Comparison between neurectomy and botulinum toxin A injection for denervated skeletal muscle

Endoscopic Concurrent Gastrocnemius Muscle Resection and Soleus Muscle Neurectomy for Severe Muscular Calf Hypertrophy

BACKGROUND

Selective neurectomy or muscle resection techniques for calf reduction conventionally focus on the gastrocnemius muscle. However, the underlying soleus muscle plays an important role in muscular calf hypertrophy. In the authors' experience, the results of calf reduction have been suboptimal in patients with severe muscular calf hypertrophy who underwent gastrocnemius muscle resection only. This article describes a new calf reduction method that uses concurrent gastrocnemius muscle resection and soleus muscle neurectomy using an endoscope-assisted single-incision approach in patients with severe muscular calf hypertrophy.

METHODS

A total of 139 patients who underwent simultaneous gastrocnemius muscle resection and soleus muscle neurectomy for severe calf hypertrophy from March of 2017 to June of 2020 were retrospectively analyzed.

RESULTS

After combined gastrocnemius resection (mean weight per calf, 349 g) and soleus neurectomy, about 3.8 to 8.2 cm (mean, 6.4 cm) or 12.8% to 24.3% (mean, 16.6%) of the calf was reduced. Complications included cellulitis, hematoma, seroma, and mild depression ( n = 1 each). Two patients had traction injury to the sural nerve. One patient developed Achilles tendon rupture at 2 months postoperatively. No patient complained of functional impairment with respect to easy fatigability, stability, gait, or sport activities at 6 months postoperatively.

CONCLUSION

This study is the first to combine gastrocnemius muscle resection with selective soleus muscle neurectomy to achieve the most efficient calf reduction for severe muscular calf hypertrophy.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Noninvasive analysis of overactive muscle structure and elasticity after botulinum toxin type A injection: a systematic review and meta-analysis

INTRODUCTION

Injections of botulinum toxin type A (BoNT-A) are the first-line treatment for spastic muscle overactivity (MO). Some authors observed that BoNT-A injections lead to changes in muscle structure and muscle elasticity that are probably not completely reversible. This possible effect is critical, as it could lead to negative impacts on the effectiveness of BoNT-A interventions. Our study aimed to evaluate the current literature regarding changes in muscle elasticity and structure after BoNT-A injection, by diagnostic imaging, in neurological populations with MO. Our second objective was to pool all articles published on this topic in order to provide a quantitative synthesis of the data.

EVIDENCE ACQUISITION

A systematic search was conducted between October 2021 and April 2023 using different databases in accordance with PRISMA guidelines. Two independent reviewers screened articles for inclusion, extracted data, and evaluated methodological quality of the studies. A meta-analysis was performed to compare muscle elasticity and structure before and after BoNT-A injections.

EVIDENCE SYNTHESIS

A sample of 34 studies was selected for qualitative review and 19 studies for quantitative review. Meta-analysis of pre-post studies demonstrated significant improvement with a medium effect size (standardized mean difference=0.74; 95% CI 0.46-1.02; P<0.001) of muscle elasticity assessed by ultrasound elastography (USE) 4 weeks after BoNT-A injection. No statistically significant difference was found for muscle thickness, pennation angle, and muscle echo-intensity assessed by magnetic resonance imaging and/or ultrasonography at short-term. On the other hand, normalized muscle volume decreased with a small effect size (standardized mean difference = -0.17; 95% CI -0.25 - -0.09; P<0.001) 6 months after BoNT-A injection.

CONCLUSIONS

Muscle elasticity measured by USE improves with a temporary effect at short-term following BoNT-A injections. Synthesis of studies that assesses muscle structure is hindered by methodological differences between studies. However, based on a small amount of data, normalized muscle volume seems to decrease at long-term after BoNT-A injections in children with CP suggesting that the timing of re-injection should be considered with caution in this population. Further work should focus on the long-term effect of repeated injections on muscle structure and elasticity in neurological populations.

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.

Recombinant botulinum neurotoxin serotype A1 in vivo characterization

Clinically used botulinum neurotoxins (BoNTs) are natural products of Clostridium botulinum. A novel, recombinant BoNT type A1 (rBoNT/A1; IPN10260) has been synthesized using the native amino acid sequence expressed in Escherichia coli and has previously been characterized in vitro and ex vivo. Here, we aimed to characterize rBoNT/A1 in vivo and evaluate its effects on skeletal muscle. The properties of rBoNT/A1 following single, intramuscular administration were evaluated in the mouse and rat digit abduction score (DAS) assays and compared with those of natural BoNT/A1 (nBoNT/A1). rBoNT/A1-injected tibialis anterior was assessed in the in situ muscle force test in rats. rBoNT/A1-injected gastrocnemius lateralis (GL) muscle was assessed in the compound muscle action potential (CMAP) test in rats. The rBoNT/A1-injected GL muscle was evaluated for muscle weight, volume, myofiber composition and immunohistochemical detection of cleaved SNAP25 (c-SNAP25). Results showed that rBoNT/A1 and nBoNT/A1 were equipotent and had similar onset and duration of action in both mouse and rat DAS assays. rBoNT/A1 caused a dose-dependent inhibition of muscle force and a rapid long-lasting reduction in CMAP amplitude that lasted for at least 30 days. Dose-dependent reductions in GL weight and volume and increases in myofiber atrophy were accompanied by immunohistochemical detection of c-SNAP25. Overall, rBoNT/A1 and nBoNT/A1 exhibited similar properties following intramuscular administration. rBoNT/A1 inhibited motoneurons neurotransmitter release, which was robust, long-lasting, and accompanied by cleavage of SNAP25. rBoNT/A1 is a useful tool molecule for comparison with current natural and future modified recombinant neurotoxins products.

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.

Botulinum neurotoxin A promotes functional recovery after peripheral nerve injury by increasing regeneration of myelinated fibers

The injection of safe doses of botulinum neurotoxin A (BoNT/A) have been reported to be useful for the treatment of neuropathic pain, but it is still unknown how functional recovery is induced after peripheral nerve injury. We evaluated the effects of intranerve application of BoNT/A, on regeneration and sensorimotor functional recovery in partial and complete peripheral nerve injuries in the mouse. After sciatic nerve crush (SNC) and intranerve delivery of BoNT/A (15pg), axonal regeneration was measured by nerve pinch test at different days. Regeneration of myelinated and unmyelinated fibers was assessed by immunohistochemical double labeling for NF200/GAP43 and CGRP/GAP43. S100 was used as Schwann cells marker. Medial footpad skin reinnervation was assessed by PGP staining. Motor functions were assessed by means of nerve conduction tests. In other mice groups, nerve conduction tests were performed also after chronic constriction injury (CCI) of the sciatic nerve and intraplantar injection of BoNT/A (15pg). In SNC mice, BoNT/A increased the rate of axonal regeneration. The advantage of regrowing myelinated axons after BoNT/A injection was evidenced by longer NF200+ nerve profiles and confirmed by nerve histology. We observed also a higher expression of S100 in the distal portion of BoNT/A-injected regenerated nerves. In CCI mice, BoNT/A induced an increase in reinnervation of gastrocnemius and plantar muscles. These results show that a low dose of BoNT/A, insufficient to produce muscular dysfunction, conversely speeds up sensorimotor recovery by stimulating myelinated axonal regeneration, and points out its application as a multipotent treatment for peripheral neuropathies.

Assessing the immediate impact of botulinum toxin injection on impedance of spastic muscle

This study aimed to investigate the immediate impacts of Botulinum Toxin A (BoNT-A) injections on the inherent electrical properties of spastic muscles using a newly developed electrical impedance myography (EIM) technique. Impedance measures were performed before and after a BoNT-A injection in biceps brachii muscles of 14 subjects with spasticity. Three major impedance variables, resistance (R), reactance (X) and phase angle (θ) were obtained from three different configurations, and were evaluated using the conventional EIM frequency at 50kHz as well as multiple frequency analysis. Statistical analysis demonstrated a significant decrease of resistance in the injected muscles (Multiple-frequency: R_pre=25.17±1.94Ohm, R_post=23.65±1.63Ohm, p<0.05; 50kHz: R_pre=29.06±2.16Ohm, R_post=27.7±1.89Ohm, p<0.05). Despite this decrease, there were no substantial changes in the reactance, phase angle, or anisotropy features after a BoNT-A injection. The significant changes of muscle resistance were most likely associated with the liquid injection of the BoNT-A-saline solution rather than the immediate toxin effects on the muscle. This study demonstrated high sensitivity of the EIM technique in the detection of alterations to muscle composition.

Apoptotic action of botulinum toxin on masseter muscle in rats: early and late changes in the expression of molecular markers

The purpose of this study was to compare the early or late expression levels of p65, Bcl-2, and type II myosin and the frequency of TUNEL-positive nuclei in the rat masseter muscle after injection of different concentrations of botulinum toxin-A (BTX-A). We injected either 5 U or 10 U of BTX-A into both masseter muscles of the rat. As a control group, the same volume of saline was injected. After 2 or 12 weeks, the animals were sacrificed. Subsequently, a biopsy and immunohistochemical staining of the samples were performed using a p65, Bcl-2, or type II myosin antibody. Additionally, a TUNEL assay and transmission electron microscopic analysis were performed. The expression of p65, Bcl-2, and type II myosin increased significantly with increasing concentrations of BTX-A at 2 weeks after BTX-A injection (P < 0.05). The number of TUNEL-positive nuclei was also significantly increased in the BTX-A-treated groups in comparison to the saline-treated control at 2 weeks after BTX-A injection (P < 0.05). Elevated expression of Bcl-2 was also observed in 10-unit BTX-A-treated group at 12 weeks after injection (P < 0.05). At 12 weeks after injection, the number of enlarged mitochondria was increased, and many mitochondria displayed aberrations in cristae morphology after BTX-A injection. In conclusion, BTX-A injection into the masseter muscle increased the expression level of p65, Bcl-2, and type II myosin at an early stage. The morphological changes of mitochondria were more evident at 12 weeks after injection.

Anatomical study of the nerve regeneration after selective neurectomy in the rabbit: clinical application for esthetic calf reduction

The purposes of this study were therefore to characterize the degeneration and regeneration of nerves to the calf muscles after selective neurectomy, both macroscopically and microscopically, and to determine the incidence of such regeneration in a rabbit model. Seventy four New Zealand white rabbits were used. Selective neurectomy to the triceps surae muscles was performed, and the muscles were subsequently harvested and weighed 1-4 months postneurectomy. The gastrocnemius muscles were stained with Sihler's solution to enable the macroscopic observation of any nerve regeneration that may have occurred subsequent to neurectomy. The change in triceps surae muscle weight was measured along the time course of the experiment. After neurectomy, nerve degeneration was followed by regeneration in all cases. The weight of the triceps surae muscle decreased dramatically between completion of the neurectomy and 1 month postneurectomy, but increased thereafter. The nerve branches were weakly stained with Sihler's solution until 2 months postneurectomy, and then strongly stained after 3 months. The number of myelinated axons was decreased at 2 month after neurectomy compared to nonneurectomized controls, but then gradually increased thereafter. Although there are currently no reports on the incidence of recovery after calf reduction, it may be a very common occurrence in the clinical field based on our findings. The findings of this study provide fundamental anatomical and surgical information to aid planning and practice in calf-reduction surgery.

Heat shock protein 70 overexpression does not attenuate atrophy in botulinum neurotoxin type A-treated skeletal muscle

Botulinum neurotoxin type A (BoNT/A) is used clinically to induce therapeutic chemical denervation of spastically contracted skeletal muscles. However, BoNT/A administration can also cause atrophy. We sought to determine whether a major proteolytic pathway contributing to atrophy in multiple models of muscle wasting, the ubiquitin proteasome system (UPS), is involved in BoNT/A-induced atrophy. Three and ten days following BoNT/A injection of rat hindlimb, soleus muscle fiber cross-sectional area was reduced 25 and 65%, respectively. The transcriptional activity of NF-κB and Foxo was significantly elevated at 3 days (2- to 4-fold) and 10 days (5- to 6-fold). Muscle RING-finger protein-1 (MuRF1) activity was elevated (2-fold) after 3 days but not 10 days, while atrogin-1 activity was not elevated at any time point. BoNT/A-induced polyubiquitination occurred after 3 days (3-fold increase) but was totally absent after 10 days. Proteasome activity was elevated (1.5- to 2-fold) after 3 and 10 days. We employed the use of heat shock protein 70 (Hsp70) to inhibit NF-κB and Foxo transcriptional activity. Electrotransfer of Hsp70 into rat soleus, before BoNT/A administration, was insufficient to attenuate atrophy. It was also insufficient to decrease BoNT/A-induced Foxo activity at 3 days, although NF-κB activity was abolished. By 10 days both NF-κB and Foxo activation were abolished by Hsp70. Hsp70-overexpression was unable to alter the levels of BoNT/A-induced effects on MuRF1/atrogin-1, polyubiquitination, or proteasome activity. In conclusion, Hsp70 overexpression is insufficient to attenuate BoNT/A-induced atrophy. It remains unclear what proteolytic mechanism/s are contributing to BoNT/A-induced atrophy, although a Foxo-MuRF1-ubiquitin-proteasome contribution may exist, at least in early BoNT/A-induced atrophy. Further clarification of UPS involvement in BoNT/A-induced atrophy is warranted.

Botulinum toxin type A injections in the psoas muscle of children with cerebral palsy: muscle atrophy after motor end plate-targeted injections

MEP targeting during BoNT-A injections has been demonstrated to improve outcome. Two injection techniques of the psoas muscle - proximal MEP targeting versus a widely used more distal injection technique - are compared using muscle volume assessment by digital MRI segmentation as outcome measure.

METHOD

7 spastic diplegic children received injections in both psoas muscles: two different injection techniques randomly in 5 patients, in 2 patients bilateral MEP targeting. MRI images of the psoas were taken before, after 2 months and in 3 patients after 6 months.

RESULTS

Average post injection volume (in relation to pre-injection volume) for the MEP targeted muscles (9) is 79.5% versus 107.8% in the 5 distal injected psoas muscles (p=0.0033). In all 5 asymmetric injected patients the MEP targeted psoas had a larger volume reduction than the more distal injected psoas muscle. This atrophy remains even 6 months after the injection. This is the first study were a longitudinal follow-up by MRI demonstrates muscle atrophy after BoNT-A in children with CP. Injections in the MEP zone of the muscle, which is the more proximal part of the psoas muscle, cause atrophy in contrary to more distal injections were this atrophy is not observed.

Spatiotemporal dynamics of the biological interface between cancer and the microenvironment: a fractal anomalous diffusion model with microenvironment plasticity

BACKGROUND

The invasion-metastasis cascade of cancer involves a process of parallel progression. A biological interface (module) in which cells is linked with ECM (extracellular matrix) by CAMs (cell adhesion molecules) has been proposed as a tool for tracing cancer spatiotemporal dynamics.

METHODS

A mathematical model was established to simulate cancer cell migration. Human uterine leiomyoma specimens, in vitro cell migration assay, quantitative real-time PCR, western blotting, dynamic viscosity, and an in vivo C57BL6 mouse model were used to verify the predictive findings of our model.

RESULTS

The return to origin probability (RTOP) and its related CAM expression ratio in tumors, so-called "tumor self-seeding", gradually decreased with increased tumor size, and approached the 3D Pólya random walk constant (0.340537) in a periodic structure. The biphasic pattern of cancer cell migration revealed that cancer cells initially grew together and subsequently began spreading. A higher viscosity of fillers applied to the cancer surface was associated with a significantly greater inhibitory effect on cancer migration, in accordance with the Stokes-Einstein equation.

CONCLUSION

The positional probability and cell-CAM-ECM interface (module) in the fractal framework helped us decipher cancer spatiotemporal dynamics; in addition we modeled the methods of cancer control by manipulating the microenvironment plasticity or inhibiting the CAM expression to the Pólya random walk, Pólya constant.

Sensitivity of skeletal muscle to pro-apoptotic factors

In mononuclear cells, apoptosis leads to DNA fragmentation and cell destruction, regardless of the activated pathway. As regards multinuclear cells, e.g. skeletal muscle fibers, apoptosis rarely induces the death of the entire cell, and it generally affects single nuclei. This process, referred to as nuclear apoptosis, has a negative effect on the expression of genes in the myonuclear domain. Apoptosis may be initiated in muscle cells by external stimuli which activate cell membrane death receptors as well as by internal stimuli which stimulate the mitochondrial release of pro-apoptotic proteins. Reactive oxygen species also play an important role in the initiation of apoptosis. In muscle cells, ROS are produced in response to extracellular reactions or by cell mitochondria. It is, therefore, believed that mitochondria play a central role in apoptosis within skeletal muscle. Skeletal muscles have a well-developed system that protects them against oxidative damage. Myogenic stem cells are an integral part of multinucleated myofibers, and they are critically important for the maintenance of normal muscle mass, muscle growth, regeneration and hypertrophy. The latest research results indicate that myogenic cells are more sensitive to oxidative stress and pro-apoptotic factors than well-differentiated cells, such as myotubes. The complex structure and activity of skeletal muscle prompted research into the role of apoptosis and its intensity under various physiological and pathological conditions. This review summarizes the results of research investigating control mechanisms and the apoptosis process in skeletal muscle fibers, and indicates unresearched areas where further work is required.