Quantifying how location and dose of botulinum toxin injections affect muscle paralysis

Territories of Nerve Endings of the Medial Plantar Nerve within the Abductor Hallucis Muscle: Clinical Implications for Potential Pain Management

This study aimed to elucidate the intramuscular distribution pattern of the medial plantar nerve and determine its motor nerve ending territories within the abductor hallucis muscle using modified Sihler's staining and external anatomical landmarks. The study included 40 specimens of the abductor hallucis muscle (13 men and seven women) from formalin-fixed (ten cadavers) and fresh cadavers (ten cadavers), with a mean age of 77.6 years. The entry point of the medial plantar nerve into the muscle was examined, followed by Sihler's staining to analyze the intramuscular distribution pattern and motor nerve ending location within the abductor hallucis muscle. Ultrasound- and palpation-guided injections were performed to verify the applicability of motor nerve ending location-based injections. The areas with the highest concentrations of nerve entry points and nerve endings were identified in the central portion of the muscle. Ultrasound- and palpation-guided injections were safely positioned near the densest nerve ending region of the muscle. These detailed anatomical data and injection methods would be beneficial for proceeding with safe and effective injection treatments using various analgesic agents to alleviate abductor hallucis muscle-associated pain disorders.

Division of neuromuscular compartments and localization of the center of the highest region of muscle spindles abundance in deep cervical muscles based on Sihler's staining

Purpose

The overall distribution pattern of intramuscular nerves and the regions with the highest spindle abundance in deep cervical muscles have not been revealed. This study aimed to reveal neuromuscular compartmentalization and localize the body surface position and depth of the center of the region of highest muscle spindle abundance (CRHMSA) in the deep cervical muscles.

Methods

This study included 36 adult cadavers (57.7 ± 11.5 years). The curved line joining the lowest point of the jugular notch and chin tip was designated as the longitudinal reference line (line L), and the curved line connecting the lowest point of the jugular notch and acromion was designated as the horizontal reference line (line H). Modified Sihler's staining, hematoxylin-eosin staining and computed tomography scanning were employed to determine the projection points (P) of the CRHMSAs on the anterior surfaces of the neck. The positions (PH and PL) of point P projected onto the H and L lines, and the depth of each CRHMSA, and puncture angle were determined using the Syngo system.

Results

The scalenus posterior and longus capitis muscles were divided into two neuromuscular compartments, while the scalenus anterior and longus colli muscles were divided into three neuromuscular compartments. The scalenus medius muscle can be divided into five neuromuscular compartments. The PH of the CRHMSA of the scalenus muscles (anterior, medius, and posterior), and longus capitis and longus colli muscles, were located at 36.27, 39.18, 47.31, 35.67, and 42.71% of the H line, respectively. The PL positions were at 26.53, 32.65, 32.73, 68.32, and 51.15% of the L line, respectively. The depths of the CRHMSAs were 2.47 cm, 2.96 cm, 2.99 cm, 3.93 cm, and 3.17 cm, respectively, and the puncture angles were 87.13°, 85.92°, 88.21°, 58.08°, and 77.75°, respectively.

Conclusion

Present research suggests that the deep cervical muscles can be divided into neuromuscular compartments; we recommend the locations of these CRHMSA as the optimal target for administering botulinum toxin A injections to treat deep cervical muscle dystonia.

A Bayesian Network Meta-Analysis and Systematic Review of Guidance Techniques in Botulinum Toxin Injections and Their Hierarchy in the Treatment of Limb Spasticity

Accurate targeting of overactive muscles is fundamental for successful botulinum neurotoxin (BoNT) injections in the treatment of spasticity. The necessity of instrumented guidance and the superiority of one or more guidance techniques are ambiguous. Here, we sought to investigate if guided BoNT injections lead to a better clinical outcome in adults with limb spasticity compared to non-guided injections. We also aimed to elucidate the hierarchy of common guidance techniques including electromyography, electrostimulation, manual needle placement and ultrasound. To this end, we conducted a Bayesian network meta-analysis and systematic review with 245 patients using the MetaInsight software, R and the Cochrane Review Manager. Our study provided, for the first time, quantitative evidence supporting the superiority of guided BoNT injections over the non-guided ones. The hierarchy comprised ultrasound on the first level, electrostimulation on the second, electromyography on the third and manual needle placement on the last level. The difference between ultrasound and electrostimulation was minor and, thus, appropriate contextualization is essential for decision making. Taken together, guided BoNT injections based on ultrasound and electrostimulation performed by experienced practitioners lead to a better clinical outcome within the first month post-injection in adults with limb spasticity. In the present study, ultrasound performed slightly better, but large-scale trials should shed more light on which modality is superior.

Muscle innervation zone estimation from monopolar high-density M-waves using principal component analysis and radon transform

This study examined methods for estimating the innervation zone (IZ) of a muscle using recorded monopolar high density M waves. Two IZ estimation methods based on principal component analysis (PCA) and Radon transform (RT) were examined. Experimental M waves, acquired from the biceps brachii muscles of nine healthy subjects were used as testing data sets. The performance of the two methods was evaluated by comparing their IZ estimations with manual IZ detection by experienced human operators. Compared with manual detection, the agreement rate of the estimated IZs was 83% and 63% for PCA and RT based methods, respectively, both using monopolar high density M waves. In contrast, the agreement rate was 56% for cross correlation analysis using bipolar high density M waves. The mean difference in estimated IZ location between manual detection and the tested method was 0.12 ± 0.28 inter-electrode-distance (IED) for PCA, 0.33 ± 0.41 IED for RT and 0.39 ± 0.74 IED for cross correlation-based methods. The results indicate that the PCA based method was able to automatically detect muscle IZs from monopolar M waves. Thus, PCA provides an alternative approach to estimate IZ location of voluntary or electrically-evoked muscle contractions, and may have particular value for IZ detection in patients with impaired voluntary muscle activation.

Botulinum Toxin Intervention in Cerebral Palsy-Induced Spasticity Management: Projected and Contradictory Effects on Skeletal Muscles

Spasticity, following the neurological disorder of cerebral palsy (CP), describes a pathological condition, the central feature of which is involuntary and prolonged muscle contraction. The persistent resistance of spastic muscles to stretching is often followed by structural and mechanical changes in musculature. This leads to functional limitations at the respective joint. Focal injection of botulinum toxin type-A (BTX-A) is effectively used to manage spasticity and improve the quality of life of the patients. By blocking acetylcholine release at the neuromuscular junction and causing temporary muscle paralysis, BTX-A aims to reduce spasticity and hereby improve joint function. However, recent studies have indicated some contradictory effects such as increased muscle stiffness or a narrower range of active force production. The potential of these toxin- and atrophy-related alterations in worsening the condition of spastic muscles that are already subjected to changes should be further investigated and quantified. By focusing on the effects of BTX-A on muscle biomechanics and overall function in children with CP, this review deals with which of these goals have been achieved and to what extent, and what can await us in the future.

Toxic Relationships and Arms-Race Coevolution Revisited

Toxin evolution in animals is one of the most fascinating and complex subjects of scientific inquiry today. Gaining an understanding of toxins poses a multifaceted challenge given the diverse modes of acquisition, evolutionary adaptations, and abiotic components that affect toxin phenotypes. Here, we highlight some of the main genetic and ecological factors that influence toxin evolution and discuss the role of antagonistic interactions and coevolutionary dynamics in shaping the direction and extent of toxicity and resistance in animals. We focus on toxic Pacific newts (family Salamandridae, genus Taricha) as a system to investigate and better evaluate the widely distributed toxin they possess, tetrodotoxin (TTX), and the hypothesized model of arms-race coevolution with snake predators that is used to explain phenotypic patterns of newt toxicity. Finally, we propose an alternative coevolutionary model that incorporates TTX-producing bacteria and draws from an elicitor-receptor concept to explain TTX evolution and ecology.

A consensus statement on the use of botulinum toxin in pediatric patients

Botulinum toxin has been used in medicine for the past 30 years. However, there continues to be controversy about the appropriate uses and dosing, especially in the pediatric population. A panel of nine pediatric physiatrists from different regions and previous training programs in the United States were nominated based on institutional reputation and botulinum toxin (BoNT) experience. Based on a review of the current literature, the goal was to provide the rationale for recommendations on the administration of BoNT in the pediatric population. The goal was not only to review safety, dosing, and injection techniques but also to develop a consensus on the appropriate uses in the pediatric population. In addition to upper and lower limb spasticity, the consensus also provides recommendations for congenital muscular torticollis, cervical dystonia, sialorrhea, and brachial plexus palsies.

An Approach to Maximize Retrograde Transport Based on the Spatial Distribution of Motor Endplates in Mouse Hindlimb Muscles

Knowledge regarding the relationship between muscles and the corresponding motor neurons would allow therapeutic genes to transport into specific spinal cord segments. Retrograde tracing technique by targeting the motor endplate (MEP), a highly specialized structure that offers direct access to the spinal motor neurons, has been used to elucidate the connectivity between skeletal muscles and the innervating motor neuron pools. However, current injection strategies mainly based on blind injection or the local MEP region might lead to an underestimation of the motor neuron number due to the uneven distribution of MEP in skeletal muscles. In this work, we proposed a novel intramuscular injection strategy based on the 3D distribution of the MEPs in skeletal muscles, applied the 3D intramuscular injection to the gastrocnemius and tibialis anterior for retrograde tracing of the corresponding motor neurons, and compared this with the existing injection strategy. The intramuscular diffusion of the tracer demonstrated that 3D injection could maximize the retrograde transport by ensuring a greater uptake of the tracer by the MEP region. In combination with optical clearing and imaging, we performed 3D mapping and quantification of the labeled motor neurons and confirmed that 3D injection could label more motor neurons than the current injection method. It is expected that 3D intramuscular injection strategy will help elucidate the connective relationship between muscles and motor neurons faithfully and becomes a promising tool in the development of gene therapy strategies for motor neuron diseases.

The Use of Botulinum Toxin to Prevent Anastomotic Thrombosis and Promote Flap Survival: A Bridge to Developing Clinical Studies

BACKGROUND

Despite the possibility of using botulinum toxin to improve perfusion and prevent vasospasm, only a few studies have examined the use of botulinum toxin in the setting of flap surgery and thrombosis, and the mechanisms have not been fully explained.

OBJECTIVE

The primary objective of this study was to provide a comprehensive review of the effectiveness of botulinum toxin in anastomotic thrombosis prevention and surgical flap survival to determine the value of conducting large-scale human trials.

METHODS

Using the SYRCLE and CAMRADES criteria, a systematic review was performed. PubMed, Medline, EmBase, and the Cochrane Library were searched for studies that met our eligibility criteria.

RESULTS

Twenty studies were included in the final selection. A total of 397 subjects were included. Eighteen studies used botulinum toxin type A alone, one used botulinum toxin type B alone, and only one used both botulinum toxin type A and botulinum toxin type B. The most commonly used injection technique was a preoperative intradermal injection. The most common procedure performed was a pedicled flap with random pattern skin flaps (65%). The mean injection dose was 28.17 ± 49.21 IU, whereas the mean reported injection time for studies using animal models was 7.4 ± 6.84 days.

CONCLUSIONS

Similar mechanisms demonstrated in animal models may be replicable in humans, allowing botulinum toxin to be used to prolong flap survival. However, many factors, such as optimal injection techniques, dosages, and long-term outcomes of botulinum use in flap surgery, need to be further assessed before applying this to clinical practice.

Long-term BTX-A effects on bi-articular muscle: Higher passive force, limited length range of active force production and unchanged intermuscular interactions

Botulinum toxin type-A (BTX-A) is commonly used for spasticity management aiming at reducing joint stiffness and increasing joint range of motion in CP patients. However, previous animal studies showed acutely increased passive forces and a narrowerlength range of active force exertion (l_range) for muscles exposed. BTX-A can spread affecting mechanics of several muscles in a compartment, but it was shown acutely to diminishepimuscular myofascial force transmission (EMFT). Yet, our understanding of these effects in the long-term is limited and they need to be tested in a bi-articular muscle. The goal was to test the following hypotheses in a long-term rat model: exposure to BTX-A (i) has no effects onl_rangeand passive forces of bi-articular extensor digitorum longus (EDL) muscle and (ii) diminishes EMFT. Male Wistar rats were divided into two groups: BTX-A and control (0.1 units of BTX-A or only saline was injected into the tibialis anterior). Isometric proximal and distal EDL forces were measured simultaneously, one-month post-injection. Proximally and distally lengthening the muscle showed that BTX-A causes a significantly narrowerl_range(by 14.7% distally and 32.2% proximally) and significantly increased passive muscle forces (over 2-fold both distally and proximally). Altering muscle position at constant length showed that BTX-A does not change EMFT. The findings reject both hypotheses showing that long-term exposure to BTX-A compromises bi-articular muscle's contribution to motion for both joints and the muscle's mechanical interaction with the surroundings remains unaffected. These effects which may compromise long-term spasticity management should be studied in CP patients.

Assessing redistribution of muscle innervation zones after spinal cord injuries

This study aimed to examine the redistribution of neuromuscular junctions or innervation zones (IZs) after spinal cord injuries (SCI). Fifteen able-bodied subjects and 15 subjects with SCI (American Spinal Injury Association Impairment Scale A to D), participated in the study. Surface electromyography (EMG) signals were collected from the biceps brachii muscle by a customized linear electrode array when subjects generated maximal isometric voluntary contractions. The Radon transform was applied to detect the IZ locations in the multiple channel surface EMG signals which were differentiated between consecutive channels. The distribution of IZs was compared between the SCI and control groups using the student-t test. Statistical analysis disclosed a significantly wider range of IZs in the SCI group compared with the control group (SCI: 3.83 ± 1.32 IED, control: 2.83 ± 0. 87 IED, IED: inter-electrode distance, p < 0.05). No remarkable shifts of the center of the distribution were observed between the two groups (SCI: 9.23 ± 2.35 IED, control: 8.53 ± 2.33 IED, p = 0.42). Changes of IZ distribution in the paralyzed muscles could be associated with the complex neuromuscular reorganization after the SCI.

Morphological characteristics of the posterior neck muscles and anatomical landmarks for botulinum toxin injections

PURPOSE

Cervical dystonia is a common movement disorder for which botulinum toxin (BoNT) is the first choice treatment. Injecting the specific neck muscles can be challenging because of their thin morphology and deep locations. We, therefore, designed a study to investigate the locations of the posterior neck muscles to help the physician predict the locations of the targeted neck muscles and to protect the vertebral vessels from injury during deep injections.

METHODS

The posterior neck region was divided into four quadrants by imaginary lines passing vertically and transversely through the spinous process of C2 vertebra (C2_sp). The thicknesses and depth of the posterior neck muscles were measured in ten formaldehyde-fixed adult male cadavers. These muscles were located and a projection of them was drawn on the neck. Using the measurements, colored latex in place of BoNT was injected into them in one cadaver. The cadaver was dissected to investigate whether the muscles were colored.

RESULTS

2 cm above the C2_sp, trapezius, splenius capitis (SPC) and semispinalis capitis (SSC) were colored at depths of 10.70 mm, 11.88 mm and 15.91 mm, respectively. 2 cm below the C2_sp, the trapezius, SPC and SSC were colored at depths of 20.89 mm, 23.25 mm and 27.63 mm, respectively. The posterior neck muscles were had taken up their assigned colors when they were injected according to the results obtained in this study. The vertebral vessels were not colored.

CONCLUSIONS

Although BoNT injection into the posterior neck muscles is challenging, we think that it can be practically and safely applied using the measurements obtained in this study.

The Use of Botulinum Toxin for Treatment of Spasticity

Spasticity is one component of the upper motor neuron (UMN) syndrome resulting from a multitude of neurologic conditions, such as stroke, brain injury, spinal cord injury, multiple sclerosis, and cerebral palsy. It is clinically recognized as a phenomenon of velocity-dependent increase in resistance, i.e., hypertonia. Recent advances in the pathophysiology of spasticity improve our understanding of mechanisms underlying this complex phenomenon and its relations to other components of UMN syndrome (weakness and disordered motor control), as well as the resultant clinical problems. This theoretical framework provides a foundation to set up treatment goals and to guide goal-oriented clinical assessment and treatment. Among a spectrum of treatment options, botulinum toxin (BoNT) therapy is the preferred treatment for focal spasticity. The evidence is very robust that BoNT therapy effectively reduces spasticity; however, it does not improve voluntary movement. In this chapter, we highlight a few issues on how to achieve the best clinical outcomes of BoNT therapy, such as dosing, dilution, guidance techniques, adjunctive therapies, early treatment, repeated injections, and central effects, as well as the ways to improve motor function in selected subgroups of patients with spasticity. We also discuss the reasons of poor responses to BoNT therapy and when not to use BoNT therapy.

Intramural Injection of Botulinum Toxin A in Surgical Treatment of a Long Gap Esophageal Atresia-Rat Model

INTRODUCTION

 Anastomosis with minimal tension is desirable in long-gap esophageal atresia. Prior studies in piglets showed that intraesophageal injection of botulinum toxin type A (BTX-A) results in significant esophageal elongation. Our aim was to determine the BTX-A dose, number of injections, and time necessary to elicit maximal response.

MATERIALS AND METHODS

 Adult male Wistar rats (n = 48) were randomly assorted into five groups. Four treatment groups received 2 or 4 U/kg of BTX-A, delivered using two or four injections, and a control group received 0.9% NaCl. Esophagus was removed 6 or 24-hours postinjection and tested ex vivo using a stretch tension device. Subsequently, an optimal dose and time following injection was used to study the effects of BTX-A on anastomotic healing in vivo. Rats (n = 12) received an intraesophageal injection of BTX-A or 0.9% NaCl, followed by resection of 0.5 cm of esophagus and end-to-end anastomosis. Rats were observed for 9 days, and esophagus was removed for gross and histological evaluation.

RESULTS

 The largest effect on elongation was recorded in the BTX-A (2 U/kg) 24 hour, four injection group. In the anastomosis study, stricture formation was observed in all animals in the control group. Absence of esophageal stricture was found in three out of four animals in the treatment group macroscopically and histologically.

CONCLUSION

 We found that BTX-A exerts a positive effect on stretch characteristics of esophageal tissue in rats at 2 U/kg via four-injection delivery and 24-hour waiting period. This study suggests that BTX-A might improve anastomotic healing.

Over 25 Years of Pediatric Botulinum Toxin Treatments: What Have We Learned from Injection Techniques, Doses, Dilutions, and Recovery of Repeated Injections?

Botulinum toxin type A (BTXA) has been used for over 25 years in the management of pediatric lower and upper limb hypertonia, with the first reports in 1993. The most common indication is the injection of the triceps surae muscle for the correction of spastic equinus gait in children with cerebral palsy. The upper limb injection goals include improvements in function, better positioning of the arm, and facilitating the ease of care. Neurotoxin type A is the most widely used serotype in the pediatric population. After being injected into muscle, the release of acetylcholine at cholinergic nerve endings is blocked, and a temporary denervation and atrophy ensues. Targeting the correct muscle close to the neuromuscular junctions is considered essential and localization techniques have developed over time. However, each technique has its own limitations. The role of BTXA is flexible, but limited by the temporary mode of action as a focal spasticity treatment and the restrictions on the total dose deliverable per visit. As a mode of treatment, repeated BTXA injections are needed. This literature reviewed BTXA injection techniques, doses and dilutions, the recovery of muscles and the impact of repeated injections, with a focus on the pediatric population. Suggestions for future studies are also discussed.

Botulinum Toxin to Treat Horizontal Forehead Lines: A Refined Injection Pattern Accommodating the Lower Frontalis

BACKGROUND

When treating horizontal forehead lines with botulinum toxin type A the traditional approach requires that injection points should stay 1.5 to 2 cm above the orbital rim to avoid brow ptosis. Failure to treat the lower frontalis may potentially cause worse rhytides in the lower forehead.

OBJECTIVES

The aim of this study was to present a refined injection pattern accommodating the lower frontalis and evaluate its clinical efficacy and safety.

METHODS

Patients were categorized into 4 types according to the patterns of their forehead wrinkles. Moderate and severe wrinkles in the upper forehead were treated by the "safe zone" technique. Mild wrinkles and rhytides in the lower forehead were treated by the Microbotox technique. Standard photographs and measurements were taken before and after treatment. The effect on wrinkle reduction and changes in brow heights were assessed.

RESULTS

In total, 330 treatments were followed up in the clinic, and 246 treatments were followed up by telephone. Among the 330 treatments, 213 were evaluated in our clinic 2 to 4 weeks later, and the patients who received these treatments were recruited for effect evaluation and brow height measurements. The posttreatment severity of forehead wrinkles was significantly reduced (P < 0.05), and brow heights remained unchanged (P > 0.05). No severe adverse events were documented. Patient satisfaction was quite high.

CONCLUSIONS

The refined injection pattern is an effective and safe technique to treat horizontal forehead lines. The Microbotox technique enables treatment of the lower frontalis without changes in brow position.

LEVEL OF EVIDENCE: 3

Botulinum toxin in the management of temporomandibular disorders: a systematic review

The aim of this review was to critically investigate and assess the evidence relating to the use and efficacy of botulinum toxin (BTX) in the management of temporomandibular joint disorders (TMD) and masticatory myofascial pain. A comprehensive search was conducted of PubMed, Scopus, Embase, and Cochrane CENTRAL, to find relevant studies from the last 30 years up to the end of July 2018. Seven were identified. Three showed a significant reduction in pain between the BTX and placebo groups and one showed a clinical, but not a significant, difference. In one that compared BTX with another novel treatment, myofascial pain reduced equally in both groups, and in the remaining two there was no significant difference in pain reduction between the BTX and control groups. Of the four studies that assessed mouth opening, two reported that BTX had resulted in a slight improvement; one reported no improvement, and the other a worsening of the condition. A meta-analysis was not possible because of the considerable variation in the studies' designs, the heterogeneity between the groups, and the different assessment tools used. Despite showing benefits, consensus on the therapeutic benefit of BTX in the management of myofascial TMD is lacking. Further randomised controlled trials with larger sample sizes, minimal bias, and longer follow-up periods are now needed.

Botulinum toxin injection, dilution confusion: The impact of toxin diffusion on clinical practice

Botulinum toxins (BoNT) are a standard of care for spasticity management of children with a variety of neuromuscular (NM) conditions. BoNT relaxes skeletal muscles by inhibiting the release of acetylcholine from the neuromuscular junction (NMJ). As part of their training physiatrist become proficient in the targeted injections of BoNT into affected skeletal musculature. While the pharmacology and pharmacokinetics of BoNT are well characterized, there is limited literature on the clinical impact that varying the volume of diluent that a toxin is reconstituted within. In theory, injection of a larger volume of dilute BoNT would allow for a larger spread affect reaching more distant NMJs; the reverse is also be true. Dilution volume of BoNT injections in children produces some unique situations due to their low weight, smaller muscle bulk, an increased relative risk of spread to surrounding structures, and novel differences in concentration of NMJ in immature muscle. Some of these factors may act as guiding principles that providers can use when adjusting from their standard BoNT dilutional practices. Although, there are recommended dosing strategies available each child's spasticity pattern represents a unique situation and providers must be allowed flexibility to think creatively about dilution strategies for BoNT injections.

A pragmatic approach to Botulinum Toxin safety

Botulinum Toxin (BoNT) is widely used to treat hypertonia in pediatric patients. Although serious adverse events (AEs) occur infrequently, they can lead to significant patient morbidity and mortality. This paper will discuss potential safety risks that may affect outcomes, medical comorbidities, medication dosing, targeting techniques, and muscle morphology. It is the responsibility of the physician to discuss risks and benefits regarding the use of BoNT and mitigate risks of AEs while maximizing the effectiveness of the medication.

Safe Needle Insertion Locations for Motor Point Injection of the Triceps Brachii Muscle: A Pilot Cadaveric and Ultrasonography Study

Objective

To determine the location of the motor endplate zones (MoEPs) for the three heads of the triceps brachii muscles during cadaveric dissection and estimate the safe injection zone using ultrasonography.

Methods

We studied 12 upper limbs of 6 fresh cadavers obtained from body donations to the medical school anatomy institution in Seoul, Korea. The locations of MoEPs were expressed as the percentage ratio of the vertical distance from the posterior acromion angle to the midpoint of the olecranon process. By using the same reference line as that used for cadaveric dissection, the safe injection zone away from the neurovascular bundle was identified in 6 healthy volunteers via ultrasonography. We identified the neurovascular bundle and its location with respect to the distal end of the humerus and measured its depth from the skin surface.

Results

The MoEPs for the long, lateral, and medial heads were located at a median of 43.8%, 54.8%, and 60.4% of the length of the reference line in cadaver dissection. The safe injection zone of the medial head MoEPs corresponded to a depth of approximately 3.5 cm from the skin surface and 1.4 cm away from the humerus, as determined by sonography.

Conclusion

Correct identification of the motor points for each head of the triceps brachii would increase the precision and efficacy of motor point injections to manage elbow extensor spasticity.

Innervation zone distribution of the biceps brachii muscle examined using voluntary and electrically-evoked high-density surface EMG

BACKGROUND

High density surface electromyography (EMG) can be used to estimate muscle innervation zones (IZ). The objective of this study was to compare the differences in the distribution of the biceps brachii (BB) IZ derived from voluntary contractions (VC) and electrical stimulation (ES) of the musculocutaneous nerve.

METHODS

Surface EMG signals were recorded from the medial and lateral BB with two 64-channel high density electrode matrices in eight healthy men. The surface EMG was recorded at different percentages of the maximal voluntary contraction (MVC) force (20-100% MVC) and at different percentages of the current needed to elicit a maximal M-wave (20-100% Imax). The IZs of the medial and lateral BB were identified from the EMG signals and expressed as a row number within a given medial-lateral column.

RESULTS

ES current intensity had no significant effect on the group mean IZ location (p > 0.05). However, The IZ during VC was located more proximally with increasing force (p < 0.05), likely due to muscle shortening. The position of the IZ varied slightly (by up to ~ 8 mm) in a medial-lateral direction under both contraction types, but this spatial effect was not significant. The IZ during ES and weak VC (20, 40% MVC) was similar (p > 0.05), but was more proximal in the latter than the former during 60-100% MVC (p < 0.05).

CONCLUSION

ES can be used to detect spatial differences in IZ location free of the confounding effects of muscle shortening and recruitment order of different sized motor units. The method may prove beneficial for locating the IZ in patients who lack voluntary control of their musculature.

Botulinum toxin treatment of spasticity targeted to muscle endplates: an international, randomised, evaluator-blinded study comparing two different botulinum toxin injection strategies for the treatment of upper limb spasticity

OBJECTIVES

The therapeutic effects of botulinum neurotoxin (BoNT) are well documented in upper limb spasticity. However, several factors may influence treatment efficacy, including targeting of neuromuscular junctions (NMJs). We examined whether NMJ-targeted BoNT injections were non-inferior, in terms of efficacy, to current injection practices.

DESIGN

Open-label prospective evaluator-blinded study.

SETTING

Conducted across 20 medical centres in Denmark, Finland, Norway and Sweden (24 September 2012 to 11 March 2015).

PARTICIPANTS

Aged ˃18 years with upper limb spasticity (Modified Ashworth Scale [MAS] score of 2 or 3) following stroke or traumatic brain injury, had received ≥2 consecutive BoNT-A treatment cycles (the latest of which was abobotulinumtoxinA [aboBoNT-A]) and needed BoNT-A retreatment (same modality as previous cycle). Patients requiring aboBoNT-A doses >800units were excluded. In total, 88 patients were randomised (intention-to-treat [ITT] population), most were male (n=58/88, 65.9%) and 54/88 (61.4%) completed the study (per protocol [PP] population).

INTERVENTIONS

Randomisation (1:1) to receive a single dose of aboBoNT-A (≤800 U) according to either current clinical practice (300 U/mL) or as an NMJ-targeted injection (100 U/mL).

PRIMARY OUTCOME MEASURE

Proportion of patients with a ≥1 level reduction from baseline in MAS score at week 4 post-injection (responders).

RESULTS

In the ITT population, the proportion of responders at elbow flexors was 72.7% in the current practice group and 56.8% in the NMJ-targeted group (adjusted difference -0.1673 [95% CIs: -0.3630 to 0.0284]; p=0.0986). Similar results were observed in the PP population (69.0% vs 68.0%, respectively, adjusted difference 0.0707 [-0.1948 to 0.3362]; p=0.6052).

CONCLUSIONS

Owing to the limited number of participants, non-inferiority of NMJ-targeted injections could not be determined. However, there was no statistical difference between groups. Larger studies are needed confirm whether the two techniques offer comparable efficacy.

TRIAL REGISTRATION NUMBER

NCT01682148.

Three dimensional innervation zone imaging in spastic muscles of stroke survivors

OBJECTIVE

The outcome of botulinum toxin (BTX) therapy of post-stroke spasticity relies largely on accuracy of BTX injection to the proximity of innervation zones (IZs). Recently developed three-dimensional IZ imaging (3DIZI) is the only technique currently available to provide 3D distributions of IZs in vivo, yet its performance has not been validated under pathological conditions.

APPROACH

The performance of 3DIZI was evaluated in the spastic biceps brachii muscles of four chronic stroke subjects. High-density surface electromyography (sEMG) and intramuscular electromyography (iEMG) were simultaneously recorded. The IZ location in the 3D space of the spastic biceps calculated using the 3DIZI technique from sEMG recordings were compared against the IZ location detected using intramuscular wires.

MAIN RESULTS

3DIZI successfully reconstructed the IZs in the 3D space of the spastic biceps of all four stroke subjects, with a localization error of 4.7  ±  2.7 mm, and specifically a depth error of 1.8  ±  0.4 mm.

SIGNIFICANCE

Results have demonstrated the robust performance of 3DIZI under pathological conditions, laying a solid foundation for clinical application of 3D source imaging in leading precise BTX injections for spasticity management.

Botulinum neurotoxin formulations: overcoming the confusion

Botulinum toxin A is produced by anaerobic spore-forming bacteria and is used for various therapeutic and cosmetic purposes. Botulinum toxin A injections are the most popular nonsurgical procedure worldwide. Despite an increased demand for botulinum toxin A injections, the clinical pharmacology and differences in formulation of commonly available products are poorly understood. The various products available in the market are unique and vary in terms of units, chemical properties, biological activities, and weight, and are therefore not interchangeable. For safe clinical practice and to achieve optimal results, the practitioners need to understand the clinical issues of potency, conversion ratio, and safety issues (toxin spread and immunogenicity). In this paper, the basic clinical pharmacology of botulinum toxin A and differences between onabotulinum toxin A, abobotulinum toxin A, and incobotulinum toxin A are discussed.

Assessing adverse effects of intra-articular botulinum toxin A in healthy Beagle dogs: A placebo-controlled, blinded, randomized trial

OBJECTIVE

To investigate the clinical, cytological, and histopathological adverse effects of intra-articularly injected botulinum toxin A in dogs and to study whether the toxin spreads from the joint after the injection.

METHODS

A longitudinal, placebo-controlled, randomized clinical trial was conducted with six healthy laboratory Beagle dogs. Stifle joints were randomized to receive either 30 IU of onabotulinum toxin A or placebo in a 1:1 ratio. Adverse effects and spread of the toxin were examined by evaluating dynamic and static weight-bearing of the injected limbs, by assessing painless range of motion and pain on palpation of joints, and by performing synovial fluid analysis, neurological examination, and electrophysiological recordings at different examination time-points in a 12-week period after the injections. The dogs were then euthanized and autopsy and histopathological examination of joint structures and adjacent muscles and nerves were performed.

RESULTS

Intra-articular botulinum toxin A did not cause local weakness or injection site pain. Instead, static weight-bearing and painless range of motion of stifle joints decreased in the placebo limbs. No clinically significant abnormalities associated with intra-articular botulinum toxin A were detected in the neurological examinations. Electrophysiological recordings showed low compound muscle action potentials in two dogs in the botulinum toxin A-injected limb. No significant changes were detected in the synovial fluid. Autopsy and histopathological examination of the joint and adjacent muscles and nerves did not reveal histopathological adverse effects of the toxin.

CONCLUSION

Intra-articular botulinum toxin A does not produce significant clinical, cytological, or histopathological adverse effects in healthy dogs. Based on the electrophysiological recordings, the toxin may spread from the joint, but its clinical impact seems to be low.

Botulinum Toxin in Management of Limb Tremor

Essential tremor is characterized by persistent, usually bilateral and symmetric, postural or kinetic activation of agonist and antagonist muscles involving either the distal or proximal upper extremity. Quality of life is often affected and one's ability to perform daily tasks becomes impaired. Oral therapies, including propranolol and primidone, can be effective in the management of essential tremor, although adverse effects can limit their use and about 50% of individuals lack response to oral pharmacotherapy. Locally administered botulinum toxin injection has become increasingly useful in the management of essential tremor. Targeting of select muscles with botulinum toxin is an area of active research, and muscle selection has important implications for toxin dosing and functional outcomes. The use of anatomical landmarks with palpation, EMG guidance, electrical stimulation, and ultrasound has been studied as a technique for muscle localization in toxin injection. Earlier studies implemented a standard protocol for the injection of (predominantly) wrist flexors and extensors using palpation and EMG guidance. Targeting of muscles by selection of specific activators of tremor (tailored to each patient) using kinematic analysis might allow for improvement in efficacy, including functional outcomes. It is this individualized muscle selection and toxin dosing (requiring injection within various sites of a single muscle) that has allowed for success in the management of tremors.

[Mapping of motor-points in the flexor muscles of the arm for the optimization of botulinum toxin injections in treatment of spasticity]

AIM

To study the location and verification of motor points (MP) of the upper limbs for targeting botulinum toxin (BT) type A injections in the treatment of spasticity.

MATERIAL AND METHODS

Twenty healthy people were examined. Using electromyography a complete study of the muscles of the upper limbs was conducted.

RESULTS

Anatomical localization of MP was performed. The location of MP is identical and does not depend on sex, age and the dominant limb. Tables and maps of MP locations are presented.

CONCLUSION

MP in the flexor muscles of the arm were identified. A surface map with MP location was created. This data may improve the clinical efficacy and feasibility of MP targeting, when injecting BT in spasticity.

Detection of Botulinum Toxin Muscle Effect in Humans Using Magnetic Resonance Imaging: A Qualitative Case Series

BACKGROUND

Although important for dosing and dilution, there are few data describing botulinum toxin (BT) movement in human muscle.

OBJECTIVE

To better understand BT movement within human muscle.

DESIGN

Proof-of-concept study with descriptive case series.

SETTING

Outpatient academic practice.

PARTICIPANTS

Five subjects with stroke who were BT naive with a mean age of 60.4 ± 14 years and time poststroke of 4.6 ± 3.7 years.

METHODS

Three standardized injections were given to the lateral gastrocnemius muscle (LGM): 2 contained 25 units (U) of onabotulinumtoxinA (Botox) in 0.25 mL of saline solution and the third 0.25 mL of saline solution only. The tibialis anterior muscle (TAM) was not injected in any subject. A leg magnetic resonance image was obtained at baseline, 2 months, and 3 months later with a 3.0 Tesla Siemens scanner. Three muscles, the LGM, lateral soleus muscle (LSM), and TAM, were manually outlined on the T2 mapping sequence at each time point. A histogram of T2 relaxation times (T2-RT) for all voxels at baseline was used to calculate a mean and standard deviation (SD) T2-RT for each muscle. Botulinum toxin muscle effect (BTME) at 2 months and 3 months was defined as a subject- and muscle-specific T2-RT voxel threshold ≥3 SD above the baseline mean at or near BT injection sites.

MAIN OUTCOME MEASURES

BTME volume for each leg magnetic resonance imaging slice at 3 time points and 3 muscles for all subjects.

RESULTS

One subject missed the 3-month scan, leaving 18 potential observations of BTME. Little to no BTME effect was seen in the noninjected TAM. A BTME was detected in the LGM in 13 of 18 possible observations, and no effect was detected in 5 observations. Possible BTME effect was seen in the LSM in 3 subjects due to either diffusion through fascia or needle misplacement. Volume of BTME, as defined here, appeared to be substantially greater than the 0.25-mL injection volume.

CONCLUSIONS

This descriptive case series is among the first attempts to quantify BTME within human muscle. Our findings are preliminary and are limited by a few inconsistencies. However, we conclude that use of magnetic resonance imaging to detect the volume of BTME is feasible and may assist researchers in modeling the spread and diffusion of BT within human muscle.

LEVEL OF EVIDENCE

IV.

Utility of ultrasound-guided injection of botulinum toxin type A for muscle imbalance in children with obstetric brachial plexus palsy: Description of the procedure and action protocol

INTRODUCTION

Obstetric brachial plexus palsy (OBPP) usually has a favourable prognosis. However, nearly one third of all severe cases have permanent sequelae causing a high level of disability. In this study, we explore the effectiveness of ultrasound-guided injection of botulinum toxin A (BoNT-A) and describe the procedure.

PATIENTS AND METHODS

We designed a prospective, descriptive study including patients with moderate to severe OBPP who were treated between January 2010 and December 2014. We gathered demographic data, type of OBPP, and progression. Treatment effectiveness was assessed with the Active Movement Scale (AMS), the Mallet classification, and video recordings.

RESULTS

We gathered a total of 14 133 newborns, 15 of whom had OBPP (1.6 per 1000 live births). Forty percent of the cases had severe OBPP (0.4/1000), a dystocic delivery, and APGAR scores < 5; mean weight was 4038g. Mean age at treatment onset was 11.5 months. The muscles most frequently receiving BoNT-A injections were the pronator teres, subscapularis, teres major, latissimus dorsi, and pectoralis major. All the patients who completed the follow-up period (83%) experienced progressive improvements: up to 3 points on the AMS and a mean score of 19.5 points out of 25 on the Mallet classification at 2 years. Treatment improved muscle function and abnormal posture in all cases. Surgery was avoided in 3 patients and delayed in one. Adverse events were mild and self-limited.

CONCLUSIONS

Due to its safety and effectiveness, BoNT-A may be used off-label as an adjuvant to physical therapy and/or surgery in moderate to severe OBPP. Ultrasound may increase effectiveness and reduce adverse effects.

Botulinum Toxin Injection-Site Selection for a Smooth Shoulder Line: An Anatomical Study

Introduction. This study aimed to improve the accuracy of manual needle placement into the trapezius (TM) for smooth shoulder line. Methods. For macroscopic study 12 TMs and for microscopic study 4 cadavers were detached and then sampled, 1⁎1 cm at the four points from the origin to insertion site (0% at the most lateral point of external occipital protuberance and 100% at the most lateral point of acromion). Results. Most of the nerve endings observed during macroscopic investigations were concentrated in the 60–80% region, and the second most distributed region was the 40–60% region. The microscopic results revealed that the 60–80% region on the reference line had the most dense neuromuscular junction area, while the 40–60% and 80–100% areas were similar in their neuromuscular junction densities. Discussion. These anatomical results will be useful in clinical settings especially for cosmetic surgeons.

Muscle histopathology in children with spastic cerebral palsy receiving botulinum toxin type A

INTRODUCTION

Botulinum toxin A (BoNTA) is routine treatment for hypertonicity in children with cerebral palsy (CP).

METHODS

This single-blind, prospective, cross-sectional study of 10 participants (mean age 11 years 7 months) was done to determine the relationship between muscle histopathology and BoNTA in treated medial gastrocnemius muscle of children with CP. Open muscle biopsies were taken from medial gastrocnemius muscle and vastus lateralis (control) during orthopedic surgery.

RESULTS

Neurogenic atrophy in the medial gastrocnemius was seen in 6 participants between 4 months and 3 years post-BoNTA. Type 1 fiber loss with type 2 fiber predominance was significantly related to the number of BoNTA injections (r = 0.89, P < 0.001).

CONCLUSIONS

The impact of these changes in muscle morphology on muscle function in CP is not clear. It is important to consider rotating muscle selection or injection sites within the muscle or allowing longer time between injections.

Approach for needle insertion into the tibialis posterior: An ultrasonography study

INTRODUCTION

To avoid neurovascular damage by needle electrode insertion into the tibialis posterior, we used ultrasonography to determine the proper insertion point based on anatomic landmarks.

METHODS

Using ultrasonography, the safety window, the corrected safety window, and the depth of the tibialis posterior were measured at 4 points (the upper third and midpoint of the tibia using anterior and posterior approaches) in healthy volunteers.

RESULTS

The safety window at the midpoint for the posterior approach was significantly larger than at the other points. The corrected safety window could be defined only at the upper third for the anterior approach and at the midpoint for the posterior approach.

CONCLUSIONS

Among the 4 points used for needle insertion into the tibialis posterior, the midpoint by the posterior approach may be the most favorable insertion point. The upper third may be better for the anterior approach.

Changes of masseter muscle activity following injection of botulinum toxin type A in adult rats

OBJECTIVES

To investigate changes in masseter muscle function following intramuscular injection of different dose-dependent botulinum toxin type A (BTXA).

SETTING AND SAMPLE POPULATION

Department of Orthodontics at Taipei Medical University. Fifty-two, 70-day-old male Wistar rats were randomly divided into four groups. Group I received 7.5 U of BTXA (0.3 ml), Group II received 5.0 U, and Group III received 2.5 U in the right masseter muscle, respectively. Group IV is the control and received no BTXA injection.

MATERIALS AND METHODS

A wire electrode device was implanted to record muscle activity. One week after implantation, the rats were fed every 2 h and EMG signals were recorded during the first hour. All signals were recorded for 12 weeks. Thereafter, EMG data were analyzed for statistical calculation and weights of masseter muscles were measured.

RESULTS

Masseter muscle activity decreased 99% during the first week after BTXA injection and gradually recovered from the 3rd week on in Groups I-III. By the 12th week, muscle activity recovered to 41% in Groups I and II and 56.26% in Group III. No significant changes of muscle activity were observed in Group IV.

CONCLUSION

BTXA induced a reduction in masseter muscle activity and an increased toxin dose resulted in greater depression of muscle activity.

Motor endplate-targeted botulinum toxin injections of the gracilis muscle in children with cerebral palsy

AIM

Intramuscular botulinum toxin-A (BoNT-A) injections reduce spasticity by blocking neurotransmission at the motor endplate (MEP). The goal of this study was to assess the reduction in spasticity achieved by injecting BoNT-A at different sites of the gracilis muscle.

METHOD

Thirty-four gracilis muscles, in 27 children (10 females and 17 males, mean age of 8.6y [SD 2.5y]) with spastic cerebral palsy (unilateral and bilateral, Gross Motor Function Classification System [GMFCS] levels I-IV), were randomly assigned to one of two groups. In one group BoNT-A was injected proximally (at a site 25% of the distance from the pubic tubercle and the medial epicondyle) and in the other it was injected at the MEP zones (half of the dose was administered at 30% of this distance and half at 60%). Spasticity was assessed before and after BoNT-A injection using simultaneous measurements of surface electromyography (sEMG) and angular velocity during passive muscle stretch applied at different velocities. The primary outcome measure included the velocity-dependent change in average root mean square electromyography (RMS-EMG). Secondary outcome was assessed with the Modified Ashworth Scale (MAS) and Modified Tardieu Scale (MTS).

RESULTS

Spasticity decreased more in MEP-targeted muscles than in proximally injected muscles, as demonstrated by a larger reduction in average RMS-EMG values (p=0.04), though this difference was not found with the MAS or MTS.

INTERPRETATION

The results suggest that BoNT-A injection of the gracilis at sites with a high concentration of MEPs is effective at reducing spasticity. These preliminary findings should be confirmed by larger studies. In the case of long muscles, such as the gracilis, the injection site is important.

Determination of injection site in flexor digitorum longus for effective and safe botulinum toxin injection

OBJECTIVE

To determine the optimal injection site in the flexor digitorum longus (FDL) muscle for effective botulinum toxin injection.

METHODS

Fourteen specimens from eight adult Korean cadavers were used in this study. The most proximal medial point of the tibia plateau was defined as the proximal reference point; the most distal tip of the medial malleolus was defined as the distal reference point. The distance of a line connecting the proximal and distal reference points was defined as the reference length. The X-coordinate was the distance from the proximal reference point to the intramuscular motor endpoint (IME), or motor entry point (MEP) on the reference line, and the Y-coordinate was the distance from the nearest point from MEP on the medial border of the tibia to the MEP. IME and MEP distances from the proximal reference point were evaluated using the raw value and the X-coordinate to reference length ratio was determined as a percentage.

RESULTS

The majority of IMEs were located within 30%-60% of the reference length from the proximal reference point. The majority of the MEPs were located within 40%-60% of the reference length from the proximal reference point.

CONCLUSION

We recommend the anatomical site for a botulinum toxin injection in the FDL to be within a region 30%-60% of the reference length from the proximal reference point.

Targeting the motor end plates in the mouse hindlimb gives access to a greater number of spinal cord motor neurons: an approach to maximize retrograde transport

Lower motor neuron dysfunction is one of the most debilitating neurological conditions and, as such, significantly impacts on the quality of life of affected individuals. Within the last decade, the engineering of mouse models of lower motor neuron diseases has facilitated the development of new therapeutic scenarios aimed at delaying or reversing the progression of these conditions. In this context, motor end plates (MEPs) are highly specialized regions on the skeletal musculature that offer minimally invasive access to the pre-synaptic nerve terminals, henceforth to the spinal cord motor neurons. Transgenic technologies can take advantage of the relationship between the MEP regions on the skeletal muscles and the corresponding motor neurons to shuttle therapeutic genes into specific compartments within the ventral horn of the spinal cord. The first aim of this neuroanatomical investigation was to map the details of the organization of the MEP zones for the main muscles of the mouse hindlimb. The hindlimb was selected for the present work, as it is currently a common target to challenge the efficacy of therapies aimed at alleviating neuromuscular dysfunction. This MEP map was then used to guide series of intramuscular injections of Fluoro-Gold (FG) along the muscles' MEP zones, therefore revealing the distribution of the motor neurons that supply them. Targeting the entire MEP regions with FG increased the somatic availability of the retrograde tracer and, consequently, gave rise to FG-positive motor neurons that are organized into rostro-caudal columns spanning more spinal cord segments than previously reported. The results of this investigation will have positive implications for future studies involving the somatic delivery and retrograde transport of therapeutic transgenes into affected motor neurons. These data will also provide a framework for transgenic technologies aiming at maintaining the integrity of the neuromuscular junction for the treatment of lower motor neuron dysfunctions.

Systematic test of neurotoxin dose and volume on muscle function in a rat model

INTRODUCTION

Onabotulinum toxin serotype A (BT-A) is used for a variety of motor and sensory disorders related to abnormal muscle activity.

METHODS

We developed a high-resolution rodent model to allow precise determination of the effect of BT-A dose (measured in units) and injectate volume (measured in μl) on the efficacy of the injection and systemic side effects. Dorsiflexion is the best indicator of injected and contralateral muscle function.

RESULTS

One month after injection, dorsiflexion torque of BT-A-injected limbs was decreased significantly in all experimental groups compared with saline controls (P < 0.05). Torque was also compared among the BT-A groups, which demonstrated a significant effect of dose (P < 0.001), but no effect of volume (P > 0.2) and no dose × volume interaction (P > 0.3). Similar results were observed for other parameters measured.

CONCLUSIONS

These data demonstrate that injection dose and not volume or concentration is the primary determinant of neurotoxin efficacy in a rodent model.