The Central Effects of Botulinum Toxin in Dystonia and Spasticity

Ultrasonography for Assessment and Intervention With Botulinum Toxin Injection for Tremors

OBJECTIVE

Tremors are caused by contractions of reciprocally innervated muscles. The role of ultrasound in diagnosing tremors has not yet been investigated, although it appears to be promising because it can visualize muscle movements. In the present study, we report four cases of tremor (Holmes' tremor, extremity tremor associated with palatal myoclonus, dystonic tremor, and tremor associated with dystonia), which were evaluated using ultrasound and treated with botulinum toxin injections.

METHODS

The muscles of patients with tremors were examined using B- or M-mode ultrasound while they were in the supine position. Tremor was determined by involuntary muscular contraction (B-mode) or fasciculation (M-mode) from recorded sonography clips. Thereafter, tremors were measured as frequency and amplitude of specific muscles. Ultrasound-guided botulinum toxin type A injection was administered, and follow-up ultrasonography was used to assess tremors.

RESULTS

Tremors, which manifest as a specific set of muscle contractions, were measured using ultrasonography and treated with botulinum toxin injection. Follow-up ultrasonography revealed improved tremors as seen with decreased frequency and amplitude of specific muscle after the intervention, which included medication and botulinum toxin injections.

CONCLUSION

Ultrasonography is an effective assessment tool for tremors, allowing further information regarding tremor characteristics with high sensitivity, playing a role in detecting specific muscles that are affected by tremors, and guiding an exact intervention with botulinum toxin.

Clinical benefit of botulinum toxin for treatment of persistent TMD-related myofascial pain: A randomized, placebo-controlled, cross-over trial

BACKGROUND

Injections of botulinum toxin type A (BoNT-A) have been proposed as an additional treatment modality for patients suffering chronic temporomandibular disorder (TMD)-related myofascial pain (MFP). BoNT-A impairs muscle function, along with its analgesic effect, and a minimal effective dose should be used. The objective of this randomized placebo-controlled crossover study was to evaluate the clinical benefit of a moderate dose (50 U) of BoNT-A.

METHODS

Sixty-six subjects were randomized into two groups, one which received BoNT-A first and a second which received a saline solution (SS) first. Follow-ups were performed 2, 11, and 16 weeks after the injections. Diagnostic criteria for temporomandibular disorders (DC/TMD) diagnostic algorithms were used to evaluate characteristic pain intensity (CPI) and pain-related disability based on the Graded Chronic Pain Scale (GCPS). Electromyographic and bite force were also evaluated.

RESULTS

The within-group analysis showed a significant improvement in pain intensity and pain-related disability after BoNT-A (p < 0.001, p = 0.005, p = 0.011) and SS (p = 0.003, p = 0.005, p = 0.046) injections up to week 16. The between-group analysis of pain-related variables revealed no differences between groups at any time. Nonetheless, BoNT-A, but not SS, caused a significant decline in muscle performance. The number needed to treat (NNT) regarding a clinically significant pain reduction (≥30%) was 6.3, 57.0, and 19.0 at 2, 11, and 16-week follow-ups favoring BoNT-A.

CONCLUSIONS

Injections of 50 U of BoNT-A might improve MFP symptoms, but the specific effect of the drug on pain compared to the placebo is not obvious.

Memory-Guided Saccades and Non-Motor Symptoms Improve after Botulinum Toxin Therapy in Cervical Dystonia

Background/Objectives: Cervical dystonia (CD) is a condition characterized by involuntary activity of cervical muscles, which is often accompanied by various non-motor symptoms. Recent studies indicate impaired saccadic eye movements in CD. Local administration of botulinum toxin type A (BoNT/A), which causes temporary paralysis of the injected muscle, is the first-line treatment of focal dystonia, including CD. To our knowledge, concurrent observation of the effect of BoNT/A on smooth eye movements, voluntary saccades, memory-guided saccades, and antisaccades in CD has not yet been explored. The aim of this study was to assess the effect of BoNT/A on eye movements and non-motor symptoms in patients with CD, which, when altered, could imply a central effect of BoNT/A. Methods: Thirty patients with CD performed smooth pursuit, prosaccadic expression, memory-guided saccades, and antisaccade tasks; eye movements were recorded by an eye tracker. Motor and non-motor symptoms, including depression, anxiety, pain, disability, and cognitive changes prior to and after BoNT/A administration, were also evaluated. Results: The number of correct onward counts (p < 0.001), overall correct memory-guided saccades count (p = 0.005), motor symptoms (p = 0.001), and non-motor symptoms, i.e., anxiety (p = 0.04), depression (p = 0.02), and cognition (p < 0.001) markedly improved after BoNT/A administration. Conclusions: Memory-guided saccades, depression, and anxiety improve after BoNT/A in CD.

Use of Botulinum Toxin in Upper-Limb Tremor: Systematic Review and Perspectives

BACKGROUND

Tremor is the most common movement disorder, with significant functional and psychosocial consequences. Oral medications have been disappointing or limited by side effects. Surgical techniques are effective but associated with risks and adverse events. Botulinum toxin (BT) represents a promising avenue but there is still no double-blind evidence of efficacy on upper limb function. A systematic review on the effects of BT in upper-limb tremor was conducted.

METHODS

A systematic search of the literature was conducted up to July 2023, including the keywords "botulinum toxin" and "tremor". All randomized controlled trials (RCTs) and open-label studies were analyzed. Independent reviewers assessed their methodological quality.

RESULTS

There were only eight published RCTs and seven published open-label studies, with relatively small sample sizes. This review suggests that BT is more effective when injections are patient-tailored, with analyses based on clinical judgement or kinematics. Subjective and objective measures frequently improve but transient weakness may occur after injections, especially if wrist or fingers extensors are targeted. A number of studies had methodological limitations.

CONCLUSIONS

The authors discuss how to optimize tremor assessments and effects of BT injection. Controlled evidence is still lacking but it is suggested that distal "asymmetric" BT injections (targeting flexors/pronators while sparing extensors/supinators) and proximal injections, involving shoulder rotators when indicated, may avoid excessive weakness while optimizing functional benefit.

Peripheral and central neurobiological effects of botulinum toxin A (BoNT/A) in neuropathic pain: a systematic review

ABSTRACT

Botulinum toxin (BoNT), a presynaptic inhibitor of acetylcholine (Ach) release at the neuromuscular junction (NMJ), is a successful and safe drug for the treatment of several neurological disorders. However, a wide and recent literature review has demonstrated that BoNT exerts its effects not only at the "periphery" but also within the central nervous system (CNS). Studies from animal models, in fact, have shown a retrograde transport to the CNS, thus modulating synaptic function. The increasing number of articles reporting efficacy of BoNT on chronic neuropathic pain (CNP), a complex disease of the CNS, demonstrates that the central mechanisms of BoNT are far from being completely elucidated. In this new light, BoNT might interfere with the activity of spinal, brain stem, and cortical circuitry, modulating excitability and the functional organization of CNS in healthy conditions. Botulinum toxins efficacy on CNP is the result of a wide and complex action on many and diverse mechanisms at the basis of the maladaptive plasticity, the core of the pathogenesis of CNP. This systematic review aims to discuss in detail the BoNT's mechanisms and effects on peripheral and central neuroplasticity, at the basis for the clinical efficacy in CNP syndromes.

Neurobiological mechanisms of botulinum neurotoxin-induced analgesia for neuropathic pain

Botulinum neurotoxins (BoNTs) are a family of neurotoxins produced by Clostridia and other bacteria that induce botulism. BoNTs are internalized into nerve terminals at the site of injection and cleave soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins to inhibit the vesicular release of neurotransmitters. BoNTs have been approved for multiple therapeutic applications, including the treatment of migraines. They have also shown efficacies for treating neuropathic pain, such as diabetic neuropathy, and postherpetic and trigeminal neuralgia. However, the mechanisms underlying BoNT-induced analgesia are not well understood. Peripherally administered BoNT is taken up by the nerve terminals and reduces the release of glutamate, calcitonin gene-related peptide, and substance P, which decreases neurogenic inflammation in the periphery. BoNT is retrogradely transported to sensory ganglia and central terminals in a microtubule-dependent manner. BoNTs decrease the expression of pronociceptive genes (ion channels or cytokines) from sensory ganglia and the release of neurotransmitters and neuropeptides from primary afferent central terminals, which likely leads to decreased central sensitization in the dorsal horn of the spinal cord or trigeminal nucleus. BoNT-induced analgesia is abolished after capsaicin-induced denervation of transient receptor potential vanilloid 1 (TRPV1)-expressing afferents or the knockout of substance P or the neurokinin-1 receptor. Although peripheral administration of BoNT leads to changes in the central nervous system (e.g., decreased phosphorylation of glutamate receptors in second-order neurons, reduced activation of microglia, contralateral localization, and cortical reorganization), whether such changes are secondary to changes in primary afferents or directly mediated by trans-synaptic, transcytotic, or the hematogenous transport of BoNT is controversial. To enhance their therapeutic potential, BoNTs engineered for specific targeting of nociceptive pathways have been developed to treat chronic pain. Further mechanistic studies on BoNT-induced analgesia can enhance the application of native or engineered BoNTs for neuropathic pain treatment with improved safety and efficacy.

Early effect of onabotulinumtoxinA on EEG-based functional connectivity in patients with chronic migraine: A pilot study

OBJECTIVE

In this pilot prospective cohort study, we aimed to evaluate, using high-density electroencephalography (HD-EEG), the longitudinal changes in functional connectivity (FC) in patients with chronic migraine (CM) treated with onabotulinumtoxinA (OBTA).

BACKGROUND

OBTA is a treatment for CM. Several studies have shown the modulatory action of OBTA on the central nervous system; however, research on migraine is limited.

METHODS

This study was conducted at the Neurology Unit of "Policlinico Tor Vergata," Rome, Italy, and included 12 adult patients with CM treated with OBTA and 15 healthy controls (HC). Patients underwent clinical scales at enrollment (T0) and 3 months (T1) from the start of treatment. HD-EEG was recorded using a 64-channel system in patients with CM at T0 and T1. A source reconstruction method was used to identify brain activity. FC in δ-θ-α-β-low-γ bands was analyzed using the weighted phase-lag index. FC changes between HCs and CM at T0 and T1 were assessed using cross-validation methods to estimate the results' reliability.

RESULTS

Compared to HCs at T0, patients with CM showed hyperconnected networks in δ (p = 0.046, area under the receiver operating characteristic curve [AUC: 0.76-0.98], Cohen's κ [0.65-0.93]) and β (p = 0.031, AUC [0.68-0.95], Cohen's κ [0.51-0.84]), mainly involving orbitofrontal, occipital, temporal pole and orbitofrontal, superior temporal, occipital, cingulate areas, and hypoconnected networks in α band (p = 0.029, AUC [0.80-0.99], Cohen's κ [0.42-0.77]), predominantly involving cingulate, temporal pole, and precuneus. Patients with CM at T1, compared to T0, showed hypoconnected networks in δ band (p = 0.032, AUC [0.73-0.99], Cohen's κ [0.53-0.90]) and hyperconnected networks in α band (p = 0.048, AUC [0.58-0.93], Cohen's κ [0.37-0.78]), involving the sensorimotor, orbitofrontal, cingulate, and temporal cortex.

CONCLUSION

These preliminary results showed that patients with CM presented disrupted EEG-FC compared to controls restored by a single session of OBTA treatment, suggesting a primary central modulatory action of OBTA.

Effects of dry needling on spasticity and motor function in paralympic athletes: a study protocol for a randomised controlled trial

No study has evaluated the effects of dry needling on Paralympic athletes. Therefore, in this study, we will evaluate the effect of dry needling on lower limb spasticity and motor performance, as well as the range of motion of Paralympic athletes. The study will be a triple-blinded, randomised controlled trial. Twenty-four athletes aged 18-45 in T35-T38 groups of the International Paralympic Committee classification will be included in the study. Twelve participants will receive dry needling of the quadriceps and gastrocnemius muscles, and 12 will receive placebo treatment with sham needles at similar points. We will assess the spasticity of the quadriceps and gastrocnemius muscles using the Modified Ashworth Scale, evaluate motor function using the Selective Control Assessment of the Lower Extremity Scale and measure ankle range of motion (ROM) with a goniometer. Considering our hypothesis, the athletes who will undergo the dry needling are supposed to achieve better improvements in spasticity, ROM and motor performance. This study can provide useful information to help better decide on managing complications in Paralympics and its long-term outcomes, to cover the current lack in the literature.

Flawed prosthodontic treatment as a triggering factor of orofacial dyskinesia: A case report

Orofacial dyskinesia (ODk) is an involuntary, repetitive and stereotyped movement disorder of the oro-bucco-lingual muscles, which can be classified as primary (idiopathic) or secondary to medical conditions such as oral peripheral factors, that may act as triggers or aggravators. The present case describes a 70 years female with ODk, non-associated to drug use, without central etiological factors or morbid conditions, but with the presence of a flawed prosthodontic treatment, which complaint from spasms in the masticatory muscles that alters jaw dynamics, and her ability for maintain a relaxed jaw in maximal intercuspal position. After an unsuccessful oral drug treatment, botulinum toxin was injected to the jaw muscles with favorable results. The case illustrated that peripheral factors, such as defective dental prosthetics, may trigger or aggravate orofacial movement disorders, and peripheral strategies such as botulinum toxin may contribute to improve clinical parameters and quality of life. Key words:Botulinum toxin, case report, dyskinesia, movement disorder, orofacial dyskinesia.

Effects of an 11-week vibro-tactile stimulation treatment on voice symptoms in laryngeal dystonia

Background

Laryngeal dystonia is a task-specific focal dystonia of laryngeal muscles that impairs speech and voice production. At present, there is no cure for LD. The most common therapeutic option for patients with LD involves Botulinum neurotoxin injections.

Objective

Provide empirical evidence that non-invasive vibro-tactile stimulation (VTS) of the skin over the voice box can provide symptom relief to those affected by LD.

Methods

Single-group 11-week randomized controlled trial with a crossover between two dosages (20 min of VTS once or 3 times per week) self-administered in-home in two 4-week blocks. Acute effects of VTS on voice and speech were assessed in-lab at weeks 1, 6 and 11. Participants were randomized to receive either 40 Hz or 100 Hz VTS.

Main outcome measures

Primary: smoothed cepstral peak prominence (CPPS) of the voice signal to quantify voice and speech abnormalities, and perceived speech effort (PSE) ranked by participants as a measure of voice effort (scale 1-10). Secondary: number of voice breaks during continuous speech, the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) inventory as a measure of overall disease severity and the Voice Handicap Index 30-item self report.

Results

Thirty-nine people with a confirmed diagnosis of adductor-type LD (mean [SD] age, 60.3 [11.3] years; 18 women and 21 men) completed the study. A single application of VTS improved voice quality (median CPPS increase: 0.41 dB, 95% CI [0.20, 0.61]) and/or reduced voice effort (PSE) by at least 30% in up to 57% of participants across the three study visits. Effects lasted from less than 30 min to several days. There was no effect of dosage and no evidence that the acute therapeutic effects of VTS increased or decreased longitudinally over the 11-week study period. Both 100 and 40 Hz VTS induced measurable improvements in voice quality and speech effort. VTS induced an additional benefit to those receiving Botulinum toxin. Participants, not receiving Botulinum treatment also responded to VTS.

Conclusion

This study provides the first systematic empirical evidence that the prolonged use of laryngeal VTS can induce repeatable acute improvements in voice quality and reductions of voice effort in LD.

Clinical trial registration

ClinicalTrials.gov ID: NCT03746509.

Neurosurgical and pharmacological management of dystonia

Dystonia characterizes a group of neurological movement disorders characterized by abnormal muscle movements, often with repetitive or sustained contraction resulting in abnormal posturing. Different types of dystonia present based on the affected body regions and play a prominent role in determining the potential efficacy of a given intervention. For most patients afflicted with these disorders, an exact cause is rarely identified, so treatment mainly focuses on symptomatic alleviation. Pharmacological agents, such as oral anticholinergic administration and botulinum toxin injection, play a major role in the initial treatment of patients. In more severe and/or refractory cases, focal areas for neurosurgical intervention are identified and targeted to improve quality of life. Deep brain stimulation (DBS) targets these anatomical locations to minimize dystonia symptoms. Surgical ablation procedures and peripheral denervation surgeries also offer potential treatment to patients who do not respond to DBS. These management options grant providers and patients the ability to weigh the benefits and risks for each individual patient profile. This review article explores these pharmacological and neurosurgical management modalities for dystonia, providing a comprehensive assessment of each of their benefits and shortcomings.

Genetic Update and Treatment for Dystonia

A neurological condition called dystonia results in abnormal, uncontrollable postures or movements because of sporadic or continuous muscular spasms. Several varieties of dystonia can impact people of all ages, leading to severe impairment and a decreased standard of living. The discovery of genes causing variations of single or mixed dystonia has improved our understanding of the disease's etiology. Genetic dystonias are linked to several genes, including pathogenic variations of VPS16, TOR1A, THAP1, GNAL, and ANO3. Diagnosis of dystonia is primarily based on clinical symptoms, which can be challenging due to overlapping symptoms with other neurological conditions, such as Parkinson's disease. This review aims to summarize recent advances in the genetic origins and management of focal dystonia.

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

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

Function and dysfunction of the dystonia network: an exploration of neural circuits that underlie the acquired and isolated dystonias

Dystonia is a highly prevalent movement disorder that can manifest at any time across the lifespan. An increasing number of investigations have tied this disorder to dysfunction of a broad "dystonia network" encompassing the cerebellum, thalamus, basal ganglia, and cortex. However, pinpointing how dysfunction of the various anatomic components of the network produces the wide variety of dystonia presentations across etiologies remains a difficult problem. In this review, a discussion of functional network findings in non-mendelian etiologies of dystonia is undertaken. Initially acquired etiologies of dystonia and how lesion location leads to alterations in network function are explored, first through an examination of cerebral palsy, in which early brain injury may lead to dystonic/dyskinetic forms of the movement disorder. The discussion of acquired etiologies then continues with an evaluation of the literature covering dystonia resulting from focal lesions followed by the isolated focal dystonias, both idiopathic and task dependent. Next, how the dystonia network responds to therapeutic interventions, from the "geste antagoniste" or "sensory trick" to botulinum toxin and deep brain stimulation, is covered with an eye towards finding similarities in network responses with effective treatment. Finally, an examination of how focal network disruptions in mouse models has informed our understanding of the circuits involved in dystonia is provided. Together, this article aims to offer a synthesis of the literature examining dystonia from the perspective of brain networks and it provides grounding for the perspective of dystonia as disorder of network function.

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

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

Intrathecal administration of botulinum toxin type a antagonizes neuropathic pain by countering increased vesicular nucleotide transporter expression in the spinal cord of chronic constriction injury of the sciatic nerve rats

Botulinum toxin type A (BoNT/A) induces direct analgesic effects in neuropathic pain by inhibiting the release of substance P, calcitonin gene-related peptide (CGRP) and glutamate. Vesicular nucleotide transporter (VNUT) was responsible for the storage and release of ATP in vivo, and one of the mechanisms underlying neuropathic pain is VNUT-dependent release of extracellular ATP from dorsal horn neurons. However, the analgesic effect of BoNT/A by affecting the expression of VNUT remained largely unknown. Thus, in this study, we aimed to elucidate the antinociceptive potency and analgesic mechanism of BoNT/A in chronic constriction injury of the sciatic nerve (CCI) induced neuropathic pain. Our results showed that a single intrathecal injection of 0.1 U BoNT/A seven days after CCI surgery produced significant analgesic activity and decreased the expression of VNUT in the spinal cord of CCI rats. Similarly, BoNT/A inhibited the CCI-induced increase in ATP content in the rat spinal cord. Overexpression of VNUT in the spinal cord of CCI-induced rats markedly reversed the antinociceptive effect of BoNT/A. Furthermore, 33 U/mL BoNT/A dramatically reduced the expression of VNUT in pheochromocytoma (PC12) cells but overexpressing SNAP-25 increased VNUT expression in PC12 cells. Our current study is the first to demonstrate that BoNT/A is involved in neuropathic pain by regulating the expression of VNUT in the spinal cord in rats.

Interhemispheric parietal cortex connectivity reflects improvement in post-stroke spasticity due to treatment with botulinum toxin-A

In post-stroke spasticity (PSS), effective treatment with botulinum neurotoxin (BoNT) is associated with transient decrease in activation of the ipsilesional superior parietal lobule (SPL) and intraparietal sulcus (IPS). We hypothesized that this would be reflected in changes in resting-state functional connectivity (rsFC) of the SPL/IPS. Our aim was therefore to assess rsFC of the ipsilesional SPL/IPS in chronic stroke patients with hemiparesis both with and without PSS and to explore the relationship between SPL/IPS rsFC and PSS severity. To this end, fourteen chronic stroke patients with upper limb weakness and PSS (the PSS group) and 8 patients with comparable weakness but no PSS (the control group) underwent clinical evaluation and 3 fMRI examinations, at baseline (W0) and 4 and 11 weeks after BoNT (W4 and W11, respectively). Seed-based rsFC of the atlas-based SPL and IPS was evaluated using a group×time interaction analysis and a correlation analysis with PSS severity (modified Ashworth scale), integrity of the ipsilesional somatosensory afferent pathway (evoked potential N20 latency), and age. In the PSS group, transient improvement in PSS was associated with increase in rsFC between the ipsilesional IPS and the contralesional SPL at W4. The interhemispheric connectivity was negatively correlated with PSS severity at baseline and with PSS improvement at W4. We propose adaptation of the internal forward model as the putative underlying mechanism and discuss its possible association with increased limb use, diminished spastic dystonia, or improved motor performance, as well as its potential contribution to the clinical effects of BoNT.

Botulinum toxin for motor disorders

Botulinum neurotoxins are a group of biological toxins produced by the gram-negative bacteria Clostridium botulinum. After intramuscular injection, they produce dose-related muscle relaxation, which has proven useful in the treatment of a large number of motor and movement disorders. In this chapter, we discuss the utility of botulinum toxin treatment in three major and common medical conditions related to the dysfunction of the motor system, namely dystonia, tremor, and spasticity. A summary of the existing literature is provided along with different techniques of injection including those recommended by the authors.

Botulinum Neurotoxin Therapy in the Clinical Management of Laryngeal Dystonia

Laryngeal dystonia (LD), or spasmodic dysphonia (SD), is a chronic, task-specific, focal movement disorder affecting the larynx. It interferes primarily with the essential functions of phonation and speech. LD affects patients' ability to communicate effectively and significantly diminishes their quality of life. Botulinum neurotoxin was first used as a therapeutic agent in the treatment of LD four decades ago and remains the standard of care for the treatment of LD. This article provides an overview of the clinical application of botulinum neurotoxin in the management of LD, focusing on the classification for this disorder, its pathophysiology, clinical assessment and diagnosis, the role of laryngeal electromyography and a summary of therapeutic injection techniques, including a comprehensive description of various procedural approaches, recommendations for injection sites and dosage considerations.

IncobotulinumtoxinA Injection for Treating Children with Idiopathic Toe Walking: A Retrospective Efficacy and Safety Study

There is no gold-standard treatment for idiopathic toe walking (ITW). Some previous evidence suggested that botulinum neurotoxin-A injection might improve ITW. This is a single-center retrospective study on children with ITW treated with incobotulinumtoxinA injection in the gastrocnemius medialis/lateralis muscles. We screened the charts of 97 ITW children treated with incobotulinumtoxinA (January 2019-December 2021), and the data of 28 of them, who satisfied the inclusion/exclusion criteria, were analyzed. The maximal passive ankle dorsiflexion (knee extended) was assessed at three time points, i.e., immediately before incobotulinumtoxinA injection (T0), after incobotulinumtoxinA injection during the timeframe of its effect (T1), and at follow-up, when the effect was expected to disappear (T2). The maximal passive ankle dorsiflexion was improved by incobotulinumtoxinA injection, and the effect lasted up to 6 months in some children. No adverse effects were reported to incobotulinumtoxinA injections. The treatment with incobotulinumtoxinA might improve the maximal passive ankle dorsiflexion and is safe and well-tolerated in ITW with a longer-than-expected effect in comparison to cerebral palsy. These results may offer ground to future randomized controlled trials and studies assessing the effect of BoNT-A in combination with other non-invasive approaches and exercise programs in children with ITW.

Neurophysiological Basis of Deep Brain Stimulation and Botulinum Neurotoxin Injection for Treating Oromandibular Dystonia

Oromandibular dystonia (OMD) induces severe motor impairments, such as masticatory disturbances, dysphagia, and dysarthria, resulting in a serious decline in quality of life. Non-invasive brain-imaging techniques such as electroencephalography (EEG) and magnetoencephalography (MEG) are powerful approaches that can elucidate human cortical activity with high temporal resolution. Previous studies with EEG and MEG have revealed that movements in the stomatognathic system are regulated by the bilateral central cortex. Recently, in addition to the standard therapy of botulinum neurotoxin (BoNT) injection into the affected muscles, bilateral deep brain stimulation (DBS) has been applied for the treatment of OMD. However, some patients' OMD symptoms do not improve sufficiently after DBS, and they require additional BoNT therapy. In this review, we provide an overview of the unique central spatiotemporal processing mechanisms in these regions in the bilateral cortex using EEG and MEG, as they relate to the sensorimotor functions of the stomatognathic system. Increased knowledge regarding the neurophysiological underpinnings of the stomatognathic system will improve our understanding of OMD and other movement disorders, as well as aid the development of potential novel approaches such as combination treatment with BoNT injection and DBS or non-invasive cortical current stimulation therapies.

Comparison of botulinum toxin (BoNT) injection and lateral internal sphincterotomy (redo-LIS) for recurrent anal fissure treatment

Objective

Today's gold standard for treating chronic anal fissure is the Lateral Internal Sphincterotomy (LIS). Botulinum Toxin (BoNT) injection is, on the other hand, an alternative treatment for patients who do not want to have surgical treatment, patients undergoing chemotherapy, patients of high risk for surgery, and those who have the risk of anal incontinence (e.g., elderly, past anorectal surgery, vaginal multiple births, etc.). The aim of this study is to compare the effectiveness of BoNT and redo-LIS for treatment of post-LIS recurrent chronic anal fissure, and reveal differences if any.This study aims to compare redo-LIS and BoNT injection for treating post-LIS recurrent anal fissure.

Material and method

Nineteen patients who received LIS treatment and then redo-LIS or BoNT injection due to recurrence in the follow-up were included in this study. Group I (redo-LIS group) include 11 patients and group 2 (BoNT group) includes 8 patients. Their data on age, sex, anal incontinence scores and pain (VAS score) score as well.

Results

During the 3-month post-surgery follow-up period, there was statistically significant difference (p < 0.01) between groups by pain. No deterioration in the incontinence scores of patients in the group during the 6-month post-surgery period.

Conclusion

This study demonstrates that redo lateral internal sphincterotomy (LIS) is a reliable method for patients who received LIS but developed recurrent chronic anal fissure, and achieves successful results in terms of recurrence and relief of pain.

Short- and Long-term Central Action of Botulinum Neurotoxin Treatment in Laryngeal Dystonia

BACKGROUND AND OBJECTIVES

Laryngeal dystonia (LD) is isolated task-specific focal dystonia selectively impairing speech production. The first choice of LD treatment is botulinum neurotoxin (BoNT) injections into the affected laryngeal muscles. However, whether BoNT has a lasting therapeutic effect on disorder pathophysiology is unknown. We investigated short-term and long-term effects of BoNT treatment on brain function in patients with LD.

METHODS

A total of 161 participants were included in the functional MRI study. Statistical analyses examined central BoNT effects in patients with LD who were stratified based on the effectiveness and duration of treatment.

RESULTS

Patients with LD who were treated and benefited from BoNT injections had reduced activity in the left precuneus compared with BoNT-naive and treatment nonbenefiting patients. In addition, BoNT-treated patients with adductor LD had decreased activity in the right thalamus, whereas BoNT-treated abductor patients with LD had reduced activity in the left inferior frontal cortex. No statistically significant differences in brain activity were found between patients with shorter (1-5 years) and longer (13-28 years) treatment durations. However, patients with intermediate treatment duration of 6-12 years showed reduced activity in the right cerebellum compared with patients with both shorter and longer treatment durations and reduced activity in the right prefrontal cortex compared with patients with shorter treatment duration.

DISCUSSION

Our findings suggest that the left precuneus is the site of short-term BoNT central action in patients with LD, whereas the prefrontal-cerebellar axis is engaged in the BoNT response in patients with intermediate treatment duration of 6-12 years. Involvement of these structures points to indirect action of BoNT treatment on the dystonic sensorimotor network through modulation of motor sequence planning and coordination.

Characterizing the temporal discrimination threshold in musician's dystonia

The temporal discrimination threshold (TDT) has been established as a biomarker of impaired temporal processing and endophenotype in various forms of focal dystonia patients, such as cervical dystonia, writer's cramp or blepharospasm. The role of TDT in musician's dystonia (MD) in contrast is less clear with preceding studies reporting inconclusive results. We therefore compared TDT between MD patients, healthy musicians and non-musician controls using a previously described visual, tactile, and visual-tactile paradigm. Additionally, we compared TDT of the dystonic and non-dystonic hand and fingers in MD patients and further characterized the biomarker regarding its potential influencing factors, i.e. musical activity, disease variables, and personality profiles. Repeated measures ANOVA and additional Bayesian analyses revealed lower TDT in healthy musicians compared to non-musicians. However, TDTs in MD patients did not differ from both healthy musicians and non-musicians, although pairwise Bayesian t-tests indicated weak evidence for group differences in both comparisons. Analyses of dystonic and non-dystonic hands and fingers revealed no differences. While in healthy musicians, age of first instrumental practice negatively correlated with visual-tactile TDTs, TDTs in MD patients did not correlate with measures of musical activity, disease variables or personality profiles. In conclusion, TDTs in MD patients cannot reliably be distinguished from healthy musicians and non-musicians and are neither influenced by dystonic manifestation, musical activity, disease variables nor personality profiles. Unlike other isolated focal dystonias, TDT seems not to be a reliable biomarker in MD.

Modulation of Motor Cortex Activity After Intrathecal Baclofen Delivery in Chronic Thoracic Spinal Cord Injury

Objectives

Intrathecal baclofen (ITB) is commonly used for reduction of spasticity in chronic spinal cord injury (SCI). Its clinical effect is well-known; however, exact mechanisms of long-term effect of continuous ITB administration (cITBa) on modulation of cortical processes have not been elucidated. The aim of this study was to evaluate changes in motor cortex activation for healthy upper limbs in comparison to impaired lower limbs by functional magnetic resonance imaging (fMRI).

Methods

Ten subjects (eight males, 20–69 years) with thoracic SCI presenting no voluntary movements of lower limbs (except one) were enrolled in the fMRI study. fMRI at 1.5T with a finger tapping paradigm and mental movement simulating foot flexion on the dominant side were performed before, 3 months, and 1 year after start of cITBa. fMRI data processing was carried out using FMRI Expert Analysis Tool (FEAT), part of FSL. A second-level analysis was carried out using FLAME stages 1 and 2. The level of spasticity was assessed with the Modified Ashworth scale (MAS).

Results

Continuous ITB significantly decreased limb spasticity in all the subjects (group MAS spasticity dropped from 3 to 0.3). The second-level analysis (Z &gt; 1.6, cluster significance threshold p =0.05) revealed increased activation of the primary sensorimotor cortex of the foot between baseline and 3 months, and 3 months and 1 year.

Conclusion

Increased sensorimotor cortex activation with spasticity reduction after cITBa may reflect distant functional reorganization because of long-term mediated neuroplastic changes in the sensorimotor cortex. Better understanding of modulation of brain function in SCI after cITBa may influence the field of neurorehabilitation.

Impairment of sleep homeostasis in cervical dystonia patients

Alterations in brain plasticity seem to play a role in the pathophysiology of cervical dystonia (CD). Since evidences indicate that sleep regulates brain plasticity, we hypothesized that an alteration in sleep homeostatic mechanisms may be involved in the pathogenesis of CD. We explored sleep in control subjects (CTL) and CD patients before (T_pre-BoNT) and after (T_post-BoNT) botulinum toxin (BoNT) treatment. A physiological slow wave activity (SWA) power decrease throughout the night was observed in CTL but not in CD at T_pre-BoNT. BoNT restored the physiological SWA decrease in CD at T_post-BoNT. Furthermore, in the first part of the night, CD at T_post-BNT showed a frontal increase and parietal decrease in SWA power compared to CD at T_pre-BoNT, with a SWA distribution comparable to that observed in CTL. Our data highlighted a pathophysiological relationship between SWA during sleep and CD and provided novel insight into the transient central plastic effect of BoNT.

Postmarketing safety surveillance data reveals protective effects of botulinum toxin injections against incident anxiety

Randomized controlled trials (RCTs) have shown an antidepressant effect of glabellar botulinum toxin (BoNT) injections. In the FDA Adverse Event Reporting System (FAERS) database, BoNT injection is associated with reduced incidence rates of depression across various non-psychiatric indications, which confirms the previous findings independently of specific expectations to an antidepressant effect of BoNT. The rationale of using BoNT to treat depression is to interrupt proprioceptive body feedback that may reinforce negative emotions. Negative emotions also occur in other mental disorders, suggesting a transdiagnostic therapeutic potential of BoNT in psychiatry. Here we report an analysis of the FAERS database, in which we found that, compared to alternative treatments, BoNT injections were associated with lower incidence of anxiety symptoms and related disorders. Among seven indications/injection sites, we found this protective effect of BoNT in cosmetic use/facial muscles, migraine/facial and head muscles, spasms and spasticity/upper and lower limbs, torticollis and neck pain/neck muscles, and sialorrhea/parotid and submandibular glands (reporting odds ratios 0.79-0.27). These findings are encouraging for possible future RCTs on the use of BoNT as a treatment for anxiety and related disorders.

Botulinum Neurotoxins in Central Nervous System: An Overview from Animal Models to Human Therapy

Botulinum neurotoxins (BoNTs) are potent inhibitors of synaptic vesicle fusion and transmitter release. The natural target of BoNTs is the peripheral neuromuscular junction (NMJ) where, by blocking the release of acetylcholine (ACh), they functionally denervate muscles and alter muscle tone. This leads them to be an excellent drug for the therapy of muscle hyperactivity disorders, such as dystonia, spasticity, and many other movement disorders. BoNTs are also effective in inhibiting both the release of ACh at sites other than NMJ and the release of neurotransmitters other than ACh. Furthermore, much evidence shows that BoNTs can act not only on the peripheral nervous system (PNS), but also on the central nervous system (CNS). Under this view, central changes may result either from sensory input from the PNS, from retrograde transport of BoNTs, or from direct injection of BoNTs into the CNS. The aim of this review is to give an update on available data, both from animal models or human studies, which suggest or confirm central alterations induced by peripheral or central BoNTs treatment. The data will be discussed with particular attention to the possible therapeutic applications to pathological conditions and degenerative diseases of the CNS.

Effect of Botulinum Toxin on Non-Motor Symptoms in Cervical Dystonia

Patients with cervical dystonia (CD) may display non-motor symptoms, including psychiatric disturbances, pain, and sleep disorders. Intramuscular injection of botulinum toxin type A (BoNT-A) is the most efficacious treatment for motor symptoms in CD, but little is known about its effects on non-motor manifestations. The aim of the present study was to longitudinally assess BoNT-A’s effects on CD non-motor symptoms and to investigate the relationship between BoNT-A-induced motor and non-motor changes. Forty-five patients with CD participated in the study. Patients underwent a clinical assessment that included the administration of standardized clinical scales assessing dystonic symptoms, psychiatric disturbances, pain, sleep disturbances, and disability. Clinical assessment was performed before and one and three months after BoNT-A injection. BoNT-A induced a significant improvement in dystonic symptoms, as well as in psychiatric disturbances, pain, and disability. Conversely, sleep disorders were unaffected by BoNT-A treatment. Motor and non-motor BoNT-A-induced changes showed a similar time course, but motor improvement did not correlate with non-motor changes after BoNT-A. Non-motor symptom changes after BoNT-A treatment are a complex phenomenon and are at least partially independent from motor symptom improvement.