Diffusion, spread, and migration of botulinum toxin

Sonoanatomy of injecting botulinum neurotoxin into the facial muscles

INTRODUCTION

Ultrasonography (US) has become an essential tool for guiding botulinum neurotoxin (BoNT) injections in facial muscles, enhancing precision and safety. This narrative review explores the role of US in BoNT administration, particularly in complex anatomical regions, highlighting its impact on treatment customization, real-time visualization, and complication reduction.

MATERIALS AND METHODS

A comprehensive literature search was conducted using PubMed, MEDLINE, Embase, and Cochrane Library for articles published from January 2018 to December 2023. Search terms included "Botulinum neurotoxin," "facial anatomy," "ultrasonography guided injection," and "facial muscle sonoanatomy." Studies focusing on US-guided BoNT injections in facial muscles were included. Data extraction and synthesis were performed independently by two reviewers, focusing on study design, ultrasonography techniques, outcomes, and conclusions.

RESULTS

The review found that US guidance significantly enhances the precision of BoNT injections by providing real-time visualization of facial muscles and blood vessels, thereby reducing the risk of adverse events. US enables tailored injection strategies, ensuring symmetrical facial expressions and minimizing over-treatment. The technique also offers immediate feedback, allowing for on-the-spot adjustments to improve treatment efficacy and safety. However, the review identified limitations, including potential selection bias and variability in US techniques across different studies.

CONCLUSION

US guidance for BoNT injections into facial muscles offers substantial benefits in terms of precision, safety, and treatment customization. Despite the identified limitations, the integration of US into clinical practice is poised to enhance patient outcomes in aesthetic and therapeutic procedures. Further research is needed to standardize US techniques and broaden the inclusivity of studies to validate these findings comprehensively.

Ultrasound-Guided Botulinum Neurotoxin Injection for Alleviating Cricopharyngeus Muscle Spasticity: A Cadaveric Feasibility Study with Nerve Ending Analysis

Botulinum neurotoxin (BNT) injection into the cricopharyngeus muscle (CPM) under ultrasound (US) guidance is a minimally invasive technique performed to relieve cricopharyngeal dysphagia by reducing CPM spasticity. This technique is basically accessible only to both lateral sides of the CPM. This cadaveric study aimed to evaluate whether US-guided injection could effectively deliver BNT to abundant areas of gross nerve endings within the CPM. We utilized a newly modified Sihler's staining method to identify regions with abundant neural endings within the CPM while preserving the three-dimensional morphology of the muscle in 10 sides of 5 fresh cadavers. A mixture of 0.2 mL dye was injected into the 16 sides of CPM under US guidance in 8 cadavers. Nerve endings were abundant in posterolateral areas of the CPM; the injected dye was identified at the posterolateral area on 12 sides (12/16 side, 75%) without diffusion into the posterior cricoarytenoid muscle. The injection failed on four sides (two sides of the prevertebral fascia and two sides of the esophagus below the CPM). These results suggest that US-guided injection could be a feasible technique as it can deliver BNT to the most abundant nerve distribution areas within the CPM in most cases.

Understanding Clinical Effectiveness and Safety Implications of Botulinum Toxin in Children: A Narrative Review of the Literature

Since its first approval by the Food and Drug Administration in 1989 for strabismus, botulinum toxin indications of use have been widely expanded. Due to its anticholinergic properties, this toxin is currently approved in adult patients for the treatment of a wide range of neuromuscular, otolaryngologic, orthopedic, gastrointestinal, and urologic disorders. Approved pediatric indications of use include the treatment of blepharospasm associated with dystonia, strabismus, lower-limb spasticity, focal spasticity in patients with cerebral palsy, and neurogenic detrusor overactivity. Alongside these approved indications, botulinum toxin is extensively used off-label. Although several clinical studies have shown that botulinum toxin is effective and well-tolerated in children, uncertainties persist regarding its long-term effects on growth and appropriate dosing in this population. As such, further research is needed to better define the botulinum toxin risk-benefit profile and expand approved uses in pediatrics. This narrative review aimed to provide a broad overview of the evidence concerning the clinical effectiveness and safety of BoNT with respect to its principal authorized and non-authorized pediatric therapeutic indications, as well as to describe perspectives on its future use in children.

Use of botulinum toxin type A in the prehabilitation of abdominal wall musculature for hernia repair: a consensus proposal

The prehabilitation of the abdominal wall through the infiltration of botulinum toxin type A, which induces temporary chemical denervation ("chemical component separation") in the lateral abdominal musculature, is a common practice in units specialized in abdominal wall surgery. However, its use for this indication is currently off-label. The main objective of this article is to describe a consensus proposal regarding indications, contraindications, dosages employed, potential side effects, administration method, and measurement of possible outcomes. Additionally, a proposal for an informed consent document endorsed by the Abdominal Wall Section of the Spanish Association of Surgeons is attached.

Self-Administered Botulinum Injection Causing Rare Masquerade of Systemic Botulism

This report describes the case of a patient who presented to the Emergency Department (ED) with a one-week history of difficulty in breathing, generalized weakness, dysphagia, and difficulty in walking. She had self-administered 100 units of onabotulinumtoxin A (BoNT-A) by injection into her face two weeks prior for cosmetic purposes. This case study highlights the rare but potential complication of systemic botulism.

Update on Non-Interchangeability of Botulinum Neurotoxin Products

The growing use of botulinum neurotoxins (BoNTs) for medical and aesthetic purposes has led to the development and marketing of an increasing number of BoNT products. Given that BoNTs are biological medications, their characteristics are heavily influenced by their manufacturing methods, leading to unique products with distinct clinical characteristics. The manufacturing and formulation processes for each BoNT are proprietary, including the potency determination of reference standards and other features of the assays used to measure unit potency. As a result of these differences, units of BoNT products are not interchangeable or convertible using dose ratios. The intrinsic, product-level differences among BoNTs are compounded by differences in the injected tissues, which are innervated by different nerve fiber types (e.g., motor, sensory, and/or autonomic nerves) and require unique dosing and injection sites that are particularly evident when treating complex therapeutic and aesthetic conditions. It is also difficult to compare across studies due to inherent differences in patient populations and trial methods, necessitating attention to study details underlying each outcome reported. Ultimately, each BoNT possesses a unique clinical profile for which unit doses and injection paradigms must be determined individually for each indication. This practice will help minimize unexpected adverse events and maximize efficacy, duration, and patient satisfaction. With this approach, BoNT is poised to continue as a unique tool for achieving individual goals for an increasing number of medical and aesthetic indications.

Evaluation of Regio Temporalis in 3 Steps in Terms of Interventional Procedures

Regio temporalis is a site where botulinum neurotoxin is applied for various medical reasons, such as migraine, bruxism, and myofascial pain syndrome. The region is also one of the target regions in flap surgery. This study aimed to define the region topographically. In addition, it was aimed to reveal the intramuscular nerve distribution of the temporalis.11 fixed cephalus (cadaver head) and 2 fresh cephalus were used. The lateral canthus of the eye was marked as point A, and the middle of the ear tragus as point B. The transverse and vertical distances of the branching point of the superficial temporal artery to the A and B points were measured. Transverse distances of the superficial temporal artery and superficial temporal vein to A and B points were measured. The muscle was examined in 5 equal parts (L0-L1-L2-L3-L4), and each part's vertical muscle and tendon lengths were examined. Intramuscular nerve density was demonstrated by applying the modified Sihler staining to fresh temporalis'. Superficial temporal artery had an average transverse distance of 8.56±1.9 mm in women and 12.56±1.94 mm in men from the middle of the ear tragus. The artery was 64.21±5.59 mm posterior in females and 63.48±6.53 mm in males from the lateral canthus of the eye. Our study determined that the branching point of the superficial temporal artery was below the upper level of the arcus zygomaticus in 10% of cases and above it in 90% of cases. In our study, the L2 point had the highest vertical muscle length at 45.67 mm, while the L3 point had the highest vertical tendon length at 41.25 mm. The point where the muscle length had the highest ratio with 1.49 compared to the tendon length, was the L2 point. The temporalis' for which the modified Sihler staining was applied was examined in 5 quadrants. It was determined that the nerve densities were in the second and third quadrants from anterior to posterior. The distance of superficial landmarks to neurovascular structures is extremely important in interventions to the regio temporalis. Considering the average distances given in our study is important in avoiding damage in surgical procedures and not injecting into vascular structures. The point where the muscle length had the highest ratio of 1.49 compared to the tendon length was the L2 point. The area in line with this point is the most suitable area for injection. The L2 point is also the most suitable area for injection as it has the highest muscle length. Since the nerve densities were observed in the modified Sihler staining applied temporalis' 2 and 3 quadrants from anterior to posterior, botulinum neurotoxin injections to these areas will give more effective results.

Intramuscular Botulinum Neurotoxin Serotypes E and A Elicit Distinct Effects on SNAP25 Protein Fragments, Muscular Histology, Spread and Neuronal Transport: An Integrated Histology-Based Study in the Rat

Botulinum neurotoxins E (BoNT/E) and A (BoNT/A) act by cleaving Synaptosome-Associated Protein 25 (SNAP25) at two different C-terminal sites, but they display very distinct durations of action, BoNT/E being short acting and BoNT/A long acting. We investigated the duration of action, spread and neuronal transport of BoNT/E (6.5 ng/kg) and BoNT/A (125 pg/kg) after single intramuscular administrations of high equivalent efficacious doses, in rats, over a 30- or 75-day periods, respectively. To achieve this, we used (i) digit abduction score assay, (ii) immunohistochemistry for SNAP25 (N-ter part; SNAP25N-ter and C-ter part; SNAP25C-ter) and its cleavage sites (cleaved SNAP25; c-SNAP25E and c-SNAP25A) and (iii) muscular changes in histopathology evaluation. Combined in vivo observation and immunohistochemistry analysis revealed that, compared to BoNT/A, BoNT/E induces minimal muscular changes, possesses a lower duration of action, a reduced ability to spread and a decreased capacity to be transported to the lumbar spinal cord. Interestingly, SNAP25C-ter completely disappeared for both toxins during the peak of efficacy, suggesting that the persistence of toxin effects is driven by the persistence of proteases in tissues. These data unveil some new molecular mechanisms of action of the short-acting BoNT/E and long-acting BoNT/A, and reinforce their overall safety profiles.

Efficacy and Safety of DaxibotulinumtoxinA for Injection in Cervical Dystonia: ASPEN-1 Phase 3 Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

ASPEN-1 was a phase 3, randomized, double-blind, placebo-controlled study to evaluate the efficacy, duration of response, and safety of 2 doses of DaxibotulinumtoxinA for Injection (DAXI), a novel botulinum toxin type A formulation in participants with cervical dystonia (CD).

METHODS

Adults (aged 18-80 years) with moderate-to-severe CD (Toronto Western Spasmodic Torticollis Rating Scale [TWSTRS] total score ≥20) were enrolled at 60 sites across 9 countries in Europe and North America. Participants were randomized (3:3:1) to single-dose intramuscular DAXI 125U, 250U, or placebo and followed for up to 36 weeks after injection. The primary end point was change from baseline in TWSTRS total score averaged across weeks 4 and 6. Key secondary end points included duration of effect, Clinical and Patient Global Impression of Change (CGIC, PGIC), TWSTRS subscale scores, and safety. Multiplicity-adjusted intent-to-treat hypothesis tests with multiple imputation were performed using ANCOVA and Cochran-Mantel-Haenszel analyses.

RESULTS

Of 444 individuals screened, 301 were randomized to DAXI 125U (n = 125) or 250U (n = 130) or placebo (n = 46). DAXI 125U and 250U significantly improved the mean TWSTRS total score vs placebo (least squares mean [standard error] difference vs placebo: DAXI 125U, -8.5 [1.93], p < 0.0001; DAXI 250U, -6.6 [1.92], p = 0.0006). The median duration of effect (time from treatment until loss of ≥80% of the peak improvement in average TWSTRS total score achieved at weeks 4 and 6) was 24.0 (95% confidence interval 20.3-29.1) weeks with DAXI 125U and 20.3 (16.7-24.0) weeks with DAXI 250U. Significant improvements were also observed with DAXI in CGIC and PGIC responder rates and TWSTRS subscales. Treatment-related treatment-emergent adverse events (TEAEs) were reported by 29.6% of participants with DAXI 125U, 23.8% with DAXI 250U, and 17.4% with placebo, with injection site pain being the most common overall. The most frequently reported treatment-related TEAEs of interest in DAXI 125U, DAXI 250U, and placebo, respectively, were muscular weakness (4.8%, 2.3%, 0%), musculoskeletal pain (2.4%, 3.1%, 0%), and dysphagia (1.6%, 3.8%, 0%).

DISCUSSION

This study demonstrated that DAXI, at doses of 125U and 250U, is an effective, safe, long-acting, and well-tolerated treatment for CD.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov identifier (NCT03608397, submitted July 11, 2018) and EU Clinical Trials Register (ClinicalTrialsRegister.eu EudraCT identifier 2018-000446-19, submitted September 13, 2018). First participant enrolled on June 11, 2018. Trial registration was performed in accordance with the Food and Drug Administration Amendments Act (FDAAA 801), which stipulates that the responsible party register an applicable clinical trial not later than 21 calendar days after enrolling the first human participant (42 CFR 11.24).

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that in adults with moderate-to-severe idiopathic cervical dystonia, DAXI reduces dystonia more effectively than placebo.

Anatomical Proposal for Botulinum Neurotoxin Injection for Horizontal Forehead Lines

SUMMARY

The frontalis muscle is situated across the forehead and is a representative target muscle for botulinum neurotoxin (BoNT) injections aimed at treating horizontal wrinkles in this region. However, a lack of anatomical information regarding the shape and thickness of the frontalis may lead to unexpected adverse effects, such as ptosis and samurai eyebrows, caused by the lack of detail on anatomical variation. Achieving the maximum effect using the minimal amount of BoNT requires a precise injection into the frontalis muscle. The anatomical factors associated with BoNT injection into the frontalis muscle have been reviewed in the current study. Up-to-date understanding of the localization of the BoNT injection point according to an updated understanding of the anatomy leads to more accurate localization of the injection point into the frontalis muscle. Optimal injection sites have been provided for the frontalis muscle, and the injection method has been recommended. The authors suggest optimal injection sites according to the external anatomical landmarks of the forehead. Furthermore, these proposals could aid in a more precise procedure that avoids the deleterious effects of BoNT.

A practical guide to botulinum neurotoxin treatment of teres major muscle in shoulder spasticity: Intramuscular neural distribution of teres major muscle in cadaver model

BACKGROUND

Botulinum neurotoxin treatment typically focuses on the teres major muscle as a primary target for addressing shoulder spasticity. The muscle is located deep within a large muscle group and optimal injection locations have not been identified.

OBJECTIVE

To identify the preferred location for administering botulinum toxin injections in the teres major muscle.

METHODS

Teres major specimens were removed from 18 cadaveric models and stained with Sihler's method to reveal the neural distribution within the muscle. The muscles were systematically divided into equal lengths from origin to insertion. The neural density in each section was evaluated to determine the location that would be likely to increase effectiveness of the injection.

RESULTS

The greatest density of intramuscular nerve endings was located in the middle 20% of the muscle. The tendinous portion was observed at the ends of the muscle.

CONCLUSIONS

The results suggest that botulinum neurotoxin should be delivered in the middle 20% of the teres major muscle.

Beyond neuromuscular activity: botulinum toxin type A exerts direct central action on spinal control of movement

Overt muscle activity and impaired spinal locomotor control hampering coordinated movement is a hallmark of spasticity and movement disorders like dystonia. While botulinum toxin A (BoNT-A) standard therapy alleviates mentioned symptoms presumably due to its peripheral neuromuscular actions alone, the aim of present study was to examine for the first time the toxin's trans-synaptic activity within central circuits that govern the skilled movement. The rat hindlimb motor pools were targeted by BoNT-A intrasciatic bilateral injection (2 U per nerve), while its trans-synaptic action on premotor inputs was blocked by intrathecal BoNT-A-neutralising antitoxin (5 i.u.). Effects of BoNT-A on coordinated and high intensity motor tasks (rotarod, beamwalk swimming), and localised muscle weakness (digit abduction, gait ability) were followed until their substantial recovery by day 56 post BoNT-A. Later, (day 62-77) the BoNT-A effects were examined in unilateral calf muscle spasm evoked by tetanus toxin (TeNT, 1.5 ng). In comparison to peripheral effect alone, combined peripheral and central trans-synaptic BoNT-A action induced a more prominent and longer impairment of different motor tasks, as well as the localised muscle weakness. After near-complete recovery of motor functions, the BoNT-A maintained the ability to reduce the experimental calf spasm evoked by tetanus toxin (TeNT 1.5 ng, day 62) without altering the monosynaptic reflex excitability. These results indicate that, in addition to muscle terminals, BoNT-A-mediated control of hyperactive muscle activity in movement disorders and spasticity may involve the spinal premotor inputs and central circuits participating in the skilled locomotor performance.

Safety of botulinum toxin injections in children less than one year old: A retrospective chart review

PURPOSE

Infants can have muscle hypertonia due to cerebral palsy, muscle strength imbalances due to brachial plexus palsy, refractory clubfoot, and torticollis. These muscle problems can cause significant development impairments. A child with severe sialorrhea and dysphagia from leukodystrophy can aspirate, causing respiratory problems. Botulinum toxin (BoNT) injections can improve these conditions but may lead to adverse effects from the toxin spreading to non-targeted muscles, potentially impacting breathing, swallowing, and overall strength. This is particularly concerning in infants. This study assessed the safety of BoNT injections in children less than one year of age.

METHODS

This was a retrospective cohort study.

RESULTS

Forty-seven patients (22 male, 25 female) received BoNT injections before one year of age (three to 12 months). Thirty-seven received one round of injections and 10 were injected on multiple occasions. Forty-five received onabotulinumtoxinA (15-100 units [U], 1.9-15.2 U/kg), one received abobotulinumtoxinA (70 U, 9.0 U/kg), and one received incobotulinumtoxinA (25 U, 3.5 U/kg). Lower extremities were treated in 15 patients, upper extremities in 38, the sternocleidomastoid in two, and the salivary glands in one. Forty-five patients had no reported complications. One experienced transient fever, vomiting, and diarrhea. The parent of another reported subjective weakness in one muscle.

CONCLUSION

BoNT injections in children less than one year of age appear to be safe.

Basis of movement control in dystonia and why botulinum toxin should influence it?

Dystonia is a network disorder involving multiple brain regions, such as the motor cortex, sensory cortex, basal ganglia, and cerebellum. Botulinum toxin (BoNT) is the first-line therapy for treating focal dystonia and is a potent molecule that blocks the release of acetylcholine at the peripheral neuromuscular junction. However, the clinical benefits of BoNT are not solely related to peripheral muscle relaxation or modulation of afferent input from the muscle spindle. An increasing body of evidence, albeit in smaller cohorts, has shown that BoNT leads to distant modulation of the pathological brain substrates implicated in dystonia. A single treatment session of BoNT has been observed to reduce excessive motor excitability and improve sensory processing. Furthermore, owing to plasticity effects that are induced by botulinum, neural reorganization of pathological networks occurs, presumably leading to defective motor programs of dystonia replaced with normal movement patterns. However, longitudinal studies investigating the effects of multiple treatment sessions in large, well-characterized homogenous cohorts of dystonia will provide further compelling evidence supporting central botulinum mechanisms.

The significance of split-face studies and electromyography in forehead rejuvenation

BACKGROUND

Botulinum toxin is a neurotoxic substance with a wide range of uses, from the treatment of musculoskeletal spasms to antiaging regimens by improving wrinkles. Split-face studies in which drugs are injected in the right and left sides of the faces have been actively conducted in botulinum toxin studies. In this study, we aimed to investigate the reliability of a split-face study for determining the effectiveness of botulinum toxin based on eyebrow height and movement, and electromyography results.

METHODS

Thirty-one women aged 35 to 55 years were included in the study. Eyebrow height was measured as the distance from the eyebrows to the upper eyelid margin on the primary gaze, and eyebrow movement was measured as the distance when the forehead was wrinkled for 5 seconds. A noninvasive method was used for electromyography of the frontalis muscles.

RESULTS

No statistically significant differences in right and left eyebrow heights and movements, and electromyography findings (p= 0.256, p= 1.000, and p= 0.978, respectively) were found. Pearson correlation analysis showed that electromyography muscle activity is positively associated with eyebrow movement, respectively (p< 0.001).

CONCLUSION

We advocate the reliability of split-face study and the usefulness of electromyography of frontalis muscle in forehead rejuvenation research.

Comparison of Oropharyngeal Dysphagia Before and After Botulinum Toxin Injection in Cervical Dystonia

Cervical dystonia (CD) is the most common form of focal dystonia with Botulinum neurotoxin (BoNT) being a frequent method of treatment. Dysphagia is a common side effect of BoNT treatment for CD. Instrumental evaluation of swallowing in CD using standardized scoring for the videofluoroscopic swallowing study (VFSS) and validated and reliable patient-reported outcomes measures is lacking in the literature. (1) to determine if BoNT injections change instrumental findings of swallowing function using the Modified Barium Swallow Impairment Profile (MBSImP) in individuals with CD; (2) to determine if BoNT injections change self-perception of the psychosocial handicapping effects of dysphagia in individuals with CD, using the Dysphagia Handicap Index (DHI); (3) to determine the effect of BoNT dosage on instrumental swallowing evaluation and self-reported swallowing outcomes measures. 18 subjects with CD completed a VFSS and the DHI before and after BoNT injection. There was a significant increase in pharyngeal residue for pudding consistency after BoNT injection, p = 0.015. There were significant positive associations between BoNT dosage and self-perception of the physical attributes of the handicapping effect of dysphagia, the grand total score and patient self-reported severity of dysphagia on the DHI; p = 0.022; p = 0.037; p = 0.035 respectively. There were several significant associations between changes in MBSImP scores and BoNT dose. Pharyngeal efficiency of swallowing may be affected by BoNT for thicker consistencies. Individuals with CD perceive greater physical handicapping effects of dysphagia with increased amounts of BoNT units and have greater self-perceptions of dysphagia severity with increased amounts of BoNT units.

Intramuscular neural distribution of the obturator internus muscle regarding injective treatment

INTRODUCTION

The obturator internus muscle is frequently targeted for injective treatments such as botulinum toxin injections in the management of pain syndromes. However, there are controversies over injective method delivering injection to the muscle.

METHOD

A method called modified Sihler's method was used to stain the OI muscle in 16 specimens to reveal the intramuscular neural distribution of the muscle.

RESULT

The greatest intramuscular neural distribution was located on the 2/10-4/10 of the muscle in the medial edge of the obturator foramen (0/0) to the greater trochanter of the femur (10/10).

CONCLUSION

The result suggests that botulinum neurotoxin should be delivered in the intrapelvic portion of the obturator internus muscle. As most of the extrapelvic portion of the obturator muscle is composed of a tendinous portion, it should be considered unsuitable as an injection site by medical professionals.

Intramuscular Neural Distribution of Adductor Pollicis Muscle Spasticity in Cadaver Model Regarding Botulinum Neurotoxin Treatment

PURPOSE

The adductor pollicis muscle is frequently targeted for botulinum neurotoxin injective treatment for spasticity. However, there are no injective guidelines for delivering injection to the muscle.

MATERIALS AND METHODS

A method known as the modified Sihler's method was used to stain the adductor pollicis muscle in 16 specimens to reveal intramuscular neural distribution of the muscle.

RESULTS

The most intramuscular neural distribution was located on 1/5 to 3/5 of the muscle regarding midline of 3rd metacarpal bone (0) to the base of the 1st proximal phalanx (5/5). The nerve entry point was mostly located on 0 to 1/5 of the muscle.

CONCLUSION

The result suggests that botulinum neurotoxin should be delivered at the middle of second metacarpal bone via deep injection.

Intramuscular Neural Distribution of the Gastrocnemius for Botulinum Neurotoxin Injection: Application to Cosmetic Calf Shaping

PURPOSE

Anatomical landmarks can provide vital information on the distribution of nerves in the gastrocnemius muscle. We aimed to provide an anatomical perspective on appropriate locations for botulinum neurotoxin (BoNT) injections in the medial and lateral parts of the gastrocnemius for calf shaping.

MATERIALS AND METHODS

A modified Sihler's method was applied to both the medial and lateral parts of the gastrocnemius muscles (16 specimens). Intramuscular neural distributions were revealed by dissecting along a transverse line crossing the fibular head and superior margin of the calcaneal tuberosity.

RESULTS

The intramuscular neural distribution for the medial and lateral parts of the gastrocnemius had the greatest arborized patterns in the 7/10-8/10 section of the medial head and 7.5/10-8.5/10 section of the lateral part of the gastrocnemius.

CONCLUSION

We propose that BoNT injections should be directed to the 7/10-8/10 section of the medial head and the 7.5/10-8.5/10 section of the lateral part of the gastrocnemius. Following our guidelines, clinicians can ensure satisfactory results with the use of minimal doses to limit adverse effects, such as gait disturbance, antibody production, and bruising, due to multiple injections. The results can also be altered and applied to electromyography.

Treatment of crow's feet lines and forehead lines with Botox (onabotulinumtoxinA): Development, insights, and impact

Extrinsic and age-related intrinsic factors contribute to the development of facial lines, including lateral canthal lines (called crow's feet lines [CFL]) and horizontal forehead lines (FHL). OnabotulinumtoxinA is a highly effective treatment for facial lines that inhibits acetylcholine release at the neuromuscular junction. This temporary chemical denervation leads to localized muscle relaxation and subsequent wrinkle reduction. Early studies of onabotulinumtoxinA treatment for facial neuronal disorders such as dystonia documented improvements in FHL and CFL. After the neurotoxin was approved for treating frown lines (glabellar lines [GL]), individuals requested treatment for other rhytids, and physicians continued assessing use in new areas. Once onabotulinumtoxinA was in clinical trial development, its efficacy and safety for CFL and FHL were successively evaluated as required by the US Food and Drug Administration and by key global health authorities, including those in the European Union, Japan, and China. Allergan, collaborating with leading physicians, established clinical programs that included novel safety and efficacy measures to meet regulatory requirements. Global, phase 3, randomized, controlled studies of CFL and FHL met rigorous primary endpoints. Some countries mandated clinical trial data beyond US and European regulations, and Allergan conducted 11 studies in total, fulfilling diverse regulatory and study population data requirements. Adverse events associated with local spread, including brow and eyelid ptosis, diplopia, headache, and eyelid sensory disorder, were infrequent and well tolerated. Consequently, onabotulinumtoxinA treatment of upper facial lines is now established globally as a highly effective, minimally invasive treatment for patients to achieve a natural appearance and look younger.

Botulinum neurotoxin injection in the deltoid muscle: application to cosmetic shoulder contouring

BACKGROUND AND OBJECTIVES

This study describes the intramuscular nerve branching of the deltoid muscle in relation to shoulder surface anatomy, with the aim of providing essential information regarding the most appropriate sites for botulinum neurotoxin injection during shoulder line contouring.

METHODS

The modified Sihler's method was used to stain the deltoid muscles (16 specimens). The intramuscular arborization areas of the specimens were demarcated using the marginal line of the muscle origin and the line connecting the anterior and posterior upper edges of the axillary region.

RESULTS

The intramuscular neural distribution of the deltoid muscle had the greatest arborization patterns in the area between the horizontal 1/3 and 2/3 lines of the anterior and posterior deltoid bellies, and 2/3 to axillary line in middle deltoid bellies. The greatest part of the posterior circumflex artery and axillary nerve ran below the areas with the highest aborizations.

CONCLUSION

We propose that botulinum neurotoxin injections should be administered in the area between the 1/3 and 2/3 lines of the anterior and posterior deltoid bellies, and 2/3 to axillary line on middle deltoid bellies. Accordingly, clinicians will ensure minimal dose injections and fewer adverse effects of the botulinum neurotoxin injection. Deltoid intramuscular injections, such as vaccines and trigger point injections, should ideally be adapted according to our results.

The Efficacy of Transvaginal Ultrasound-Guided BoNT-A External Sphincter Injection in Female Patients with Underactive Bladder

Owing to the diverse treatment outcomes after a botulinum toxin A (BoNT-A) injection to the external sphincter, this study aimed to develop a new technique: an ultrasound-guided BoNT-A external sphincter injection. This single-center prospective cohort study was conducted at a tertiary medical center in Taichung, Taiwan. From December 2020 to September 2022, 12 women were enrolled. The patients were evaluated for lower urinary tract syndrome using patient perception of bladder condition (PPBC), international prostate symptom score (IPSS), uroflowmetry, post-void residual volume (PVR), cystometry, and external sphincter electromyography. We evaluated the patients the day before surgery and 1 week after the BoNT-A injection. For the patients requiring self-catheterization, we recorded the number of times they required clean intermittent catheterization (CIC) per day before the procedure and 1 month after the procedure. The IPSS, PPBC, and PVR were significantly better after the transvaginal ultrasound-guided BoNT-A external sphincter injection. The number of times the patients required daily CIC was also reduced after the injection. Only one patient developed de novo urge urinary incontinence. Our results demonstrated that a transvaginal ultrasound-guided BoNT-A injection was efficacious and safe in the treatment of underactive bladder.

The safety of botulinum neurotoxin type A's intraarticular application in experimental animals

In vivo studies of botulinum neurotoxin type A (BoNT-A) enabled characterization of its activity in the nociceptive sensory system separate from its preferred action in motor and autonomic nerve terminals. However, in the recent rodent studies of arthritic pain which employed high intra-articular (i.a.) doses (expressed as a total number of units (U) per animal or U/kg), possible systemic effects have not been conclusively excluded. Herein we assessed the effect of two pharmaceutical preparations, abobotulinumtoxinA (aboBoNT-A, 10, 20, and 40 U/kg corresponding to 0.05, 0.11, and 0.22 ng/kg neurotoxin) and onabotulinumtoxinA (onaBoNT-A, 10 and 20 U/kg corresponding to 0.09 and 0.18 ng/kg, respectively) injected into the rat knee, on safety-relevant readouts: digit abduction, motor performance and weight gain during 14 days post-treatment. The i. a. toxin produced dose-dependent impairment of the toe spreading reflex and rotarod performance, which was moderate and transient after 10 U/kg onaBoNT-A and ≤20 U/kg aboBoNT-A doses, and severe and long-lasting (examined up to 14 days) after ≥20 U/kg of onaBoNT-A and 40 U/kg aboBoNT-A. In addition, lower toxin doses prevented the normal weight gain compared to controls, while higher doses induced marked weight loss (≥20 U/kg of onaBoNT-A and 40 U/kg aboBoNT-A). Commonly employed BoNT-A formulations, depending on the doses, cause local relaxation of the surrounding muscles and systemic adverse effects in rats. Thus, to evade possible toxin unwanted local or systemic spread, careful dosing and motor testing should be mandatory in preclinical behavioral studies, irrespective of the sites and doses of toxin application.

Evaluating intramuscular neural distribution in the cricopharyngeus muscle for injecting botulinum toxin

OBJECTIVES

The objective of this study was to determine the area in the cricopharyngeus muscle (CPM) where botulinum neurotoxin (BoNT) can be injected safely and effectively by evaluating neural distribution in the CPM.

METHODS

Eleven specimens of the CPM were gathered from human cadavers. The anatomical relationship between the posterior cricoarytenoid muscle (PCAM) and the CPM was evaluated. Myelinated nerve fibers in the CPM were stained using modified Sihler's method. The CPM was classified into five zones according to the area accessible within the CPM via transcutaneous and transluminal approaches for BoNT injection as follows: i) lateral area including upper area (zone 1) and lower area (zone 2); ii) posterolateral area including upper area (zone 3) and lower area (zone 4); and iii) posterior area (zone 5). Neural distribution originating from the pharyngeal plexus and the extralaryngeal branches of recurrent laryngeal nerve (EBRLN) within each classified zone in stained specimens was determined.

RESULTS

Six specimens (12 lateral areas, 12 posterolateral areas, and 6 posterior areas) were suitable for evaluating neural distribution within the CPM. Zone 1 was adjacent to the PCAM the most in all specimens. Nerve endings originating from the EBRLN were observed on four sides of zone 2 (33.3%, 4/12 sides) in three specimens (3/6, 50%). Neural distribution originating from the pharyngeal plexus was found on ten sides (83.3%, 10/12 sides) of zone 3 in five specimens (83.3%, 5/6 specimens) and on nine sides (75.0%, 9/12 sides) of zone 4 in five specimens (83.3%, 5/6 specimens).

CONCLUSION

The posterolateral area (zone 3 and zone 4) is thought to be the most suitable area for alleviating the spasticity of CPM with a minimum dose of BoNT.

A Preclinical Study Comparing the Activity and Potency of OnabotulinumtoxinA and PrabotulinumtoxinA

Objective

The goal of this study was to compare the unit-to-unit biological activity of the vacuum-dried formulation of prabotulinumtoxinA (prabotA) and onabotulinumtoxinA (onabotA) in preclinical assays.

Methods

Reconstituted 100 U vials of prabotA and onabotA were tested in 3 distinct assays: plate-capture light chain activity (PC-LCA), measuringlight chain enzymatic activity after recovery of toxin from reconstituted product using a proprietary toxin capture step; cell-based potency assay (CBPA), measuring the intoxication steps of binding, translocation, and light chain activity (synaptosomal-associated protein 25 [SNAP25] cleavage); and mouse Digit Abduction Score (DAS), evaluating muscle paresis. Each assay tested 3 separate prabotA and onabotA lots on several independent test dates.

Results

Multiple orthogonal assays established that when assessed on a unit-to-unit basis, the biological activity of prabotA is lower than that of onabotA. In the PC-LCA and CBPA assays, onabotA displayed 1.51 ± 0.14-fold higher (mean ± SD) and 1.33 ± 0.07-fold higher (mean of pooled lots ± SEM) activity than prabotA, respectively. Similarly, the mouse DAS data showed that onabotA had 1.4 ± 0.1-fold higher (mean ± SEM) potency than prabotA. Results of all 3 assays demonstrated differences in potency, efficacy, and duration of action between onabotA and prabotA on a unit-to-unit basis.

Conclusion

Preclinical assays established differences in the biological activity of onabotA and prabotA, supporting that the units of biological activity are not interchangeable.

Types of periocular wrinkles based on anatomical and contractile characteristics of participating periocular muscles: A modified classification method and personalized injection technique

BACKGROUND

Clinical classification methods for periocular wrinkles based on participating muscle behavior are lacking, and traditional treatment lacks detailed and individualized methods.

AIMS

This study aimed to propose a modified classification system and individualized treatment for periocular wrinkles based on the participating muscles.

PATIENTS/METHODS

Periocular wrinkles were classified into types I.I, I.II, I.III, II, and III. A personalized treatment pattern with a multipoint, low-dose technique was developed based on wrinkle classification and severity. Standard photographs were taken and assessments made at follow-up to evaluate wrinkle severity.

RESULTS

Wrinkle severity was reduced at 1 and 3 months after periorbital botulinum toxin injection, and no serious adverse events were recorded.

CONCLUSIONS

Periorbital wrinkles were classified according to participating muscles. The modified injection pattern was individualized, effective, and safe for the treatment of periorbital wrinkles.

Comparison of Ultrasound and Electrical Stimulation Guidance for Onabotulinum Toxin-A Injections: A Randomized Crossover Study

Background

Botulinum neurotoxin (BoNT) injection is an established therapy for limb spasticity and focal limb dystonia. Comparative benefits of injection guidance procedures have not been rigorously studied.

Objectives

We compared 2 targeting techniques for onabotulinumtoxin-A (onabotA) injection for the treatment of focal hand dystonia and upper limb spasticity: electrophysiologic guidance using electrical stimulation (E-stim) and ultrasound (US).

Methods

This was a 2-center, randomized, crossover, assessor-blinded trial. Participants with focal hand dystonia or upper limb spasticity, on stable onabotA therapy for at least 2 previous injection cycles, were randomly assigned to either E-stim or US with crossover at 3 months. The primary outcome was improvement in dystonia or spasticity severity on a visual analog scale (VAS; 0-100) measured 1 month after each injection. The secondary outcome was participant discomfort assessed on a VAS. Repeated-measures analysis of covariance was used with linear mixed-model covariate selection.

Results

A total of 19 participants (13 men) completed the study, 10 with upper limb spasticity and 9 with dystonia. Benefit was equivalent between the 2 techniques (VAS least-square mean [LSmean] 51.5 mm with US and 53.1 with E-stim). E-stim was perceived as more uncomfortable by participants (VAS LSmean 34.5 vs. 19.9 for E-stim and US, respectively). Procedure duration was similar with the 2 procedures. There were no serious adverse events related to either approach.

Conclusions

US and E-Stim localization guidance techniques provide equivalent efficacy in onabotA injections for spasticity and dystonia. US guidance injections are more comfortable for participants. Both techniques are effective guidance methods, with US potentially preferable based on participant comfort.

Botulinum toxin injection strategy of intractable and relapsed piriformis syndrome: A case report

RATIONALE

Piriformis syndrome (PS) is neuromuscular disorder caused by sciatic nerve compression by piriformis muscle and related to sciatic-type pain. When the conservative care fails, local injection or surgery can be also performed into piriformis. In recent years, botulinum toxin (BoNT) has also been considered as a new therapeutic option of piriformis syndrome.

PATIENT CONCERNS

A man in his late 40s came to pain clinic for left low back pain. The symptom was aggravated with sitting position.

DIAGNOSIS

Piriformis syndrome.

INTERVENTIONS

The patient underwent BoNT injection with 100 IU with 2 mL into piriformis muscle for piriformis syndrome treatment, and his pain was relieved. However, it recurred 8 months later. BoNT injection was repeated with 100 IU with 5 mL.

OUTCOMES

At the time of this writing, his pain was reduced for 2 years without any medication.

LESSONS

We report a case of treating relapsed piriformis syndrome with BoNT injection of different dilution volume, suggesting that the higher the dilution volume, the more effective for therapeutic effect of BoNT.

The Lack of Systemic and Subclinical Side Effects of Botulinum Neurotoxin Type-A in Patients Affected by Post-Stroke Spasticity: A Longitudinal Cohort Study

Botulinum Neurotoxin type-A (BoNT-A) is the treatment of choice for focal post-stroke spasticity (PSS). Due to its mechanism of action and the administration method, some authors raised concern about its possible systemic diffusion leading to contralateral muscle weakness and autonomic nervous system (ANS) alterations. Stroke itself is a cause of motor disability and ANS impairment; therefore, it is mandatory to prevent any source of additional loss of strength and adjunctive ANS disturbance. We enrolled 15 hemiparetic stroke survivors affected by PSS already addressed to BoNT-A treatment. Contralateral handgrip strength and ANS parameters, such as heart rate variability, impedance cardiography values, and respiratory sinus arrythmia, were measured 24 h before (T0) and 10 days after (T1) the ultrasound (US)-guided BoNT-A injection. At T1, neither strength loss nor modification of the basal ANS patterns were found. These findings support recent literature about the safety profile of BoNT-A, endorsing the importance of the US guide for a precise targeting and the sparing of “critical” structures as vessels and nerves.

Novel Anatomical Proposal for Botulinum Neurotoxin Injection Targeting Lateral Canthal Rhytids

Botulinum neurotoxin injections near the lateral canthal rhytids are commonly used in cosmetic settings; however, there is a lack of thorough anatomical knowledge, and an effective way to treat them with accumulating knowledge is needed. The anatomical characteristics concerning the injection of botulinum neurotoxin into the orbicularis oculi muscle were evaluated in this review. Current knowledge on the identification of botulinum neurotoxin injection points from recent anatomical research was assessed. The lateral canthal lines are involved with the orbicularis oculi muscle and nearby anatomical structures, and the injection points can be more precisely defined. The best possible injection sites were provided, and the injection procedure was described. This review proposes evidence for injection sites associated with the surface anatomy of the orbicularis oculi muscles to enhance the effectiveness of easing lateral canthal rhytids.

Guidelines for botulinum neurotoxin injection for facial contouring

SUMMARY

The hypertrophied temporalis and masseter muscles give a muscular shaped and bulky contour to the face. Botulinum neurotoxin injection methods are commonly used for facial contouring; however, adverse effects have been reported owing to a lack of delicate anatomical information. The anatomical considerations when injecting botulinum neurotoxin into the temporalis and masseter muscles have been reviewed in the present study. Current knowledge on the localization of the botulinum neurotoxin injection point with more recent anatomical dissection and modified Sihler's staining procedures was assessed. We found that for the muscles, the injection point can be more precisely demarcated. Optimal injection sites are presented for the temporalis and masseter muscles, and the injection technique has been suggested. We propose the optimal injection sites in relation to external anatomical landmarks for the frequently injected muscles of the face to facilitate the efficiency of botulinum neurotoxin injections. In addition, these guidelines would aid in more precise practice without the adverse effects of botulinum neurotoxin.

Repeated botulinum treatment of rabbit masseter causes cumulative tissue damage

OBJECTIVE

Botulinum neurotoxins (BoNT) are used in masticatory muscles for pain relief, unloading of the mandible, and cosmetic facial contouring. Treatment is often repeated every few months as function returns. This study assessed masticatory function and musculoskeletal structure after multiple BoNT treatment of the rabbit masseter.

DESIGN

Female rabbits received 3 injections of BoNT (n = 13) or saline (n = 5) into one masseter muscle at intervals of 12 weeks. The contralateral side served as control. Periodic measurements of masticatory electromyography (EMG) and stimulated anterior bite force were made. After the final 12-week recovery interval, neuromuscular connection was investigated by stimulating the masseteric nerve to elicit an evoked EMG response. Mandibular specimens were collected for microCT analysis, and masseters were collected for histomorphometry and counts of replicating cells.

RESULTS

Control and saline-injected muscles maintained consistent masticatory EMG and anterior bite force throughout the study. BoNT-injected masseters showed strong declines after each injection; during the 12-week recovery period, masticatory EMG and anterior bite force improved, although only electrical activity reached normal levels. Multiple injection resulted in persistently atrophied muscle fibers with fibrosis, and notable loss of bone from the mandibular body and condyle. The uninjected masseters of the BoNT group also showed evidence of mild toxin-related changes.

CONCLUSIONS

Although muscle function is mostly regained after each injection, masseters receiving multiple doses of BoNT show extensive damage. In addition, mandibular bone density is decreased on the injected side.

Guidance to trigger point injection for treating myofascial pain syndrome: Intramuscular neural distribution of the quadratus lumborum

Postural habits and repetitive motion contribute toward the progress of myofascial pain by affecting overload on specific muscles, the quadratus lumborum (QL) muscle being the most frequently involved. The therapy of myofascial pain syndrome includes the release of myofascial pain syndrome using injective agents such as botulinum neurotoxin, lidocaine, steroids, and normal saline. However, an optimal injection point has not been established for the QL muscle. This study aimed to propose an optimal injection point for this muscle by studying its intramuscular neural distribution using the whole mount staining method. A modified Sihler's procedure was completed on 15 QL muscles to visualize the intramuscular arborization areas in terms of the inferior border of the 12th rib, the transverse processes of L1-L4, and the iliac crest. The intramuscular neural distribution of the QL had the densely arborized areas in the three lateral portions of L3-L4 and L4-L5 and the medial portion between L4 and L5.

Botulinum Toxin Injection for the Treatment of Upper Esophageal Sphincter Dysfunction

Dysphagia associated with upper esophageal sphincter (UES) dysfunction remarkably affects the quality of life of patients. UES injection of botulinum toxin is an effective treatment for dysphagia. In comparison with skeletal muscles of the limb and trunk, the UES is a special therapeutic target of botulinum toxin injection, owing to its several anatomical, physiological, and pathophysiological features. This review focuses on (1) the anatomy and function of the UES and the pathophysiology of UES dysfunction in dysphagia and why the entire UES rather than the cricopharyngeal muscle before/during botulinum toxin injection should be examined and targeted; (2) the therapeutic mechanisms of botulinum toxin for UES dysfunction, including the choice of injection sites, dose, and volume; (3) the strengths and weaknesses of guiding techniques, including electromyography, ultrasound, computed tomography, and balloon catheter dilation for botulinum toxin injection of the UES.

Intramuscular Innervation of the Supraspinatus Muscle Assessed Using Sihler’s Staining: Potential Application in Myofascial Pain Syndrome

Despite the positive effects of botulinum neurotoxin (BoNT) injection into the neural arborized area, there is no anatomical evidence in the literature regarding the neural arborization of the supraspinatus muscle. The present study aimed to define the intramuscular neural arborized pattern of the supraspinatus muscle using the modified Sihler’s staining method to facilitate the establishment of safe and effective injection sites in patients with myofascial pain in the supraspinatus muscle. Seventeen supraspinatus muscles from 15 embalmed cadavers were dissected. Precise suprascapular nerve entry locations were also observed. Intramuscular neural arborization was visualized by Sihler’s staining. The supraspinatus muscle was divided into four portions named A, B, C, and D. The nerve entry points were observed in 88.2% (15 of 17 cases) of section B and 76.5% (13 of 17 cases) of section C of the supraspinatus muscle, respectively. The concentration of intramuscular neural arborization was highest in section B of the supraspinatus muscle, which was the center of the supraspinatus muscle. When the clinician performs a trigger point and a BoNT injection into the supraspinatus muscle, injection within the medial 25–75% of the supraspinatus muscle will lead to optimal results when using small amounts of BoNT and prevent undesirable paralysis.

Anatomical Proposal for Botulinum Neurotoxin Injection for Glabellar Frown Lines

Botulinum neurotoxin injection for treating glabellar frown lines is a commonly used method; however, side effects, such as ptosis and samurai eyebrow, have been reported due to a lack of comprehensive anatomical knowledge. The anatomical factors important for the injection of the botulinum neurotoxin into the corrugator supercilii muscle has been reviewed in this study. Current understanding on the localization of the botulinum neurotoxin injection point from newer anatomy examination was evaluated. We observed that for the glabellar-frown-line-related muscles, the injection point could be more accurately demarcated. We propose the injection method and the best possible injection sites for the corrugator supercilii muscle. We propose the optimal injection sites using external anatomical landmarks for the frequently injected muscles of the face to accelerate effective glabellar frown line removal. Moreover, these instructions would support a more accurate procedure without adverse events.

Intramuscular Neural Arborization of the Latissimus Dorsi Muscle: Application of Botulinum Neurotoxin Injection in Flap Reconstruction

Postoperative pain after breast reconstruction surgery with the latissimus dorsi flap is a common occurrence. Botulinum neurotoxin (BoNT) injection during surgery is effective in reducing postoperative pain. This study aimed to determine the most appropriate locations for BoNT injection. A modified Sihler’s method was performed on the latissimus dorsi muscles in 16 specimens. Intramuscular nerve arborization was noted under the landmark of the medial side surgical neck of the humerus to the line crossing the spinous process of T5 and the middle of the iliac crest. The latissimus dorsi muscles were divided into medial, middle, and lateral segments with 10 transverse divisions to give 10 sections (each 10%). Intramuscular nerve arborization of the latissimus dorsi muscle was the largest from the medial and lateral part of the muscle ranging from 40 to 60%, middle part from 30 to 60% and medial, middle and lateral part from 70 to 90%. The nerve entry points were at the medial and lateral part with 20–40% regarding the medial side of surgical neck of the humerus to the line crossing spinous process of T5 to the middle of iliac crest. These outcomes propose that an injection of BoNT into the latissimus dorsi muscles should be administered into specific zones.

The botulinum neurotoxin for pain control after breast reconstruction: neural distribution of the pectoralis major muscle

INTRODUCTION

The use of the botulinum neurotoxin injection is a growing area of research and clinical activity, with a focus on its role in facilitating postoperative pain management after reconstructive breast surgery. The study aimed to find out the standard injection points for botulinum neurotoxin injection by revealing the intramuscular nerve arborization of the pectoralis major.

METHODS

Sihler's technique was conducted on the pectoralis major muscles (16 cadaveric specimens). The intramuscular nerve arborization was documented relative to the inferior border of the clavicle bone and lateral border of the sternum.

RESULTS

After the staining, the pectoralis major was divided into fifths transversely from the inferior border of the clavicle and vertically into fifths from the lateral border of the sternum. Intramuscular nerve arborization of the pectoralis major muscle was the largest in the middle sections of the muscle belly.

DISCUSSION

The results indicate that botulinum neurotoxin should be applied to the pectoralis major in certain regions. The regions of major arborization are optimal as the most effective and most reliable points for injecting botulinum neurotoxin.

A Pragmatic Approach to the Management of Severe Awake Bruxism in an Adolescent with Cerebral Palsy and Global Developmental Delay

Cerebral palsy is a neurological and motor condition characterised by muscle balance and posture impairments. Bruxism and malocclusion were frequently observed in patients with cerebral palsy, in contrast to other oral anomalies. The report outlines how severe awake bruxism is managed in a 16-year-old Korean boy who has nonverbal spastic cerebral palsy and global developmental delay. The treatment protocol involved the fabrication of soft occlusal splints of three and four millimetres in thickness, followed by the placement of stainless-steel crowns on all first permanent molars whilst video recording and a bruxism diary was kept. Fixed restorations demonstrate increased endurance in withstanding bruxism force in persons who are dependent on their caretaker.

Botulinum Toxins for Aesthetic Facial Injections - A scientific review to support evidence-based best practice

Botulinum Toxins (BoNT) are complex biological products. Each licensed BoNTA has its own individual characteristics resulting into different attributes, some of them being of clinical relevance. Besides profound anatomical knowledge and understanding of aesthetic principles, the responsible injecting physician should be aware of those pharmaceutical and clinical properties. Especially against the background of new BoNTA formulations receiving approval by the authorities a critical and dedicated discussion on the individual characteristics should take place and the potential relevance on the treatment outcome should be taken into consideration.

Incobotulinum toxin A with a one-year long-lasting effect for trapezius contouring and superior efficacy for the treatment of trapezius myalgia

Context:

Based on various Botulinum toxin A products, reports of the lower efficacy of Incobotulinum toxin A compared with Onabotulinum toxin A for muscle contouring were observed. In addition, complications of trapezius myalgia and shoulder contouring treatment from malpractice have been reported.

Aims:

The study aimed at comparing the efficacy between Incobotulinum toxin A and Onabotulinum toxin A; research was conducted on a safe treatment technique for trapezius hypertrophy and trapezius myalgia.

Materials and Methods:

A split-shoulder, double-blind, randomized controlled trial was performed. Twenty volunteers with trapezius hypertrophy and trapezius myalgia were randomly injected with 30 units of Incobotulinum toxin A and Onabotulinum toxin A in each trapezius muscle guided by ultrasound.

Results:

The trapezius thickness among those receiving treatment with Onabotulinum toxin A and Incobotulinum toxin A on day 60 was 7.35 ± 1.11 and 7.33 ± 1.21 mm, respectively, which did not portray a significant difference (P = 0.991). Compared with the muscle size from day 60 to one year, the size of the trapezius muscle that had been treated by Onabotulinum toxin type A regained a significantly larger size compared with that treated by Incobotulinum toxin A (P = 0.027). On comparing the size of the trapezius muscle treated by Incobotulinum toxin A between one year and day 0, it was observed that the trapezius thickness at one year had significantly decreased (P < 0.001). On comparing the pain score from day 60 to day 0, it was observed that the pain scores of trapezius myalgia treated by Onabotulinum toxin A and Incobotulinum toxin A significantly differed (P = 0.003).

Conclusions:

Incobotulinum toxin A had the same efficacy but a longer lasting effect for the trapezius size contouring and a higher efficacy for trapezius myalgia treatment compared with Onabotulinum toxin A.

Pivotal role of injection volume on sunken cheek prevention in masseter muscle BoNT-A injection: A cadaver study

BACKGROUND

Botulinum neurotoxin A injection is a popular noninvasive alternative for the treatment of masseter hypertrophy. This study was conducted to identify a safe injection volume to avoid sunken lateral cheek after botulinum neurotoxin A injection in the masseter muscle.

METHODS

One milliliter or 0.5 ml of indocyanine green was randomly injected into either side of the masseter muscles of 18 fresh cadaver heads. The bilateral spreads of indocyanine green within the masseter were observed by a fluorescence imager. The masseters were then dissected, and the spreading distance was measured.

RESULTS

Dye spreading showed an oval shape parallel to the long axis of the masseter muscle. The lower edges of the masseters were all stained with indocyanine green. The upward spreading exceeded the mouth corner-tragus line in 94.44% (17/18) of the masseters on the 1-ml side, and 11.11% (2/18) of the masseters on the 0.5-ml side. The spreading area and upward spreading distance on the 1-ml side (9.95 ± 0.48 cm² , 3.18 ± 0.31 cm) were significantly larger than the 0.5-ml side (7.13 ± 0.80 cm² , 2.08 ± 0.32 cm).

CONCLUSIONS

The spread of indocyanine green within the masseter occurs in direct proportion to its volume. A bolus of 1 ml easily exceeded the mouth corner-tragus line and cause sunken cheek.

Ultrasonographic Evaluation of Three Approaches for Botulinum Toxin Injection into Tibialis Posterior Muscle in Chronic Stroke Patients with Equinovarus Foot: An Observational Study

Spastic equinovarus (SEV) foot deformity is commonly observed in patients with post-stroke spasticity. Tibialis posterior (TP) is a common target for botulinum toxin type-A (BoNT-A) injection, as a first-line treatment in non-fixed SEV deformity. For this deep muscle, ultrasonographic guidance is crucial to achieving maximum accuracy for the BoNT-A injection. In current clinical practice, there are three approaches to target the TP: an anterior, a posteromedial, and a posterior. To date, previous studies have failed to identify the best approach for needle insertion into TP. To explore the ultrasonographic characteristics of these approaches, we investigated affected and unaffected legs of 25 stroke patients with SEV treated with BoNT-A. We evaluated the qualitative (echo intensity) and quantitative (muscle depth, muscle thickness, overlying muscle, subcutaneous tissue, cross-sectional area) ultrasound characteristics of the three approaches for TP injection. In our sample, we observed significant differences among almost all the parameters of the three approaches, except for the safety window. Moreover, our analysis showed significant differences in cross-sectional area between treated and untreated. Advantages and disadvantages of each approach were investigated. Our findings can thus provide a suitable reference for clinical settings, especially for novice operators.

AbobotulinumtoxinA provides flexibility for the treatment of cervical dystonia with 500 U/1 mL and 500 U/2 mL dilutions

INTRODUCTION

Cervical dystonia (CD) is a neurologic movement disorder with potentially disabling effects and significant impact on quality of life of those affected. AbobotulinumtoxinA (aboBoNT-A) was initially approved for a dilution of 500 U/1 mL and subsequently for a dilution of 500 U/2 mL, providing flexibility for clinicians to treat CD. Here, we explore the safety and efficacy of the 500 U/2 mL dilution versus 500 U/1 mL dilution of aboBoNT-A in a retrospective analysis based on published clinical trial data.

METHODS

The safety and efficacy of aboBoNT-A in patients with CD was evaluated in three multicenter, double-blind, randomized, placebo-controlled trials and open-label extensions. Trials 1 (NCT00257660) and 2 (NCT00288509) evaluated the 500 U/1 mL dilution in 80 and 116 patients, respectively; Trial 3 (NCT01753310) evaluated the 500 U/2 mL dilution in 125 patients.

RESULTS

Comparison of the adjusted mean difference in TWSTRS total scores at Week 4 from baseline for aboBoNT-A in Trial 1 (-6.0; 95% CI, -10.8, -1.3), Trial 2 (-8.8; 95% CI, -12.9, -4.7), and Trial 3 (-8.7; 95% CI, -13.2, -4.2) showed similar, significant improvements. Dysphagia and muscle weakness patterns were comparable across the three trials, indicating that an increased dilution of aboBoNT-A does not result in an increased risk of diffusion-related adverse events.

CONCLUSION

The results of these trials show that aboBoNT-A is similarly efficacious using either dilution, with similar safety and tolerability across trials. Having the 500 U/1 mL and 500 U/2 mL dilution volumes available provides further flexibility in administration, benefiting patient care.

Time course response after single injection of botulinum toxin to treat spasticity after stroke: Systematic review with pharmacodynamic model-based meta-analysis

BACKGROUND

The time-course response after a single injection of botulinum toxin (BoNT) for post-stroke spasticity is debated. We addressed this issue by conducting a systematic review and a pharmacodynamic model-based meta-analysis.

METHODS

We searched Medline, PeDro and Google Scholar databases up to March 2020, selecting randomized controlled trials of post-stroke and traumatic brain injury patients with arm or leg muscle hypertonia, comparing BoNT to placebo, or different BoNT preparations. The main outcome was change in Modified Ashworth Scale (MAS) score. A non-linear mixed effect model was used to estimate maximal toxin and placebo effects (Emax and EPlacebo), the effect disappearance half-life (T1/2off) of BoNT and the doses achieving 50 and 80% of Emax (D50 and D80). The equivalence ratios between different BoNT preparations were calculated from D50 values. Adverse events were recorded.

RESULTS

Altogether, 2,236 unique records were screened by 2 independent reviewers: 35 eligible trials including 3011 patients (95% post-stroke) were identified. For all BoNT preparations, the BoNT Emax of -1.11 (95% credible interval -1.31; -0.29) was reached at 5 weeks; the maximal placebo effect was -0.30 (-0.37; -0.22). Both D50 and D80 differed significantly by muscle volume. At D50, the equivalence ratio was significantly higher for abobotulinumtoxinA (3.35) than onabotulinumtoxinA and lower for letibotulinumtoxinA (0.41). T1/2off was longer for abobotulinumtoxinA than for onabotulinumtoxinA and the other preparations (13.1 weeks [95% credible interval 7.7; 19.3] vs 8.6 weeks [7.1; 10.1]). Adverse events were minor, with a weak, but significant, dose-response relation for muscle weakness.

CONCLUSIONS

This first pharmacodynamic model-based meta-analysis of individuals with stroke revealed that for all BoNT-A preparations, BoNT-A injections to treat spasticity have maximal effect at 5 weeks. The T1/2off was longer for abobotulinumtoxinA than other preparations. Differences between certain BoNT unit scales were also confirmed.