Botulinum neurotoxins in the treatment of refractory pain

Comprehensive pain management in spinal surgery: The role of botulinum toxin

The use of botulinum toxin in pre- and post-operative management of pain in spinal surgery is described, following a specific administration protocol. The initial encouraging results (particularly the absence of opioid use in the post-operative period) support the potential role of BoNT-A (Botulinum Neurotoxin type A) as a targeted therapeutic option in this specific clinical setting.

An update on botulinum toxin treatment of painful diabetic neuropathy, post-traumatic painful neuropathy/neuralgia, post-herpetic neuralgia and occipital neuralgia

The literature in botulinum toxin treatment for painful diabetic neuropathy (PDN), post traumatic neuralgia (PTN), postherpetic neuralgia (PHN) and occipital neuralgia (ON) was reviewed up to Oct 1st, 2024. Using the efficacy criteria set forth by the Assessment and Guideline subcommittee of the American Academy of Neurology, the current levels of efficacy for these conditions could be designated as followings: PDN: B (probably effective, two class II study), PTN: A (effective, two class I studies); PHN: A (effective, two class I studies), ON: (undetermined due to lack of blinded investigations). Due to the small number of patients in these studies, proof of efficacy requires conduction of controlled and blinded studies in large cohorts of patients with longer follow ups. Future prospects of botulinum therapy for these pain disorders were discussed along with the advantages of this mode of treatment over the current modes of treatment.

Paradoxical masseteric bulging after botulinum neurotoxin type A injection

Paradoxical masseteric bulging refers to an unexpected occurrence of masseter muscle bulging or protrusion following the administration of botulinum toxin injections, contrary to the anticipated muscle weakening effect. It may occur secondary to toxin failing to diffuse through the entire masseter muscle due to the presence of an inferior tendon structure within the superficial masseter that divides it into a superficial and deep belly. We report a clinical case of paradoxical masseteric bulging in a female in her late 40s who developed this adverse effect within a week of her masseter botulinum neurotoxin type A injections. We also describe the masseter two-site injection technique for the management of this complication.

Xeomin®, a Commercial Formulation of Botulinum Neurotoxin Type A, Promotes Regeneration in a Preclinical Model of Spinal Cord Injury

Xeomin® is a commercial formulation of botulinum neurotoxin type A (BoNT/A) clinically authorized for treating neurological disorders, such as blepharospasm, cervical dystonia, limb spasticity, and sialorrhea. We have previously demonstrated that spinal injection of laboratory purified 150 kDa BoNT/A in paraplegic mice, after undergoing traumatic spinal cord injury (SCI), was able to reduce excitotoxic phenomena, glial scar, inflammation, and the development of neuropathic pain and facilitate regeneration and motor recovery. In the present study, as proof of concept in view of a possible clinical application, we studied the efficacy of Xeomin® in the same preclinical SCI model in which we highlighted the positive effects of lab-purified BoNT/A. Data comparison shows that Xeomin® induces similar pharmacological and therapeutic effects, albeit with less efficacy, to lab-purified BoNT/A. This difference, which can be improved by adjusting the dose, can be attributable to the different formulation and pharmacodynamics. Although the mechanism by which Xeomin® and laboratory purified BoNT/A induce functional improvement in paraplegic mice is still far from being understood, these results open a possible new scenario in treatment of SCI and are a stimulus for further research.

The efficacy and safety of intra-articular botulinum toxin type A injection for knee osteoarthritis: A meta-analysis of randomized controlled trials

The purpose of this study was to investigate the efficacy and safety of intra-articular Botulinum Toxin type A (BTA) injection in the management of patients with knee osteoarthritis (KOA). The literature retrieval was conducted based on PRISMA guidelines. Databases including Pubmed, Web of science, EMBASE, and Cochrane Library were searched to identify RCTs that comparing the effects of intra-articular BTA injection with control interventions on patients with KOA. The primary outcomes involved pain and function improvements as well as the occurrence of adverse events. Seven RCTs comprising 548 participants were included in this meta-analysis. Compared with the control group, BTA injection exhibited greater pain reduction at 4 weeks posttreatment (SMD = -0.86, 95% CI [-1.52, -0.19], p = 0.011), but not 8-24 weeks posttreatment (wk 8, SMD = -0.53, 95% CI [-1.21, 0.15], p = 0.127; wk 12, SMD = -0.34, 95% CI [-0.73, 0.04], p = 0.081; wk 24, SMD = -0.65, 95% CI [-1.52, 0.22], p = 0.144). Additionally, no differences were found between BTA injection versus control intervention on functional improvement at all time points assessed (wk 4, WMD = -5.16, 95% CI [-12.31, 2.00], p = 0.158; wk 8, WMD = -0.98, 95% CI [-5.66, 3.71], p = 0.683; wk 12, WMD = -2.52, 95% CI [-7.54, 2.50], p = 0.325); wk 24, WMD = -3.66, 95% CI [-14.09, 6.76], p = 0.491). There was no significant difference in adverse event rate between the BTA and control group (OR = 0.88, 95% CI [0.24, 3.18], p = 0.843). This meta-analysis suggests that intra-articular BTA injection could be an efficious and safe strategy for analgesic treatment of KOA. However, evidence is limited due to the small number and heterogeneity of included studies, this urges further and stronger trials to confirm our findings.

Effects of Botulinum Toxin Type A on the Nociceptive and Lemniscal Somatosensory Systems in Chronic Migraine: An Electrophysiological Study

(1) Background: OnabotulinumtoxinA (BoNT-A) is a commonly used prophylactic treatment for chronic migraine (CM). Although randomized placebo studies have shown its clinical efficacy, the mechanisms by which it exerts its therapeutic effect are still incompletely understood and debated. (2) Methods: We studied in 15 CM patients the cephalic and extracephalic nociceptive and lemniscal sensory systems using electrophysiological techniques before and 1 and 3 months after one session of pericranial BoNT-A injections according to the PREEMPT protocol. We recorded the nociceptive blink reflex (nBR), the trigemino-cervical reflex (nTCR), the pain-related cortical evoked potential (PREP), and the upper limb somatosensory evoked potential (SSEP). (3) Results: Three months after a single session of prophylactic therapy with BoNT-A in CM patients, we found (a) an increase in the homolateral and contralateral nBR AUC, (b) an enhancement of the contralateral nBR AUC habituation slope and the nTCR habituation slope, (c) a decrease in PREP N-P 1st and 2nd amplitude block, and (d) no effect on SSEPs. (4) Conclusions: Our study provides electrophysiological evidence for the ability of a single session of BoNT-A injections to exert a neuromodulatory effect at the level of trigeminal system through a reduction in input from meningeal and other trigeminovascular nociceptors. Moreover, by reducing activity in cortical pain processing areas, BoNT-A restores normal functioning of the descending pain modulation systems.

Post Hoc Subgroup Analysis of the BCause Study Assessing the Effect of AbobotulinumtoxinA on Post-Stroke Shoulder Pain in Adults

Botulinum toxin type A is approved for the focal treatment of spasticity; however, the effectiveness of abobotulinumtoxinA (aboBoNT-A) in patients with shoulder pain who have set reduced pain as a treatment goal is understudied. In addition, some patients encounter delays in accessing treatment programs; therefore, the suitability of aboBoNT-A for pain reduction in this population requires investigation. These factors were assessed in aboBoNT-A-naive Brazilian patients in a post hoc analysis of data from BCause, an observational, multicenter, prospective study (NCT02390206). Patients (N = 49, n = 25 female; mean (standard deviation) age of 60.3 (9.1) years; median (range) time since onset of spasticity of 16.1 (0-193) months) received aboBoNT-A injections to shoulder muscles in one or two treatment cycles (n = 47). Using goal attainment scaling (GAS), most patients achieved their goal of shoulder pain reduction after one treatment cycle (72.1%; 95% confidence interval: 57.2-83.4%). Improvements in GAS T-score from baseline, clinically meaningful reductions in pain score at movement, and clinically meaningful increases in passive shoulder abduction angle further improved with repeated treatment more than 4 months later, despite treatment starting at a median of 16.1 months after the onset of spasticity. These findings support the further investigation of aboBoNT-A injections in chronic post-stroke shoulder pain.

Incobotulinum toxin type A for treatment of chronic myofascial pain

PURPOSE

This study assessed the effectiveness of incobotulinum toxin type A (IBTx) for chronic myofascial pain affecting the masseter and temporal muscles.

METHODS

Twenty two patients who received a diagnosis of chronic masseter and temporalis myofascial pain were evaluated by using a visual analog pain scale (VAS), digital pressure algometry, and the SF-36 Health Survey at baseline (T0), before IBTx injection. Patients were again evaluated at 2 months (T1) and 7 months (T2) after IBTx injection.

RESULTS

VAS scores for pain significantly differed (P = 0.029, Friedman test). Post-hoc tests showed a significant reduction in pain at 2 months (T0-T1) and 7 months (T0-T2) (P = 0.011 and P = 0.028, respectively; Wilcoxon test) but not between 2 and 7 months (P = 0.676; Wilcoxon test). There was no significant difference in pressure algometry values (P = 0.385, Friedman test). Quality of life (QOL) assessment showed a significant difference (P = 0.002, Friedman test). Post-hoc tests showed a significant improvement in QOLat 2 months, but no significant difference at 7 months (P = 0.004 and P = 0.260, Wilcoxon test).

CONCLUSION

IBTx injection resulted in safe, effective short-term pain relief for patients with chronic facial pain affecting the masseter and temporalis muscles.

Botulinum Toxin and Neuronal Regeneration after Traumatic Injury of Central and Peripheral Nervous System

Botulinum neurotoxins (BoNTs) are toxins produced by the bacteria Clostridiumbotulinum, the causing agent for botulism, in different serotypes, seven of which (A-G) are well characterized, while others, such as H or FA, are still debated. BoNTs exert their action by blocking SNARE (soluble N-ethylmale-imide-sensitive factor-attachment protein receptors) complex formation and vesicle release from the neuronal terminal through the specific cleavage of SNARE proteins. The action of BoNTs at the neuromuscular junction has been extensively investigated and knowledge gained in this field has set the foundation for the use of these toxins in a variety of human pathologies characterized by excessive muscle contractions. In parallel, BoNTs became a cosmetic drug due to its power to ward off facial wrinkles following the activity of the mimic muscles. Successively, BoNTs became therapeutic agents that have proven to be successful in the treatment of different neurological disorders, with new indications emerging or being approved each year. In particular, BoNT/A became the treatment of excellence not only for muscle hyperactivity conditions, such as dystonia and spasticity, but also to reduce pain in a series of painful states, such as neuropathic pain, lumbar and myofascial pain, and to treat various dysfunctions of the urinary bladder. This review summarizes recent experimental findings on the potential efficacy of BoNTs in favoring nerve regeneration after traumatic injury in the peripheral nervous system, such as the injury of peripheral nerves, like sciatic nerve, and in the central nervous system, such as spinal cord injury.

Comparison of the efficacy of intramuscular botulinum toxin type-A injection into the pectoralis major and the teres major muscles and suprascapular nerve block for hemiplegic shoulder pain: a prospective, double-blind, randomized, controlled trial

INTRODUCTION

This study aims to investigate the effect of botulinum toxin-A (BoNT-A) injection into pectoralis major and teres major muscles and suprascapular nerve block (SSNB) on pain, range of motion (ROM), and upper extremity function for (hemiplegic shoulder pain) HSP, and to compare the effectiveness of these two methods.

MATERIALS AND METHODS

Sixty patients with HSP were randomly assigned into 2 groups. The Group 1 (n = 30) received BoNT-A injection into the pectoralis major and teres major, and the Group 2 (n = 30) received SSSB. Patients were evaluated just before the start of the study, and 2 and 6 weeks after the start of the study with visual analog scale (VAS), Modified Ashworth Scale (MASH), the passive ROM, and the Fugl-Meyer Scale (FMS) arm section.

RESULTS

In Group 1, statistically significant improvement was found in all evaluation parameters on 2th and 6th week. Group 2 showed significant improvement in all parameters on week 2 (p < 0.05), and significant improvement was observed in MASH and pain in abduction in the 6th week (p < 0.05). When the groups were compared with each other, a statistically significant difference was observed in MASH, ROM, and FMS parameters on week 2 in favor of Group 1; in all evaluation parameters, there was a statistically significant difference in favor of Group 1 on week 6 (p < 0.05).

CONCLUSION

We concluded that BoNT-A injection into the pectoralis major and teres major muscles for HSP was equal in the short term and more effective in the middle term compared with SSNB treatment in improving pain, ROM, and function.

Intra-articular injection of botulinum toxin type A for shoulder pain in glenohumeral osteoarthritis: a case series summary and review of the literature

INTRODUCTION

Shoulder pain is one of the most common musculoskeletal diseases, and can be due to glenohumeral osteoarthritis, rotator cuff tear, impingement, tendinitis, adhesive capsulitis, and subacromial bursitis. Several therapies have been proposed, including steroids, nonsteroidal anti-inflammatory drugs, intra-articular injections, and physical therapies. Many published studies have reported on the employment of botulinum toxin type A (BoNT-A) to reduce pain in subjects with neurological and musculoskeletal diseases by inhibiting substance P release and other inflammatory factors.

METHODS

In the present article, we briefly update current knowledge regarding intra-articular BoNT therapy, reviewing existing literature on intra-articular use of BoNT-A, including nonrandomized and randomized prospective and retrospective cohort studies and case series published from December 1989 to November 2017. We also describe a case series of six subjects treated with intra-articular injection of incobotulinumtoxin A for the treatment of pain deriving from osteoarthritis.

CONCLUSION

Intra-articular BoNT-A is effective and minimally invasive. Pain reduction with an increase in shoulder articular range of motion in our experience confirms the effectiveness of BoNT-A injection for the management of this syndrome.

Botulinum Toxin Type A-A Modulator of Spinal Neuron-Glia Interactions under Neuropathic Pain Conditions

Neuropathic pain represents a significant clinical problem because it is a chronic condition often refractory to available therapy. Therefore, there is still a strong need for new analgesics. Botulinum neurotoxin A (BoNT/A) is used to treat a variety of clinical diseases associated with pain. Glia are in continuous bi-directional communication with neurons to direct the formation and refinement of synaptic connectivity. This review addresses the effects of BoNT/A on the relationship between glia and neurons under neuropathic pain. The inhibitory action of BoNT/A on synaptic vesicle fusion that blocks the release of miscellaneous pain-related neurotransmitters is known. However, increasing evidence suggests that the analgesic effect of BoNT/A is mediated through neurons and glial cells, especially microglia. In vitro studies provide evidence that BoNT/A exerts its anti-inflammatory effect by diminishing NF-κB, p38 and ERK1/2 phosphorylation in microglia and directly interacts with Toll-like receptor 2 (TLR2). Furthermore, BoNT/A appears to have no more than a slight effect on astroglia. The full activation of TLR2 in astroglia appears to require the presence of functional TLR4 in microglia, emphasizing the significant interaction between those cell types. In this review, we discuss whether and how BoNT/A affects the spinal neuron–glia interaction and reduces the development of neuropathy.

Comparison of the Expression Changes after Botulinum Toxin Type A and Minocycline Administration in Lipopolysaccharide-Stimulated Rat Microglial and Astroglial Cultures

Botulinum neurotoxin type A (BoNT/A) and minocycline are potent drugs used in clinical therapies. The primary molecular mechanism of BoNT/A is the cleavage of SNARE proteins, which prevents cells from releasing neurotransmitters from vesicles, while the effects of minocycline are related to the inhibition of p38 activation. Both BoNT/A and minocycline exhibit analgesic effects, however, their direct impact on glial cells is not fully known. Therefore, the aim of the present study was to determine the effects of those drugs on microglial and astroglial activity after lipopolysaccharide (LPS) stimulation and their potential synergistic action. Our results show that BoNT/A and minocycline influenced primary microglial cells by inhibiting intracellular signaling pathways, such as p38, ERK1/2, NF-κB, and the release of pro-inflammatory factors, including IL-1β, IL-18, IL-6, and NOS2. We have revealed that, in contrast to minocycline, BoNT/A treatment did not decrease LPS-induced release of pro-inflammatory factors in the astroglia. In addition, BoNT/A decreased SNAP-23 in both types of glial cells and also SNAP-25 expressed only in astrocytes. Moreover, BoNT/A increased TLR2 and its adaptor protein MyD88, but not TLR4 exclusively in microglial cells. Furthermore, we have shown the impact of BoNT/A on microglial and astroglial cells, with a particular emphasis on its molecular target, TLR2. In contrast, minocycline did not affect any of those factors. We have revealed that despite of different molecular targets, minocycline, and BoNT/A reduced the release of microglia-derived pro-inflammatory factors. In conclusion, we have shown that BoNT/A and minocycline are effective drugs for the management of neuroinflammation by dampening the activation of microglial cells, with minocycline also affecting astroglial activity.

Reduction of adhesion formation after knee surgery in a rat model by botulinum toxin A

Adhesion of the knee is a major concern after knee surgery, the treatment of which is difficult. Botulinum toxin A (BTX-A) injection is demonstrated as efficient in treating knee adhesion after surgery. However, the treatment outcomes and the mechanism of action are not yet determined. The aim of the present study was to examine the effects and molecular mechanism of a BTX-A treatment in preventing adhesion of the knee. Twenty-four Wistar rats were randomly divided into a BTX-A treatment group and a control group. BTX-A or saline was injected into the cavity of the knee in the BTX-A treatment or control group respectively. Gross and histopathological examinations of interleukin 1 (IL-1) and fibroblast growth factor (FGF) levels, as well as fibroblast cell numbers, were assessed in the knee intra-articular adhesions in each group 6 weeks after recovery from the surgery. Macroscopic observations showed a significant reduction in adhesion severity in the BTX-A treatment group compared with the control group. In addition, the levels of IL-1 and FGF were lower and the number of fibroblasts was smaller in the BTX-A treatment group compared with those in the control group. BTX-A prevented intra-articular adhesion of knee in the rats, which might be associated with reduced expressions of IL-1 and FGF.

Botulinum Toxin A Injection into the Subscapularis Muscle to Treat Intractable Hemiplegic Shoulder Pain

Objective

To evaluate the beneficial effect of botulinum toxin A (Botox) injection into the subscapularis muscle on intractable hemiplegic shoulder pain.

Methods

Six stroke patients with intractable hemiplegic shoulder pain were included. Botulinum toxin A was injected into the subscapularis muscle. Intractable hemiplegic shoulder pain was evaluated using an 11-point numerical rating scale. Pain-free range of motion was assessed for shoulder abduction and external rotation. The spasticity of the shoulder internal rotator was measured using the modified Ashworth scale. Assessments were carried out at baseline and at 1, 2, 4, and, if possible, 8 weeks.

Results

Intractable hemiplegic shoulder pain was improved (p=0.004) after botulinum toxin injection into the subscapularis muscle. Restricted shoulder abduction (p=0.003), external rotation (p=0.005), and spasticity of the shoulder internal rotator (p=0.005) were also improved. Improved hemiplegic shoulder pain was correlated with improved shoulder abduction (r=–1.0, p<0.001), external rotation (r=–1.0, p<0.001), and spasticity of the internal rotator (r=1.0, p<0.001).

Conclusion

Botulinum toxin A injection into the subscapularis muscle appears to be valuable in the management of intractable hemiplegic shoulder pain.

Botulinum Toxin Type a as a Therapeutic Agent against Headache and Related Disorders

Botulinum neurotoxin A (BoNT/A) is a toxin produced by the naturally-occurring Clostridium botulinum that causes botulism. The potential of BoNT/A as a useful medical intervention was discovered by scientists developing a vaccine to protect against botulism. They found that, when injected into a muscle, BoNT/A causes a flaccid paralysis. Following this discovery, BoNT/A has been used for many years in the treatment of conditions of pathological muscle hyperactivity, like dystonias and spasticities. In parallel, the toxin has become a “glamour” drug due to its power to ward off facial wrinkles, particularly frontal, due to the activity of the mimic muscles. After the discovery that the drug also appeared to have a preventive effect on headache, scientists spent many efforts to study the potentially-therapeutic action of BoNT/A against pain. BoNT/A is effective at reducing pain in a number of disease states, including cervical dystonia, neuropathic pain, lower back pain, spasticity, myofascial pain and bladder pain. In 2010, regulatory approval for the treatment of chronic migraine with BoNT/A was given, notwithstanding the fact that the mechanism of action is still not completely elucidated. In the present review, we summarize experimental evidence that may help to clarify the mechanisms of action of BoNT/A in relation to the alleviation of headache pain, with particular emphasis on preclinical studies, both in animals and humans. Moreover, we summarize the latest clinical trials that show evidence on headache conditions that may obtain benefits from therapy with BoNT/A.

The efficacy of botulinum toxin A in post-mastectomy breast reconstruction: a pilot study

BACKGROUND

Botulinum toxin A has been successfully used in a variety of areas to temporarily obliterate muscle mobility for either functional or aesthetic gain. Tissue expander-based breast reconstruction has been plagued with pain and discomfort.

OBJECTIVE

The purpose of this pilot study was to evaluate the role of a neurotoxin (Botulinum toxin A) in expander-based breast reconstruction.

METHODS

Thirty patients underwent mastectomies with immediate expander or acellular dermal matrix reconstruction. The neurotoxin group (n = 15) received 40 units of neurotoxin (Botulinum toxin A, Allergan, Inc, Irvine, CA) into each pectoralis major muscle through 4 serial injections and the placebo group (n = 15) received 4 serial injections of 0.9% NaCl. All patients were followed over 1 year, and patient demographics, VAS (visual analog score), laterality, office visits, amount of expansion and number of times to full expansion, and amount of narcotics required were recorded. Statistical significance was considered as p < .05.

RESULTS

There were no significant differences between the two groups in terms of age, laterality, expander size, or complications (p = .46-.66). There was a significant difference between the two groups in the VAS score, demonstrating decreased pain in the neurotoxin group (p < .05). In addition, there was a significant increase in the volume of expansion per visit in the neurotoxin group as compared to the placebo group (p < .05). There was no significant difference in narcotic use in the first 3 days after surgery; however, there was a significant decrease in use of narcotics from 7 to 45 days in the neurotoxin group (p < .05). There were no complications associated with the use of the neurotoxin.

CONCLUSIONS

The infiltration of the pectoralis major muscle with neurotoxin in immediate, expander-based reconstruction may be beneficial in reducing pain and expediting expansions.

Analgesic effects of botulinum neurotoxin type A in a model of allyl isothiocyanate- and capsaicin-induced pain in mice

We evaluate analgesic effects of BoNT/A in relation to the two main transient receptor potentials (TRP), the vanilloid 1 (TRPV1) and the ankyrin 1 (TRPA1), having a role in migraine pain. BoNT/A (15 pg/mouse) was injected in the inner side of the medial part of hindlimb thigh of mice, where the superficial branch of femoral artery is located. We chosen this vascular structure because it is similar to other vascular structures, such as the temporal superficial artery, whose perivascular nociceptive fibres probably contributes to migraine pain. After an interval, ranging from 7 to 30 days, capsaicin (agonist of TRPV1) or allyl isothiocyanate (AITC; agonist of TRPA1) were injected in the same region previously treated with BoNT/A and nocifensive response to chemicals-induced pain was recorded. In absence of BoNT/A, capsaicin and AITC induced extensive nocifensive response, with a markedly different temporal profile: capsaicin induced maximal pain during the first 5 min, while AITC induced maximal pain at 15-30 min after injection. Pretreatment with BoNT/A markedly reduced both the capsaicin- and AITC-induced pain for at least 21 days. These data suggest a long lasting analgesic effect of BoNT/A exerted via prevention of responsiveness of TRPV1 and TRPA1 toward their respective agonists.

Botulinum toxin type a injections for cervical and shoulder girdle myofascial pain using an enriched protocol design

BACKGROUND

Myofascial pain syndrome is a regional condition of muscle pain and stiffness and is classically characterized by the presence of trigger points in affected musculature. Botulinum toxin type A (BoNT-A) has been shown to have antinociceptive properties and elicit sustained muscle relaxation, thereby possibly affording even greater relief than traditional strategies. Our goal was to determine whether direct injection of BoNT-A into painful muscle groups is effective for cervical and shoulder girdle myofascial pain.

METHODS

An enriched protocol design was used, wherein 114 patients with cervical and shoulder girdle myofascial pain underwent injection of BoNT-A to determine their response to the drug. Fifty-four responders were then enrolled in a 12-week, randomized, double-blind, placebo-controlled trial. Pain scales and quality of life measures were assessed at baseline and at routine follow-up visits until completion of the study after 26 weeks.

RESULTS

Injection of BoNT-A into painful muscle groups improved average visual numerical pain scores in subjects who received a second dose of BoNT-A compared to placebo (P = 0.019 [0.26, 2.78]). Subjects who received a second dose of BoNT-A had a reduced number of headaches per week (P = 0.04 [0.07, 4.55]). Brief Pain Inventory interference scores for general activity and sleep were improved (P = 0.046 [0.038, 3.700] and 0.02 [0.37, 4.33], respectively) in those who received a second dose of BoNT-A.

CONCLUSION

BoNT-A injected directly into painful muscle groups improves average pain scores and certain aspects of quality of life in patients experiencing severe cervical and shoulder girdle myofascial pain.

Efficacy of Long-term Effect and Repeat Intraarticular Botulinum toxin in Patients with Painful Total Joint Arthroplasty: A Retrospective Study

Objective

Based on recent success of intra-articular (IA) Botulinum neurotoxin type A (BoNT/A; OnabotulinumtoxinA) in patients with osteoarthritis, we examined if repeat IA-BoNT/A is an effective antinociceptive in patients with refractory arthroplasty pain.

Methods

11 patients with refractory chronic arthroplasty joint pain without any evidence of infection or prosthesis loosening were referred by orthopedic surgeons. After discussion of off-label use, each patient underwent IA injection of BoNT/A, repeated based on return of pain on numeric rating scale (NRS) and functional limitation on composite validated scales, Western Ontario McMaster Osteoarthritis index (WOMAC) or Shoulder Pain and Disability (SPADI).

Results

11 patients (10 men, 1 woman) with 14 painful arthroplasty joints (3 bilateral; 12 knee and 2 shoulder) underwent ≥1 IA-BoNT/A injections (8 joints injected once, one joint injected twice only, five joints injected thrice) with doses ranging 100–300 units. Mean age was 68 years (standard deviation, 12) and follow-up ranged 1–28 months. Clinically meaningful reduction of 2-units in pain severity and really meaningful reduction in pain severity (50% reduction) were reported by 6/11 patients (6/13 joints) and 3/11 patients (3/13 joints), respectively, 1 month after the first IA-BoNT/A (100-units each). Significant improvements were noted in composite functional scales (WOMAC/SPADI). Pain relief was sustained at 3–4 month follow-up and was reproducible in those who received repeat injections. No significant adverse events were seen in any patients.

Conclusions

A single intra-articular injection of BoNT/A improved pain and function in patients with chronic, refractory painful knee or shoulder arthroplasty, which sustained with repeat injections. Patients who were refractory to the first injection, did not respond to subsequent injections of higher dose of IA-BoNT/A.

Progress towards the prevention and treatment of norovirus infections

Noroviruses are now recognized as the major cause of acute gastroenteritis in the developed world, yet our ability to prevent and control infection is limited. Recent work has highlighted that, while typically an acute infection in the population, immunocompromised patients often experience long-term infections that may last many years. This cohort of patients and those regularly exposed to infectious material, for example, care workers and others, would benefit greatly from the development of a vaccine or antiviral therapy. While a licensed vaccine or antiviral has yet to be developed, work over the past 10 years in this area has intensified and trials with a vaccine candidate have proven promising. Numerous antiviral targets and small molecule inhibitors that have efficacy in cell culture have now been identified; however, further studies in this area are required in order to make these suitable for clinical use.

Botulinum toxin A increases analgesic effects of morphine, counters development of morphine tolerance and modulates glia activation and μ opioid receptor expression in neuropathic mice

The use of botulinum neurotoxin type A (BoNT/A) against pain, with emphasis for its possible use in alleviating chronic pain, still represents an outstanding challenge for experimental research. In this study, we examined the effects of BoNT/A on morphine-induced tolerance during chronic morphine treatment in neuropathic CD1 mice subjected to sciatic nerve lesion according to the Chronic Constriction Injury (CCI) model of neuropathic pain. We measured the effects of BoNT/A on CCI-induced allodynia and hyperalgesia and on the expression of glial fibrillary acidic protein (GFAP, marker of astrocytes), complement receptor 3/cluster of differentiation 11b (CD11b, marker of microglia), and neuronal nuclei (NeuN) at the spinal cord level. We also analyzed the colocalized expression of GFAP, CD11b and NeuN with phosphorylated p-38 mitogen-activated protein kinase and with μ-opioid receptor (MOR). A single intraplantar injection of BoNT/A (15 pg/paw) into the injured hindpaw, the day before the beginning of chronic morphine treatment (9 days of twice daily injections of 40 mg/kg morphine), was able to counteract allodynia and enhancement of astrocytes expression/activation induced by CCI. In addition, BoNT/A increased the analgesic effect of morphine and countered morphine-induced tolerance during chronic morphine treatment. These effects were accompanied, in neurons, by re-expression of MORs that had been reduced by repeated morphine administration. The combinatory effects of BoNT/A and morphine could have relevant therapeutic implications for sufferers of chronic pain who could benefit of pain relief reducing tolerance due to repeated treatment with opiates.

Alleviation of abnormal synaptic neurotransmitter release by cell-permeable form of the truncated SNAP-25 upon transcutaneous delivery

Abnormal releases of neurotransmitters result in movement disorders such as dystonia, chorea, tics, blepharospasm and wrinkle formation, and intra-muscular injection of Botulinum neurotoxin is widely used for the treatment of these complications. But it is potentially poisonous and must be intra-muscularly injected with precision by a well-trained physician. For novel therapeutic development with high safety profile and easy skin penetration for these complications, we generated Trans-X, a cell permeable form of the truncated SNAP-25 that is one of the SNARE complex for vesicle exocytosis of neuron. Upon topical administration, Trans-X efficiently penetrated through skin, reached the dermis layer and remained stable. Trans-X, which did not show any ocular or skin allergic sensitivity, can block the pre-synaptic neurotransmitter transport via acting as a competitive inhibitor of SNARE complex formation, and effectively induced muscle paralysis comparable to BOTOX(®) evaluated by measuring compound muscle action potential. Topical treatment of the facial skin with Trans-X in clinical study can prevent the wrinkle formation and improve the skin roughness. Therefore, our study suggests that Trans-X may be a convenient and effective medical and cosmetic treatment for local management of movement disorder without systemic toxicity.

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.

Pharmacological and other interventions for head and neck cancer pain: a systematic review

Objectives

Pain is a common complication in head and neck cancer. The aim of this paper is to evaluate the evidence from randomised control trials investigating pharmacological and non-pharmacological methods of pain management in head and neck cancer.

Material and Methods

Medline, Embase and the Cochrane library databases were searched. Squamous cell carcinomas of the head and neck excluding nasopharyngeal and salivary gland cancers were included. The limits were "human" and "randomised clinical trials". A quality assessment was carried out.

Results

13 studies were included with a total of 644 participants. The primary outcome for most of these papers was pain control post-treatment. Levels of bias varied between the studies. Majority (12 out of the 13 studies) reported intervention to be superior to the control or standard therapy in pain management. Only 46% of the studies were carried out on an intention to treat basis. Two studies reported high dropout rates, with one at 66%.

Conclusions

There is insufficient evidence from randomised clinical trials to suggest an optimal pharmacological intervention for head and neck cancer pain post-treatment. Further high quality randomised clinical trials should be conducted to develop an optimal management strategy for head and neck cancer pain.

Antinociceptive effects of A1 and A2 type botulinum toxins on carrageenan-induced hyperalgesia in rat

We performed a study on the antinociceptive effects of A1 and A2 type (A1LL and A2NTX, respectively) botulinum toxin on carrageenan-induced hyperalgesia in the rat. Both A1LL and A2NTX had antinociceptive effects in the carrageenan-induced inflammatory pain model, reducing the mechanical and thermal hyperalgesia. A2NTX also reduced the increase in c-fos immunoreactivity in L4-L5 spinal segments induced by carrageenan, suggesting that A2NTX inhibits the activation of spinal nociceptive afferent fibers that project to the CNS. Our results indicate that A2NTX may offer a new therapeutic tool to treat inflammatory pain.

A phase II, open-label, non-comparative study of Botulinum toxin in Restless Legs Syndrome

OBJECTIVE

To assess the efficacy of intradermally injected botulinum neurotoxin type A (BoNT/A) in patients with Restless Legs Syndrome (RLS).

METHODS

We conducted an optimal two-stage, phase II exploratory, open label, non-comparative clinical trial. The primary outcome measure was the efficacy of BoNT/A defined by the proportion of patients (responders) with ⩾50% improvement of their RLS severity score at week 2 following injections compared to baseline score at inclusion. Twenty-seven patients were to be included in the first stage of the trial, which was to be stopped if less than nine responders were documented. Selected patients had a minimum score of 21 on the International RLS Rating Scale. They all received a series of 20 intradermal injections of 0.05 ml of BoNT/A in symptomatic areas in their lower limbs. Change of RLS severity was evaluated over a 6 months period.

RESULTS

Of the 27 selected patients, only six achieved the primary endpoint at week 2. In these six patients, the median duration (Inter-Quartile Range) of the IRLSRS score improvement of at least 50% was 46 days (42-126).

CONCLUSIONS

Considering the proportion of responders as the primary endpoint of this trial, BoNT/A showed no efficacy in alleviating RLS sensory symptoms.

Accurate targeting of botulinum toxin injections: how to and why

Botulinum toxin (BTX), the exotoxin of the obligate anaerobe, Clostridium botulinum, is used to ameliorate pain and treat conditions associated with glandular, smooth and skeletal muscle overactivity. The benefits derived from the injection of BTX may be negated by unintended weakness of uninjected muscles. Performance of BTX injections may be facile, requiring only surface marking or clinical-localisation techniques but may be more technically demanding, necessitating the use of equipment, such as electromyography (EMG) or ultrasonography (U/S). Less often, endoscopic, fluoroscopic or computed tomographic (CT) guidance may be required. Despite evidence to support the efficacy of BTX injections in treating many conditions, there is no evidence to support the superiority of any one injection technique over needle localisation using surface anatomy. This is possibly due to the lack of well-designed controlled studies, that is, current studies are hampered by small patient numbers, lack of consistency of injection technique and the application of different rating scales. Intuitively, certain injection techniques are more suited to injection of specific muscles or conditions, for example, U/S or passive-monitoring EMG should be used to treat cervical dystonia, active-monitoring EMG applied for strabismus injections, whereas either active-monitoring EMG or endoscopy is indicated when giving BTX for spasmodic dysphonia. Finally, electrical-stimulation EMG or U/S (or a combination of both) would be most suitable when injecting the forearm muscles for spasticity or writer's cramps.

Botulinum injection for the management of myofascial pain in the masticatory muscles. A prospective outcome study

We prospectively analysed the outcome after botulinum injection in patients who did not recover after conservative measures to manage masticatory myofascial pain, and who were not willing to take low dose tricyclic antidepressants as a muscle relaxant. We prospectively 62 patients were assessed with visual analogue scores (VAS) for pain on the affected side before, and 6 weeks after botulinum injection(s) (50 units Dysport in up to 3 sites), and measured mouth opening in mm. Of those treated 49 (79%) showed at least some improvement (pain reduced by more than 25%). Patients reported more than a 90% reduction in the VAS for 25 (30%) of the 84 sides of the face treated. Only 22 of the 62 patients had more than one course of treatment to the same side. Interincisal distance improved by a mean/median of 0.9 mm (p<0.03) after treatment. Side effects included 3 cases of temporary weakness of a facial muscle. Ranking the VAS pain scores using the Wilcoxon test before and after injection showed a significant reduction in pain (median change -29.5, interquartile range -53 to -16, p<0.0001). The treatment significantly improved patients' pain scores and the overall mean/median reduction in pain was 57%. Botulinum injection does not guarantee complete resolution of myofascial pain, but it usually has some beneficial effect in improving the symptoms, and should be considered as an alternate treatment for masticatory myofascial pain if conservative methods have failed.

OnabotulinumtoxinA for treatment of focal cancer pain after surgery and/or radiation

OBJECTIVE

To report the relief from refractory focal post-radiation and/or postsurgical cancer pain after local treatment with onabotulinumtoxinA.

SETTING AND DESIGN

We studied the effect of onabotulinumtoxinA in seven cancer patients who suffered from severe focal pain (visual analog scale >5) at the site of local surgery or radiotherapy or both. OnabotulinumtoxinA (20-100 units) was injected into the focal pain areas (skin or muscle or both). Five of seven patients were followed beyond 1 year (1.5-5 years) with repeat treatment.

RESULTS

All seven patients reported a significant improvement in pain (mean drop in visual analog scale score of 5.1). They described their response on the patient global assessment as satisfactory (two patients) or very satisfactory (five patients). Six of seven patients found the pain relief associated with significant improvement in quality of life. One patient developed weakness of jaw muscles after bilateral masseter injection that was not observed during second injection (reduced dose). Improvements with treatment persisted with repeat injections during long-term follow-up (five patients).

CONCLUSION

Local treatment with onabotulinumtoxinA can significantly reduce pain and improve quality of life in cancer patients suffering from pain in the area of surgery and radiation and was well tolerated in cancer patients.

Botulinum neurotoxin A enhances the analgesic effects on inflammatory pain and antagonizes tolerance induced by morphine in mice

Over the recent years compelling evidence has accumulated indicating that botulinum neurotoxin serotype A (BoNT/A) results in analgesic effects on neuropathic as well as inflammatory pain, both in humans and in animal models. In the present study, the pharmacological interaction of BoNT/A with morphine in fighting inflammatory pain was investigated in mice using the formalin test. Moreover, the effects of BoNT/A on the tolerance-induced by chronic administration of morphine were tested and the behavioral effects were correlated with immunofluorescence staining of glial fibrillary acidic protein, the specific marker of astrocytes, at the spinal cord level. An ineffective dose of BoNT/A (2 pg/paw) combined with an ineffective dose of morphine (1 mg/kg) exerted a significant analgesic action both during the early and the late phases of formalin test. A single intraplantar injection of BoNT/A (15 pg/paw; i.pl.), administered the day before the beginning of chronic morphine treatment (7 days of s.c. injections of 20 mg/kg), was able to counteract the occurrence of tolerance to morphine. Moreover, BoNT/A reduces the enhancement of the expression of astrocytes induced by inflammatory formalin pain. Side effects of opiates, including the development of tolerance during repeated use, may limit their therapeutic use, the possibility of using BoNT/A for lowering the effective dose of morphine and preventing the development of opioid tolerance would have relevant implications in terms of potential therapeutic perspectives.

Efficacy of intra-articular injection of botulinum toxin type A in refractory hemiplegic shoulder pain

OBJECTIVE

To evaluate the efficacy of intra-articular injection of botulinum toxin type A (BTX-A) in relieving hemiplegic shoulder pain (HSP).

DESIGN

Pilot study with assessments before and after BTX-A intra-articular injection.

SETTING

Hospital rehabilitation department.

PARTICIPANTS

Patients (N=5) with HSP refractory to standard treatments and pain score at rest greater than 7 on a pain visual analog scale (VAS) of 0 to 10cm.

INTERVENTION

Intra-articular BTX-A injection.

MAIN OUTCOME MEASURE

Variation in VAS score at rest and during 90° passive arm abduction 2 and 8 weeks after BTX-A intra-articular injection.

RESULTS

Baseline VAS score was 8.7±1 at rest and 9.8±0.4 during passive arm abduction. It clearly decreased at 2 (1.5±1.1 at rest, P=.001; 3±1.2 during arm abduction, P<.001) and 8 weeks (1.5±1.2 at rest, P=.001; 2.3±1.1 during arm abduction, P<.001) after BTX-A intra-articular injection.

CONCLUSIONS

We found a strong correlation between intra-articular BTX-A injection and pain relief in patients with HSP. This result could provide the rationale for blind randomized controlled trials designed to better evaluate the safety and efficacy of intra-articular BTX-A injection in patients with refractory HSP.

OnabotulinumtoxinA for treatment of chronic migraine: pooled analyses of the 56-week PREEMPT clinical program

OBJECTIVE

To evaluate safety and efficacy of onabotulinumtoxinA (BOTOX(®) ) as headache prophylaxis in adults with chronic migraine.

BACKGROUND

Chronic migraine is a prevalent, disabling, and undertreated neurological disorder. OnabotulinumtoxinA is the only approved prophylactic therapy in this highly disabled patient population.

DESIGN AND METHODS

Two phase III, 24-week, double-blind, parallel-group, placebo-controlled studies, followed by a 32-week, open-label, single-treatment, onabotulinumtoxinA phase, were conducted (January 23, 2006 to August 11, 2008). Qualified subjects were randomized (1:1) to injections of onabotulinumtoxinA (155-195 U) or placebo every 12 weeks for 5 cycles (double-blind: 2, open-label: 3). The pooled primary variable was mean change from baseline in frequency of headache days. Secondary variables included proportion of patients with severe Headache Impact Test-6 score (≥ 60) and mean changes from baseline in frequencies of migraine days, moderate/severe headache days, and migraine episodes; cumulative hours of headache on headache days; and acute headache medication intakes. The primary time point was week 24. Assessments for the open-label phase (all patients treated with onabotulinumtoxinA) compared double-blind treatment groups (onabotulinumtoxinA/onabotulinumtoxinA vs placebo/onabotulinumtoxinA) and are summarized to give a descriptive view of consistent study results, with inferences regarding statistical significance only examined for week 56.

RESULTS

A total of 1384 patients were randomized to onabotulinumtoxinA (n = 688) or placebo (n = 696) in the double-blind phase; 607 (88.2%) onabotulinumtoxinA/onabotulinumtoxinA and 629 (90.4%) placebo/onabotulinumtoxinA patients continued into the open-label phase. OnabotulinumtoxinA/onabotulinumtoxinA treatment statistically significantly reduced headache-day frequency vs placebo/onabotulinumtoxinA in patients with chronic migraine at week 56 (-11.7 onabotulinumtoxinA/onabotulinumtoxinA, -10.8 placebo/onabotulinumtoxinA; P = .019). Statistically significant reductions also favored onabotulinumtoxinA/onabotulinumtoxinA for several secondary efficacy variables at week 56, including frequencies of migraine days (-11.2 onabotulinumtoxinA/onabotulinumtoxinA, -10.3 placebo/onabotulinumtoxinA; P = .018) and moderate/severe headache days (-10.7 onabotulinumtoxinA/onabotulinumtoxinA, -9.9 placebo/onabotulinumtoxinA; P = .027) and cumulative headache hours on headache days (-169.1 onabotulinumtoxinA/onabotulinumtoxinA, -145.7 placebo/onabotulinumtoxinA; P = .018). After the open-label phase (all treated with onabotulinumtoxinA), statistically significant within-group changes from baseline were observed for all efficacy variables. Most patients (72.6%) completed the open-label phase; few discontinued because of adverse events. No new safety or tolerability issues emerged.

CONCLUSIONS

Repeated treatment with ≤ 5 cycles of onabotulinumtoxinA was effective, safe, and well tolerated in adults with chronic migraine.

The role of botulinum toxin in management of pain: an evidence-based review

PURPOSE OF REVIEW

In the present review we discuss the role of botulinum neurotoxins (BoNTs) in the management of different pain conditions, with evidence-based data on the toxins' efficacy on pain and its mechanisms.

RECENT FINDINGS

Experimental in-vitro studies have reported promising results of a novel recombinant chimera of BoNT A and E that inhibits the calcitonin gene-related peptide exocytosis from brainstem sensory neurons. Animal studies in neuropathic pain rat models have reported an analgesic effect of BoNT A given after the neuropathic procedure and a bilateral antinociceptive effect to the unilateral noxious stimuli. There is a growing body of evidence that BoNTs are effective in myofascial pain syndrome, neuropathic pain, and joint pain. The pre-existing evidence that BoNTs are ineffective in migraine or other headache disorders has not yet been challenged. In other pain syndromes, studies published in the last review year have not contributed significantly in either demonstrating or invalidating the research that has so far proved inconclusive.

SUMMARY

The role of BoNTs in management of pain is not yet well established. Larger studies in neuropathic pain, joint pain, and myofascial pain syndrome are needed to fully ascertain the role for BoNT therapy in those areas.

Botulinum neurotoxin for pain management: insights from animal models

The action of botulinum neurotoxins (BoNTs) at the neuromuscular junction has been extensively investigated and knowledge gained in this field laid the foundation for the use of BoNTs in human pathologies characterized by excessive muscle contractions. Although much more is known about the action of BoNTs on the peripheral system, growing evidence has demonstrated several effects also at the central level. Pain conditions, with special regard to neuropathic and intractable pain, are some of the pathological states that have been recently treated with BoNTs with beneficial effects. The knowledge of the action and potentiality of BoNTs utilization against pain, with emphasis for its possible use in modulation and alleviation of chronic pain, still represents an outstanding challenge for experimental research. This review highlights recent findings on the effects of BoNTs in animal pain models.

Targeted secretion inhibitors-innovative protein therapeutics

Botulinum neurotoxins are highly effective therapeutic products. Their therapeutic success results from highly specific and potent inhibition of neurotransmitter release with a duration of action measured in months. These same properties, however, make the botulinum neurotoxins the most potent acute lethal toxins known. Their toxicity and restricted target cell activity severely limits their clinical utility. Understanding the structure-function relationship of the neurotoxins has enabled the development of recombinant proteins selectively incorporating specific aspects of their pharmacology. The resulting proteins are not neurotoxins, but a new class of biopharmaceuticals, Targeted Secretion Inhibitors (TSI), suitable for the treatment of a wide range of diseases where secretion plays a major role. TSI proteins inhibit secretion for a prolonged period following a single application, making them particularly suited to the treatment of chronic diseases. A TSI for the treatment of chronic pain is in clinical development.

Intraarticular botulinum toxin A for refractory painful total knee arthroplasty: a randomized controlled trial

OBJECTIVE

To assess short-term efficacy of single intraarticular botulinum toxin (IA-BoNT/A) injection in patients with chronically painful total knee arthroplasty (TKA) in a randomized, placebo-controlled, triple-blind study.

METHODS

Patients with chronic TKA pain (pain > 6 on 0-10 scale and > 6 months post-TKA) evaluated in and referred from orthopedic surgery clinics were recruited. The primary outcome, proportion of patients with clinically meaningful decrease of at least 2 points on 0-10 visual analog scale (VAS) for pain, was compared between treatment groups at 2 months using comparison of proportions test and for all efficacy timepoints (2, 3, and 4 months) using generalized estimating equations (GEE). Secondary outcomes of global assessment, function, and quality of life were compared using GEE, duration of pain relief by t-test, and adverse events by chi-square test.

RESULTS

In total, 54 patients with 60 painful TKA were randomized, with main analyses restricted to one TKA per patient (49 TKA in 49 patients). Mean age was 67 years, 84% were men, and mean duration of TKA pain was 4.5 years. A significantly greater proportion of patients (71%) in the IA-BoNT/A group compared to IA-placebo (35%) achieved clinically meaningful reduction in VAS pain at 2 months (p = 0.028) and at all efficacy timepoints (p = 0.019). Duration of meaningful pain relief was significantly greater after IA-BoNT/A, 39.6 days (SD 50.4) compared to IA-placebo, 15.7 days (SD 22.6; p = 0.045). Statistically significantly better scores were seen in IA-BoNT/A vs IA-placebo for all efficacy timepoints for the following outcomes: "very much improved" on physician global assessment of change (p = 0.003); Western Ontario McMaster Osteoarthritis Index physical function (p = 0.026), stiffness (p = 0.004), and total scores (p = 0.024); and Short-Form 36 pain subscale score (p = 0.049). Number of total and serious adverse events was similar between groups, with no patients in either group with new objective motor or sensory deficits during followup.

CONCLUSION

In this single-center randomized trial, single IA-BoNT/A injection provided clinically meaningful short-term improvements in pain, global assessment, and function in patients with chronic painful TKA. A multicenter trial is needed to confirm these findings.

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.