Muscle biopsy substantiates long-term MRI alterations one year after a single dose of botulinum toxin injected into the lateral gastrocnemius muscle of healthy volunteers

The Role of Botulinum Neurotoxin A in the Conservative Treatment of Fractures: An Experimental Study on Rats

This paper explores the role of botulinum neurotoxin in aiding fracture recovery through temporary muscle paralysis. Specifically, it investigates the effects of botulinum neurotoxin-induced paralysis of the sternocleidomastoid muscle on clavicle fractures in rats. The research aims to assess safety, effectiveness, and the impact on fracture healing. Healthy male Albino Wistar rats were divided into four groups: clavicle fracture, botulinum neurotoxin injection, both, and control. Surgeries were conducted under anaesthesia, and postoperatively, animals were monitored for 28 days. Euthanasia and radiological assessment followed, examining fracture healing and muscle changes, while tissues were histopathologically evaluated. The modified Lane-Sandhu scoring system was used for the radiographic evaluation of clavicle fractures, and the results varied from complete healing to nonunion. Histopathological examination at 28 days postfracture showed fibrous tissue, mesenchymal cells, and primary callus formation in all groups. Despite varied callus compositions, botulinum neurotoxin administration did not affect clavicle healing, as evidenced by similar scores to the control group. Several studies have explored botulinum neurotoxin applications in fracture recovery. Research suggests its potential to enhance functional recovery in certain types of fractures. Theoretical benefits include managing muscle spasticity, aiding reduction techniques, and preventing nonunion. However, botulinum neurotoxin's transient effect and nonuniversal applications should be considered. The present study found that botulinum toxin had no clear superiority in healing compared to controls, while histological evaluation showed potential adverse effects on muscle tissue. Further research is essential to understand its risk-benefit balance and long-term effects.

Assessing muscle architecture with ultrasound: implications for spasticity

Botulinum Neurotoxin Type A (BoNT-A) injections using Ultrasound (US) guidance have led to research evaluating changes in muscle architecture. Controversy remains as to what constitutes increased Echo-Intensity (EI) in spastic muscles and whether this may affect outcomes. We aim to provide a narrative review of US muscle architecture changes following Central Nervous System (CNS) lesions and explore their relationship to spasticity. Medline, CINAHL, and Embase databases were searched with keywords: ultrasonography, hypertonia, spasticity, fibrosis, and Heckmatt. Three physicians reviewed the results of the search to select relevant papers. Reviews identified in the search were used as a resource to identify additional studies. A total of 68 papers were included. Four themes were identified, including histopathological changes in spastic muscle, effects of BoNT-A on the muscle structure, available US modalities to assess the muscle, and utility of US assessment in clinical spasticity. Histopathological studies revealed atrophic and fibro-fatty changes after CNS lesions. Several papers described BoNT-A injections contributing to those modifications. These changes translated to increased EI. The exact significance of increased muscle EI remains unclear. The Modified Heckmatt Scale (MHS) is a validated tool for grading muscle EI in spasticity. The use of the US may be an important tool to assess muscle architecture changes in spasticity and improve spasticity management. Treatment algorithms may be developed based on the degree of EI. Further research is needed to determine the incidence and impact of these EI changes in spastic muscles.

Proteomic changes of botulinum neurotoxin injection on muscle growth in children with spastic cerebral palsy

PURPOSE

The study aims to explore the proteomic profile and specific target proteins associated with muscle growth in response to botulinum neurotoxin A (BoNT-A) treatment, in order to improve spasticity management in children with cerebral palsy (CP).

EXPERIMENTAL DESIGN

A total of 54 participants provided 60 plasma samples for proteomic analysis. Among them, six children were sampled before and after receiving their first BoNT-A injection. In addition, 48 unrelated children were enrolled, among whom one group had never received BoNT-A injections and another group was sampled after their first BoNT-A injection. Differentially expressed proteins were identified using the data-independent acquisition (DIA) mass spectrometry approach. Gene Ontology (GO), protein-protein interaction network, and Kyoto Encyclopedia of Genes and Genome analysis were conducted to explore the function and relationship among differentially expressed proteins. The expression levels of target proteins were verified by quantitative real-time PCR and western blotting.

RESULTS

Analysis identified significant differential expression of 90 proteins across two time points, including 48 upregulated and 42 downregulated proteins. The upregulated thioredoxin, α-actinin-1, and aggrecan, and the downregulated integrin beta-1 may affect the growth of muscles affected by spasticity 3 months after BoNT-A injection. This effect is potentially mediated through the activation or inhibition of PI3K-Akt, focal adhesion, and regulation of actin cytoskeleton signaling pathways.

CONCLUSION AND CLINICAL RELEVANCE

BoNT-A injection could lead to a disruption of protein levels and signaling pathways, a condition subsequently associated with muscle growth. This finding might aid clinicians in optimizing the management of spasticity in children with CP.

Short-Term Effects of Botulinum Toxin-A Injection on the Medial Gastrocnemius Histological Features in Ambulant Children with Cerebral Palsy: A Longitudinal Pilot Study

Botulinum toxin-A (BoNT-A) injection is known to exert beneficial effects on muscle tone, joint mobility and gait in children with cerebral palsy (CP). However, recent animal and human studies have raised the concern that BoNT-A might be harmful to muscle integrity. In CP-children, the impact of BoNT-A on muscle structure has been poorly studied, and inconsistent results have been reported. This study was aimed at determining the time course effect of a single BoNT-A administration on medial gastrocnemius (MG) morphology in CP-children. MG microbiopsies from 12 ambulant and BoNT-A-naïve CP-children (age, 3.4 (2.3) years, ranging from 2.5 to 7.8 years; seven boys and five girls; GMFCS I = 5, II = 4 and III = 3) were collected before and 3 and 6 months after BoNT-A treatment to analyze the fiber cross-sectional area (fCSA) and proportion; capillarization; and satellite cell (SC) content. Compared with the baseline, the fCSA decreased at 3 months (-14%, NS) and increased at 6 months (+13%, NS). Fiber size variability was significantly higher at 3 months (type I: +56%, p = 0.032; type IIa: +37%, p = 0.032) and 6 months (type I: +69%, p = 0.04; type IIa: +121%, p = 0.032) compared with the baseline. The higher type I proportion seen at 3 months was still present and more pronounced at 6 months (type I: +17%, p = 0.04; type IIx: -65%, p = 0.032). The capillary fiber density was reduced at 3 months (type I: -43%, NS; type II: -44%, p = 0.0320) but normalized at 6 months. There was a non-significant increase in SC/100 fibers at 3 months (+75%, NS) and 6 months (+40%, NS) compared with the baseline. These preliminary data suggest that BoNT-A induced alterations in the MG of children with CP, which were still present 6 months after BoNT-A injection but with signs of muscle recovery.

Time course of surface electromyography during walking of children with spastic cerebral palsy treated with botulinum toxin type A and its rehabilitation implications

BACKGROUND

The timing of the effects of botulinum toxin A on spastic muscles is not yet fully clarified. The goal of this study was to follow the temporal changes of surface electromyographic activity of lower limb muscles during walking, after a therapeutic dose of botulinum toxin A injected into the calf muscles of children with spastic cerebral palsy.

METHODS

A group of children with spastic equinus foot was administered botulinum toxin A into the gastrocnemius medialis and lateralis muscles. Surface electromyographic activity of the tibialis anterior, gastrocnemius medialis, rectus femoris and medial hamstrings, was recorded before botulinum toxin A injections and after 4, 8, and 16 weeks. Children walked on ground and on a treadmill at an incline of 0% and 12%. The area of electromyographic activity and the index of muscle co-contraction were calculated for specific segments of gait cycle.

FINDINGS

Botulinum toxin A did not modify the speed of gait on ground. ANOVA showed significant differences in electromyography during the stance phase segments with a maximum decrease between 4 and 8 weeks' post botulinum toxin A and a full recovery at 16 weeks. A significant co-contraction of rectus femoris/gastrocnemius medialis, between 0 and 20% and 35-50% of the gait cycle, was observed from the 4th to the 8th week post- botulinum toxin A for both treadmill settings.

INTERPRETATION

The temporal identification of deterioration/recovery of electromyographic activity as well as of muscle co-contractions, could be key elements in a rehabilitation program planning combined with botulinum toxin A.

Botulinum Toxin Treatment of Adult Muscle Stem Cells from Children with Cerebral Palsy and hiPSC-Derived Neuromuscular Junctions

Botulinum neurotoxin type-A (BoNT) injections are commonly used as spasticity treatment in cerebral palsy (CP). Despite improved clinical outcomes, concerns regarding harmful effects on muscle morphology have been raised, and the BoNT effect on muscle stem cells remains not well defined. This study aims at clarifying the impact of BoNT on growing muscles (1) by analyzing the in vitro effect of BoNT on satellite cell (SC)-derived myoblasts and fibroblasts obtained from medial gastrocnemius microbiopsies collected in young BoNT-naïve children (t0) compared to age ranged typically developing children; (2) by following the effect of in vivo BoNT administration on these cells obtained from the same children with CP at 3 (t1) and 6 (t2) months post BoNT; (3) by determining the direct effect of a single and repeated in vitro BoNT treatment on neuromuscular junctions (NMJs) differentiated from hiPSCs. In vitro BoNT did not affect myogenic differentiation or collagen production. The fusion index significantly decreased in CP at t2 compared to t0. In NMJ cocultures, BoNT treatment caused axonal swelling and fragmentation. Repeated treatments impaired the autophagic-lysosomal system. Further studies are warranted to understand the long-term and collateral effects of BoNT in the muscles of children with CP.

Long-Term Muscular Atrophy and Weakness Following Cessation of Botulinum Toxin Type A Injections in the Flexor Digitorum Muscle of Musicians with Focal Hand Dystonia

The present study assessed muscular atrophy and weakness of the flexor digitorum superficialis (FDS) and profundus (FDP) muscle as possible long-term side effects of botulinum toxin (BoNT) injections in hand dystonia patients after the termination of their treatment. For the assessment of both parameters, a group of 12 musicians diagnosed with focal hand dystonia was compared with a group of 12 healthy matched musicians. The minimum and maximum times since the last injection across patients were 0.5 to 3.5 years, respectively. The thickness and strength of the FDS and FDP were assessed via ultrasonography and a strength measurement device. Group differences were estimated through the calculation of the symmetry index between the dominant and non-dominant hand. The results revealed that compared to the control group, thickness and flexion strength of the injected FDS and FDP were decreased by 10.6% ± 5.3% (95% CI) and 12.5% ± 6.4% (95% CI), respectively, in the patient group. The amount of weakness and atrophy was predicted significantly by the total amount of BoNT injected throughout the entire treatment period. In contrast, the time after the last injection did not predict the amount of strength and muscle mass recovery after the cessation of the treatment. The current study revealed that even up to 3.5 years after the termination of BoNT injections, long-term side effects such as weakness and atrophy can still be observed. We suggest that the total BoNT dose should remain as small as possible to reduce long-lasting side effects to the minimum. Although side effects differ significantly among patients, a potential full recovery of atrophy and weakness after the cessation of BoNT treatment might be observed after periods longer than 3.5 years.

Shear Wave Velocity to Evaluate the Effect of Botulinum Toxin on Post-Stroke Spasticity of the Lower Limb

(1) Background: The evaluation of muscles with spasticity using ultrasound elastography has attracted attention recently, and the shear wave velocity (SWV) technique can measure the mechanical properties of tissues objectively and quantitatively. The purpose of this study was to evaluate the effect of using SWV to assess the effect of Botulinum toxin type A (BoNT-A) treatment in adult patients with post-stroke lower limb spasticity. (2) Methods: We assessed the modified Ashworth Scale, the modified Tardieu Scale, and SWV at rest and after stretching before and at 1 month after BoNT-A treatment in 10 adult participants with post-stroke lower limb spasticity. (3) Results: Significant changes in SWV of the ankle joint in maximum dorsiflexion to the extent possible (SWV stretched) were observed after BoNT-A treatment. SWV stretched was positively correlated with joint range of motion. Participants whose joint range of motion did not improve (i.e., gastrocnemius medialis muscle (GCM) extension distance did not change) had significantly more reductions in SWV stretched after BoNT-A treatment. (4) Conclusions: Our results suggest that the SWV measurements may serve as a quantitative assessment to determine the effect of the BoNT-A treatment in adult stroke patients. SWV measurements to assess GCM spasticity should consider the effects of tension, material properties and activation level of muscles. The challenge is to measure SWV with matching limb positions in patients without contractures.

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.

The Short-Term Impact of Botulinum Neurotoxin-A on Muscle Morphology and Gait in Children with Spastic Cerebral Palsy

Children with spastic cerebral palsy (SCP) are often treated with intramuscular Botulinum Neurotoxin type-A (BoNT-A). Recent studies demonstrated BoNT-A-induced muscle atrophy and variable effects on gait pathology. This group-matched controlled study in children with SCP compared changes in muscle morphology 8-10 weeks post-BoNT-A treatment (n = 25, median age 6.4 years, GMFCS level I/II/III (14/9/2)) to morphological changes of an untreated control group (n = 20, median age 7.6 years, GMFCS level I/II/III (14/5/1)). Additionally, the effects on gait and spasticity were assessed in all treated children and a subgroup (n = 14), respectively. BoNT-A treatment was applied following an established integrated approach. Gastrocnemius and semitendinosus volume and echogenicity intensity were assessed by 3D-freehand ultrasound, spasticity was quantified through electromyography during passive muscle stretches at different velocities. Ankle and knee kinematics were evaluated by 3D-gait analysis. Medial gastrocnemius (p = 0.018, -5.2%) and semitendinosus muscle volume (p = 0.030, -16.2%) reduced post-BoNT-A, but not in the untreated control group, while echogenicity intensity did not change. Spasticity reduced and ankle gait kinematics significantly improved, combined with limited effects on knee kinematics. This study demonstrated that BoNT-A reduces spasticity and partly improves pathological gait but reduces muscle volume 8-10 weeks post-injections. Close post-BoNT-A follow-up and well-considered treatment selection is advised before BoNT-A application in SCP.

Anomalies of motor unit amplitude and territory after botulinum toxin injection

OBJECTIVE

Botulinum toxin (BT) induced cholinergic denervation of hyperactive motor units is a clinically accepted and extensively practiced way of managing focal spasticity after stroke. The denervation potentially initiates a temporary reorganization of the motor unit (MU) structure by inducing the emergence of a large number of newly innervated muscle fibers. In this study, we quantify the effect of the BT on motor unit action potential (MUAP) amplitudes and on the motor unit territory areas (MUTA) as seen on the surface of the skin over the biceps brachii (BB) muscle.

APPROACH

We have used a 128 channel high-density electromyography (HDsEMG) grid on the spastic and contralateral BB muscle and recorded the myoelectric activity along with the contraction force during isometric contraction of elbow muscles. We have decomposed the recorded EMG signal into individual MU potentials and estimated the MUAP amplitudes and territory areas before and two weeks after a BT injection.

MAIN RESULT

We found that there were significantly larger median (47±9%) MUAP amplitudes as well as reduction of MUTA (20±2%) two weeks after the injection compared to the respective pre-injection recording.

SIGNIFICANCE

The observed covariation of the amplitude and the territory area indicates that the large amplitude MUs that appeared after the BT injection have a relatively smaller territory area. We discuss the potential contributing factors to these changes subsequent to the injection in the context of the investigated subject cohort.

Reduced Cross-Sectional Muscle Growth Six Months after Botulinum Toxin Type-A Injection in Children with Spastic Cerebral Palsy

Botulinum Neurotoxin type-A (BoNT-A) injections are widely used as first-line spasticity treatment in spastic cerebral palsy (SCP). Despite improved clinical outcomes, concerns regarding harmful effects on muscle morphology have been raised. Yet, the risk of initiating BoNT-A to reduce muscle growth remains unclear. This study investigated medial gastrocnemius (MG) morphological muscle growth in children with SCP (n = 26, median age of 5.2 years (3.5)), assessed by 3D-freehand ultrasound prior to and six months post-BoNT-A injections. Post-BoNT-A MG muscle growth of BoNT-A naive children (n = 11) was compared to (a) muscle growth of children who remained BoNT-A naive after six months (n = 11) and (b) post-BoNT-A follow-up data of children with a history of BoNT-A treatment (n = 15). Six months after initiating BoNT-A injection, 17% decrease in mid-belly cross-sectional area normalized to skeletal growth and 5% increase in echo-intensity were illustrated. These muscle outcomes were only significantly altered when compared with children who remained BoNT-A naive (+4% and -3%, respectively, p < 0.01). Muscle length growth persevered over time. This study showed reduced cross-sectional growth post-BoNT-A treatment suggesting that re-injections should be postponed at least beyond six months. Future research should extend follow-up periods investigating muscle recovery in the long-term and should include microscopic analysis.

Characteristic Variation of Electromechanical Delay After the Botulinum Toxin Injection in Spastic Biceps Brachii Muscles

The objective of this study was to characterize the effects of intramuscular botulinum toxin (BT) injections on the electromechanical delay (EMD) in spastic human biceps muscles. The EMD is calculated as the time lag between the muscle activation onset, as recorded from the surface electromyogram (sEMG), and the onset of recorded force. In a cohort of chronic stroke survivors, we compared the computed EMD derived from the spastic (injected) biceps brachii with that from the contralateral muscle. Eight participants were tested before and up to 3 months after a BT injection. At each session, participants followed an isometric trapezoidal force trajectory at 50 and 30%, respectively, of the tested maximum voluntary contraction (MVC). Joint force and sEMG signals were recorded as well. The number of zero crossings (ZC) of the sEMG during the steady-state portion of the task was also computed. The EMD post-BT was found to increase by 64 ± 10% (at 50% MVC) and 93 ± 18% (at 30% MVC) when compared to pre-BT values, while the number of sEMG-ZC, the mean MVC values, and the force-EMD slope exhibited striking reductions. These parameters, calculated on the contralateral side, remained relatively constant across sessions, with the EMD significantly lower and the MVC values much higher. We discuss potential contributing factors to an increase in EMD values on the affected side, both pre- and post-BT. The observed co-variation across sessions of the increased EMD values with the decreased ZC estimates, a surrogate of motor outflow, and, potentially, more compliant muscle fascicles suggests that the altered motor unit (MU) behavior contributes, at least in part, to the delayed force production.

High Precision Use of Botulinum Toxin Type A (BONT-A) in Aesthetics Based on Muscle Atrophy, Is Muscular Architecture Reprogramming a Possibility? A Systematic Review of Literature on Muscle Atrophy after BoNT-A Injections

Improvements in Botulinum toxin type-A (BoNT-A) aesthetic treatments have been jeopardized by the simplistic statement: “BoNT-A treats wrinkles”. BoNT-A monotherapy relating to wrinkles is, at least, questionable. The BoNT-A mechanism of action is presynaptic cholinergic nerve terminals blockage, causing paralysis and subsequent muscle atrophy. Understanding the real BoNT-A mechanism of action clarifies misconceptions that impact the way scientific productions on the subject are designed, the way aesthetics treatments are proposed, and how limited the results are when the focus is only on wrinkle softening. We designed a systematic review on BoNT-A and muscle atrophy that could enlighten new approaches for aesthetics purposes. A systematic review, targeting articles investigating BoNT-A injection and its correlation to muscle atrophy in animals or humans, filtered 30 publications released before 15 May 2020 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Histologic analysis and histochemistry showed muscle atrophy with fibrosis, necrosis, and an increase in the number of perimysial fat cells in animal and human models; this was also confirmed by imaging studies. A significant muscle balance reduction of 18% to 60% after single or seriated BoNT-A injections were observed in 9 out of 10 animal studies. Genetic alterations related to muscle atrophy were analyzed by five studies and showed how much impact a single BoNT-A injection can cause on a molecular basis. Seriated or single BoNT-A muscle injections can cause real muscle atrophy on a short or long-term basis, in animal models and in humans. Theoretically, muscular architecture reprogramming is a possible new approach in aesthetics.

MRI changes in calf muscles of two children with cerebral palsy following Botulinum Toxin Type A injections: a preliminary report

Intramuscular injections of Botulinum Toxin Type A (BoNT-A) in children with spastic cerebral palsy (CP) have been introduced in clinical practice with the aim of reducing muscle tone, preventing muscle contractures and, ultimately, improving function. The aim of this study was to evaluate prospectively the MRI changes in the calf muscles, gastrocnemius (GN) and soleus (S) of two children with unilateral spastic CP (US-CP), prior and more than 1-year following BoNT-A injections. Two male patients with US-CP were injected at the level of the GN and S muscles. Patients underwent a first lower extremity MRI prior to the first BoNT-A injection at the level of GN and S muscles of the affected side. A second MRI was perfomed 34 and 22 months after the index procedure, respectively. Both legs were investigated together symmetrically, to allow a precise comparison between muscles and structures. The MRI protocol included three sequences: axial-T2 weighted tse, SPACE and axial-T1 weighted. We found that BoNT-A injected GN and S muscles had increased signal intensity on the MRI performed 22 and 34 months after index procedure, when compared to the contralateral, not placebo injected (NaCl) leg. To the best of our knowledge, no previous studies have investigated the changes induced in muscle structures in ambulatory children with US-CP managed by BoNT-A injections. Level of evidence: II.

Triceps Surae Muscle Characteristics in Spastic Hemiparetic Stroke Survivors Treated with Botulinum Toxin Type A: Clinical Implications from Ultrasonographic Evaluation

Equinovarus foot is one of the most commonly spasticity related conditions in stroke survivors, leading to an impaired gait and poor functional performances. Notably, spastic muscles undergo a dynamic evolution following typical pathophysiological patterns. Botulinum Neurotoxin Type A (BoNT-A) is the gold standard for focal spasticity treatment, and ultrasound (US) imaging is widely recommended to guide injections and monitor muscle evolution. The role of BoNT-A in influencing muscle fibroadipose degeneration is still unclear. In this study, we analyzed medial gastrocnemius (MG) and soleus (SOL) US characteristics (cross-sectional area, muscle thickness, pennation angle, and mean echo intensity) in 53 patients. MG and SOL alterations, compared to the unaffected side, depend on the spasticity only and not on the BoNT-A treatment. In functionally preserved patients (functional ambulation classification, FAC > 3; modified Ashworth scale, MAS ≤ 2), the ultrasonographic changes of MG compared to ipsilateral SOL observed in the paretic limb alone seems to be due to histological, anatomical, pathophysiological, and biomechanical differences between the two muscles. In subjects with poor walking capability and more severe spasticity, such ipsilateral difference was found in both calves. In conclusion, BoNT-A does not seem to influence muscle degeneration. Similar muscles undergo different evolution depending on the grade of walking deficit and spasticity.

Denervation Dynamics After Intramuscular BNT Injection in Patients With Focal Spasticity Monitored by MRI and Dynamometry-a Blinded Randomized Controlled Pilot Study

Introduction: Botulinumtoxin associated muscle denervation (BNTMD) can be detected by magnet resonance imaging (MRI), MRI may provide further insights into the exact timeline of BNTMD and the potential impact and timing of physical exercise. We aimed to assess the time interval until detection of BNTMD by MRI and whether immediate physical exercise after intramuscular BNT injection has a measurable effect on clinical parameters and the intramuscular denervation dynamics illustrated by MRI.

Materials and Methods: Eleven age-matched patients were randomized to an “exercise” or “no-exercise” group. Eighty mouse-units of incobotulinumtoxin were injected into the spastic biceps muscle. MRI of the injected region, hand-held dynamometry of elbow flexor strength and clinical rating scales (mAS, CGI-I) were conducted in predefined intervals.

Results: We could not detect BNTMD within 24 h but 7 days after injection independent of group allocation (exercise n = 6, no-exercise n = 5). Denervation signs were more diffuse and spread into adjacent muscles in patients having received exercise. We could not detect differences concerning clinical measures between the two groups.

Conclusions: Physical exercise might influence BNTMD dynamics and promote propagation of T2-MR muscle denervation signs from the injected site into adjacent muscles.

Trial registration:clinicaltrialsregister.eu, Identifier 2017-003117-25.

Effect of Botulinum Toxin Injection on the Progression of Hip Dislocation in Patients with Spastic Cerebral Palsy: A Pilot Study

Hip adductor spasticity is a contributing factor to hip dislocation in patients with cerebral palsy (CP). We hypothesized that botulinum toxin injected into the hip adductor muscles would reduce spasticity and help prevent hip dislocation. Twenty patients with bilateral spastic CP aged 2 to 10 years with gross motor function classification system level IV or V were included. Botulinum toxin was injected into the hip adductor muscles at baseline and at 6-month follow-up. Muscle tone was measured with an eight-channel surface electromyography (EMG) recorder. A hip X-ray was performed, and Reimer’s hip migration index (MI) was measured. The Wilcoxon signed-rank test was used to compare the surface EMG values of the hip muscles at baseline and follow-up. The mean root mean square surface EMG value of the hip adductor muscles was significantly reduced at 1, 2, 3, and 7 months after the first injection, up to approximately 53% of the baseline. The 1-year progression of the hip MI was −0.04%. Repeated sessions of botulinum toxin injections at the hip adductor muscles significantly reduced muscle tone and hip displacement. A botulinum toxin injection may be used as an adjunctive treatment in the prevention of hip dislocation.

The effectiveness of a Botulinum Toxin A infiltration in the management of bicipital cramps after arthroscopic biceps tenotomy

A challenging complication of arthroscopic biceps surgery is the persistent painful cramping of the biceps. There is a paucity of data upon nonsurgical treatment of this debilitating complication. We pro- pose an intramuscular injection of botulinum toxin A (BTX-A) for painful bicipital cramping after tenotomy of the long head of the biceps brachii tendon (LHBT). Ten patients with a painful Popeye sign after tenotomy of LHBT, were treated with intramuscular injection of 100 IU of BTX-A. Mean patient age was 56 years and mean time from surgery to infiltration was 317 days. The Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score was obtained. Pain was objectified by a visual analogue scale (VAS). Patient satisfaction was described as excellent, good, satisfactory, or poor, three and six months after injection. Mean VAS prior to infiltration was 6.8 and decreased significantly to 2.6 at follow-up. Mean QuickDash was 54.04 prior to infiltration and decreased to 19.84 at follow-up. Patient satisfaction was excellent in 9 and good in 1 patient. We report a significant pain reduction and functional improvement following BTX-A infiltration as treatment of painful bicipital cramping after tenotomy of LHBT.

Botulinum toxin in the masseter muscle: Lingering effects of denervation

Botulinum neurotoxins (BoNTs) are paralytic agents used to treat a variety of conditions in jaw muscles. Although their effect is considered temporary, there are reports of persistent functional changes. Using rabbits that received BoNT injection in one masseter muscle, the recovery of neuromuscular connection was investigated using nerve stimulation to evoke an electromyographic (EMG) response, and the recovery of muscle fibers was investigated using histological morphometry and bromodeoxyuridine (BrdU) immunohistochemistry. One month after treatment, evoked EMG was greatly reduced in both amplitude and duration, indicating that little reinnervation had taken place. Muscle fibers were atrophied and collagenous tissue was increased. Three months after treatment, evoked EMG duration was normal, indicating that at least some neuromuscular junctions were functional. Histologically, some muscle fibers were hypertrophied, some were still atrophied, and some appeared to have died. Fibrosis was still apparent amid slight increases in dividing cells and regenerating fibers. The histological effects of BoNT were evident although attenuated at a distance of about 1 cm from the injection level, but no regional differences could be discerned for the evoked EMGs. In conclusion, there were persistent muscular deficits seen 3 months after BoNT treatment that may have been caused by the failure of some affected muscle fibers to become reinnervated.

The Contribution of Decreased Muscle Size to Muscle Weakness in Children With Spastic Cerebral Palsy

Muscle weakness is a common clinical symptom in children with spastic cerebral palsy (SCP). It is caused by impaired neural ability and altered intrinsic capacity of the muscles. To define the contribution of decreased muscle size to muscle weakness, two cohorts were recruited in this cross-sectional investigation: 53 children with SCP [median age, 8.2 (IQR, 4.1) years, 19/34 uni/bilateral] and 31 children with a typical development (TD) [median age, 9.7 (IQR, 2.9) years]. Muscle volume (MV) and muscle belly length for m. rectus femoris, semitendinosus, gastrocnemius medialis, and tibialis anterior were defined from three-dimensional freehand ultrasound acquisitions. A fixed dynamometer was used to assess maximal voluntary isometric contractions for knee extension, knee flexion, plantar flexion, and dorsiflexion from which maximal joint torque (MJT) was calculated. Selective motor control (SMC) was assessed on a 5-point scale for the children with SCP. First, the anthropometrics, strength, and muscle size parameters were compared between the cohorts. Significant differences for all muscle size and strength parameters were found (p ≤ 0.003), except for joint torque per MV for the plantar flexors. Secondly, the associations of anthropometrics, muscle size, gross motor function classification system (GMFCS) level, and SMC with MJT were investigated using univariate and stepwise multiple linear regressions. The associations of MJT with growth-related parameters like age, weight, and height appeared strongest in the TD cohort, whereas for the SCP cohort, these associations were accompanied by associations with SMC and GMFCS. The stepwise regression models resulted in ranges of explained variance in MJT from 29.3 to 66.3% in the TD cohort and from 16.8 to 60.1% in the SCP cohort. Finally, the MJT deficit observed in the SCP cohort was further investigated using the TD regression equations to estimate norm MJT based on height and potential MJT based on MV. From the total MJT deficit, 22.6–57.3% could be explained by deficits in MV. This investigation confirmed the disproportional decrease in muscle size and muscle strength around the knee and ankle joint in children with SCP, but also highlighted the large variability in the contribution of muscle size to muscle weakness.

Contribution of Single-Fiber Evaluation on Monitoring Outcomes Following Injection of Botulinum Toxin-A: A Narrative Review of the Literature

Botulinum toxin-A (BoNT-A) blocks acetylcholine release at the neuromuscular junction (NMJ) and is widely used for neuromuscular disorders (involuntary spasms, dystonic disorders and spasticity). However, its therapeutic effects are usually measured by clinical scales of questionable validity. Single-fiber electromyography (SFEMG) is a sensitive, validated diagnostic technique for NMJ impairment such as myasthenia. The jitter parameter (µs) represents the variability of interpotential intervals of two muscle fibers from the same motor unit. This narrative review reports SFEMG use in BoNT-A treatment. Twenty-four articles were selected from 175 eligible articles searched in Medline/Pubmed and Cochrane Library from their creation until May 2020. The results showed that jitter is sensitive to early NMJ modifications following BoNT-A injection, with an increase in the early days’ post-injection and a peak between Day 15 and 30, when symptoms diminish or disappear. The reappearance of symptoms accompanies a tendency for a decrease in jitter, but always precedes its normalization, either delayed or nonexistent. Increased jitter is observed in distant muscles from the injection site. No dose effect relationship was demonstrated. SFEMG could help physicians in their therapeutic evaluation according to the pathology considered. More data are needed to consider jitter as a predictor of BoNT-A clinical efficacy.

Quantification and Monitoring of the Effect of Botulinum Toxin A on Paretic Calf Muscles of Children With Cerebral Palsy With MRI: A Preliminary Study

Background: Muscles from patients with cerebral palsy (CP) are often spastic and form contractures that limit the range of motion. Injections of botulinum toxin A (BTX) into the calf muscles are an important treatment for functional equinus; however, improvement in gait function is not always achieved. BTX is also used to test muscle weakening for risk evaluation of muscle lengthening surgery. Our aim was to assess the effect of BTX over time on calf muscle properties in pediatric CP patients with MRI.

Material and Methods: Six toe-walking CP patients (mean age 11.6 years) with indication for lengthening surgery were prospectively enrolled and received BTX injections into the gastrocnemius and soleus muscles. MRI scans at 3T of the lower legs and clinical examinations were performed pre-BTX, 6 weeks (6w), and 12 weeks (12w) post-BTX. A fat-suppressed 2D multi-spin-echo sequence was used to acquire T₂ maps and for segmentation. Fat fraction maps were calculated from 3D multi-echo Dixon images. Diffusion tensor imaging (DTI) with a 2D echo-planar imaging (EPI) sequence yielded maps of the mean apparent diffusion coefficient (ADC) and of the fractional anisotropy (FA). Hyperintense regions of interest (ROIs) on the T₂-weighted (T₂w) images at 6w were segmented in treated muscles. Mean values of T₂, fat fraction, ADC, and FA were calculated in hyperintense ROIs and in reference ROIs in non-treated muscles.

Results: Hyperintensity on T₂w scans and increased T₂ (group mean ± standard deviation: 35 ± 1 ms pre-BTX, 45 ± 2 ms at 6w, and 44 ± 2 ms at 12w) were observed in all patients at the injection sites. The T₂ increase was spatially limited to parts of the injected muscles. FA increased (0.30 ± 0.03 pre-BTX, 0.34 ± 0.02 at 6w, and 0.36 ± 0.03 at 12w) while ADC did not change in hyperintense ROIs, indicating a BTX-induced increase in extracellular space and a simultaneous decrease of muscle fiber diameter. Fat fraction showed a trend for increase at 12w. Mean values in reference ROIs remained unchanged.

Conclusion: MRI showed limited spatial distribution of the BTX-induced effects in pediatric CP patients. It could be a promising non-invasive tool for future studies to test BTX treatment protocols.

Changes in Muscle Mass after Botulinum Toxin Injection in Children with Spastic Hemiplegic Cerebral Palsy

We aimed to evaluate muscle mass changes after injection of botulinum toxin (BoNT) in children with spastic hemiplegic cerebral palsy (CP). Children aged between 2 and 12 years who were diagnosed with hemiplegic CP with spastic equinus foot were prospectively recruited and administered BoNT in the affected leg. Lean body mass (LBM) of both legs and total limbs was measured by dual-energy X-ray absorptiometry (DXA) preinjection and 4 and 12 weeks after injection. A total of 15 children were enrolled into the study. LBM of both legs and total limbs increased significantly over 12 weeks of growth. The ratio of LBM of the affected leg to total limbs and to the unaffected leg significantly reduced at 4 weeks after injection compared with preinjection but significantly increased at 12 weeks after injection compared with 4 weeks after injection. In conclusion, the muscle mass of the affected leg after BoNT injection in children with hemiplegic spastic CP decreased at 4 weeks after BoNT injection but significantly recovered after 12 weeks after injection.

Skeletal Muscle in Cerebral Palsy: From Belly to Myofibril

This review will provide a comprehensive, up-to-date review of the current knowledge regarding the pathophysiology of muscle contractures in cerebral palsy. Although much has been known about the clinical manifestations of both dynamic and static muscle contractures, until recently, little was known about the underlying mechanisms for the development of such contractures. In particular, recent basic science and imaging studies have reported an upregulation of collagen content associated with muscle stiffness. Paradoxically, contractile elements such as myofibrils have been found to be highly elastic, possibly an adaptation to a muscle that is under significant in vivo tension. Sarcomeres have also been reported to be excessively long, likely responsible for the poor force generating capacity and underlying weakness seen in children with cerebral palsy (CP). Overall muscle volume and length have been found to be decreased in CP, likely secondary to abnormalities in sarcomerogenesis. Recent animal and clinical work has suggested that the use of botulinum toxin for spasticity management has been shown to increase muscle atrophy and fibrofatty content in the CP muscle. Given that the CP muscle is short and small already, this calls into question the use of such agents for spasticity management given the functional and histological cost of such interventions. Recent theories involving muscle homeostasis, epigenetic mechanisms, and inflammatory mediators of regulation have added to our emerging understanding of this complicated area.

Intramuscular BoNT/A injections cause an inflammatory response in the muscle tissue of rats

Objectives

The purpose of the present study was to investigate whether intramuscular BoNT/A injections cause an systemic inflammatory response and a local inflammatory response in the muscle tissue.

Methods

Thirty-two male Sprague Dawley rats treated with BoNT/A (i.m., 1IU) were divided in four groups, depending on the time of BoNT/A injection (2 days before, 1, 2, and 4 weeks before the experiment). Bio-Plex Pro Rat Cytokine 23-plex Multiplex Assay (Bio-Rad, USA).

Results

Systemic inflammation: 17 cytokines (IL1-α ( p = 0.005), IL-1β ( p = 0.01), IL-2 ( p = 0.04), IL-4 ( p = 0.03), IL-6 ( p = 0.03), IL-10 ( p = 0.02), IL12(p70) ( p = 0.03), IL-13 ( p = 0.04), IL-17 ( p = 0.03), GM-CSF ( p = 0.03), INF-γ ( p = 0.03), MIP-1α ( p = 0.03), MIP-3α ( p = 0.04), RANTES ( p = 0.001), TNF-α ( p = 0.04), vascular endothelial growth factor ( p = 0.03), and MCP-1 ( p = 0.02)) showed significantly higher expression levels 2 days after intramuscular BoNT/A injections compared to other time points (1, 2, and 4 weeks). Local inflammation: 12 cytokines (IL-1β ( p = 0.02), IL-6 ( p = 0.002), IL-10 ( p = 0.02), IL-13 ( p = 0.04), IL-17 ( p = 0.02), TNF-α ( p = 0.001), GM-CSF ( p = 0.01), M-CSF ( p = 0.04), MIP-1α ( p = 0.04), MIP-3α ( p = 0.002), RANTES ( p = 0.02), and MCP-1( p = 0.004)) showed higher expression levels 2 and/or 4 weeks after intramuscular BoNT/A injections compared to the other time points (2 days and 1 week).

Conclusion

Intramuscular BoNT/A injections result in a rapid systemic inflammatory response that only lasts a couple of days. At the same time, intramuscular BoNT/A injections cause an inflammatory response locally in the muscle with significantly higher cytokine levels 2 and/or 4 weeks after injections.

Does Botulinum Toxin Treatment Affect the Ultrasonographic Characteristics of Post-Stroke Spastic Equinus? A Retrospective Pilot Study

Equinovarus/equinus foot is a pattern most commonly treated with botulinum toxin type A in patients with post-stroke spasticity involving the lower limbs; the gastrocnemius is the muscle most frequently injected. Spastic equinovarus/equinus can present a mixture of conditions, including spasticity, muscle/tendon shortening, muscle weakness and imbalance. In this study, we wanted to determine whether botulinum toxin treatment affects the ultrasonographic characteristics of post-stroke spastic equinus. The same dose of AbobotulinumtoxinA was injected into the gastrocnemius medialis and lateralis of 21 chronic stroke patients with spastic equinus. Clinical (Ashworth scale and ankle range of motion) and ultrasound (conventional and sonoelastography) evaluation of the treated leg was carried out before and 4 weeks after injection. No significant effects of botulinum toxin treatment on the ultrasonographic characteristics of spastic equinus were observed. As expected, there were significant improvements in ankle passive dorsiflexion range of motion and calf muscle spasticity at 1 month after treatment. There was a direct association between Achilles tendon elasticity and calf muscle spasticity at baseline evaluation. Larger studies with a long-term timeline of serial evaluations are needed to further investigate the possible effects of botulinum toxin injection on spastic muscle characteristics in patients with post-stroke spasticity.

Rectus Femoris Characteristics in Post Stroke Spasticity: Clinical Implications from Ultrasonographic Evaluation

In stroke survivors, rectus femoris (RF) spasticity is often implicated in gait pattern alterations such as stiff knee gait (SKG). Botulinum toxin type A (BoNT-A) is considered the gold standard for focal spasticity treatment. However—even if the accuracy of injection is crucial for BoNT-A efficacy—instrumented guidance for BoNT-A injection is not routinely applied in clinical settings. In order to investigate the possible implications of an inadequate BoNT-A injection on patients’ clinical outcome, we evaluated the ultrasound-derived RF characteristics (muscle depth, muscle thickness, cross-sectional area and mean echo intensity) in 47 stroke survivors. In our sample, we observed wide variability of RF depth in both hemiparetic and unaffected side of included patients (0.44 and 3.54 cm and between 0.25 and 3.16 cm, respectively). Moreover, our analysis did not show significant differences between treated and non-treated RF in stroke survivors. These results suggest that considering the inter-individual variability in RF muscle depth and thickness, injection guidance should be considered for BoNT-A treatment in order to optimize the clinical outcome of treated patients. In particular, ultrasound guidance may help the clinicians in the long-term follow-up of muscle quality.

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.

Effectiveness and safety of early intramuscular botulinum toxin injections to prevent shoulder deformity in babies with brachial plexus birth injury (POPB-TOX), a randomised controlled trial: study protocol

INTRODUCTION

In children with brachial plexus birth injury (BPBI), denervation of the shoulder muscles leads to bony deformity in the first months of life, reducing active and passive range of motion (ROM) and causing activity limitation. The aim of this multicentre randomised controlled trial is to evaluate the effectiveness of botulinum toxin injections (BTI) in the shoulder internal rotator muscles of 12-month-old babies in limiting the progression of posterior subluxation of the glenohumeral joint, compared with a sham procedure mimicking BTI. The secondary aims are to evaluate the effectiveness of BTI in (1) limiting the progression of glenoid retroversion and three-dimensional (3D) deformity and (2) improving shoulder ROM and upper limb function, as well as to confirm the tolerance of BTI.

METHODS AND ANALYSIS

Sixty-two babies with unilateral BPBI and a risk of posterior humeral head subluxation will be included. Only those with at least 7% posterior subluxation of the humeral head compared with the contralateral shoulder on the MRI will be randomised to one of two groups: 'BTI' and 'Sham'. The BTI group will receive BOTOX injections at the age of 12 months in the internal shoulder rotator muscles (8 UI/kg). The sham group will undergo a sham BTI procedure. Both groups will undergo repeated shoulder MRI at 18 months of age to quantify changes in the percentage of posterior migration of the humeral head (primary outcome), glenoid version and 3D bone deformity. Clinical evaluations (passive shoulder ROM, active movement scale) will be carried out at baseline and 15 and 18 months of age. The mini-assisting hand assessment will be rated between 10 and 11 months and at 18 months of age. Adverse events will be recorded at least monthly for each child.

ETHICS AND DISSEMINATION

Full ethical approval for this study has been obtained. The findings will be disseminated in peer-reviewed publications.

TRIAL REGISTRATION NUMBER

EudraCT: 2015-001402-34 in European Clinical Trial database; NCT03198702 in Clinical Trial database; Pre-results.

Comprehensive evaluation of gait, spasticity, and muscle morphology: A case report of a child with spastic paresis treated with Botulinum NeuroToxin‐A, serial casting, and physiotherapy

Comprehensive instrumented muscle and joint assessments should be considered when prescribing Botulinum NeuroToxin‐A (BoNT‐A) treatment in spastic paresis. In a child with spastic paresis, comprehensive evaluation following treatment with BoNT‐A, serial casting, and physiotherapy showed that short‐term improvements in gait occurred without changes in muscle morphology. Rather, foot flexibility increased.

Architectural Changes in the Medial Gastrocnemius on Sonography after Nerve Ablation in Healthy Adults

Architectural changes in healthy muscle after denervation have not yet been reported. This study aimed to investigate architectural changes in the medial head of the gastrocnemius muscle (GCM) after aesthetic tibial nerve ablation in healthy adults using ultrasonography (US). The effects of tibial nerve ablation were verified by visual observation and surface electromyography analysis. US images of medial GCMs were taken by one trained physician using B-mode and real-time US with a linear-array probe before nerve ablation, at 1 week after nerve ablation and at 3 months after nerve ablation in an anatomic standing position with the feet about shoulder-width apart in 19 healthy adults (17 females and 2 males). Muscle thickness was significantly reduced on the left side at 1 week and 3 months after the procedure and on the right side at 3 months after the procedure (p<0.050). Although fascicle length was not significantly changed, pennation angle was significantly reduced on both sides at 3 months after the procedure (p<0.050). Muscle thickness and pennation angle of the muscle fascicle were significantly reduced, although fascicle length was not significantly changed, after tibial nerve ablation in the medial GCM of healthy adults.

Botulinum Toxin in the Management of Children with Cerebral Palsy

During the past 25 years, botulinum toxin type A (BoNT-A) has become the most widely used medical intervention in children with cerebral palsy. In this review we consider the gaps in our knowledge in the use of BoNT-A and reasons why muscle morphology and function in children with cerebral palsy are impaired. We review limitations in our knowledge regarding the mechanisms underlying the development of contractures and the difficulty in preventing them. It is clear from this review that injection of BoNT-A in the large muscles of both the upper and lower limbs of children with cerebral palsy will result in a predictable decrease in muscle activity, which is usually reported as a reduction in spasticity, for between 3 and 6 months. These changes are noted by the use of clinical tools such as the Modified Ashworth Scale and the Modified Tardieu Scale. Decreased muscle over-activity usually results in improved range of motion in distal joints. Injection of the gastrocnemius muscle for toe-walking in a child with hemiplegia or diplegia usually has the effect of increasing the passive range of dorsiflexion at the ankle. In our review, we found that this may result in a measurable improvement in gait by the use of observational gait scales or gait analysis, in some children. However, improvements in gait function are not always achieved and are small in magnitude and short lived. We found that some of the differences in outcomes in clinical trials may relate to the use of adjunctive interventions such as serial casting, orthoses, night splints and intensive therapy. We note that the majority of clinical trials of the use of BoNT-A in children with cerebral palsy have focussed on a single injection cycle and this is insufficient to understand the balance between benefit and harm. Most outcomes were reported in terms of changes in muscle tone and there were fewer studies with robust methodology that reported improvements in function. Changes in the domains of activities and participation have rarely been reported in studies to date. There were no clinical reviews to date that consider the findings of studies in human volunteers and in experimental animals and their relevance to clinical protocols. In this review we found that studies in human volunteers and in experimental animals show muscle atrophy after an injection of BoNT-A for at least 12 months. Muscle atrophy was accompanied by loss of contractile elements in muscle and replacement with fat and connective tissue. It is not currently known if these changes, mediated at a molecular level, are reversible. We conclude that there is a need to revise clinical protocols by using BoNT-A more thoughtfully, less frequently and with greatly enhanced monitoring of the effects on injected muscle for both short-term and long-term benefits and harms.

Botulinum toxin A-induced muscle paralysis stimulates Hdac4 and differential miRNA expression

At sufficient dose, intramuscular injection of Botulinum toxin A causes muscle wasting that is physiologically consistent with surgical denervation and other types of neuromuscular dysfunction. The aim of this study was to clarify early molecular and micro-RNA alterations in skeletal muscle following Botulinum toxin A-induced muscle paralysis. Quadriceps were analyzed for changes in expression of micro- and messenger RNA and protein levels after a single injection of 0.4, 2 or 4U Botulinum toxin A (/100g body weight). After injection with 2.0U Botulinum toxin A, quadriceps exhibited significant reduction in muscle weight and increased levels of ubiquitin ligase proteins at 7, 14 and 28 days. Muscle miR-1 and miR-133a/b levels were decreased at these time points, whereas a dose-responsive increase in miR-206 expression at day 14 was observed. Expression of the miR-133a/b target genes RhoA, Tgfb1 and Ctfg, and the miR-1/206 target genes Igf-1 and Hdac4, were upregulated at 28 days after Botulinum toxin A injection. Increased levels of Hdac4 protein were observed after injection, consistent with anticipated expression changes in direct and indirect Hdac4 target genes, such as Myog. Our results suggest Botulinum toxin A-induced denervation of muscle shares molecular characteristics with surgical denervation and other types of neuromuscular dysfunction, and implicates miR-133/Tgf-β1/Ctfg and miR-1/Hdac4/Myog signaling during the resultant muscle atrophy.

Muscle volume alterations after first botulinum neurotoxin A treatment in children with cerebral palsy: a 6-month prospective cohort study

AIM

This study aimed to track alterations in muscle volume for 6 months in children with cerebral palsy (CP) after the first exposure to botulinum neurotoxin A (BoNT-A), a commonly used focal spasticity treatment.

METHOD

Eleven ambulant children (eight males, three females) with spastic CP, mean age 8 years 10 months (SD 3y 1mo) participated. Participants received injections to the affected gastrocnemius. The muscle volume of the gastrocnemius, soleus, tibialis anterior, and hamstrings was measured using magnetic resonance imaging. Muscle volume was normalized to bone length, and changes analysed relative to baseline. Assessments were conducted 1 week before, and 4 weeks, 13 weeks, and 25 weeks after BoNT-A treatment.

RESULTS

All children demonstrated positive clinical and functional gains. Muscle volume of the injected gastrocnemius was found to be significantly reduced at 4 weeks (-5.9%), 13 weeks (-9.4%), and 25 weeks (-6.8%). Significant increases in normalized soleus muscle volume were identified at each follow-up, while hamstrings showed significant increase at 4 weeks only.

INTERPRETATION

Absolute and normalized muscle volume of the injected muscle reduces after first BoNT-A exposure, and does not return to baseline volume by 25 weeks. Hypertrophy is seen in the soleus up to 25 weeks; the volume of the plantar flexor compartment is stable.

WHAT THIS PAPER ADDS

Muscle atrophy after first botulinum neurotoxin A (BoNT-A) exposure in children with cerebral palsy is noted. Mild BoNT-A-induced muscle atrophy is still apparent 6 months after BoNT-A exposure. Hypertrophy is evident in soleus after gastrocnemius BoNT-A exposure. Total plantarflexor volume is unchanged.

Determinants of muscle preservation in individuals with cerebral palsy across the lifespan: a narrative review of the literature

In individuals with cerebral palsy (CP), smaller muscle and atrophy are present at young age. Many people with CP also experience a decline in gross motor function as they age, which might be explained by the loss of muscle mass. The clinical observation of muscle wasting has prompted a comparison with sarcopenia in older adults, and the term accelerated musculoskeletal ageing is often used to describe the hallmark phenotype of CP through the lifespan. However, there has been very little research emphasis on the natural history of ageing with CP and even less with respect to the determinants or prevention of muscle loss with CP. Considering the burgeoning interest in the science of muscle preservation, this paper aims to (i) describe the characteristics of accelerated musculoskeletal ageing in people with CP, (ii) describe the pathophysiology of sarcopenia and parallels with CP, and (iii) discuss possible therapeutic approaches, based on established approaches for sarcopenia.

Ultrasonographic evaluation of changes in the muscle architecture of the gastrocnemius with botulinum toxin treatment for lower extremity spasticity in children with cerebral palsy

BACKGROUND

Botulinum toxin A treatment involves injecting botulinum toxin A to relax muscle spasticity. Using ultrasonography, this study examined changes in the muscle architecture before and after treatment to evaluate the influence of botulinum toxin A injection on muscles.

METHODS

The participants included 18 children (mean age, 6.2 years) with cerebral palsy who were treated with botulinum toxin A for lower extremity spasticity and 27 healthy children (mean age, 6.4 years) as a control group. In all cases, botulinum toxin A was injected into the gastrocnemius muscle. The muscle length, muscle width, and pennation angle (which indicates the degree of muscle fiber tone), were measured using B-mode ultrasonography before and 12 weeks after injection.

RESULTS

The muscle length and muscle width were shorter in the cerebral palsy group than in the control group. The pennation angle in the cerebral palsy group significantly decreased after injection from 28.2 ± 3.6° to 25.8 ± 2.5° in the resting position of the ankle and from 18.6 ± 2.8° to 15.9 ± 1.7° in the maximum dorsiflexion position of the ankle. In the control group, the pennation angle was 25.9 ± 3.2° in the resting position of the ankle and 15.1 ± 2.5° in the maximum dorsiflexion position of the ankle. The rate of increase of fascicle length during passive movement from the resting position of the ankle to the maximum dorsiflexion position was 143.9% in the cerebral palsy group, which was significantly less than the value of 157.7% in the control group. After botulinum toxin A treatment, the rate of increase of fascicle length in the cerebral palsy group increased to 155.1%.

CONCLUSIONS

The decrease in the pennation angle after botulinum toxin A treatment is considered to be the result of a reduction of spasticity and subsequent structural changes in flaccid muscle fibers.

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.

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.

Is Botulinum Toxin Type A a Valuable Adjunct During Femoral Lengthening? A Randomized Trial

BACKGROUND

Reduced joint ROM and distraction-induced pain are common complaints of patients who have undergone gradual femoral lengthening. Attempts to reduce the effects of lengthening on joint motion have included the use of botulinum toxin to reduce the muscle forces that restrict motion. The benefits of this approach during femoral lengthening, however, have not been conclusively established.

QUESTIONS/PURPOSES

We wished to evaluate the effects of botulinum toxin type A (BtX-A) injection in the anterior thigh muscles during femoral distraction osteogenesis on adjacent joint ROM and distraction-induced pain. We asked: (1) Does injection of BtX-A in the quadriceps muscles lead to improved knee and hip motion during femoral lengthening? (2) Does injection of BtX-A reduce pain during femoral lengthening?

METHODS

A single-center, double-blind, randomized placebo-controlled trial was conducted. Forty-four patients (88 femurs) undergoing bilateral femoral lengthening for familial short stature were included in the study. BtX-A (200 IU) was injected intraoperatively in the quadriceps muscles of one thigh. An equal volume of sterile normal saline was injected in the other thigh as a control. Selection of the limb receiving the toxin was randomized. Clinical evaluation included a VAS score for pain measurement, ROM evaluation of the hips and knees, and measurement of thigh circumference. Side-to-side differences were analyzed throughout the entire consolidation phase. No patients were lost to followup, leaving 44 patients (88 femurs). The mean followup was 26 months (range, 14-40 months). The distraction rate and final length of gain were similar between treated and control limbs. A priori power analysis suggested that 44 legs were required in each group to achieve statistical significance of 0.05 with 90% power to detect a 50% difference in treatment effect between treatment and control groups.

RESULTS

There were no differences in hip ROM, knee ROM, or maximal thigh circumference between the two lower extremities at any time during the study period. VAS scores were no different between the patients who received BtX-A and those who received saline.

CONCLUSIONS

Local injection of 200 IU BtX-A in the quadriceps muscles does not appear to reduce distraction-induced pain nor enhance ROM in the hip or knee during femoral lengthening. Additional studies are needed to evaluate the effect of larger doses or different injection methods. Based on our findings, we do not recommend routine use of botulinum injections during limb lengthening and believe any further use of this drug should only be in the context of a controlled trial.

LEVEL OF EVIDENCE

Level II, therapeutic study.

Medial gastrocnemius muscle volume in ambulant children with unilateral and bilateral cerebral palsy aged 2 to 9 years

AIM

Calf muscle growth in children with unilateral cerebral palsy (UCP) and bilateral cerebral palsy (BCP) is unknown. This cross-sectional study examines the medial gastrocnemius growth rates of ambulatory children with UCP and BCP compared with children with typical development (CTD), aged 2 to 9 years.

METHOD

Fifty children with UCP (mean age 66mo [SD 18], 29 males, Gross Motor Function Classification System [GMFCS] I=32, II=18), 50 children with BCP (age 64mo [SD 19], 31 males, GMFCS I=21, II=29), and 78 CTD (age 64mo [SD 16], 40 males) participated in the study. The medial gastrocnemius muscle volume was measured at rest using a validated freehand three-dimensional (3D) ultrasound method.

RESULTS

Normalized medial gastrocnemius muscle growth rate was significantly less in the children with UCP (0.001 mL/kg/mo) compared with the BCP (0.015 mL/kg/mo, p=0.001) and CTD (0.014 mL/kg/mo, p<0.001) groups. Normalized medial gastrocnemius muscle growth rate was the same in the BCP and CTD groups (p=0.77).

INTERPRETATION

The normalized growth rate of the medial gastrocnemius muscle in children aged 2 to 9 years with UCP is significantly lower compared with children with BCP and CTD. The growth rate differences in the children with UCP compared with BCP raises questions about the underlying mechanisms that lead to reduced growth in each cerebral palsy (CP) group and potential differences in muscle recovery response in UCP and BCP following treatment.

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.

Dramatic changes in muscle contractile and structural properties after 2 botulinum toxin injections

INTRODUCTION

Botulinum toxin is frequently administered serially to maintain therapeutic muscle paralysis, but the effect of repeated doses on muscle function are largely unknown. This study characterized the muscle response to 2 onabotulinum toxin (BoNT) injections separated by 3 months.

METHODS

Animal subjects received a single toxin injection (n = 8), 2 BoNT injections separated by 3 months (n = 14), or 1 BoNT and 1 saline injection separated by 3 months (n = 8).

RESULTS

The functional effect of 2 serial injections was exponentially greater than the effect of a single injection. While both groups treated with a single BoNT injection had decreased torque in the injected leg by approximately 50% relative to contralateral legs, the double BoNT injected group had decreased torque by over 95% relative to the preinjection level. Both single and double BoNT injections produced clear signs of fiber-type grouping.

CONCLUSIONS

These experiments demonstrate a disproportionately greater effect of repeated BoNT injections.