Botulinum neurotoxin A: a review

Efficacy and Safety Analysis of Botox Application and Iatrogenic Botulism: Panacea or Peril?

Clostridium botulinum toxin-A (BoNT-A) creates temporary paralysis in the muscles by acting on the muscle-nerve junction. It is injected into the mimic muscles when a decrease in the movements of the mimic muscles is desired. Despite many favorable applications, the use of BoNT-A is not without drawbacks. Although there is no expected serious side effect on health in BoNT-A treatments, various problems can be encountered in patients treated for aesthetic purposes. Botulism is a rare but potentially life-threatening syndrome, which is caused by the toxin produced by the bacterium Clostridium botulinum, which acts on the nervous system, vegetative forms of C. botulinum can only survive in anaerobic conditions, while spore forms are common in nature and can withstand harsh conditions. Botulism can stem from bacterial spores which release toxin in the body; in the form of enteric botulism, and wound botulism. The cases that develop 'iatrogenic botulism' after such procedures are usually those receiving high-dose toxin for therapeutic purposes. The treatment of botulism mainly consists of anti-toxin therapy and, if necessary, intensive care to prevent organ failures, including respiratory support. This article aims to cover all these issues related to botulism and other adverse outcomes related to BoNT-A injection in light of the most recent literature.

Skin Toxicities Associated with Botulin Toxin Injection for Aesthetic Procedures: Data from the European Spontaneous Reporting System

Botulinum toxin is a protein deriving from the bacteria Clostridium botulinum and it is widely used for the treatment of a variety of muscle hyperactivity syndromes and for cosmetic indications. Having a long-lasting effect, Botulinum toxin type A (BTA) is one of the most botulin toxin products used. Even if BTA has shown benefits in reducing the vertical lines between the eyebrows, Adverse Drug Reactions (ADRs) have been experienced as well, of which the most common ones are headache and drooping eyelids. In addition, since other local and systemic risks have been identified, a non-interventional post-authorization safety study (PASS) has been started. The aim of the present study was to report cases of skin toxicity associated with this drug, considering Individual Case Safety Reports (ICSRs) existing on the Eudravigilance website. Among 1464 ICSRs sent to the EV database, 718 ICSRs, including 5154 PTs, reported BTA as a suspected drug associated with cutaneous toxicity. The majority of patients experiencing BTA-induced skin toxicity were female (92.1%) belonging mostly to the age group of 18-64 years. The most serious criteria, when reported, were "Other Medically Important Condition" and "Caused/prolonged hospitalization", although the outcome was mainly reported as "Unknown". The most reported PTs, related to skin disorders, were: "Erythema", "Rash", "Pruritus", "Urticaria", "Swelling face", "Brow ptosis", "Eyelid ptosis", "Injection site pain", and "Angioedema". Considering that in most ICSRs, ADRs related to skin disorders were symptoms of hypersensitivity reactions which in some conditions could be life-threatening, further studies are required to better define the safety profile of BTA used for aesthetic procedures.

Botulinum toxin type A for facial wrinkles

BACKGROUND

Botulinum toxin type A (BontA) is the most frequent treatment for facial wrinkles, but its effectiveness and safety have not previously been assessed in a Cochrane Review.

OBJECTIVES

To assess the effects of all commercially available botulinum toxin type A products for the treatment of any type of facial wrinkles.

SEARCH METHODS

We searched the following databases up to May 2020: the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase, and LILACS. We also searched five trials registers, and checked the reference lists of included studies for further references to relevant randomised controlled trials (RCTs).

SELECTION CRITERIA

We included RCTs with over 50 participants, comparing BontA versus placebo, other types of BontA, or fillers (hyaluronic acid), for treating facial wrinkles in adults.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Primary outcomes were participant assessment of success and major adverse events (AEs) (eyelid ptosis, eyelid sensory disorder, strabismus). Secondary outcomes included physician assessment of success; proportion of participants with at least one AE and duration of treatment effect. We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included 65 RCTs, involving 14,919 randomised participants. Most participants were female, aged 18 to 65 years. All participants were outpatients (private office or day clinic). Study duration was between one week and one year. No studies were assessed as low risk of bias in all domains; the overall risk of bias was unclear for most studies. The most common comparator was placebo (36 studies). An active control was used in 19 studies. There were eight dose-ranging studies of onabotulinumtoxinA, and a small number of studies compared against fillers. Treatment was given in one cycle (54 studies), two cycles (three studies), or three or more cycles (eight studies). The treated regions were glabella (43 studies), crow's feet (seven studies), forehead (two studies), perioral (two studies), full face (one study), or more than two regions (nine studies). Most studies analysed moderate to severe wrinkles; mean duration of treatment was 20 weeks. The following results summarise the main comparisons, based on studies of one treatment cycle for the glabella. AEs were collected over the duration of these studies (over four to 24 weeks). Compared to placebo, onabotulinumtoxinA-20 U probably has a higher success rate when assessed by participants (risk ratio (RR) 19.45, 95% confidence interval (CI) 8.60 to 43.99; 575 participants; 4 studies; moderate-certainty evidence) or physicians (RR 17.10, 95% CI 10.07 to 29.05; 1339 participants; 7 studies; moderate-certainty evidence) at week four. Major AEs are probably higher with onabotulinumtoxinA-20 U (Peto OR 3.62, 95% CI 1.50 to 8.74; 1390 participants; 8 studies; moderate-certainty evidence), but there may be no difference in any AEs (RR 1.14, 95% CI 0.89 to 1.45; 1388 participants; 8 studies; low-certainty evidence). Compared to placebo, abobotulinumtoxinA-50 U has a higher participant-assessed success rate at week four (RR 21.22, 95% CI 7.40 to 60.56; 915 participants; 6 studies; high-certainty evidence); and probably has a higher physician-assessed success rate (RR 14.93, 95% CI 8.09 to 27.55; 1059 participants; 7 studies; moderate-certainty evidence). There are probably more major AEs with abobotulinumtoxinA-50 U (Peto OR 3.36, 95% CI 0.88 to 12.87; 1294 participants; 7 studies; moderate-certainty evidence). Any AE may be more common with abobotulinumtoxinA-50 U (RR 1.25, 95% CI 1.05 to 1.49; 1471 participants; 8 studies; low-certainty evidence). Compared to placebo, incobotulinumtoxinA-20 U probably has a higher participant-assessed success rate at week four (RR 66.57, 95% CI 13.50 to 328.28; 547 participants; 2 studies; moderate-certainty evidence), and physician-assessed success rate (RR 134.62, 95% CI 19.05 to 951.45; 547 participants; 2 studies; moderate-certainty evidence). Major AEs were not observed (547 participants; 2 studies; moderate-certainty evidence). There may be no difference between groups in any AEs (RR 1.17, 95% CI 0.90 to 1.53; 547 participants; 2 studies; low-certainty evidence). AbobotulinumtoxinA-50 U is no different to onabotulinumtoxinA-20 U in participant-assessed success rate (RR 1.00, 95% CI 0.92 to 1.08, 388 participants, 1 study, high-certainty evidence) and physician-assessed success rate (RR 1.01, 95% CI 0.95 to 1.06; 388 participants; 1 study; high-certainty evidence) at week four. Major AEs are probably more likely in the abobotulinumtoxinA-50 U group than the onabotulinumtoxinA-20 U group (Peto OR 2.65, 95% CI 0.77 to 9.09; 433 participants; 1 study; moderate-certainty evidence). There is probably no difference in any AE (RR 1.02, 95% CI 0.67 to 1.54; 492 participants; 2 studies; moderate-certainty evidence). IncobotulinumtoxinA-24 U may be no different to onabotulinumtoxinA-24 U in physician-assessed success rate at week four (RR 1.01, 95% CI 0.96 to 1.05; 381 participants; 1 study; low-certainty evidence) (participant assessment was not measured). One participant reported ptosis with onabotulinumtoxinA, but we are uncertain of the risk of AEs (Peto OR 0.02, 95% CI 0.00 to 1.77; 381 participants; 1 study; very low-certainty evidence). Compared to placebo, daxibotulinumtoxinA-40 U probably has a higher participant-assessed success rate (RR 21.10, 95% CI 11.31 to 39.34; 683 participants; 2 studies; moderate-certainty evidence) and physician-assessed success rate (RR 23.40, 95% CI 12.56 to 43.61; 683 participants; 2 studies; moderate-certainty evidence) at week four. Major AEs were not observed (716 participants; 2 studies; moderate-certainty evidence). There may be an increase in any AE with daxibotulinumtoxinA compared to placebo (RR 2.23, 95% CI 1.46 to 3.40; 716 participants; 2 studies; moderate-certainty evidence). Major AEs reported were mainly ptosis; BontA is also known to carry a risk of strabismus or eyelid sensory disorders.

AUTHORS' CONCLUSIONS

BontA treatment reduces wrinkles within four weeks of treatment, but probably increases risk of ptosis. We found several heterogeneous studies (different types or doses of BontA, number of cycles, and different facial regions) hindering meta-analyses. The certainty of the evidence for effectiveness outcomes was high, low or moderate; for AEs, very low to moderate. Future RCTs should compare the most common BontA (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, daxibotulinumtoxinA, prabotulinumtoxinA) and evaluate long-term outcomes. There is a lack of evidence about the effects of multiple cycles of BontA, frequency of major AEs, duration of effect, efficacy of recently-approved BontA and comparisons with other treatments.

Botulinum toxin in the management of primary and secondary Raynaud's phenomenon

Raynaud's phenomenon (RP) is common in rheumatic diseases. In the setting of systemic sclerosis (SSc), it can be complicated by digital ischemia that includes ulceration and gangrene. Systemic adverse effects may preclude the use of oral or topical vasodilators for the treatment of RP and its complications. In this article, we review effectiveness/efficacy of botulinum toxin injection in primary and secondary RP. We discuss botulinum toxin formulations, dosage, sites of administration, and adverse effects. The evidence for botulinum toxin in the treatment of primary and SSc-associated RP is promising. Consistency across patient populations, treatment options (botulinum serotype, dose, and injection site), and outcome measures will be essential for further research.

Can the Jankovic-assessment be used as an alternative to electromyography? A cross-sectional study on facial dystonia patients treated with Botulinum toxin

PURPOSE

This study aims to quantitatively compare the Jankovic assessment (JA) with electromyography (EMG)-based measures for assessing changes in facial movements in patients with facial dystonia.

MATERIALS AND METHODS

Thirteen patients (five males and eight females) affected with different forms of facial dystonia (hemifacial spasm and synkinesis) participated in this study. All patients were treated with Botulinum Toxin (BTX) and evaluated with the JA scale and EMG-based measures, including motor unit potentials (MUP) latency and presence of polyphasic potentials before and after BTX injection. Correlation between the JA scores and the EMG-based measures was calculated. Statistical analysis was performed with the Pearson test.

RESULTS

Correlation between the JA scores and the EMG-based measures was found to be statistically significant, both before and after treatment with BTX.

CONCLUSION AND RELEVANCE

JA scores significantly correlated with more objective EMG-based measures, suggesting that the JA scale can be used to assess facial movement changes, for example elicited by a treatment such as BTX injection. Thus, in facial dystonia patients, the JA scale may be used for evaluating treatment outcomes as a valid and low-cost alternative to EMG.

The effects of Botulinum toxin on the detection of gradual changes in facial emotion

When we feel sad or depressed, our face invariably “drops”. Conversely, when we try to cheer someone up, we might tell them “keep your smile up”, so presupposing that modifying the configuration of their facial muscles will enhance their mood. A crucial assumption that underpins this hypothesis is that mental states are shaped by information originating from the peripheral neuromotor system — a view operationalised as the Facial Feedback Hypothesis. We used botulinum toxin (BoNT-A) injected over the frown area to temporarily paralyse muscles necessary to express anger. Using a pre-post treatment design, we presented participants with gradually changing videos of a face morphing from neutral to full-blown expressions of either anger or happiness and asked them to press a button as soon as they had detected any change in the display. Results indicate that while all participants (control and BoNT-A) improved their reaction times from pre-test to post-test, the BoNT-A group did not when detecting anger in the post-test. We surmise that frown paralysis disadvantaged participants in their ability to improve the detection of anger. Our finding suggests that facial feedback causally affects perceptual awareness of changes in emotion, as well as people’s ability to use perceptual information to learn.

Vibration Versus Ice to Reduce Cosmetic Botulinum Toxin Injection Pain-A Randomized Controlled Trial

Botulinum toxin is the most commonly performed facial cosmetic procedure and pain at the injection site is a frequent patient concern. While various topical interventions have been described for analgesia, there have not been any studies comparing different techniques. We compared the use of a vibratory stimulus, ice pack application, and no intervention on injection site pain for cosmetic botulinum toxin injection. A prospective-, randomized-, individual-controlled study was conducted using a visual analog scale to assess pain. Patients received bilateral glabellar injections, with randomization into unilateral vibration, unilateral ice application, or vibration and ice on either side. We analyzed 88 injections on 22 patients. Mean visual analog scores were 26.5 (standard deviation [SD]: 23.1) among injections with vibration, 24.4 (SD: 22.9) with ice, and 29.4 (SD: 27.1) without analgesia. There was no significant difference in pain scale scores with the use of vibration, ice, or no topical anesthesia (P = .737). Further, pain scale scores did not differ significantly between medial and lateral injections nor did patients have a reduction in pain on either side of the forehead regardless of which method was used. While there may be a role for topical interventions to improve injection site analgesia, we maintain that consistently proper technique plays a greater role in improving patient tolerance. Future studies will continue to investigate the role of topical anesthesia in cosmetic facial injections and address patient-specific factors contributing to discomfort.

Use of a botulinum toxin A in dentistry and oral and maxillofacial surgery

Botulinum toxin (BT) was the first toxin to be used in the history of human medicine. Among the eight known serotypes of this toxin, those currently used in medicine are types A and B. This review article mainly discusses BT type A (BTA) because it is usually used in dentistry including dental anesthesiology and oral and maxillofacial surgery. BTA has been used mainly in the treatment of temporomandibular joint disorder (TMD) and hypertrophy and hyperactivity of the masticatory muscles, along with being a therapeutic option to relieve pain and help in functional recovery from dental and oral and maxillofacial surgery. However, it is currently used broadly for cosmetic purposes such as reducing facial wrinkles and asymmetry. Although the therapeutic effect of BTA is temporary and relatively safe, it is essential to have knowledge about related anatomy, as well as the systemic and local adverse effects of medications that are applied to the face.

Botulinum Toxin A: Dose-dependent Effect on Reepithelialization and Angiogenesis

Background:

Botulinum (neuro)toxin A (BoNT) is widely used in the field of plastic and reconstructive surgery. Among treatment of pain, hyperhidrosis, or aesthetic purposes, it is also used to enhance wound healing and prevent excessive scar formation. Some clinical data already exist, but only little is known on a cellular level. The aim of this study was to evaluate the effect of BoNT on cells essential for wound healing in vitro. Therefore, primary human keratinocytes and endothelial cells were treated with different concentrations of BoNT and tested on proliferation, migration, and angiogenic behavior.

Methods:

BoNT was exposed to human keratinocytes and endothelial cells in a low (1 IU/mL), medium (10 IU/mL), and high (20 IU/mL) concentrations in cell culture. Proliferation and migration of the 2 cell types were observed and also the angiogenic potential of endothelial cells in vitro.

Results:

BoNT 20 IU/mL negatively influenced proliferation and migration of keratinocytes but not those of endothelial cells. Angiogenesis in vitro was less effective with the highest BoNT concentrations tested. Low concentrations of BoNT supported sprouting of endothelial cells.

Conclusions:

High concentrations of botulinum toxin interfered with wound closure as keratinocytes’ proliferation and migration were deteriorated. Furthermore, BoNT concentrations of 20 IU/mL constrain in vitro vessel formation but do not influence proliferation or migration of endothelial cells.

Cross-specialty developments: a summary of the mutually relevant recent literature from the journal of plastic, reconstructive and aesthetic surgery

Keeping abreast of current developments is increasingly challenging when the volume of specialty articles being published is rising exponentially, and it is most acute when surgical specialties overlap, as in the case of head, neck, and facial reconstructive surgery. Here, the potential for missing key developments presents a compelling case for a summary article that highlights articles likely to be of mutual relevance. We evaluated 129 original studies and 6 reviews published in the Journal of Plastic, Reconstructive, and Aesthetic Surgery between September 2012 and August 2014, and summarised the main papers of interest and merit under the subheadings of head and neck reconstruction, cleft lip and palate, craniomaxillofacial surgery, facial palsy, facial trauma, and aesthetic surgery. Most of the evidence presented (86%) is level 4.

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.

Differential response of pig masseter to botulinum neurotoxin serotypes a and b

INTRODUCTION

Pigs respond to direct administration of botulinum neurotoxins (BoNTs), although they are resistant to botulism. The human masseter is frequently targeted for BoNT therapy. We aimed to understand how BoNT affects chewing by injecting porcine masseters.

METHODS

One masseter of minipigs was injected with BoNT serotype A or B at doses comparable to those used in humans. Masticatory function was evaluated electromyographically. Muscle force was measured during tetany. Four weeks after injection, strain gauges affixed to the mandible assessed bone strain during chewing. Masseter mass and fiber diameter were measured after euthanasia.

RESULTS

BoNT-A had no measurable effect. In contrast, BoNT-B reduced electrical activity and muscle force, producing substantial asymmetry between injected and uninjected muscles.

CONCLUSIONS

The pig masseter is highly resistant to direct injection of BoNT-A, but it is affected by BoNT-B.

Abnormal vocal cord movement treated with botulinum toxin in patients with asthma resistant to optimised management

BACKGROUND AND OBJECTIVE

Abnormal vocal cord movement may coexist with asthma and cause additional upper/middle airway obstruction. The condition may be a form of muscular dystonia that could contribute to asthma resistant to optimised treatments. Botulinum toxin causes temporary paralysis of muscle and may be an effective local treatment that improves asthma control.

METHODS

In an observational study, we evaluated the benefits of unilateral vocal cord injection with botulinum toxin in 11 patients (total 24 injections). Subjects had asthma resistant to optimised treatment and abnormal vocal cord movement. Responses after botulinum toxin treatment were assessed using asthma control test (ACT) scores, vocal cord narrowing quantified by computerised tomography (CT) of the larynx and spirometry. Side-effects were recorded.

RESULTS

ACT scores improved overall (9.1 ± 2.4 before and 13.5 ± 4.5 after treatment; difference 4.4 ± 4.2; P < 0.001). There was also an improvement in airway size on CT larynx (time below lower limit of normal at baseline 39.4 ± 37.63% and improved to 17.6 ± 25.6% after injection; P = 0.032). Spirometry was not altered. One patient experienced an asthma exacerbation but overall side-effects were moderate, chiefly dysphonia and dysphagia.

CONCLUSIONS

Although a placebo effect cannot be ruled out, local injection of botulinum toxin may be an effective treatment for intractable asthma associated with abnormal vocal cord movement. Further mechanistic studies and a double-blind randomised controlled trial of botulinum toxin treatment are merited.