Evidence for the use of botulinum toxin in the chronic pain setting--a review of the literature

Clinical Conditions Targeted by OnabotulinumtoxinA in Different Ways in Medicine

OnabotulinumtoxinA (BT-A) is used in different medical fields for its beneficial effects. BT-A, a toxin originally produced by the bacterium Clostridium botulinum, is widely known for its ability to temporarily paralyze muscles by blocking the release of acetylcholine, a neurotransmitter involved in muscle contraction. The literature continually reports new hypotheses regarding potential applications that do not consider blockade of acetylcholine release at the neuromuscular junction as a common pathway. In this opinion article, it is our aim to investigate the different pathway targets of BT-A in different medical applications. First of all, the acetylcholine effect of BT-A is used to reduce wrinkles for cosmetic purposes, in the treatment of urological problems, excessive sweating, temporomandibular joint disorders, obesity, migraine, spasticity in neurological diseases, and in various cases of muscle overactivity such as cervical dystonia, blepharospasm, and essential head tremor. In another potential pathway, glutamate A, CGRP, and substance P are targeted for pain inhibition with BT-A application in conditions such as migraine, trigeminal neuralgia, neuropathic pain, and myofascial pain syndrome. On the other hand, as a mechanism different from acetylcholine and pain mediators, BT-A is used in the treatment of hair loss by increasing oxygenation and targeting transforming growth factor-beta 1 cells. In addition, the effect of BT-A on the apoptosis of cancer cells is also known and is being developed. The benefits of BT-A applied in different doses to different regions for different medical purposes are shown in literature studies, and it is also emphasized in those studies that repeating the applications increases the benefits in the long term. The use of BT-A continues to expand as researchers discover new potential therapeutic uses for this versatile toxin.

Cellular and molecular mechanisms involved in the analgesic effects of botulinum neurotoxin: A literature review

Botulinum neurotoxins (BoNTs), derived from Clostridium botulinum, have been employed to treat a range of central and peripheral neurological disease. Some studies indicate that BoNT may be beneficial for pain conditions as well. It has been hypothesized that BoNTs may exert their analgesic effects by preventing the release of pain-related neurotransmitters and neuroinflammatory agents from sensory nerve endings, suppressing glial activation, and inhibiting the transmission of pain-related receptors to the neuronal cell membrane. In addition, there is evidence to suggest that the central analgesic effects of BoNTs are mediated through their retrograde axonal transport. The purpose of this review is to summarize the experimental evidence of the analgesic functions of BoNTs and discuss the cellular and molecular mechanisms by which they can act on pain conditions. Most of the studies reviewed in this article were conducted using BoNT/A. The PubMed database was searched from 1995 to December 2022 to identify relevant literature.

Botulinum Toxin A in the treatment of frostbite sequelae - results from a blinded, early-phase, comparative trial

INTRODUCTION

Freezing Cold Injuries (FCI) have been associated with long-term sequelae including vasospasm. The aims of the pilot study are to explore the research methodology and investigate the tolerability and safety of treatment with Botulinum Toxin-A (BTX-A) in FCI Sequelae.

METHODOLOGY

This pilot study tests the logistics, the treatment setting and the follow-up procedure in an early-phase, double-blinded, randomized, controlled trial study-design. The variables in the study were subjective symptoms, peripheral micro-vascularization/rewarming, somatosensory responsiveness, and generic measure of health status.

RESULTS

No major challenges or difficulties were noticed according to the protocol or the study methodology. The monitoring of tolerability and safety of treatment with BTX-A did not reveal any major unwanted and/or adverse reactions among the patients in the pilot study and no challenges occurred during data collection of endpoints. The study revealed an inaccuracy of the 2nd degree FCI diagnosis and uncover a need for relevant and sufficient clinical information for FCI classification.

CONCLUSIONS

This pilot study showed the study methodology with minor adjustments is feasible in a future full-scale clinical trial. The recruitment process needs to be more refined to ensure that the eligible study participants are a homogenous group of FCI patients.

The Efficacy of Intradermal Injection of Botulinum Toxin Type-A on Painful Diabetic Neuropathy: A Systematic Review

Context

Diabetes is one of the most common causes of neuropathy. Morbidity and mortality increase in patients suffering from diabetic polyneuropathy and are experienced by approximately 10 to 54% of diabetic patients. Severe pain, loss of sensation, increased risk of ulceration, and even amputation are the complications of diabetic neuropathy. Intradermal injection of botulinum toxin type-A (BTX-A) is a relatively novel method for the treatment of painful diabetic neuropathy. This method is becoming popular considering its acceptable and long-lasting pain control and minimal systemic side effects.

Methods

This narrative systematic review aimed to evaluate the effectiveness of intradermal BTX-A injection on painful diabetic neuropathy. The queried databases included PubMed, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, Web of Science, Scopus, and Google Scholar. The final search was performed in February 2022, and no time limits were set for the search. All the relevant clinical trials were included. The inclusion criteria and search strategy were set as follows: Type of study: Randomized clinical trial (RCT) or other types of interventional studies; publication date: All published studies until February 22, 2022; sample size: No restrictions; outcomes: Effect on diabetic neuropathy pain; quality: Earning a minimum acceptable score based on critical appraisal; and language: English. The searches and article screening were performed by two independent reviewers to minimize the possibility of bias. In case of disagreement about a study, the comments of an expert (as a third person) were used to resolve the ambiguity.

Results

In a review of 4 RCTs and 1 case-control study on the effectiveness of BTX-A in reducing the pain of diabetic neuropathy, 273 patients were evaluated in total. The lowest and highest number of subjects was 18 and 141. The sex distribution included 43.22% men and 56.77% women, all of whom were 47.8 to 74.8 years old. Three studies were conducted in Iran, Taiwan, and Egypt. The results of this review showed significant improvement in pain reduction, e.g., based on the Visual Analog Scale (VAS) and Neuropathic Pain Scale (NPS). A few studies evaluated sleep and psychosocial complications, and their results indicated a statistically significant improvement in the Pittsburgh sleep quality index (PSQI) and the physical subscale of the 36-Item Short Form Survey (SF-36).

Conclusions

The results of this systematic review demonstrated that intradermal injection of BTX-A causes significant and long-term (up to 12 weeks) improvement in diabetic neuropathy pain. The improvement in sleep and mental or physical functions was not consistent, and no conclusive result could be reached.

Discrimination of the Activity of Low-Affinity Wild-Type and High-Affinity Mutant Recombinant BoNT/B by a SIMA Cell-Based Reporter Release Assay

Botulinum neurotoxin (BoNT) is used for the treatment of a number of ailments. The activity of the toxin that is isolated from bacterial cultures is frequently tested in the mouse lethality assay. Apart from the ethical concerns inherent to this assay, species-specific differences in the affinity for different BoNT serotypes give rise to activity results that differ from the activity in humans. Thus, BoNT/B is more active in mice than in humans. The current study shows that the stimulus-dependent release of a luciferase from a differentiated human neuroblastoma–based reporter cell line (SIMA-hPOMC1-26-Gluc) was inhibited by clostridial and recombinant BoNT/A to the same extent, whereas both clostridial and recombinant BoNT/B inhibited the release to a lesser extent and only at much higher concentrations, reflecting the low activity of BoNT/B in humans. By contrast, the genetically modified BoNT/B-MY, which has increased affinity for human synaptotagmin, and the BoNT/B protein receptor inhibited luciferase release effectively and with an EC50 comparable to recombinant BoNT/A. This was due to an enhanced uptake into the reporter cells of BoNT/B-MY in comparison to the recombinant wild-type toxin. Thus, the SIMA-hPOMC1-26-Gluc cell assay is a versatile tool to determine the activity of different BoNT serotypes providing human-relevant dose-response data.

Cutaneous Neuroimmune Interactions in Peripheral Neuropathic Pain States

Bidirectional interplay between the peripheral immune and nervous systems plays a crucial role in maintaining homeostasis and responding to noxious stimuli. This crosstalk is facilitated by a variety of cytokines, inflammatory mediators and neuropeptides. Dysregulation of this delicate physiological balance is implicated in the pathological mechanisms of various skin disorders and peripheral neuropathies. The skin is a highly complex biological structure within which peripheral sensory nerve terminals and immune cells colocalise. Herein, we provide an overview of the sensory innervation of the skin and immune cells resident to the skin. We discuss modulation of cutaneous immune response by sensory neurons and their mediators (e.g., nociceptor-derived neuropeptides), and sensory neuron regulation by cutaneous immune cells (e.g., nociceptor sensitization by immune-derived mediators). In particular, we discuss recent findings concerning neuroimmune communication in skin infections, psoriasis, allergic contact dermatitis and atopic dermatitis. We then summarize evidence of neuroimmune mechanisms in the skin in the context of peripheral neuropathic pain states, including chemotherapy-induced peripheral neuropathy, diabetic polyneuropathy, post-herpetic neuralgia, HIV-induced neuropathy, as well as entrapment and traumatic neuropathies. Finally, we highlight the future promise of emerging therapies associated with skin neuroimmune crosstalk in neuropathic pain.

Current advances and research in ultrasound imaging to the assessment and management of musculoskeletal disorders

Currently evidence-based practice has given scientific weight to the physical therapist profession; it is essential that all medical professional and physical therapists know the usefulness of new tools that optimize the effectiveness of their interventions and allow the growing of the scientific knowledge base. The use of ultrasound imaging (USI) by physiotherapists has evolved in recent years, consolidating as an increasingly standardized technique, low cost compared to other imaging techniques, quickly of execution, feasible and reliable tool. USI offers a wide range of opportunities in clinical practice as well as in different research areas. Therefore, ultrasound has been currently used as a diagnostic tool by physicians and in recent years there has been an expansion of the use of ultrasound equipment by non-physicians professionals such as physical therapist or physical trainers, who incorporates USI as a means of assessing musculoskeletal system architecture and composition, musculoskeletal changes in dysfunction, pain or injury conditions, as an interventional technique assisting echo-guided procedures or using the visual real-time information as a biofeedback in control motor approaches, as guiding tool in clinical decisions as well as to improve the understanding of tissue adaptations to exercise or movement. The purpose of this article is to review and provide an overview about the currently research of the USI applications and their benefits for the diagnosis and management in individuals with musculoskeletal conditions.

Periorbital botulinum toxin A improves photophobia and sensations of dryness in patients without migraine: Case series of four patients

Purpose

Individuals receiving botulinum toxin A (BoNT-A) injections in the head and neck for migraine treatment have reported decreases in photophobia and sensations of dryness, independent of ocular surface parameters. We hypothesized that patients without migraine but with similar ocular neuropathic-like symptoms would also experience symptomatic improvement with periocular BoNT-A injections, independent of ocular surface changes.

Observations

We identified four individuals without a history of migraine but with neuropathic ocular pain (symptoms of dryness, burning, and photophobia that were out of proportion to ocular surface findings and unresponsive to ongoing dry eye (DE) therapies). Individuals underwent 1 session of periocular BoNT-A injections. Validated questionnaires (Visual Light Sensitivity Questionnaire-8, Dry Eye Questionnaire-5) assessed photophobia and DE symptoms pre- and 1-month post-injections. All four reported improvements in frequency and severity of photophobia and eye discomfort following BoNT-A injections. Tear film parameters (phenol red thread test, tear break-up time, corneal staining, and Schirmer test) and eyelid (palpebral fissure height and levator palpebrae superioris function) and eyebrow (position) anatomy were also evaluated before and after injections. Despite a unanimous improvement in symptoms, there were no consistent changes in ocular surface parameters with BoNT-A injections across individuals.

Conclusions

Periocular BoNT-A shows promise in reducing photophobia and sensations of dryness in individuals with neuropathic-like DE symptoms without a history of migraine, independent of tear film, eyelid, or eyebrow parameters.

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.

Cervical Kyphotic Deformity Worsening After Extensor Cervical Muscle Paralysis from Botulinum Toxin Injection

BACKGROUND

Botulinum toxin (Botox) has long been used therapeutically to treat a variety of diseases, including migraine headaches, cervical spine dystonia, and chronic cervical spine pain, among many others. Although quite useful, Botox has been reported to cause adverse events, some of which may lead to devastating morbidity.

CASE DESCRIPTION

An elderly woman presented with severe neck pain after a motor vehicle collision. She underwent Botox administration to the neck extensor muscles, after which she developed severe cervical kyphotic deformity, a complication previously reported only in patients with a history of cervical fusion. In addition, the patient had a pre-existing cervical spine degenerative disc disease with listhesis resulting in cervical kyphotic deformity and loss of cervical lordosis.

CONCLUSIONS

This case illustrates a potential danger of using Botox in the neck of an elderly patient who may have pre-existing cervical spine instability, underlying cervical musculature weakness, and pre-existing cervical kyphosis. It demonstrates the need to evaluate patients who are predisposed to developing cervical kyphotic deformities before offering them Botox treatment.

Chronic orofacial pain animal models - progress and challenges

INTRODUCTION

Chronic orofacial pain is one of the most common pain conditions experienced by adults. Animal models are often selected as the most useful scientific methodology to explore the pathophysiology of the disorders that cause this disabling pain to facilitate the development of new treatments. The creation of new models or the improvement of existing ones is essential for finding new ways to approach the complex neurobiology of this type of pain. Areas covered: The authors describe and discuss a variety of animal models used in chronic orofacial pain (COFP). Furthermore, they examine in detail the mechanisms of action involved in orofacial neuropathic pain and orofacial inflammatory pain. Expert opinion: The use of animal models has several advantages in chronic orofacial pain drug discovery. Choosing an animal model that most closely represents the human disease helps to increase the chances of finding effective new therapies and is key to the successful translation of preclinical research to clinical practice. Models using genetically modified animals seem promising but have not yet been fully developed for use in chronic orofacial pain research. Although animal models have provided significant advances in the pharmacological treatment of orofacial pain, several barriers still need to be overcome for better treatment options.

Lumbar Sympathetic Block with Botulinum Toxin Type A and Type B for the Complex Regional Pain Syndrome

A lumbar sympathetic ganglion block (LSB) is a therapeutic method for complex regional pain syndrome (CRPS) affecting the lower limbs. Recently, LSB with botulinum toxin type A and B was introduced as a novel method to achieve longer duration of analgesia. In this study, we compared the botulinum toxin type A (BTA) with botulinum toxin type B (BTB) in performing LSB on patients with CRPS. LSB was performed with either BTA or BTB on patients with CRPS in their lower extremities. The length of time taken for patients to return to the pre-LSB pain score and the adverse effect of LSB with BTA/BTB were investigated. The median length of time taken for the patients to return to the pre-LSB pain score was 15 days for the BTA group and 69 days for the BTB group (P = 0.002). Scores on a visual analogue scale decreased in the patients of both groups, and no significant adverse effects were experienced. In conclusion, the administration of either BTA or BTB for LSB is a safe method to prolong the sympathetic blocking effect in patients with CRPS. BTB is more effective than BTA to prolong the sympathetic blocking effect in CRPS patients.

The Effect of Botulinum Neurotoxin Serotype a Heavy Chain on the Growth Related Proteins and Neurite Outgrowth after Spinal Cord Injury in Rats

(1) Background: The botulinum toxin A (BoNT-A) heavy chain (HC) can stimulate the growth of primary motor neurites. (2) Methods: A recombinant BoNT/A HC was injected locally plus interval intrathecal catheter of BoNT/A HC to rats with ipsilateral semi-dissociated lumbar spinal cord injuries (SCIs). First, 2D gel with a silver nitrate stain was applied to detect the general pattern of protein expression. Growth associated protein 43 (GAP-43) and superior cervical ganglion 10 (SCG10) were chosen to represent the altered proteins, based on their molecular weight and pI, and were used to further detect their expression. Meanwhile, the neuronal processes were measured. The measurements of thermal hyperalgesia and grasp power at the ipsilateral hindlimb were used to evaluate spinal sensory and motor function, respectively. (3) Results: The local injection of BoNT/A HC followed by its intrathecal catheter intervally altered the spinal protein expression pattern after an SCI; protein expression was similar to normal levels or displayed a remarkable increase. The changes in the expression and distribution of phosphorylated growth associated protein 43(p-GAP 43) and superior cervical ganglion 10 (SCG 10) indicated that the administration of BoNT/A HC to the SCI significantly amplified the expression of p-GAP43 and SCG10 (p < 0.05). Meanwhile, the positive immunofluorescent staining for both p-GAP43 and SCG10 was mainly present near the rostral aspect of the injury, both in the cytoplasm and the neuronal processes. Moreover, the outgrowth of neurites was stimulated by the BoNT/A HC treatment; this was evident from the increase in neurite length, number of branches and the percentage of cells with neuronal processes. The results from the spinal function tests suggested that the BoNT/A HC did not affect sensation, but had a large role in improving the ipsilateral hindlimb grasp power (p < 0.05). (4) Conclusions: The local injection with the intermittent intrathecal administration of BoNT/A heavy chain to rats with SCI increased the local expression of GAP-43 and SCG 10, which might be affiliated with the regeneration of neuronal processes surrounding the injury, and might also be favorable to the relief of spinal motor dysfunction.

Subcutaneous Botulinum Toxin Injection for Post-Thoracotomy Pain Syndrome in Palliative Care: A Case Report

Post-thoracotomy pain syndrome (PTPS) is a traumatic neuropathy that can affect as many as 50% of patients undergoing thoracotomy. Patients are often refractory to conservative management and may require multiple analgesics for adequate pain control. Botulinum toxin, derived from Clostridium botulinum, has many uses in treating conditions involving spasticity, dystonia, chronic migraine, and a variety of pain disorders including neuropathies. Botulinum toxin type A injections may provide an alternative or adjunct to improve symptom management in patients with PTPS.

Perforator-Guided Drug Injection in the Treatment of Abdominal Wall Pain

BACKGROUND

Pain from the abdominal wall can be caused by nerve entrapment, a condition called abdominal cutaneous nerve entrapment syndrome (ACNES). As an alternative to surgery, ACNES may be treated with injection of local anesthetics, corticosteroids, or botulinum toxin at the point of maximal pain.

METHOD

The point of maximal pain was marked on the abdominal skin. Using color Doppler ultrasound, the corresponding exit point of perforating blood vessels through the anterior fascia of the rectus abdominis muscle was identified. Ultrasound-guided injection of botulinum toxin in close proximity to the perforator's exit point was performed below and above the muscle fascia.

RESULTS

The technique was used from 2008 to 2014 on 15 patients in 46 sessions with a total of 128 injections without complications. The injection technique provided safe and accurate administration of the drug in proximity to the affected cutaneous nerves. The effect of botulinum toxin on ACNES is beyond the scope of this article.

CONCLUSION

Perforator-guided injection enables precise drug administration at the location of nerve entrapment in ACNES in contrast to blind injections.

Botulinum Toxin for Neuropathic Pain: A Review of the Literature

Botulinum neurotoxin (BoNT), derived from Clostridium botulinum, has been used therapeutically for focal dystonia, spasticity, and chronic migraine. Its spectrum as a potential treatment for neuropathic pain has grown. Recent opinions on the mechanism behind the antinociceptive effects of BoNT suggest that it inhibits the release of peripheral neurotransmitters and inflammatory mediators from sensory nerves. There is some evidence showing the axonal transport of BoNT, but it remains controversial. The aim of this review is to summarize the experimental and clinical evidence of the antinociceptive effects, mechanisms, and therapeutic applications of BoNT for neuropathic pain conditions, including postherpetic neuralgia, complex regional pain syndrome, and trigeminal neuralgia. The PubMed and OvidSP databases were searched from 1966 to May 2015. We assessed levels of evidence according to the American Academy of Neurology guidelines. Recent studies have suggested that BoNT injection is an effective treatment for postherpetic neuralgia and is likely efficient for trigeminal neuralgia and post-traumatic neuralgia. BoNT could also be effective as a treatment for diabetic neuropathy. It has not been proven to be an effective treatment for occipital neuralgia or complex regional pain syndrome.

Botulinum Toxin Type A for the Treatment of Neuropathic Pain in Neuro-Rehabilitation

Pain is a natural protective mechanism and has a warning function signaling imminent or actual tissue damage. Neuropathic pain (NP) results from a dysfunction and derangement in the transmission and signal processing along the nervous system and it is a recognized disease in itself. The prevalence of NP is estimated to be between 6.9% and 10% in the general population. This condition can complicate the recovery from stroke, multiple sclerosis, spinal cord lesions, and several neuropathies promoting persistent disability and poor quality of life. Subjects suffering from NP describe it as burning, itching, lancing, and numbness, but hyperalgesia and allodynia represent the most bothersome symptoms. The management of NP is a clinical challenge and several non-pharmacological and pharmacological interventions have been proposed with variable benefits. Botulinum toxin (BTX) as an adjunct to other interventions can be a useful therapeutic tool for the treatment of disabled people. Although BTX-A is predominantly used to reduce spasticity in a neuro-rehabilitation setting, it has been used in several painful conditions including disorders characterized by NP. The underlying pharmacological mechanisms that operate in reducing pain are still unclear and include blocking nociceptor transduction, the reduction of neurogenic inflammation by inhibiting neural substances and neurotransmitters, and the prevention of peripheral and central sensitization. Some neurological disorders requiring rehabilitative intervention can show neuropathic pain resistant to common analgesic treatment. This paper addresses the effect of BTX-A in treating NP that complicates frequent disorders of the central and peripheral nervous system such as spinal cord injury, post-stroke shoulder pain, and painful diabetic neuropathy, which are commonly managed in a rehabilitation setting. Furthermore, BTX-A has an effect in relief pain that may characterize less common neurological disorders including post-traumatic neuralgia, phantom limb, and complex regional pain syndrome with focal dystonia. The use of BTX-A could represent a novel therapeutic strategy in caring for neuropathic pain whenever common pharmacological tools have been ineffective. However, large and well-designed clinical trials are needed to recommend BTX-A use in the relief of neuropathic pain.

Intraprostatic injection of botulinum toxin-A in patients with refractory chronic pelvic pain syndrome: The transurethral vs. transrectal approach

OBJECTIVE

To evaluate the outcome of an intraprostatic injection of botulinum toxin-A (BTX-A) in men with refractory chronic prostatitis-associated chronic pelvic-pain syndrome (CP/CPPS) and to compare the efficacy of the transurethral and transrectal routes.

PATIENTS AND METHODS

In an uncontrolled randomised clinical trial conducted in men with refractory CP/CPPS, the patients were classified into two groups according to the route of BTX-A injection; transurethral (group 1, 28 patients) and transrectal ultrasonography-guided (group 2, 35 patients). The chronic prostatitis symptom index (CPSI), maximum urinary flow rate (Q max) and white blood cell (WBC) count in expressed prostatic secretion (EPS) were measured before and at 3, 6 and 12 months after the injection. A significant clinical improvement (SCI, defined as a reduction of 4 points or a 25% decrease in total CPSI score) was correlated with patient age, prostate volume and symptom duration.

RESULTS

In group 1, the pain and quality-of-life domain scores improved, but statistically significantly only at 6 months. The voiding score improved at all follow-up visits. In group 2 there was a significant improvement in all the CPSI domain scores at all follow-up visits, except for pain, which was insignificantly improved by 12 months. The SCI ratings in groups 1 and 2 were 36%, 79% and 57%, and 49%, 89% and 74% in group 2 at the three follow-up visits, respectively. The Q max was significantly improved in both groups during the follow-up (except at 12 months in group 1). There was a significant reduction in the mean WBC count in the EPS in patients with inflammatory prostatitis. Both prostate volume and symptom duration were significantly associated with a lower SCI rating.

CONCLUSION

BTX-A is an available treatment option for patients with refractory CP/CPPS. It is more effective in patients with a small prostate and short symptom duration. The transrectal route provided better results than the transurethral route. More prospective longer term studies are needed.

WITHDRAWN: Botulinum toxin for subacute/chronic neck pain

Withdrawn due to non‐compliance with The Cochrane Collaboration’s Commercial Sponsorship Policy

The editorial group responsible for this previously published document have withdrawn it from publication.

Botulinum Toxin-A for Painful Diabetic Neuropathy: A Meta-Analysis

OBJECTIVES

Painful diabetic neuropathy (PDN) is a debilitating complication of diabetes that greatly affects the quality of life of those afflicted. There are many treatment options for neuropathic pain. Recent studies show a promising analgesic effect using botulinum toxin-A (BTX-A) for neuropathic pain.

METHODS

This article is a meta-analysis of two studies using BTX-A in the treatment of neuropathic pain. Electronic searches of MEDLINE/PubMed, EMBASE, and Cochrane Libraries using the terms "botulinum neurotoxin" and "neuropathic pain" were conducted. Only class I and class II therapeutic trials, as classified by the American Academy of Neurology were included. The primary outcome measured was the difference in visual analogue scale (VAS) from pre-intervention and post-intervention after 1 month. Data were analyzed for biases and heterogeneity following Cochrane and PRISMA guidelines.

RESULTS

Two studies on PDN were analyzed in the meta-analysis showing improvement of 1.96 VAS points (95% CI, -3.09 to -0.84; Z score = 3.43, P < 0.001) following treatment with BTX-A. This corresponds to clinically significant improvement of "minimum change in pain." The adverse effects of infection at injection site was not statistically significant (P = 0.49). BTX-A may be effective for PDN.

CONCLUSION

Tests for significance, low overall risk of bias, and almost no statistical heterogeneity suggests that there is a correlation between BTX-A and improvement of pain scores in PDN. Further large-scale controlled trials are needed.

Osteopenic consequences of botulinum toxin injections in the masticatory muscles: a pilot study

Patients with temporomandibular muscle and joint disorder (TMJD) increasingly seek and receive treatment for their pain with botulinum toxin (BoNTA; botulinum toxin A). Used intramuscularly in therapeutic doses, it produces localised paresis. Such paresis creates risk of reduced bone mineral density, or 'disuse osteopenia'. Animal studies have frequently used BoNTA as a model of paralysis to induce bone changes within short periods. Osteopenic effects can be enduring in animals but have yet to be studied in humans. This is the first study in humans to examine bone-related consequences of BoNTA injections in the masticatory muscles, comparing oral and maxillofacial radiologists' ratings of trabecular bone patterns in the condyles of patients with TMJD exposed to multiple masticatory muscle injection sessions with BoNTA to a sample of patients with TMJD unexposed to masticatory muscle injections with BoNTA. Cone-beam computed tomography (CBCT)-derived images of bilateral condyles were evaluated in seven patients with TMJD receiving 2+ recent BoNTA treatment sessions for facial pain and nine demographically matched patients with TMJD not receiving BoNTA treatment. Two oral and maxillofacial radiologists evaluated CBCT images for evidence of trabecular changes consistent with osteopenia. Both evaluators noted decreased density in all participants exposed to BoNTA and in none of the unexposed participants (P < 0.001). No other abnormalities associated with reduced loading were detected. These findings need replication in a larger sample and over a longer time period, to ensure safety of patients with TMJD receiving multiple BoNTA injections for their pain.

Effects of intrabursal administration of botulinum toxin type B on lameness in horses with degenerative injury to the podotrochlear apparatus

OBJECTIVE

To determine the safety and short-term efficacy of intrabursal administration of botulinum toxin type B (BTXB) to alleviate lameness in horses with degenerative injury to the podotrochlear apparatus (PA).

ANIMALS

10 Quarter Horses with degenerative injury to the PA.

PROCEDURES

Degenerative injury to the PA was confirmed with diagnostic analgesia and imaging. Then, BTXB (3.8 to 4.5 U/kg) was injected into the podotrochlear (navicular) bursa of each horse. Three horses were used in a safety evaluation. Subsequently, video recordings of lameness evaluations were obtained for 7 client-owned horses 5 days before (baseline) and 7 and 14 days after BTXB treatment and used to determine the effect of BTXB injection on lameness; 1 horse was removed from the study 8 days after BTXB treatment. Three investigators who were unaware of the treated forelimbs or time points separately reviewed the recordings and graded the lameness of both forelimbs of the horses.

RESULTS

Improvement in lameness of the treated forelimbs was detected at 1 or both time points after BTXB administration in all horses. However, all horses had some degree of lameness at the end of the study. Two horses developed transient increases in lameness 48 to 72 hours after treatment; lameness resolved uneventfully.

CONCLUSIONS AND CLINICAL RELEVANCE

Intrabursal injection of BTXB temporarily alleviated chronic lameness in horses with degenerative injury to the PA, without causing serious short-term adverse effects. Further investigation into the potential use of BTXB in horses affected by degenerative injury to the PA is warranted.

Responsiveness to botulinum toxin type A in muscles of complex regional pain patients with tonic dystonia

Tonic dystonia of the limbs in complex regional pain syndrome (CRPS) is associated with considerable disability. Treatment options are scarce. Botulinum toxin (BoNT) is sometimes used, but the effect is often said to be disappointing. However, this notion stems from case reports and clinicians' opinions but has never been formally studied. We therefore investigated responsiveness to BoNT in CRPS patients with tonic dystonia. We injected the extensor digitorum brevis (EDB) muscle with BoNT-A in 17 patients with CRPS and tonic dystonia to compare the response between affected and unaffected legs. We also investigated the right legs of 17 healthy controls. Responsiveness was defined as a decrease of the amplitude of the compound muscle action potential (CMAP) of >20% from baseline 2 weeks after BoNT-A injection. We controlled for a temperature effect on BoNT efficacy by measuring skin temperature hourly directly above the EDB muscle in the first 2 weeks. CMAP amplitude decreased >20% after injection on the affected side in 16 of 17 CRPS patients, similar to the response in unaffected legs (12/13) or legs of controls (17/17). The degree of CMAP reduction was significantly smaller in patients than in controls (56.0 ± 22.3 vs. 70.6 ± 14.6%; p = 0.031). This may be due to a lower physical activity level and a greater difficulty to localize the EDB muscle properly in affected legs. The decrease in CMAP amplitude was not related to skin temperature. Contrary to the prevailing opinion, BoNT-A has a normal, although perhaps slightly lower efficacy in CRPS patients with dystonia.

The rat Digit Abduction Score (DAS) assay: a physiological model for assessing botulinum neurotoxin-induced skeletal muscle paralysis

Botulinum neurotoxins (BoNT) are approved for a number of therapeutic indications, including blepharospasm, cervical dystonia and hyperhidrosis, and have also shown efficacy in a variety of pain disorders. The potency of any given BoNT preparation can be routinely assessed by using the Digit Abduction Score (DAS) assay, which measures the local muscle weakening efficacy of BoNT following injection into mouse hindlimb muscle. While most studies have employed mice to assess BoNT efficacy in the DAS, few have utilized rats. In this study, we applied the DAS assay to a rat model and compared the potency of IM-BOTOX(®) (onabotulinumtoxinA) injections between two separate hind limb muscles, gastrocnemius and tibialis anterior (TA). The results demonstrated that the DAS assay can be performed on rats with similar criteria and parameters as for mice. Moreover in the rat, BoNT can be injected into either the gastrocnemius or TA muscle to elicit similar DAS scoring responses. Interestingly, onabotulinumtoxinA potency in the rat DAS was ∼3-fold higher following TA injections than gastrocnemius injections. Additionally, our data showed that the durational kinetics of onabotulinumtoxinA in the rat DAS are approximately twice as long as in the mouse DAS. These results position the rat DAS as a more flexible model for examining the mechanisms of BoNT diffusion and muscle paralysis, while mouse DAS can be used for physiological screening of BoNT because of the potential for higher throughput. Overall, these data confirm the utility of the DAS assay for characterizing the physiological potency of BoNT and related compounds.

A comparison of the short-term effects of a botulinum toxin type a and triamcinolone acetate injection on adhesive capsulitis of the shoulder

OBJECTIVE

To evaluate the short-term clinical effects of the intra-articular injection of botulinum toxin type A (BoNT-A) for the treatment of adhesive capsulitis.

METHODS

A prospective, controlled trial compared the effects of intra-articular BoNT-A (Dysport; 200 IU, n=15) with the steroid triamcinolone acetate (TA; 20 mg, n=13) in patients suffering from adhesive capsulitis of the shoulder. All patients were evaluated using a Numeric Rating Scale (NRS) of the pain intensity and a measurement of the range of motion (ROM) at baseline (before treatment) and at 2, 4, and 8 weeks post-treatment.

RESULTS

The NRS at 2 weeks (BoNT-A vs. TA; 5.0 vs. 5.2), 4 weeks (4.1 vs. 4.9) and 8 weeks (3.8 vs. 4.6) of both treatment groups were significantly lower than that measured at baseline (7.4 vs. 7.6). The ROM of patients' shoulders increased significantly from baseline in both treatment groups. There was no significant difference in the NRS of pain intensity or the ROM between the two groups. Reduction in the pain intensity score was maintained for 8 weeks post-injection in both groups. There were no significant adverse events in either treatment group.

CONCLUSION

The results suggest that there are no significant short-term differences between the intra-articular injections of BoNT-A and TA. Although BoNT-A has a high cost, it may be used as a safe alternative of TA to avoid the steroid-induced side effects or as a second-line agent, for patients who have failed to respond to the current treatments.

Botulinum toxin for the treatment of myofascial pain syndromes involving the neck and back: a review from a clinical perspective

Introduction. Botulinum toxin inhibits acetylcholine (ACh) release and probably blocks some nociceptive neurotransmitters. It has been suggested that the development of myofascial trigger points (MTrP) is related to an excess release of ACh to increase the number of sensitized nociceptors. Although the use of botulinum toxin to treat myofascial pain syndrome (MPS) has been investigated in many clinical trials, the results are contradictory. The objective of this paper is to identify sources of variability that could explain these differences in the results. Material and Methods. We performed a content analysis of the clinical trials and systematic reviews of MPS. Results and Discussion. Sources of differences in studies were found in the diagnostic and selection criteria, the muscles injected, the injection technique, the number of trigger points injected, the dosage of botulinum toxin used, treatments for control group, outcome measures, and duration of followup. The contradictory results regarding the efficacy of botulinum toxin A in MPS associated with neck and back pain do not allow this treatment to be recommended or rejected. There is evidence that botulinum toxin could be useful in specific myofascial regions such as piriformis syndrome. It could also be useful in patients with refractory MPS that has not responded to other myofascial injection therapies.

Botulinum toxins: mechanisms of action, antinociception and clinical applications

Botulinum toxin (BoNT) is a potent neurotoxin that is produced by the gram-positive, spore-forming, anaerobic bacterium, Clostridum botulinum. There are 7 known immunologically distinct serotypes of BoNT: types A, B, C1, D, E, F, and G. Clostridum neurotoxins are produced as a single inactive polypeptide chain of 150kDa, which is cleaved by tissue proteinases into an active di-chain molecule: a heavy chain (H) of ∼100 kDa and a light chain (L) of ∼50 kDa held together by a single disulfide bond. Each serotype demonstrates its own varied mechanisms of action and duration of effect. The heavy chain of each BoNT serotype binds to its specific neuronal ecto-acceptor, whereby, membrane translocation and endocytosis by intracellular synaptic vesicles occurs. The light chain acts to cleave SNAP-25, which inhibits synaptic exocytosis, and therefore, disables neural transmission. The action of BoNT to block the release of acetylcholine botulinum toxin at the neuromuscular junction is best understood, however, most experts acknowledge that this effect alone appears inadequate to explain the entirety of the neurotoxin's apparent analgesic activity. Consequently, scientific and clinical evidence has emerged that suggests multiple antinociceptive mechanisms for botulinum toxins in a variety of painful disorders, including: chronic musculoskeletal, neurological, pelvic, perineal, osteoarticular, and some headache conditions.

Temporomandibular disorders in patients with craniocervical dystonia

Temporomandibular disorders are a set of musculoskeletal dysfunctions within the masticatory system, with multiple etiologies.

OBJECTIVE

Since craniocervical dystonia can involve the same neuromuscular structure as the temporomandibular joint, we sought to assess the correlation between temporomandibular disorders and craniocervical dystonia.

METHOD

We applied the Research Diagnostic Criteria for Temporomandibular Disorders to 42 patients with craniocervical dystonia, in order to identify orofacial pain and temporomandibular characteristics on the day of botulinum toxin injection.

RESULTS

Twenty-two patients (52.3%) reported temporomandibular joint pain; 24 (57.1%), joint sounds; 20 (47.6%), masticatory muscle pain; and 21 (50%), diminished jaw mobility. The patients with oromandibular dystonia presented temporomandibular disorders more frequently than did patients with other types of craniocervical dystonia (p<0.001).

CONCLUSION

Temporomandibular disorders occur frequently in patients with oromandibular dystonia. Further studies should address the proper treatment of temporomandibular disorders associated with dystonia.

Posterior hip pain in an athletic population: differential diagnosis and treatment options

Context:

Posterior hip pain is a relatively uncommon but increasingly recognized complaint in the orthopaedic community. Patient complaints and presentations are often vague or nonspecific, making diagnosis and subsequent treatment decisions difficult. The purposes of this article are to review the anatomy and pathophysiology related to posterior hip pain in the athletic patient population.

Evidence Acquisition:

Data were collected through a thorough review of the literature via a MEDLINE search of all relevant articles between 1980 and 2010.

Results:

Many patients who complain of posterior hip pain actually have pain referred from another part of the body—notably, the lumbar spine or sacroiliac joint. Treatment options for posterior hip pain are typically nonoperative; however, surgery is warranted in some cases.

Conclusions:

Recent advancements in the understanding of hip anatomy, pathophysiology, and treatment options have enabled physicians to better diagnosis athletic hip injuries and select patients for appropriate treatment.

Intradermal injection of Botulinum toxin type A alleviates infraorbital nerve constriction-induced thermal hyperalgesia in an operant assay

Recent studies have shown that infraorbital nerve constriction (IoNC)-induced mechanical allodynia has been attenuated by administration of highly purified 150-kDa Botulinum neurotoxin type A (BoNT/A). Here, we extend these studies to determine whether BoNT/A could attenuate IoNC-induced symptoms of thermal hyperalgesia. Instead of testing head withdrawal thresholds, a thermal operant assay was used to evaluate cortical processing of sensory input following IoNC. In this assay, a fasted rat's desire to obtain a food reward (sweetened condensed milk) is coupled to its ability to tolerate facial contact with a warm (45 °C) thermode. Bilateral IoNC decreased the ratio of thermode contact duration/event, which is an indicative of thermal hyperalgesia. BoNT/A injection intradermally in the area of infraorbital nerve (IoN) innervation 7 days after IoNC resulted in decreased number of facial contacts and increased the ratio of contact duration/event (measured at 14 days after IoNC). The BoNT/A (2-200 pg) effects were dose dependent and statistically significant at 100 and 200 pg (P < 0·05). Complete reversal of thermal hyperalgesia symptoms was obtained with a 200-pg dose, without affecting sham rat behaviour. Off-site (neck) injection of BoNT/A did not relieve thermal hyperalgesia, while co-injection of BoNT/A with a neutralising antibody in the area of IoN innervation prevented relief of thermal hyperalgesia. Neither IoNC nor BoNT/A injection affected operant assay parameters with a 24 °C thermode, indicating selectivity of thermal hyperalgesia measurements. These results strongly suggest that intradermal injection of BoNT/A in the area of IoN innervation alleviates IoNC-induced thermal hyperalgesia in an operant assay.

Botulinum toxin for subacute/chronic neck pain

BACKGROUND

Neck disorders are common, disabling and costly. Botulinum toxin (BoNT) intramuscular injections are often used with the intention of treating neck pain.

OBJECTIVES

To systematically evaluate the literature on the treatment effectiveness of BoNT for neck pain, disability, global perceived effect and quality of life in adults with neck pain with or without associated cervicogenic headache, but excluding cervical radiculopathy and whiplash associated disorder.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, AMED, Index to Chiropractic Literature, CINAHL, LILACS, and EMBASE from their origin to 20 September 2010.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials in which BoNT injections were used to treat subacute or chronic neck pain.

DATA COLLECTION AND ANALYSIS

A minimum of two review authors independently selected articles, abstracted data, and assessed risk of bias, using the Cochrane Back Review Group criteria. In the absence of clinical heterogeneity, we calculated standardized mean differences (SMD) and relative risks, and performed meta-analyses using a random-effects model. The quality of the evidence and the strength of recommendations were assigned an overall grade for each outcome.

MAIN RESULTS

We included nine trials (503 participants). Only BoNT type A (BoNT-A) was used in these studies.High quality evidence suggests there was little or no difference in pain between BoNT-A and saline injections at four weeks (five trials; 252 participants; SMD pooled -0.07 (95% confidence intervals (CI) -0.36 to 0.21)) and six months for chronic neck pain. Very low quality evidence indicated little or no difference in pain between BoNT-A combined with physiotherapeutic exercise and analgesics and saline injection with physiotherapeutic exercise and analgesics for patients with chronic neck pain at four weeks (two trials; 95 participants; SMD pooled 0.09 (95% CI -0.55 to 0.73)) and six months (one trial; 24 participants; SMD -0.56 (95% CI -1.39 to 0.27)). Very low quality evidence from one trial (32 participants) showed little or no difference between BoNT-A and placebo at four weeks (SMD 0.16 (95% CI -0.53 to 0.86)) and six months (SMD 0.00 (95% CI -0.69 to 0.69)) for chronic cervicogenic headache. Very low quality evidence from one trial (31 participants), showed a difference in global perceived effect favouring BoNT-A in chronic neck pain at four weeks (SMD -1.12 (95% CI: -1.89 to -0.36)).

AUTHORS' CONCLUSIONS

Current evidence fails to confirm either a clinically important or a statistically significant benefit of BoNT-A injection for chronic neck pain associated with or without associated cervicogenic headache. Likewise, there was no benefit seen for disability and quality of life at four week and six months.

International consensus statement for the use of botulinum toxin treatment in adults and children with neurological impairments--introduction

Botulinum neurotoxin (BoNT) is most commonly used to reduce focal over-activity in skeletal muscle, although newer indications such as management of drooling, pain and tremor are emerging. Treatment of spasticity incorporating BoNT is usually part of an integrated multidisciplinary rehabilitation programme. Prior to initiating this therapy, specific functional limitations, goals and expected outcomes of treatment should be discussed with the patient/carers. Muscle selection and the order/priority of treatment should be agreed. Treatment goals may involve increasing active or passive function or the avoidance of secondary complications or impairment progression. This paper describes the basic science mechanisms of the action of BoNT and subsequent nerve recovery and introduces a supplement comprising the best available evidence and expert opinion from international panels on questions of assessment, indications, BoNT regimen, adjunctive therapy, expected outcomes and recommended monitoring. Speciality areas reviewed include Paediatric Lower Limb Hypertonicity, Paediatric Upper Limb Hypertonicity, Adult Lower Limb Hypertonicity, Adult Upper Limb Hypertonicity, Cervical Dystonia, Drooling and Pain and Niche Indications. There is good quality scientific evidence to support the efficacy of BoNT to reduce muscle over-activity in the limbs secondary to central nervous system disorders in adults and children, to address primary or secondary cervical dystonia, to reduce saliva flow and to treat some pain syndromes. There is emergent evidence for the efficacy of BoNT to reduce focal tremor, to treat other types of pain including neuropathic pain and also to improve function following treatment of focal muscle over-activity.

[Types of topical treatment for peripheral neuropathic pain : Mechanism of action and indications]

The term "peripheral neuropathic pain syndromes" summarizes several chronic pain syndromes, which can occur focally or generalized in the peripheral nervous system in the course of an impairment of afferent neurons. Controlled clinical trials gave distinct indications for systemic treatments with antidepressants, anticonvulsants and opioid analgesics in several neuropathic pain syndromes. In addition to these systemic therapies, there are also two topical treatment options: topical application of lidocaine and capsaicin. An important cause of sensitization phenomena of afferent nociceptors is the upregulation of sodium channels and thermosensor channels. In the context of a partial nerve lesion that leaves behind partially preserved or regenerated afferent nerve fibres, just these channels could be used as target structures for topical medications. Topically applied drugs are absorbed systemically only in minute quantities, so systemic side effects are negligible. Pharmacological interactions with systematically acting substances are also virtually absent; thus, topically applied substances are especially appropriate for add-on therapy in addition to systemic pain medication.

Dysport® for the treatment of myofascial back pain: Results from an open-label, Phase II, randomized, multicenter, dose-ranging study

Background and purpose Botulinum toxin type A (BoNT-A) has antinociceptive and muscle-relaxant properties. The objectives of this study were to investigate the efficacy and safety of a single BoNT-A (Dysport®) treatment in myofascial back pain. Methods In this randomized, open-label, multicenter study, adults with myofascial lower back pain received Dysport® injections at four trigger points (60,80 or 120 units per injection point). Patients were followed for 12 weeks. The a priori primary endpoint was a pooled evaluation, at Week 6, of seven measures of efficacy, including pain intensity (patient diary), modified Pain Disability Index (PDI) score, use of interfering concomitant analgesics, and patient-rated global efficacy. Optional assessments of pressure thresholds and tissue compliance were conducted. Safety was also assessed. Results A total of 202 patients were randomized to treatment and 189 patients received a low (n = 57), medium (n = 57), or high (n = 75) total dose of Dysport® at 34 centers in Germany between October 2002 and October 2003. All treated patients were included in the safety population; 8 patients were excluded from the intention-to-treat population. Patients had moderate to severe pain at baseline. At baseline, 120 patients were receiving concomitant analgesic therapy; 6.7%, 74.2% and 19.2% were considered to cause mild, moderate and severe interference with pain measurements, respectively. There was no difference between doses for the a priori combined primary endpoint. Patient-reported pain intensity scores at rest and on movement decreased significantly after treatment for all groups combined (p < 0.0001 at all visits). At Week 6, reductions in pain intensity at rest were 29%, 19% and 26% for the low-, medium- and high-dose groups, respectively; reductions in pain intensity on movement were 27%, 18% and 26%, respectively. Overall, patients who reported pain intensity reductions at Week 6 were evident within 3 weeks of treatment and were maintained for the 12 weeks of the study. In the total population, significant decreases in mean PDI sum scores from baseline were observed from Week 3 and were maintained through to the end of treatment (Week 12); no differences between the dose groups were observed. Pressure thresholds and tissue compliance also increased during the study. Adverse events were generally as expected for BoNT-A; the majority were mild or moderate in severity. Conclusions Dysport® treatment was associated with reductions in myofascial back pain and was well tolerated. Nodose-response relationship was observed; treatment with Dysport® using a four-trigger-point injection protocol at 60 units per trigger point was associated with a clinically relevant and statistically significant improvement in pain and pain-related disability; there was no additional benefit from the higher doses. Implications Our findings are limited by the lack of a control group and further research is warranted to confirm the value of Dysport® for the treatment of myofascial back pain and confirm the optimum dosing in this indication.

Botulinum toxin intramuscular injections for neck pain: a systematic review and metaanalysis

OBJECTIVE

To assess the effect of intramuscular botulinum toxin type A (BoNT-A) injections on pain, function/disability, global perceived effect, and quality of life (QOL) in adults with neck pain (NP).

METHODS

We searched Central, Medline, and Embase databases up to June 2010. A minimum of 2 authors independently selected articles, abstracted data, and assessed risk of bias and clinical applicability. We estimated standard mean differences (SMD) with 95% CI, relative risks (RR), and performed metaanalyses (SMD(p)) using a random-effects model for nonheterogeneous data. The approach of the Grading of Recommendations Assessment, Development, and Evaluation working group summarizes the quality of evidence.

RESULTS

We selected 14 trials. High-quality evidence suggested BoNT-A was no better than saline at 4 weeks [4 trials/183 participants; SMD(p) -0.21 (95% CI -0.50 to 0.07)] and 6 months for chronic NP. Moderate-quality evidence showed a similar effect for subacute/chronic whiplash-associated disorder (WAD) on pain [4 trials/122 participants; SMD(p) -0.21 (95% CI -0.57 to 0.15)], disability, and QOL. Very low-quality evidence indicated BoNT-A combined with exercise and analgesics was not significant for chronic NP reduction at 4 weeks [3 trials/114 participants; SMD(p) -0.08 (95% CI -0.45 to 0.29)] but was at 6 months [2 trials/43 participants; SMD(p) -0.66 (95% CI -1.29 to -0.04)].

CONCLUSION

Current evidence does not confirm a clinically or statistically significant benefit of BoNT-A used alone on chronic NP in the short term or on subacute/chronic WAD pain, disability, and QOL. Larger trials, subgroups, and predictors of responses defined a priori (to facilitate selection of patients most likely to benefit) and factorial designs to explore BoNT as an adjunct treatment to physiotherapeutic exercise and analgesics are needed.

Botulinum neurotoxin type A counteracts neuropathic pain and facilitates functional recovery after peripheral nerve injury in animal models

A growing interest was recently focused on the use of Botulinum neurotoxin serotype A (BoNT/A) for fighting pain. The aim of this study was to investigate the effects of BoNT/A on neuropathic pain. It was observed that BoNT/A is able to counteract neuropathic pain induced by chronic constriction injury (CCI) to the sciatic nerve both in mice and in rats. This effect is already present after a single intraplantar (i.pl.) or intrathecal (i.t.) neurotoxin administration that significantly reduces the sciatic nerve ligation-induced mechanical allodynia in mice and rats and thermal hyperalgesia in rats. This effect was evident starting 24 h after the administration of BoNT/A and it was long-lasting, being present 81 or 25 days after i.pl. injection of the higher dose in mice (15 pg/paw) and rats (75 pg/paw), respectively, and 35 days after i.t. injection in rats (75 pg/rat). Moreover, BoNT/A-injected mice showed a quicker recovery of the walking pattern and weight bearing compared to control groups. The behavioral improvement was accompanied by structural modifications, as revealed by the expression of cell division cycle 2 (Cdc2) and growth associated protein 43 (GAP-43) regeneration associated proteins, investigated by immunofluorescence and Western blotting in the sciatic nerve, and by the immunofluorescence expression of S100β and glial fibrillary acidic protein (GFAP) Schwann cells proteins. In conclusion, the present research demonstrate long-lasting anti-allodynic and anti-hyperalgesic effects of BoNT/A in animal models of neuropathic pain together with an acceleration of regenerative processes in the injured nerve, as evidenced by both behavioral and immunohistochemistry/blotting analysis. These results may have important implications in the therapy of neuropathic pain.

Re-engineering clostridial neurotoxins for the treatment of chronic pain: current status and future prospects

Clostridial neurotoxins from the botulinum neurotoxin (BoNT) family are protein complexes, derived from the bacterium Clostridium botulinum, which potently inhibit acetylcholine release and result in a reversible blockade of the neuromuscular junction. This feature led to the clinical development of BoNT-A for a number of neuromuscular disorders. BoNT-A toxins are commercially available as three different preparations: Dysport/Azzalure, Botox/Vistabel, and Xeomin/Bocouture. Although BoNT-A preparations have not yet been approved for the treatment of pain, a substantial body of preclinical and clinical evidence shows that BoNT-A is effective in treating a number of different types of pain. It is thought to exert an analgesic effect both via muscle-relaxant properties and also directly, via inhibition of nociceptive neuropeptides. This review explores the mechanistic basis of this analgesic effect, summarizing current knowledge of the structure-function relationship of BoNT and discussing effects on both motor and pain neurons. For a complete picture of the analgesic properties of BoNT-A, clinical evidence of efficacy in myofascial pain and neuropathic pain is considered in tandem with a mechanistic rationale for activity. Patients experiencing chronic pain are clear candidates for treatment with a modified clostridial endopeptidase that would provide enduring inhibition of neurotransmitter release. A strong preclinical evidence base underpins the concept that re-engineering of BoNT could be used to enhance the analgesic potential of this neurotoxin, and it is hoped that the first clinical studies examining re-engineered BoNT-A will confirm this potential.