Therapeutic efficacy and safety of Botulinum Toxin A Therapy in Trigeminal Neuralgia: a systematic review and meta-analysis of randomized controlled trials

The efficacy of botulinum toxin in neuropathic pain: a systematic review

Introduction

Neuropathic pain (NP) is characterised as a lesion or disease directly affecting the somatosensory system. This study aims to analyse the efficacy of botulinum toxin type A (BT-A) in the treatment of neuropathic pain.

Methods

This systematic literature review, guided by PRISMA, applied the PICO strategy with the following criteria: (P = patients with neuropathic pain, I = botulinum toxin, C = placebo or active drug, and O = pain relief).

Results

Fourteen articles, all randomised controlled trials with a placebo control, were included in the review. A total of 645 patients were randomised, with 353 patients receiving treatment with botulinum toxin type A in doses ranging from 25U to 400U. The evaluated studies addressed trigeminal neuralgia, diabetic polyneuropathy, post-herpetic neuralgia, spinal cord injury, phantom limb pain, and peripheral neuropathic pain after trauma or surgery.

Conclusion

BT-A has emerged as a promising treatment for various origins of neuropathic pain. Therefore, future studies should adopt stricter criteria regarding dosage and routes of administration to ensure effective and consistent BT-A application.

[Trigeminal neuralgia: drug therapy : The new German guideline]

Trigeminal neuralgia is characterized by severe, lightning-like attacks of pain, which are mandatory for the diagnosis. The pain typically occurs on one side and is often triggered by simply touching the face, chewing or talking. In acute exacerbations, this can also hinder food and fluid intake, resulting in a life-threatening clinical picture. A distinction is made between classical, secondary and idiopathic trigeminal neuralgia. For the diagnosis of trigeminal neuralgia, the medical history and imaging procedures are key for classification. The only active substances approved for the treatment of trigeminal neuralgia in Germany are carbamazepine and phenytoin, which is why off-label drugs often need to be used if there is no or insufficient effect or inacceptable side effects. Cooperation between research and clinical practice to improve the care of affected patients is therefore essential.

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.

Effect of ultrasound-guided injection of botulinum toxin type A into shoulder joint cavity on shoulder pain in poststroke patients: study protocol for a randomized controlled trial

BACKGROUND

Hemiplegic shoulder pain (HSP) is a common complication after stroke. It severely affects the recovery of upper limb motor function. Early shoulder pain in hemiplegic patients is mainly neuropathic caused by central nerve injury or neuroplasticity. Commonly used corticosteroid injections in the shoulder joint can reduce shoulder pain; however, the side effects also include soft tissue degeneration or increased tendon fragility, and the long-term effects remain controversial. Botulinum toxin injections are relatively new and are thought to block the transmission of pain receptors in the shoulder joint cavity and inhibit the production of neuropathogenic substances to reduce neurogenic inflammation. Some studies suggest that the shoulder pain of hemiplegia after stroke is caused by changes in the central system related to shoulder joint pain, and persistent pain may induce the reorganization of the cortical sensory center or motor center. However, there is no conclusive evidence as to whether or not the amelioration of pain by botulinum toxin affects brain function. In previous studies of botulinum toxin versus glucocorticoids (triamcinolone acetonide injection) in the treatment of shoulder pain, there is a lack of observation of differences in changes in brain function. As the content of previous assessments of pain improvement was predominantly subjective, objective quantitative assessment indicators were lacking. Functional near-infrared imaging (fNIRS) can remedy this problem.

METHODS

This study protocol is designed for a double-blind, randomized controlled clinical trial of patients with post-stroke HSP without biceps longus tenosynovitis or acromion bursitis. Seventy-eight patients will be randomly assigned to either the botulinum toxin type A or glucocorticoid group. At baseline, patients in each group will receive shoulder cavity injections of either botulinum toxin or glucocorticoids and will be followed for 1 and 4 weeks. The primary outcome is change in shoulder pain on the visual analog scale (VAS). The secondary outcome is the assessment of changes in oxyhemoglobin levels in the corresponding brain regions by fNIRS imaging, shoulder flexion, external rotation range of motion, upper extremity Fugl-Meyer, and modified Ashworth score.

DISCUSSION

Ultrasound-guided botulinum toxin type A shoulder joint cavity injections may provide evidence of pain improvement in patients with HSP. The results of this trial are also help to analyze the correlation between changes in shoulder pain and changes in cerebral hemodynamics and shoulder joint motor function.

TRIAL REGISTRATION

Chinese clinical Trial Registry, ChiCTR2300070132. Registered 03 April 2023, https://www.chictr.org.cn/showproj.html?proj=193722 .

Evaluation of the Effect of Botulinum Toxin A on the Lymphatic Endothelial Cells

INTRODUCTION

Botulinum toxin A (BoTA) is a neurotoxin formed by Clostridium botulinum, with a broad medical application spectrum. While the primary effect of BoTA is on the muscles, the effects of BoTA in other systems including the blood vasculature have already been examined, revealing unexpected actions. However, no studies exist to the best of our knowledge regarding the potential effects of BoTA on the lymphatic vascular system, possessing a critical role in health and disease. Isolated human lymphatic endothelial cells (LECs) were cultured in dedicated in vitro culture systems. The analysis including imaging and cell culture approaches as well as molecular biology techniques is performed to examine the LEC alterations occurring upon exposure to different concentrations of BoTA.

MATERIALS AND METHODS

Human LECs were cultured and expanded on collagen-coated petri dishes using endothelial basal medium and the commercial product Botox from Allergan as used for all our experiments. Harvested cells were used in various in vitro functional tests to assess the morphologic and functional properties of the BoTA-treated LECs. Gene expression analysis was performed to assess the most important lymphatic system-related genes and pathways.

RESULTS

Concentrations of 1, 5 or 10 U of BoTA did not demonstrate a significant effect regarding the proliferation and migration capacity of the LECs versus untreated controls. Interestingly, even the smallest BoTA dose was found to significantly decrease the cord-like-structure formation capacity of the seeded LECs. Gene expression analysis was used to underpin possible molecular alterations, suggesting no significant effect of BoTA in the modification of gene expression versus the starvation medium control.

CONCLUSION

LECs appear largely unaffected to BoTA treatment, with an isolated effect on the cord-like-structure formation capacity. Further work needs to assess the effect of BoTA on the smooth-muscle-cell-covered collecting lymphatic vessels and the possible aesthetic implications of such an effect, due to edema formation.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Efficacy and Safety of Botulinum Toxin Type A in the Treatment of Trigeminal Neuralgia: An Update on Systematic Review With Meta-analyses

OBJECTIVE

Pain management in patients with TN is challenging, as facial pain often does not respond well to conventional therapies. Botulinum toxin type A (BTX-A) has been suggested as a potential treatment option, but there is limited evidence regarding its long-term efficacy. This review aimed to analyze the current data for the use of in the treatment of trigeminal neuralgia (TN) and highlight the evidence for its efficacy and safety.

METHODS

A comprehensive search was conducted in various databases (PubMed, Scopus, Embase, ClinicalTrials, and Cochrane Library) to identify clinical studies evaluating the use of BTX-A in TN until October 2023. Randomized controlled trials (RCTs), single-arm studies, and stratified studies were included in the analysis. The mean difference (MD), effect size (ES), and 95% confidence interval (CI) were estimated for visual analogue scale (VAS) scores, pain episode frequency, and the proportion of responders.

RESULTS

The analysis included 23 studies, including 4 RCTs, 14 single-arm studies, and 5 stratified studies. In the RCTs, BTX-A was found to significantly reduce mean VAS scores compared with baseline (ES: -4.05; 95% CI: -6.13, -1.97; P =0.002). In 19 non-RCTs, the pooled single-arm analysis revealed that BTX-A decreased VAS scores (ES: -5.19, 95% CI: -6.05, -4.33, P <0.001) and pain attack frequency (ES: -17.85, 95% CI: -23.36, -12.34, P <0.001) from baseline to the end of follow-up. The overall proportion of responders to BTX-A treatment was also significant (95% CI: 0.653, 0.761, P =0.003).

DISCUSSION

Current evidence indicates that BTX-A injection is an effective and safe option for patients with refractory TN or not responding to medical or surgical management. However, more high-quality studies are needed to further confirm its efficacy.

Therapeutic Options for Migraines in the Microsurgical Patient: A Scoping Review

BACKGROUND

There exists an increasing array of treatments proposed to prevent, alleviate, and abort symptoms of a migraine; however, for patients who undergo reconstructive microsurgery, caution must be taken to preserve vascular integrity. This study is the first-to-date scoping review of vascular and bleeding risk of current migraine therapies, with the purpose of identifying potential therapeutic agents for postoperative migraine management appropriate for microsurgical patients.

METHODS

Currently available migraine therapeutics were compiled from the UpToDate software system and the American Academy of Family Physicians. A PubMed literature review was performed for each therapeutic's effect on bleeding or vascular involvement. Data were compiled into tables of abortive, symptom-controlling and prophylactic, and nonpharmacologic treatments. Expert microsurgeons reviewed the data to provide recommendations for optimized patient care.

RESULTS

Triptans and other ergot derivatives demonstrated strong evidence of vasoconstriction and were greatly advised against for immediate postmicrosurgical use. Novel pharmaceutical therapies such as lasmiditan and calcitonin gene-related peptide antagonists have no literature indicating potential for vasoconstriction or hematoma and remain an investigational option for abortive medical treatment. For symptom control, acetaminophen appears the safest option, with clinical judgment and further research needed for use of nonsteroidal antiinflammatory drugs. Alternative treatment techniques may include migraine prophylaxis with botulinum toxin injection or nutraceutical treatment by means of magnesium supplementation or coenzyme Q10 administration, minimizing the need for additional medication in the postoperative setting.

CONCLUSIONS

Patients undergoing reconstructive microsurgery have a unique medical profile limiting the therapeutic options available to treat migraines. This review provides preliminary evidence to be considered as a guide for prescribing therapeutics for migraine in the postoperative setting.

Botulinum toxin-A as a treatment option for refractory idiopathic trigeminal neuralgia of the ophthalmic branch: a case report and literature review

Trigeminal neuralgia is one of the most common neurological pains affecting the head and neck and is associated with severe, lancinating, electrical pain episodes. The maxillary and mandibular branches are usually affected. The ophthalmic branch is rarely involved and, when present, it requires a comprehensive workup to rule out major conditions. Pharmacotherapy and surgery are the most common treatment options for this condition. Systemic medications may pose a wide range of side effects and effectiveness may decrease over time while surgery has inherent complications. Injectable onabotulinum toxins have been utilized for various applications in medicine and dentistry. There is, however, limited data on their use for the management of refractory trigeminal neuralgia of the ophthalmic branch. We present the case of a 58-year-old male diagnosed with refractory idiopathic trigeminal neuralgia affecting the ophthalmic branch, which was unresponsive to standard care and successfully managed with onabotulinum toxin type A. This treatment should be considered in cases of refractory trigeminal neuralgia prior to surgery. We reviewed the relevant literature concerning the application of Onabotulinum toxin A for managing trigeminal neuralgia of the ophthalmic branch. This case report and review aim to enlighten the application of Onabotulinum toxin A for managing refractory trigeminal neuralgia of the ophthalmic branch. Our case report and review show that Onabotulinum toxin A could be used for managing TN of the ophthalmic branch.

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

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

Efficacy and Safety of High-Voltage Pulsed Radiofrequency versus Standard-Voltage Pulsed Radiofrequency for Patients with Neuropathic Pain: A Literature Review and Meta-Analysis

Background

Neuropathic pain (NP) is recognized as one of the most difficult pain syndromes which lacks a safe, well-tolerated and effective treatment. Pulsed radiofrequency (PRF), a novel and minimally invasive interventions, has been introduced to alleviate various types of NP. Previous studies reported PRF with higher voltage could further improve the treatment efficacy. Therefore, we conducted this systematic review and meta-analysis to determine whether high-voltage PRF is superior to standard-voltage PRF for the treatment of NP patients.

Methods

Databases published from the date of inception until 15 March 2022 on PubMed/MEDLINE, EMBASE, Web of Science and the Cochrane Library were searched for RCTs comparing high-voltage PRF and standard-voltage PRF in NP patients. The primary outcome measures were the efficiency rates of NP patients with high-voltage PRF or standard-voltage PRF treatment. Data analysis was conducted using the Review Manager software (RevMan V.5.3).

Results

Six RCTs involving 423 patients were included in our meta-analysis. Compared with standard-voltage PRF group, the high-voltage PRF group attained a higher efficiency rate at 1 month (P = 0.04; I2 = 0%), 3 months (P = 0.04; I2 = 0%), 6 months (P = 0.002; I2 = 0%) post-procedure respectively. There was no significant difference in the complications between the two groups.

Conclusion

Our study supported that high-voltage PRF attained more satisfactory efficacy than standard-voltage PRF without increased side effects. High-voltage PRF could be a promising, effective, minimally invasive technology for NP patients.

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.

Is Botulinum Toxin Effective in Treating Orofacial Neuropathic Pain Disorders? A Systematic Review

BACKGROUND

The aim of this paper is to provide a systematic review of the literature regarding the clinical use of botulinum toxin (BTX) to treat various orofacial neuropathic pain disorders (NP).

METHODS

A comprehensive literature search was conducted using Medline, Web of Science, and the Cochrane Library databases. Only randomized clinical trials (RCT) published between 2003 and the end of June 2023, investigating the use of BTX to treat NP, were selected. PICO guidelines were used to select and tabulate the articles.

RESULTS

A total of 6 RCTs were selected. Five articles used BTX injections to treat classical trigeminal neuralgia, and one to treat post-herpetic neuralgia. A total of 795 patients received BTX injections. The selected studies utilised different doses and methods of injections and doses. All the selected studies concluded superiority of BTX injections over placebo for reducing pain levels, and 5 out 6 of them highlighted an improvement in the patient's quality of life. Most of the studies reported transient and mild side effects.

CONCLUSION

There is evidence of the efficacy of BTX injections in orofacial pain management. However, improved study protocols are required to provide direction for the clinical use of BTX to treat various orofacial neuropathic pain disorders.

Botulinum toxin type A for genitofemoral neuralgia: A case report

Genitofemoral neuralgia is an uncommon pain disorder that could be resistant to conventional treatment. A 78-year-old woman with refractory right genitofemoral neuralgia was treated with BoNT/A subcutaneous injections; the treatment was performed three times with significant pain improvement, although temporary, and without adverse events. BoNT/A may be a promising alternative intervention in the setting of genitofemoral neuralgia refractory to oral and/or topical treatment.

Management protocols of chronic Orofacial Pain: A Systematic Review

Objective

Chronic orofacial pain (CP) is a persistent and debilitating condition that affects the face, mouth, and jaw and can have a significant impact on an individual's quality of life by posing problems to eat, speak, and perform everyday activities. By the means of this narrative review, we aim to assess different types of management modalities that exist to combat chronic orofacial pain.

Design

Various databases were explored with MeSH keywords of chronic orofacial pain, orofacial pain, and interventions and treatment protocols for eligible articles. After an extensive literature search, it was ascertained that this review identified four major categories of treatment modalities for the management of chronic orofacial pain, namely pharmacological management, psychological management, lifestyle interventions-based management, and current stimulation-based management.

Results

Of the four categories discussed, although pharmacological intervention offered the most immediate relief-especially from orofacial pain that was of a sudden, stab-like in nature-psychological management demonstrated a remarkable ability to reduce/alleviate the more serious aspect of chronic orofacial pain and was deemed better in comparison to the rest. Lifestyle-based techniques and current stimulation-based management were of limited use since they tended to focus more on the causal and not the symptomatic aspect of orofacial pain.

Conclusions

Many patients with persistent orofacial discomfort can experience notable improvements in their symptoms and general well-being by all the treatment modalities evaluated.

Botulinum toxin A and neuropathic pain: An update

Botulinum toxin type A is a widely used neurotoxin for the treatment of muscle hyperactivity such as dystonia and spasticity. Several clinical trials have also reported an efficacy of subcutaneous or intradermal administrations of botulinum toxin A on various neuropathic pain conditions including idiopathic trigeminal neuralgia and found that specific sensory phenotypes were predictors of the response. This narrative review summarizes the potential mechanisms of action, efficacy and safety of botulinum toxin A in neuropathic pain as well as its place in the therapeutic algorithm of neuropathic pain.

Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a rare neuropathic pain disorder characterized by recurrent, paroxysmal episodes of short-lasting severe electric shock-like pain along the sensory distribution of the trigeminal nerve. Recent classification systems group TN into 3 main categories depending on the underlying pathophysiology. This article will present a case history and review the epidemiology, diagnostic criteria, classification, clinical features, diagnostic investigations, pathophysiology, and management of TN.

Locus coeruleus-noradrenergic modulation of trigeminal pain: Implications for trigeminal neuralgia and psychiatric comorbidities

Trigeminal neuralgia is the most common neuropathic pain involving the craniofacial region. Due to the complex pathophysiology, it is therapeutically difficult to manage. Noradrenaline plays an essential role in the modulation of arousal, attention, cognitive function, stress, and pain. The locus coeruleus, the largest source of noradrenaline in the brain, is involved in the sensory and emotional processing of pain. This review summarizes the knowledge about the involvement of noradrenaline in acute and chronic trigeminal pain conditions and how the activity of the locus coeruleus noradrenergic neurons changes in response to acute and chronic pain conditions and how these changes might be involved in pain-related comorbidities including anxiety, depression, and sleep disturbance.

Multidimensional Effectiveness of Botulinum Toxin in Neuropathic Pain: A Systematic Review of Randomized Clinical Trials

Although botulinum toxin (BoNT) has been suggested as a treatment to counter neuropathic pain, no previous systematic reviews investigated the multidimensional effects of BoNT on pain relief and Health-Related Quality of Life (HR-QoL). The aim of this systematic review is to summarize the current evidence on the effectiveness of BoNT treatment for neuropathic pain, and to characterize its multidimensional effectiveness in order to guide physicians in clinical practice. Five databases were systematically searched up to 4 April 2022, to identify randomized controlled trials satisfying the following criteria: adults suffering from neuropathic pain, BoNT administration, any comparator, multidimensional assessment of pain as primary outcome, HR-QoL, physical function, anxiety and depression, and sleep quality as secondary outcomes. Twelve studies were included. The multidimensional pain scales used were short-form McGill Pain Questionnaire, Neuropathic pain scale, Neuropathic Pain Symptom Inventory, International SCI Pain Basic Data Set, West Haven-Yale Multidimensional Pain Inventory, Brief Pain Inventory, and Douleur Neuropathique 4. These scales highlighted the positive effects of BoNT administration. According to the Jadad scale, all the RCTs included were high-quality studies. BoNT administration might be effectively introduced in the comprehensive management of neuropathic pain. Further research should focus on optimal and cost-effective therapeutic protocols.

Toxicology and pharmacology of botulinum and tetanus neurotoxins: an update

Tetanus and botulinum neurotoxins cause the neuroparalytic syndromes of tetanus and botulism, respectively, by delivering inside different types of neurons, metalloproteases specifically cleaving the SNARE proteins that are essential for the release of neurotransmitters. Research on their mechanism of action is intensively carried out in order to devise improved therapies based on antibodies and chemical drugs. Recently, major results have been obtained with human monoclonal antibodies and with single chain antibodies that have allowed one to neutralize the metalloprotease activity of botulinum neurotoxin type A1 inside neurons. In addition, a method has been devised to induce a rapid molecular evolution of the metalloprotease domain of botulinum neurotoxin followed by selection driven to re-target the metalloprotease activity versus novel targets with respect to the SNARE proteins. At the same time, an intense and wide spectrum clinical research on novel therapeutics based on botulinum neurotoxins is carried out, which are also reviewed here.

A Preliminary Study of the Efficacy of Transcranial Direct Current Stimulation in Trigeminal Neuralgia

The purpose of this study is to assess the efficacy of transcranial direct current stimulation (tDCS) in patients with treatment-refractory trigeminal neuralgia (TN) and examine the utility of neuroimaging methods in identifying markers of such efficacy. Six patients with classical TN refractory to maximal medical treatment, underwent tDCS (three cases inhibitory/cathodic and three cases excitatory/anodic stimulation). All patients underwent pre- and posttreatment functional magnetic resonance imaging (fMRI) during block-design tasks (i.e., Pain, Pain + tDCS, tDCS) as well as single-shell diffusion MRI (dMRI) acquisition. The precise locations of tDCS electrodes were identified by neuronavigation. Five therapeutic tDCS sessions were carried out for each patient with either anodic or cathodic applications. The Numeric Rating Scale of pain (NRS) and the Headache Disability Index (HDI) were used to score the subjective efficacy of treatment. Altered activity of regional sites was identified by fMRI and associated changes in the spinothalamocortical sensory tract (STCT) were measured by the dMRI indices of fractional anisotropy (FA) and mean diffusivity (MD). Fiber counts of the bilateral trigeminal root entry zone (REZ) were performed as an added measure of fiber loss or recovery. All patients experienced a significant reduction in pain scores with a substantial decline in HDI (P value < 0.01). Following a course of anodic tDCS, the ipsilateral caudate, globus pallidus, somatosensory cortex, and the contralateral globus pallidus showed a significantly attenuated activation whereas cathodic tDCS treatment resulted in attenuation of the thalamus and globus pallidus bilaterally, and the somatosensory cortex and anterior cingulate gyrus contralaterally. dMRI analysis identified a substantial increase (>50%) in the number of contralateral sensory fibers in the STCT with either anodic or cathodic tDCS treatment in four of the six patients. A significant reduction in FA (>40%) was observed in the ipsilateral REZ in the posttreatment phase in five of the six patients. Preliminary evidence suggests that navigated tDCS presents a promising method for alleviating the pain of TN. Different patterns of activation manifested by anodic and cathodic stimulation require further elaboration to understand their implication. Activation and attenuation of responses at various sites may provide further avenues for condition treatment.

A Systematic Review and Meta-Analysis of Efficacy of Botulinum Toxin A for Neuropathic Pain

We performed a systematic review and meta-analysis of randomised controlled trials (RCTs) conducted from January 2005 to June 2021 to update the evidence of Botulinum toxin A (BoNT-A) in neuropathic pain (NP) in addition to quality of life (QOL), mental health, and sleep outcomes. We conducted a Cochrane Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria analysis of RCTs from the following data sources: EMBASE, CINAHL, WHO International Clinical Trial Registry Platform, ClinicalTrials.gov, Cochrane database, Cochrane Clinical Trial Register, Australia New Zealand Clinical Trials Registry, and EU Clinical Trials Register. Meta-analysis of 17 studies showed a mean final VAS reduction in pain in the intervention group of 2.59 units (95% confidence interval: 1.79, 3.38) greater than the mean for the placebo group. The overall mean difference for sleep, Hospital Anxiety and Depression Scale (HADS) anxiety, HADS depression, and QOL mental and physical sub-scales were, respectively, 1.10 (95% CI: -1.71, 3.90), 1.41 (95% CI: -0.61, 3.43), -0.16 (95% CI: -1.95, 1.63), 0.85 (95% CI: -1.85, 3.56), and -0.71 (95% CI: -3.39, 1.97), indicating no significance. BoNT-A is effective for NP; however, small-scale RCTs to date have been limited in evidence. The reasons for this are discussed, and methods for future RCTs are developed to establish BoNT-A as the first-line agent.

Chinese expert consensus on minimally invasive interventional treatment of trigeminal neuralgia

BACKGROUND AND PURPOSE

Trigeminal neuralgia is a common condition that is associated with severe pain, which seriously affects the quality of life of patients. When the efficacy of drugs is not satisfactory or adverse drug reactions cannot be tolerated, minimally invasive interventional therapy has become an important treatment because of its simple operation, low risk, high repeatability and low cost. In recent years, minimally invasive interventional treatments, such as radiofrequency thermocoagulation (RF) of the trigeminal nerve and percutaneous microcompression (PMC), have been widely used in the clinic to relieve severe pain in many patients, however, some related problems remain to be addressed. The Pain Association of the Chinese Medical Association organizes and compiles the consensus of Chinese experts to standardize the development of minimally invasive interventional treatment of trigeminal neuralgia to provide a basis for its clinical promotion and application.

MATERIALS AND METHODS

The Pain Association of the Chinese Medical Association organizes the Chinese experts to compile a consensus. With reference to the evidence-based medicine (OCEBM) system and the actual situation of the profession, the Consensus Development Committee adopts the nominal group method to adjust the recommended level.

RESULTS

Precise imaging positioning and guidance are the keys to ensuring the efficacy and safety of the procedures. RF and PMC are the most widely performed and effective treatments among minimally invasive interventional treatments for trigeminal neuralgia.

CONCLUSIONS

The pain degree of trigeminal neuralgia is severe, and a variety of minimally invasive intervention methods can effectively improve symptoms. Radiofrequency and percutaneous microcompression may be the first choice for minimally invasive interventional therapy.

BoNT/A alleviates neuropathic pain in osteoarthritis by down-regulating the expression of P2X4R in spinal microglia

Neuropathic pain in osteoarthritis is one of the reasons why the pain is difficult to treat, and P2X4R plays an important role in neuropathic pain. In addition, BoNT/A has been proven to have analgesic effects on both neuropathic pain and osteoarthritis, but its exact mechanism is still unknown. This study aims to investigate the relationship between the analgesic effect of BoNT/A on osteoarthritis and the expression of P2X4R in spinal cord microglia. The analgesic effect was compared between BoNT/A and compound betamethasone. Western blot analysis was used to examine the expression of P2X4R and BDNF proteins in the spinal cord. Immunohistochemistry was used to determine the cellular location of P2X4R. Mechanical allodynia and weight asymmetry were identified using the hind paw withdrawal threshold and weight bearing test. The results showed that intra-articular injection of MIA induced persistent mechanical allodynia and weight asymmetry in rats. Both BoNT/A and betamethasone could relieve pain behavior in rats, but BoNT/A had a more obvious effect and lasted longer. Furthermore, BoNT/A could reverse the MIA-induced overexpression of BDNF and P2X4R in the spinal dorsal horn. To sum up, BoNT/A is more effective than betamethasone in relieving MIA-induced osteoarthritis pain in rats, and its analgesic effect may be related to the regulation of P2X4R-mediated BDNF release in spinal microglia and the relief of neuropathic pain in osteoarthritis.

Botulinum Toxin Type A for Lumbar Sympathetic Ganglion Block in Complex Regional Pain Syndrome: A Randomized Trial

BACKGROUND

The present study was designed to test the hypothesis that botulinum toxin would prolong the duration of a lumbar sympathetic block measured through a sustained increase in skin temperature. The authors performed a randomized, double-blind, controlled trial to investigate the clinical outcome of botulinum toxin type A for lumbar sympathetic ganglion block in patients with complex regional pain syndrome.

METHODS

Lumbar sympathetic ganglion block was conducted in patients with lower-extremity complex regional pain syndrome using 75 IU of botulinum toxin type A (botulinum toxin group) and local anesthetic (control group). The primary outcome was the change in the relative temperature difference on the blocked sole compared with the contralateral sole at 1 postoperative month. The secondary outcomes were the 3-month changes in relative temperature differences, as well as the pain intensity changes.

RESULTS

A total of 48 participants (N = 24/group) were randomly assigned. The change in relative temperature increase was higher in the botulinum toxin group than in the control group (1.0°C ± 1.3 vs. 0.1°C ± 0.8, respectively; difference: 0.9°C [95% CI, 0.3 to 1.5]; P = 0.006), which was maintained at 3 months (1.1°C ± 0.8 vs. -0.2°C ± 1.2, respectively; P = 0.009). Moreover, pain intensity was greatly reduced in the botulinum toxin group compared with the control group at 1 month (-2.2 ± 1.0 vs. -1.0 ± 1.6, respectively; P = 0.003) and 3 months (-2.0 ± 1.0 vs. -0.6 ± 1.6, respectively; P = 0.003). There were no severe adverse events pertinent to botulinum toxin injection.

CONCLUSIONS

In patients with complex regional pain syndrome, lumbar sympathetic ganglion block using botulinum toxin type A increased the temperature of the affected foot for 3 months and also reduced the pain.

EDITOR’S PERSPECTIVE

Trigeminal Neuralgia: Current Approaches and Emerging Interventions

Trigeminal neuralgia (TN) has been described in the literature as one of the most debilitating presentations of orofacial pain. This review summarizes over 150 years of collective clinical experience in the medical and surgical treatment of TN. Fundamentally, TN remains a clinical diagnosis that must be distinguished from other types of trigeminal neuropathic pain and/or facial pain associated with other neuralgias or headache syndromes. What is increasingly clear is that there is no catch-all medical or surgical intervention that is effective for all patients with trigeminal neuralgia, likely reflective of the fact that TN is likely a heterogenous group of disorders that jointly manifests in facial pain. The first-line treatment for TN remains anticonvulsant medical therapy. Patients who fail this have a range of surgical options available to them. In general, microvascular decompression is a safe and effective procedure with immediate and durable outcomes. Patients who are unable to tolerate general anesthesia or whose medical comorbidities preclude a suboccipital craniectomy may benefit from percutaneous methodologies including glycerol or radiofrequency ablation, or both. For patients with bleeding diathesis due to blood thinning medications who are ineligible for invasive procedures, or for those who are unwilling to undergo open surgical procedures, radiosurgery may be an excellent option-provided the patient understands that maximum pain relief will take on the order of months to achieve. Finally, peripheral neurectomies continue to provide an inexpensive and resource-sparing alternative to pain relief for patients in locations with limited economic and medical resources. Ultimately, elucidation of the molecular mechanisms underlying trigeminal neuralgia will pave the way for novel, more effective and less invasive therapies.

Awake CT-guided percutaneous stylomastoid foramen puncture and radiofrequency ablation of facial nerve for treatment of hemifacial spasm

OBJECTIVE

Hemifacial spasm (HFS) is a debilitating neuromuscular disorder with limited treatment options. The current study describes a novel minimally invasive procedure that provided effective and sustained relief for patients with HFS. The authors provide a detailed description of the awake CT-guided percutaneous radiofrequency ablation (RFA) of the facial nerve for treatment of HFS, and they examine its clinical efficacy. This is the first time in the literature that this procedure has been applied and systematically analyzed for HFS.

METHODS

Patients with a history of HFS were recruited between August 2018 and April 2020. Those with a history of cerebellopontine lesions, coagulopathy, ongoing pregnancy, cardiac pacemaker or defibrillator implants, or who declined the procedure were excluded from the study. Fifty-three patients who met the study criteria were included and underwent awake CT-guided RFA. Under minimal sedation, a radiofrequency (RF) needle was used to reach the stylomastoid foramen on the affected side under CT guidance, and the facial nerve was localized using a low-frequency stimulation current. Patients were instructed to engage facial muscles as a proxy for motor monitoring during RFA. Ablation stopped when the patients' hemifacial contracture resolved. Patients were kept for inpatient monitoring for 24 hours postoperatively and were followed up monthly to monitor resolution of HFS and complications for up to 19 months.

RESULTS

The average duration of the procedure was 32-34 minutes. Postoperatively, 91% of the patients (48/53) had complete resolution of HFS, whereas the remaining individuals had partial resolution. A total of 48 patients reported mild to moderate facial paralysis immediately post-RFA, but most resolved within 1 month. No other significant complication was observed during the study period. By the end of the study period, 5 patients had recurrence of mild HFS symptoms, whereas only 2 patients reported dissatisfaction with the treatment results.

CONCLUSIONS

The authors report for the first time that awake CT-guided RFA of the facial nerve at the stylomastoid foramen is a minimally invasive procedure and can be an effective treatment option for HFS.

[The effectiveness of botulinum therapy of trigeminal neuralgia]

OBJECTIVE

To evaluate the treatment protocol with the use of onabotulinum toxin type A (botox) and the efficacy of a single botulinum therapy procedure for clinical manifestations in patients with trigeminal neuralgia (TN).

MATERIAL AND METHODS

We studied 90 patients (57 women, 33 men), including 80 people with primary TN and 10 people with secondary TN. Then 20 patients with primary TN (11 women and 9 men, mean age 61.8 years) received local injections of onabotulinum toxin type A (botox). Clinical examination included taking anamnesis, assessment of pain on a visual analogue scale (VAS), assessment of the frequency of pain paroxysms, taking into account the average indicator (0 to 100 seizures during the day); neurosensory examination according to the developed protocol with the definition of pain, temperature, tactile sensitivity, the study of stimulus-dependent pain; MRI of the brain to diagnose neurovascular conflict.

RESULTS

A month after the injections, the pain intensity practically did not change (8.5 versus 7.2 points on the VAS), but the number of paroxysms decreased (31.2 versus 22.5 seizures per day). Two months after the use of botox, the number of pain attacks continued to decrease (31.2 versus 17.7; Mann-Whitney U-test, p=0.006). At the same time, there was a decrease in pain intensity according to the VAS (8.5 versus 6.1, t-test 2.75 points; p=0.02). After three months, there was a decrease in the number of paroxysms from 31.2 to 9.2 (paired Student's test, p<0.001) and the severity of pain (8.85 versus 4.0 points on the VAS, paired t-test 3.95 points, p<0.001). There were significant differences in the average dose of carbamazepine (867.5 versus 670.8 after 3 months, t-test 196.7 mg, p=0.02). In TN patients who underwent destructive operations with exposure to the peripheral branches of the trigeminal nerve, signs of severe neurosensory deficit on the face and burning pain are added to the main symptoms, which corresponds to the clinical criteria of post-traumatic trigeminal neuropathy.

CONCLUSION

Local injections of type A onabotulinum toxin (botox) are minimally invasive, safe and effective symptomatic therapy for patients with TN. Persistent sensory disturbances that develop in patients after destructive surgeries call into question the safety of these therapies for TN.

Trigeminal Neuralgia With Extraoral Trigger Zone Successfully Treated With Intraoral Injections of Botulinum Toxin: A Case Report

Trigeminal neuralgia is a pain condition that is frequently misdiagnosed and challenging to manage. We present the case of a patient with trigeminal neuralgia with multiple misdiagnoses and poorly managed pain. Despite the presence of trigger zones both inside and outside her mouth, complete symptom resolution was ultimately achieved through onabotulinumtoxinA injections, delivered solely intraorally.

The changing face of trigeminal neuralgia-A narrative review

OBJECTIVE

This narrative review aims to update the reader on the new classification of trigeminal neuralgia (TN), clinical signs, pathophysiologic evidence, and their implications on management. This review is based on the authors' collective experience and knowledge of the literature in addition to a literature search.

BACKGROUND

In recent years, the phenotype of TN has been intensively studied leading to discrete groups of patients. These include patients with TN with additional continuous pain, and patients with and without neurovascular compression of the trigeminal dorsal root entry zone. A number of associated clinical signs such as tearing and sensory changes need further research.

METHODS

The literature on TN was searched in PubMed with the aims of providing evidence for the recently published third edition of the International Classification of Headache Disorders (ICHD) and update the clinical phenotype and management of the TN subcategories.

RESULTS

The ICHD's new classification for TN is based on reliable clinical data, imaging, and neurophysiologic studies. The TN classification reflects current knowledge and has improved the possibility for clinicians to choose adequate management options. However, there is a lack of effective, safe drugs for the management of TN and sparse, robust data on neurosurgical options.

CONCLUSION

Research into all aspects of TN-diagnosis, pharmacotherapy, surgery, long-term management prognosis, and natural history-is needed. Research should adhere to the ICHD's schema for TN. Improved drugs are needed along with rigorous research into surgical options and their efficacy for different subtypes of TN.

Transient Receptor Potential (TRP) Ion Channels in Orofacial Pain

Orofacial pain, including temporomandibular joint disorders pain, trigeminal neuralgia, dental pain, and debilitating headaches, affects millions of Americans each year with significant population health impact. Despite the existence of a large body of information on the subject, the molecular underpinnings of orofacial pain remain elusive. Two decades of research has identified that transient receptor potential (TRP) ion channels play a crucial role in pathological pain. A number of TRP ion channels are clearly expressed in the trigeminal sensory system and have critical functions in the transduction and pathogenesis of orofacial pain. Although there are many similarities, the orofacial sensory system shows some distinct peripheral and central pain processing and different sensitivities from the spinal sensory system. Relative to the extensive review on TRPs in spinally-mediated pain, the summary of TRPs in trigeminally-mediated pain has not been well-documented. This review focuses on the current experimental evidence involving TRP ion channels, particularly TRPV1, TRPA1, TRPV4, and TRPM8 in orofacial pain, and discusses their possible cellular and molecular mechanisms.

Craniofacial neuralgias

While non-headache, non-oral craniofacial neuralgia is relatively rare in incidence and prevalence, it can result in debilitating pain. Understanding the relevant anatomy of peripheral branches of nerves, natural history, clinical presentation, and management strategies will help the clinician better diagnose and treat craniofacial neuralgias. This article will review the nerves responsible for neuropathic pain in periorbital, periauricular, and occipital regions, distinct from idiopathic trigeminal neuralgia. The infratrochlear, supratrochlear, supraorbital, lacrimal, and infraorbital nerves mediate periorbital neuralgia. Periauricular neuralgia may involve the auriculotemporal nerve, the great auricular nerve, and the nervus intermedius. The greater occipital nerve, lesser occipital nerve, and third occipital nerve transmit occipital neuralgias. A wide range of treatment options exist, from modalities to surgery, and the evidence behind each is reviewed.

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.

Advances in diagnosis, classification, pathophysiology, and management of trigeminal neuralgia

Trigeminal neuralgia is a very painful neurological condition with severe, stimulus-evoked, short-lasting stabbing pain attacks in the face. The past decade has offered new insights into trigeminal neuralgia symptomatology, pathophysiology, and treatment, leading to a change in the classification of the condition. An accurate diagnosis is crucial because neuroimaging interpretation and clinical management differ among the various forms of facial pain. MRI using specific sequences should be a part of the diagnostic workup to detect a possible neurovascular contact and exclude secondary causes. Demonstration of a neurovascular contact should not be used to confirm a diagnosis but rather to facilitate surgical decision making. Carbamazepine and oxcarbazepine are drugs of first choice for long-term treatment, whereas microvascular decompression is the first-line surgery in medically refractory patients. Advances in neuroimaging techniques and animal models will provide further insight into the causes of trigeminal neuralgia and its pathophysiology. Development of more efficacious treatment options is highly warranted.

Botulinum Neurotoxin for the Treatment of Neuropathic Pain

Botulinum neurotoxin is widely used for the treatment of central and peripherical neurological conditions. Initially used to treat strabismus, over the years its use has been expanded also to spasticity and other neurological disorders. This review summarizes the evidence from the published literature regarding its effect on neuropathic pain. Almost all investigations were performed using onabotulinum toxin type A (BoNT/A). Most studies provided positive results, even though toxin formulation, dose, dilution, injection techniques, and sites are heterogeneous across studies. Future larger, high-quality, specifically designed clinical trials are warranted to confirm botulinum neurotoxin efficacy in neuropathic pain.

Botulinum toxin type A reduces the expression of transient receptor potential melastatin 3 and transient receptor potential vanilloid type 4 in the trigeminal subnucleus caudalis of a rat model of trigeminal neuralgia

This study was designed to investigate the expression of transient receptor potential melastatin 3 (TRPM3) and transient receptor potential vanilloid type 4 (TRPV4) in the trigeminal spinal subnucleus caudalis of a rat model of trigeminal neuralgia (TN). The influence of botulinum toxin type A (BTX-A) on the expression of these channels was also explored. In this study, a model was established involving chronic constriction injury to the infraorbital nerve (ION-CCI), inducing TN. To explore the effects of BTX-A and whether it was dose related, rats were divided randomly into four groups: a control group, an ION-CCI group, a 3 U group, and a 10 U group (which received 3 and 10 U/kg BTX-A injections, respectively). Von Frey hairs were used to determine the pain threshold of the rats. The expression of TRPM3 and TRPV4 in the trigeminal spinal subnucleus caudalis was detected using western blots and immunohistochemistry. The pain thresholds of rats decreased to a minimum 14 days after ION-CCI. Compared with the ION-CCI group, the pain thresholds of the 3 and 10 U groups were significantly higher 4 days after the subcutaneous injection of BTX-A (P<0.05). The expression of TRPM3 and TRPV4 in the ION-CCI group was significantly higher than that in the control group (P<0.05). TRPM3 and TRPV4 expression in the 3 and 10 U groups was significantly lower than that in the ION-CCI group (P<0.05). In conclusion, overexpression of TRPM3 and TRPV4 can jointly mediate the occurrence of mechanical hyperalgesia in TN. The analgesic effects of BTX-A may be related to the inhibition of TRPM3 and TRPV4 expression.

CGRP Plasma Levels Decrease in Classical Trigeminal Neuralgia Patients Treated with Botulinum Toxin Type A: A Pilot Study

Objective

The aim of this study was to investigate the changes of calcitonin gene-related peptide (CGRP) plasma levels in patients with classical trigeminal neuralgia (TN) and if plasma CGRP concentrations could be used to predict the response to botulinum toxin type A (BTX-A).

Methods

Forty-seven patients with classical TN were recruited and treated with BTX-A. A patient was considered a responder when the visual analog scale (VAS) score and number of episodes were reduced by at least 50% compared with baseline data. Matched healthy subjects with no headache history served as controls. CGRP levels were measured by the enzyme-linked immunosorbent assay.

Results

A total of 45 patients and 30 healthy controls completed the study. Plasma CGRP concentrations after treatment with BTX-A (median [interquartile range {IQR}] = 28.86 [14.75–61.23] pg/mL) were significantly lower than before treatment (median [IQR] = 55.38 [22.59–71.67] pg/mL, P &lt; 0.001). Plasma CGRP concentrations in responders after treatment with BTX-A (median [IQR] = 28.02 [12.78–57.28] pg/mL) were significantly lower than before treatment (median [IQR] = 50.57 [24.30–70.09] pg/mL, P &lt; 0.001). In nonresponders, there were no significant differences between the levels before and after treatment (P = 0.938). Age, gender, VAS score, taking/not taking carbamazepine, and the number of trigeminal nerve branches involved had no significant influence on the median difference between plasma CGRP concentrations. The concentration of CGRP before treatment was not predictive of the treatment result.

Conclusions

CGRP levels decrease significantly in patients with classical TN after treatment with BTX-A. Plasma levels of CGRP cannot be used to predict the response to BTX-A. This study indicates that CGRP is likely to be involved in the pathophysiology of classical TN. Moreover, the analgesic mechanism of BTX-A may be related to the inhibition of CGRP release.

The efficacy and safety of botulinum toxin type A in treatment of trigeminal neuralgia and peripheral neuropathic pain: A meta-analysis of randomized controlled trials

BACKGROUND

Although recent studies have shown that botulinum toxin-A (BTX-A) has a good analgesic effect on trigeminal neuralgia (TN) and peripheral neuropathic pain (PNP), the quality of evidence is low due to limited data. This meta-analysis is used to synthesize existing evidence for the treatment of these conditions with BTX-A.

METHODS

Relevant trials were accessed by using an electronic search in databases (Web of Science, PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov). Data from included randomized controlled trials (RCTs) on the efficacy and safety of BTX-A in treating TN and PNP were extracted for meta-analysis.

RESULTS

Finally, 10 RCTs (n = 391) were included in this meta-analysis. The pooled effect of BTX-A was superior to placebo based on pain intensity (SMD = -0.48, 95% CI [-0.74, 0.23] at 1 month, SMD = -0.58, 95% CI [-0.91, -0.24] at 2 months, and SMD = -0.55, 95% CI [-0.87, -0.22] at 3 months). Number needed to treat (NNT) for 50% pain intensity reduction showed better effect of BTX-A on TN and postherpetic neuralgia (PN). Adverse events associated with BTX-A were similar to placebo (OR = 1.58, 95% CI [0.51, 4.87], p = .424).

CONCLUSION

Pooled data from our meta-analysis suggest that BTX-A is efficacious and safe in treating TN and PNP. However, due to the limited sample size and heterogeneity, further larger and well-designed RCTs are imperative to validate these findings.

Treatment of Frontal Secondary Headache Attributed to Supratrochlear and Supraorbital Nerve Entrapment With Oral Medication or Botulinum Toxin Type A vs Endoscopic Decompression Surgery

Importance

Endoscopic surgical decompression of the supratrochlear nerve (STN) and supraorbital nerve (SON) is a new treatment for patients with frontal chronic headache who are refractory to standard treatment options.

Objective

To evaluate and compare treatment outcomes of oral medication, botulinum toxin type A (BoNT/A) injections, and endoscopic decompression surgery in frontal secondary headache attributed to STN and supraorbital SON entrapment.

Design, Setting, and Participants

Prospective cohort study of 22 patients from a single institution (Diakonessen Hospital Utrecht) with frontal headache of moderate-to-severe intensity (visual analog scale [VAS] score, 7-10), frontally located, experienced more than 15 days per month, and described as pressure or tension that intensifies with pressure on the area of STN and SON. A screening algorithm was used that included examination, questionnaire, computed tomography of the sinus, injections of local anesthetic, and BoNT/A in the corrugator muscle.

Interventions

Different oral medication therapy for headache encountered in the study cohort, as well as BoNT/A injections (15 IU) into the corrugator muscle. Surgical procedures were performed by a single surgeon using an endoscopic surgical approach to release the supraorbital ridge periosteum and to bluntly dissect the glabellar muscle group.

Main Outcomes and Measures

Headache VAS intensity after oral medication and BoNT/A injections. Additionally, early postoperative follow-up consisted of a daily headache questionnaire that was evaluated after 1 year.

Results

In total, 22 patients (mean [SD] age, 42.0 [15.3] years; 7 men and 15 women) were included in this cohort study. Oral medication therapy reduced the headache intensity significantly (mean [standard error of the mean {SEM}] VAS score, 6.45 [0.20] [95% CI, 0.34-3.02; P < .001] compared with mean [SEM] pretreatment VAS score, 8.13 [0.22]). Botulinum toxin type A decreased the mean (SEM) headache intensity VAS scores significantly as well (pretreatment, 8.1 [0.22] vs posttreatment, 2.9 [0.42]; 95% CI, 3.89-6.56; P < .001). The mean (SEM) pretreatment headache intensity VAS score (8.10 [0.22]) decreased significantly after surgery at 3 months (1.30 [0.55]; 95% CI, 5.48-8.16; P < .001) and 12 months (1.09 [0.50]; 95% CI, 5.71-8.38; P < .001). There was a significant decrease of headache intensity VAS score in the surgical group over the BoNT/A group (mean [SEM] VAS score, 2.90 [0.42]) after 3 months (mean [SEM] VAS score, 1.30 [0.55]; 95% CI, 0.25-2.93; P < .001) and 12 months (mean [SEM] VAS score, 1.09 [0.50]; 95% CI, 0.48-3.16; P < .001) after surgery.

Conclusions and Relevance

Endoscopic decompression surgery had a long-lasting successful outcome in this type of frontal secondary headache. Even though BoNT/A had a positive effect, the effect of surgery was significantly higher.

Level of Evidence

3.

Botulinum Toxin Type A in Dental Medicine

Botulinum toxins (BoNTs) are a product of the bacteria Clostridium botulinum. By entering nerve endings, they cleave and inactivate SNARE proteins, which are essential for neurotransmitter release. Prevention of acetylcholine release at the neuromuscular junction causes long-lasting and potentially fatal flaccid paralysis-a major feature of botulism. However, an intramuscular injection of minute amounts of BoNTs, primarily type A (BoNT-A), has useful long-lasting muscle relaxation effects on spastic motor disorders. This characteristic of BoNT-A is widely used in neurology and cosmetics. Over the last few decades, it has been demonstrated that the functions of BoNT-A are not limited to muscle-relaxing or autonomic cholinergic effects but that it can act as an analgesic agent as well. More recently, it was revealed that this antinociceptive effect starts after entering the sensory nerve endings, where these agents are axonally transported to the central nervous system, suggesting that at least part of their analgesic effect might be of central origin. Because of its antinociceptive effect, BoNT-A is currently approved for treatment of chronic migraine; nonetheless, case reports and preclinical and clinical experiments indicating its benefit in numerous potential painful conditions have increased. In the field of dentistry, the US Food and Drug Administration approved BoNT-A for the treatment of sialorrhea only. Legal status of the use of BoNT-A in other countries is less known. However, there are controlled clinical trials suggesting its efficacy in other conditions, such as bruxism, temporomandibular disorders, and trigeminal neuropathic pain. Thereby, using criteria of the American Academy of Neurology, we critically reviewed the uses of BoNTs in oral medicine and found it effective for trigeminal neuralgia (category A) and probably effective in temporomandibular disorders and bruxism.