Due to the complex nature of pain, generalizing pharmacologic treatment recommendations in children with recurrent or chronic pains is challenging. This is particularly true of complicated patients with co-existing painful and psychiatric conditions. There is an unfortunate dearth of evidence to support many pharmacologic therapies to treat children with chronic pain and headache. This narrative review hopes to supplement the available treatment options for this complex population by reviewing the pediatric and adult literature for analgesic properties of medications that also have psychiatric indication. The medications reviewed belong to medication classes typically described as antidepressants, alpha 2 delta ligands, mood stabilizers, anti-psychotics, anti-sympathetic agents, and stimulants.

Chronic Facial Pain: Trigeminal Neuralgia, Persistent Idiopathic Facial Pain, and Myofascial Pain Syndrome-An Evidence-Based Narrative Review and Etiological Hypothesis

Trigeminal neuralgia (TN), the most common form of severe facial pain, may be confused with an ill-defined persistent idiopathic facial pain (PIFP). Facial pain is reviewed and a detailed discussion of TN and PIFP is presented. A possible cause for PIFP is proposed. (1) Methods: Databases were searched for articles related to facial pain, TN, and PIFP. Relevant articles were selected, and all systematic reviews and meta-analyses were included. (2) Discussion: The lifetime prevalence for TN is approximately 0.3% and for PIFP approximately 0.03%. TN is 15-20 times more common in persons with multiple sclerosis. Most cases of TN are caused by neurovascular compression, but a significant number are secondary to inflammation, tumor or trauma. The cause of PIFP remains unknown. Well-established TN treatment protocols include pharmacotherapy, neurotoxin denervation, peripheral nerve ablation, focused radiation, and microvascular decompression, with high rates of relief and varying degrees of adverse outcomes. No such protocols exist for PIFP. (3) Conclusion: PIFP may be confused with TN, but treatment possibilities differ greatly. Head and neck muscle myofascial pain syndrome is suggested as a possible cause of PIFP, a consideration that could open new approaches to treatment.

Exome Sequencing Implicates Impaired GABA Signaling and Neuronal Ion Transport in Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a common, debilitating neuropathic face pain syndrome often resistant to therapy. The familial clustering of TN cases suggests that genetic factors play a role in disease pathogenesis. However, no unbiased, large-scale genomic study of TN has been performed to date. Analysis of 290 whole exome-sequenced TN probands, including 20 multiplex kindreds and 70 parent-offspring trios, revealed enrichment of rare, damaging variants in GABA receptor-binding genes in cases. Mice engineered with a TN-associated de novo mutation (p.Cys188Trp) in the GABA_A receptor Cl⁻ channel γ-1 subunit (GABRG1) exhibited trigeminal mechanical allodynia and face pain behavior. Other TN probands harbored rare damaging variants in Na⁺ and Ca⁺ channels, including a significant variant burden in the α-1H subunit of the voltage-gated Ca²⁺ channel Ca_v3.2 (CACNA1H). These results provide exome-level insight into TN and implicate genetically encoded impairment of GABA signaling and neuronal ion transport in TN pathogenesis.

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Genomic analysis of trigeminal neuralgia (TN) using exome sequencing

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Rare mutations in GABA signaling and ion transport genes are enriched in TN cases

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Generation of a genetic TN mouse model engineered with a patient-specific mutation

Oral pharmacotherapeutics for the management of peripheral neuropathic pain conditions - a review of clinical trials

INTRODUCTION

Epidemiological studies have shown that 6.9-10% of people suffer from neuropathic pain, a complex painful condition which is often undertreated. Data regarding the effectiveness of treatment options for patients with neuropathic pain is inconsistent, and there is no single treatment option that shows cost-effectiveness across studies.

AREAS COVERED

In this narrative review, the authors present the results of different prospective, randomized controlled trials, systematic reviews and meta-analyses assessing the effects of different oral medications in the management of various peripheral neuropathic pain conditions. The authors discuss the effectiveness of commonly used oral medications such as voltage-gated calcium channels antagonists, voltage-gated sodium channel antagonists, serotonin-norepinephrine reuptake inhibitors, NMDA antagonists, and medications with other mechanisms of action.

EXPERT OPINION

Most of the presented medications were more effective than placebo; however, when compared to each other, none of them were significantly superior. The heterogeneity of the studies looking into different oral neuropathic conditions has been the major issue that prevents us from making stronger recommendations. There are multiple reasons including high placebo responsiveness, improperly treated underlying comorbidities (particularly anxiety and depression), and inter-patient variability. Different sensory phenotypes should also be taken into consideration when designing future clinical trials for neuropathic pain.

Optimizing Radiosurgery for Trigeminal Neuralgia: Impact of Radiation Dose and Anatomic Target on Patient Outcomes

OBJECTIVE

Radiosurgery is an increasingly popular treatment for trigeminal neuralgia (TN); however, several treatment variables require further study. This meta-analysis was conducted to clarify ambiguity in the literature and optimize treatment parameters.

METHODS

A random-effects proportions meta-analysis using subgroup analysis and meta-regression investigated the association of prescription dose and anatomic target on outcomes in patients with typical TN. The PRISMA guidelines were used. Radiation doses used ranged from 70 to 90 Gy and the anatomic targets were either the root entry zone or a more distal nerve location. Outcome measures were pain at last follow-up and the development of bothersome numbness.

RESULTS

Increasing radiation prescription dose was associated with improved outcomes across all analyzed doses (P < 0.001). Patients treated at a distal trigeminal nerve target had better pain control compared with a root entry zone target (P < 0.001). Despite a higher median dose, a distal target was independently associated with improved pain control. There were similar rates of bothersome numbness across radiation doses and both treatment targets.

CONCLUSIONS

Higher radiation dose was associated with superior pain control without increasing bothersome numbness. Independent of dose, the distal target was also associated with improved pain control. Bothersome numbness was not related to dose or target.

Optogenetic Activation of Dopamine Receptor D1 and D2 Neurons in Anterior Cingulate Cortex Differentially Modulates Trigeminal Neuropathic Pain

Background:

Anterior cingulate cortex (ACC) is a critical brain center for chronic pain processing. Dopamine signaling in the brain has been demonstrated to contribute to descending pain modulation. However, the role of ACC dopamine receptors in chronic neuropathic pain remains unclear.

Objective:

In this study, we investigated the effect of optogenetic activation of ACC dopamine receptors D1- and D2-expressing neurons on trigeminal neuropathic pain.

Methods:

Chronic constriction injury of infraorbital nerve (CCI-ION) was carried out to induce trigeminal neuropathic pain in mice. We conducted optogenetic stimulation to specifically activate D1- and D2-expressing neurons in the ACC. Western blotting and immunofluorescence staining were used to examine ACC D1 and D2 expression and localization. The von Frey and real-time place preference tests were performed to measure evoked mechanical pain and nonreflexive emotional pain behaviors, respectively.

Results:

We observed that dopamine receptors D1 and D2 in the ACC are primarily expressed in excitatory neurons and that the D2 receptor is differentially regulated in the early and late phases of trigeminal neuropathic pain. Optogenetic activation of D1-expressing neurons in the ACC markedly exacerbates CCI-ION-induced trigeminal neuropathic pain in both early and late phases, but optogenetic activation of D2-expressing neurons in the ACC robustly ameliorates such pain in its late phase.

Conclusion:

Our results suggest that dopamine receptors D1 and D2 in the ACC play different roles in the modulation of trigeminal neuropathic pain.

No Association of Polymorphisms in Nav1.7 or Nerve Growth Factor Receptor Genes with Trigeminal Neuralgia

OBJECTIVE

Trigeminal neuralgia is defined as a sudden severe shock-like pain within the distribution of the trigeminal nerve. Pain is a subjective experience that is influenced by gender, culture, environment, psychological traits, and genes. Sodium channels and nerve growth factor play important roles in the transmission of nociceptive signals and pain. The aim of this study was to investigate the occurrence of Nav1.7 sodium channel and nerve growth factor receptor TrkA gene polymorphisms (SCN9A/rs6746030 and NTRK1/rs633, respectively) in trigeminal neuralgia patients.

METHODS

Ninety-six subjects from pain specialty centers in the southeastern region of Brazil were divided into 2 groups: 48 with classical trigeminal neuralgia diagnosis and 48 controls. Pain was evaluated using the visual analog scale and multidimensional McGill Pain Questionnaire. Genomic DNA was obtained from oral swabs in all individuals and was analyzed by real-time polymerase chain reaction.

RESULTS

No association was observed between evaluated polymorphisms and trigeminal neuralgia. For allele analyses, patients and controls had similar frequencies for both genes. Genotype distribution or allele frequencies of polymorphisms analyzed here did not correlate to pain scores.

CONCLUSIONS

Although no association of evaluated polymorphisms and trigeminal neuralgia diagnosis or pain severity was observed, our data do not exclude the possibility that other genotypes affecting the expression of Nav1.7 or TrkA are associated with the disease. Further studies should investigate distinct genetic polymorphisms and epigenetic factors that may be important in expression of these molecules.

Long-term Follow-up of Patients Treated with Percutaneous Radiofrequency Thermocoagulation via the Foramen Rotundum for Isolated Maxillary Nerve Idiopathic Trigeminal Neuralgia

OBJECTIVE

The purpose of this study is to evaluate the effectiveness and safety of percutaneous radiofrequency thermocoagulation (PRT) via the foramen rotundum (FR) for the treatment of isolated maxillary (V2) idiopathic trigeminal neuralgia (ITN) and assess the appropriate puncture angle through the anterior coronoid process to reach the FR.

METHODS

Between January 2011 and October 2016, 87 patients with V2 ITN refractory to conservative treatment were treated by computed tomography (CT)-guided PRT via the FR at our institution. The outcome of pain relief was assessed by the visual analog scale (VAS) and Barrow Neurological Institute (BNI) pain grade and grouped as complete pain relief (BNI grades I-III) or unsuccessful pain relief (BNI grades IV-V). Recurrence and complications were also monitored and recorded. The puncture angle for this novel approach was assessed based on intraoperative CT images.

RESULTS

Of the 87 treated patients, 85 (97.7%) achieved complete pain relief, and two patients (2.3%) experienced unsuccessful pain relief immediately after operation. During the mean follow-up period of 44.3 months, 15 patients (17.2%) experienced recurring pain. No severe complications occurred, except for hypoesthesia restricted to the V2 distribution in all patients (100%) and facial hematoma in 10 patients (11.5%). The mean puncture angle to reach the FR was 33.6° ± 5.7° toward the sagittal plane.

DISCUSSION

CT-guided PRT via the FR for refractory isolated V2 ITN is effective and safe and could be a rational therapy for patients with V2 ITN.

Acupuncture in the management of trigeminal neuralgia

BACKGROUND

We aimed to assess the standing of acupuncture as a clinical tool in the management of trigeminal neuralgia against the current first-line drug treatment (carbamazepine) and the most effective surgery (microvascular decompression (MVD)).

METHODS

Data regarding efficacy, side effects and cost were compiled for each of these three modalities from the PubMed and Cochrane Library databases. Patient stress was estimated according to Holmes and Rahe's Social Readjustment Rating Scale (SRRS).

RESULTS

Acupuncture was not significantly more effective than its corresponding control (p = 0.088), but had the greatest efficacy (mean ± 95% confidence interval) of the modalities considered (86.5% ± 5.6% compared to surgery (79.3% ± 7.7%) and pharmacotherapy (71.7% ± 2.5%), respectively). Acupuncture also had fewer mean reported side effects (22.7% ± 5.9%) compared with surgery (25.3% ± 12.6%) and pharmacotherapy (88.8% ± 25.0%), and the lowest cost; after 5 years, the cost of acupuncture was estimated to be £750, compared to £1507.73 for carbamazepine and £4878.42 for MVD. Acupuncture was the least stressful according to the SRRS (53 points), whereas surgery was second most stressful (153 points) and pharmacotherapy was the most stressful intervention to patients (217 points).

CONCLUSION

Acupuncture appears more effective than pharmacotherapy or surgery. Statistical analysis of side effects was not possible due to inconsistent reporting protocols, but the data suggest that acupuncture is considerably safer than pharmacotherapy or surgery. Acupuncture also appears to be the least expensive therapeutic modality to deliver long-term (65 weeks onwards), and our analysis indicated that it was less stressful to patients than pharmacotherapy or surgery. Further study into these areas and the practicality of its availability in the UK National Health Service (NHS) and other health systems is recommended.

Percutaneous imaging-guided techniques for the treatment of benign neuropathic pain

To date, conservative management including physical and/or systemic pharmacologic therapy is considered as the first line approach for the management of neuropathic pain syndromes. In the era of an opioid overdose crisis with an increased concern upon the risks and harms arising from the misuse of medicines for pain management, percutaneous minimally invasive techniques such as nerve infiltrations as well as neurolysis or neuromodulation techniques can be proposed to control pain and improve life quality. Computed tomography can serve as an ideal guiding technique due to its specific characteristics including precise anatomic delineation, high spatial resolution and good tissue contrast. The purpose of this review is to make the reader familiar with the most common indications for minimally invasive imaging-guided techniques in patients with neuralgia and provide current evidence regarding technical considerations.

Palmatine alleviates hyperalgesia by inhibiting the expression of calcitonin gene-related peptide in the trigeminal ganglion of rats with chronic constriction injury of the infraorbital nerve

Trigeminal neuralgia is one of the most common of the neuropathic pains, and it can seriously influence patients' quality of life. Calcitonin gene-related peptide (CGRP) is a type of nociceptive neurotransmitter that is expressed in neurons of the trigeminal ganglion and plays a major part in transmitting pain. The rat model of trigeminal neuralgia was established by causing a chronic constriction injury of the infraorbital nerve (CCI-ION). Male Sprague-Dawley rats (n=24) were randomly divided into a sham control group (sham, n=6), sham-treated with palmatine group (sham+palmatine, n=6), trigeminal nerve model group (TN, n=6), and trigeminal nerve treated with palmatine group (TN+palmatine, n=6). Fifteen days after the operation the mechanical response threshold was decreased in the TN group compared with the sham group. From postoperative day 7 to day 15, the mechanical response threshold in the TN+palmatine group significantly increased compared with the TN group. On postoperative day 15 the results of quantitative polymerase chain reaction (qPCR), immunohistochemical staining, and western blotting showed an obvious increase in expression of CGRP and its receptors, serum concentrations of interleukin-1β (IL-1β), and tumour necrosis factor-α (TNF-α), and phosphorylation of protein kinase C (PKC) in the trigeminal ganglia of the TN group compared with the sham group, but these increases could be down-regulated by treatment with palmatine. Palmatine might therefore have therapeutic potential for the treatment of trigeminal neuralgia by inhibiting the expression of CGRP and its receptors in trigeminal ganglia, suppressing the serum concentrations of IL-1β and TNF-α, and decreasing the phosphorylation of PKC in the trigeminal ganglia of affected rats.

Endoscopic Infraorbital Microdissection for Localized V2 Trigeminal Neuralgia

Trigeminal neuralgia is a chronic and debilitating syndrome characterized by short paroxysms of lancinating facial pain. Patients may be medically managed; however, in cases of medically refractory trigeminal neuralgia, surgical management is often required. Our objective was to present and describe a technique for endoscopic microdissection of the infraorbital nerve, a peripheral method of management for refractory V2 trigeminal neuralgia in patients without evidence of neurovascular compression. The technique is designed to spare sensation in unaffected portions of the V2 distribution. We present 2 patients with medically refractory V2 trigeminal neuralgia localized to the lateral midface who underwent infraorbital microdissection. After first confirming that there was no neurovascular compression on imaging in these patients, we administered infraorbital bupivacaine injections to localize the symptomatic nerve. The nerve was then accessed via a 1.5-cm buccogingival incision, and the connective tissue sheath was incised. The nerve fascicles were bluntly separated, and the symptomatic branches were cauterized with fine-tipped monopolar cautery. Both patients reported complete resolution of their pain postoperatively and were pain free at last follow-up. They reported some hypoesthesia in the lateral face; however, they retained some sensation in the medial upper lip, midface, and nose. Infraorbital microdissection is a safe and effective technique for symptomatic management of V2 trigeminal neuralgia while sparing sensation in asymptomatic portions of the dermatome.

Characterizing Treatment Utilization Patterns for Trigeminal Neuralgia in the United States

BACKGROUND AND AIM

Trigeminal neuralgia (TN) is a rare orofacial disorder characterized by severe unilateral paroxysmal pain in the region of the fifth cranial nerve. Clinical guidelines recommend carbamazepine (only US Food and Drug Administration-approved drug for TN) and oxcarbazepine as first-line therapies. We utilized the US Truven Health MarketScan database to examine treatment patterns among patients with TN.

METHODS

Included patients were aged 18 years and above, newly diagnosed with TN (≥2 TN diagnoses ≥14 days apart; no diagnosis in the previous year), continuously enrolled 1 year before index, with ≥3 years' follow-up postindex. We assessed utilization of selected pharmacotherapies (carbamazepine, oxcarbazepine, pregabalin, gabapentin, baclofen, duloxetine, topiramate), surgery (posterior fossa, radiosurgery), and injections (peripheral anesthetic injections, Gasserian ganglion procedures) for TN.

RESULTS

In total, 3685 patients were included (2425 commercial, 1260 Medicare; 71.8% female; age, mean [SD], 59 [15] y). Overall, 72.5% of patients received at least 1 studied medication, most commonly carbamazepine (51.7%) or gabapentin (48.6%). In total, 65% of pharmacologically treated patients had ≥2 treatment episodes; 41.6% had ≥3 (defined by a change in pharmacotherapy [monotherapy/combination] regimen). Overall, 12.3% had surgery and 7.3% injections; 42.9% received opioids for TN.

CONCLUSIONS

In the 3 years after diagnosis, patients with TN in the United States receive a variety of pharmacological treatments, including opioids, despite carbamazepine being the only approved medication. A notable proportion utilize surgeries/injections. A high proportion of pharmacologically treated patients receive multiple treatment episodes, suggesting frequent therapy switching, perhaps because of suboptimal efficacy/tolerability. Our data suggest a high burden of illness associated with TN.

Pathological Mechanisms and Therapeutic Targets for Trigeminal Neuropathic Pain

Trigeminal neuropathic pain is a chronic pain condition caused by damage or inflammation of the trigeminal nerve or its branches, with both peripheral and central nervous system dysfunction contributing to the disorder. Trigeminal pain conditions present with diagnostic and therapeutic challenges to healthcare providers and often require multiple therapeutic approaches for pain reduction. This review will provide the overview of pathophysiology in peripheral and central nociceptive circuits that are involved in neuropathic pain conditions involving the trigeminal nerve and the current therapeutics that are used to treat these disorders. Recent advances in treatment of trigeminal pain, including novel therapeutics that target ion channels and receptors, gene therapy and monoclonal antibodies that have shown great promise in preclinical studies and clinical trials will also be described.

Differential diagnosis short-lasting unilateral neuralgiform headache attacks and trigeminal neuralgia

The article presents diagnostic criteria, comparative characteristics of short-lasting unilateral neuralgiform headache attacks, including short-term unilateral neuralgic headaches with conjunctival injection and lacrimation (SUNCT) and short-term unilateral neuralgic headaches with cranial autonomic symptoms (SUNA), differential diagnosis with trigeminal neuralgia.

Introduction of pulsed radiofrequency cautery in infraorbital nerve block method for postoperative pain management of trauma-induced zygomaticomaxillary complex fracture reduction

Although various cases of neuralgia and its treatments have been reported, not enough evidence is present to recommend a single type of treatment as the most effective. The patient we have dealt with experienced significant interferences in his daily life due to chronic allodynia, but the symptom could not be resolved via previously reported treatments. We report a case of which a patient who presented infraorbital neuralgia after trauma was successfully treated by a novel treatment strategy. The patient was treated by applying infraorbital nerve block and pulsed radiofrequency cautery side by side. Through this report, we evaluate proper prevention and treatment strategies for patients who develop infraorbital neuralgia through similar etiologies.

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Factors Predicting Successful Outcomes for Percutaneous Radiofrequency Thermocoagulation in Patients With Idiopathic Trigeminal Neuralgia: Implications for Surgical Decision Making

OBJECTIVES

In this study we aimed to identify specific factors predicting successful outcomes after percutaneous radiofrequency thermocoagulation (RFT) for idiopathic trigeminal neuralgia (ITN) and risk factors that were associated with inferior outcomes.

METHODS

We retrospectively reviewed our cohort of 1,624 patients who underwent RFT for trigeminal neuralgia between January 2000 and December 2017. Demographic and clinical data including age, gender, disease duration, affected side, baseline pain score, pain distribution, history of previous surgical intervention, and pain characteristics were collected and evaluated for their association with outcome using univariate and multivariate logistic regression analysis.

RESULTS

78.1% of patients experienced a successful outcome of RFT for ITN as predefined criteria. Pain characteristics and history of surgical treatment were significant predictors associated with successful outcomes in regression analysis. Multivariate analysis identified provoked episodic pain at diagnosis (odds ratio [OR] = 23.629, 95% confidence interval [CI]: 16.316 to 34.219, P = 0.010), mixed pain (OR = 8.394, 95% CI: 5.951 to 11.840, P = 0.011), and no history of surgical treatment (OR = 2.189, 95% CI: 1.411 to 3.396, P = 0.019) as independent predictors for successful RFT outcome.

CONCLUSION

Presence of provoked episodic pain and mixed pain were significantly associated with successful outcome of RFT for ITN. Moreover, patients with ITN who underwent RFT for the first time were more likely to benefit from successful outcome. These findings should be considered when managing ITN with RFT to improve the likelihood of a successful outcome.

Radial Extracorporeal Shock Wave Therapy in an Individual With Primary Trigeminal Neuralgia: A Case Report and Literature Review

A patient with primary trigeminal neuralgia exhibited pain relief without medication after radial extracorporeal shock wave therapy. The 52-yr-old woman had a 3-yr history of primary trigeminal neuralgia, involving the right maxillary division (V2) and the mandibular division (V3). She became refractory to carbamazepine and exhibited hepatic dysfunction. She hence received 3000 to 6000 impulses of craniofacial radial extracorporeal shock wave therapy to the region centered on the surface projection of the trigeminal ganglion and pain areas at 10 Hz; the intensity ranged from 1.4 to 4.5 bars twice per week for 8 wks. At baseline, and 1, 2, and 5 mos after treatment, the Barrow Neurological Institute scores were IV, IIIa, II, and II, and the visual analog scale scores were 8, 3, 1, and 1, respectively. No complications or adverse effects were observed. The hepatic function returned to normal after the discontinuation of carbamazepine. This case report demonstrates the feasibility of radial extracorporeal shock wave therapy for primary trigeminal neuralgia without complications or adverse effects with careful regulation of the therapy intensity.

A Clinical Study on Comparative Evaluation of the Effectiveness of Carbamazepine and Combination of Carbamazepine with Baclofen or Capsaicin in the Management of Trigeminal Neuralgia

Background:

Trigeminal neuralgia (TN) is characterized by recurrent attacks of lancinating pain in the trigeminal nerve distribution. Various medicinal and surgical procedures have been utilized for the treatment of TN. Over the time, several drugs other than carbamazepine have been used but none of them have shown satisfying results.

Objective:

The objective of the study is to evaluate the effectiveness of carbamazepine and combination of carbamazepine with baclofen or capsaicin in the management of TN.

Materials and Methods:

A total of 45 patients diagnosed with TN were randomly divided into three groups. The patients were prescribed carbamazepine in Group 1, carbamazepine and baclofen in Group 2, and carbamazepine and capsaicin in Group 3. All the patients were followed on the 7^th day, 15^th day, and 1-month period to evaluate the response to the drugs. Data were subjected to statistics.

Results:

The results are composed of a total of 45 patients (15 in each group). The mean visual analogue scale scores were calculated for each group at day 0, 7^th day, 15^th day, and 30 days, and it was found that there was statistically significant reduction of pain (P < 0.001) in all the three groups at different intervals. At day 7, comparative percentage reduction of pain in both groups was not statistically significant. At 15-days and 30 days, percentage change in pain reduction in Group 1 was 42.3% and 48.0% respectively and in Group 2 it was found to be 60.3% and 83.4%, respectively. The reduction in pain percentage was found to be statistically significant. Similarly, Group 1 was compared to Group 3, significant reduction of pain was found for carbamazepine-capsaicin combination at 30-day interval but the comparative reduction of pain at 7^th day and 15^th day was not statistically significant.

Conclusion:

Carbamazepine in combination with baclofen is more efficient and effective in reducing pain in TN patients, followed by carbamazepine-capsaicin combination compared to carbamazepine alone.

Neuropathic Pain and Sleep: A Review

Neuropathic pain is associated with sleep disturbances, and in turn poor sleep quality leads to increased pain sensitivity, so it is essential to assess sleep alongside neuropathic pain. Responses to drugs are inconsistent and identifying the best treatment option that will reduce pain and improve sleep quality remains challenging for clinicians. Anticonvulsants such as pregabalin and gabapentin improve neuropathic pain and have a positive effect on comorbid sleep disturbances. Opioids and antidepressants are effective in reducing pain but can exacerbate sleep disturbances.

FUNDING

Pfizer, Italy.

Emodin inhibits the expression of receptor and calcitonin-gene-related peptide release in trigeminal ganglia of trigeminal neuralgia rats

Trigeminal neuralgia (TN) is one of the most intense forms of facial pain. It has been reported that the P2X₃ receptor plays a crucial role in facilitating pain transmission, and the calcitonin-gene-related peptide (CGRP) from trigeminal ganglia (TGs) might perform differing function in nociceptive afferent input transmission. The present study investigated whether emodin can affect TN pain transmission by suppressing the expression of P2X₃ receptors and CGRP in TGs. Chronic constriction injury of the infraorbital branch of the trigeminal nerve (CCI-ION) was used as TN model. The TN rats were randomly divided into the following 4 groups: (1) a sham group (Sham), (2) a sham rats treated with emodin group (TN + E), (3) a TN rats treated with 0.5% sodium carboxymethyl cellulose (CMC) as vehicle group (TN) and (4) a TN rats treated with emodin group (TN + E). The mechanical hyperalgesia threshold of TN rats was tested by Electric Von Frey filaments. The change of the expression of P2X₃ receptors and CGRP in rat's TG was detected with RT-PCR, immunohistochemical staining, and Western blotting. The phosphorylation of p38 and ERK1/2 pathway of TG was detected by Western blotting. After CCI-ION injury, the threshold of mechanical hyperalgesia for the territory of ligated infraorbital nerve in TN group decreased significantly compared with that in sham group. On day 14 after operation of CCI-ION, there was also an evident increase in the expression of P2X₃ receptors and CGRP in the TG of TN group. However after treatment with emodin, the response of mechanical hyperalgesia of TN rats was clearly increased while the enhanced expression of P2X₃ receptor and CGRP in TN rats was significantly decreased. The phosphorylation of p38 and ERK1/2 in TN group was stronger than that in Sham group. But these phosphorylation changes in the TN rats were much weaker after treatment with emodin. In conclusion, P2X₃ receptor may cooperate with CGRP in the pain transmission of TN, and emodin can inhibit the expression and activation of P2X₃ receptor and CGRP in TG to relieve TN.

Cognitive effects of electro-acupuncture and pregabalin in a trigeminal neuralgia rat model induced by cobra venom

Objective

The objective of this study was to investigate the effects of electro-acupuncture (EA) and pregabalin on cognition impairment induced by chronic trigeminal neuralgia (TN) in rats.

Design

Controlled animal study.

Setting

Department of Anesthesiology, Pain Medicine and Critical Care Medicine, Aviation General Hospital of China Medical University.

Subjects

Forty adult male Sprague Dawley rats.

Methods

Rats were randomly divided into four groups. The TN model was induced by administration of cobra venom to the left infraorbital nerve. On postoperative day 14, either EA or pregabalin was administered, free behavioral activities were observed. Spatial learning and memory abilities were determined in the Morris water maze. The ultrastructural alterations of the Gasserian ganglion, medulla oblongata and hippocampus were examined by electron microscopy. The changes on long-term potentiation were investigated.

Results

After treatment, the exploratory behavior increased and the grooming behavior decreased (P<0.05) for the EA group and pregabalin group compared with the cobra venom group; moreover, demyelination of neurons in Gasserian ganglion and medulla oblongata was reversed. The number of platform site crossings, the average percentages of time in the target quadrant and the field excitatory postsynaptic potential slopes increased (P<0.05) in the EA group compared to the cobra venom group. However, the pregabalin group showed no differences compared to the cobra venom group (P>0.05). Vacuolar degeneration in the hippocampal neurons was mild in the EA group, while it was severe in the pregabalin group.

Conclusion

EA and pregabalin could alleviate TN induced by cobra venom. EA could also inhibit the cognition deficit induced by TN, while pregabalin could not.

Atypical Trigeminal Neuralgia: A Rare Neurological Manifestation of Systemic Lupus Erythematosus

Patient: Female, 53

Final Diagnosis: Atypical trigerminal neuralgia

Symptoms: Right sided facial pain

Medication: —

Clinical Procedure: None

Specialty: Rheumatology

A retrospective study of neurocombing for the treatment of trigeminal neuralgia without neurovascular compression

BACKGROUND

Microvascular decompression (MVD) is the most effective and non-ablative treatment for trigeminal neuralgia (TN). However, it is not possible when neurovascular compression (NVC) is absent. Neurocombing is a possible treatment option for TN patients without NVC.

AIM

To evaluate and describe the clinical outcome of neurocombing for the treatment of TN when NVC was absent.

METHODS

We retrospectively reviewed the clinical data of the 37 patients of Type 1 TN without NVC who underwent neurocombing in our department between January 2013 and November 2014. The Barrow Neurological Institute (BNI) Pain Intensity scale, the numerical rating scale (NRS) and the quality of life scale (QOL) were evaluated in four stages-presurgical, immediate, at 1 and at 3 years. Pain recurrence was statistically evaluated with Kaplan-Meier analysis.

RESULTS

All the 37 enrolled patients were proved to have no NVC by imaging or exploration in surgery. The mean follow-up duration was 29.50 months. After the procedure, 35 patients (94.6%) experienced immediate pain relief (BNI I) and 2 patients (5.4%) had occasional pain without any medication (BNI II). At 1 year and 3 years, the rates of successful pain relief (BNI I&II) were 86.5 and 83.3%, respectively. 34 patients (91.9%) suffered from mild facial numbness, while it did not exert a harmful impact on their quality of life.

CONCLUSIONS

This study demonstrated that neurocombing is an attractive, effective, safe and durable treatment option for TN when NVC is absent. Further study is needed to explain the complicated and exact mechanism of pain relief by neurocombing.