Botulinum toxin in cervical dystonia: low dosage with electromyographic guidance

Anatomical Proposal for Botulinum Neurotoxin Injection Targeting the Platysma Muscle for Treating Platysmal Band and Jawline Lifting: A Review

The platysma muscle is a thin superficial muscle that covers the entire neck and lower part of the face. The platysma muscle is the primary target muscle for botulinum neurotoxin injection therapy aimed at treating platysmal band and lower facial lifting. In the procedure of botulinum neurotoxin injection therapy, a lack of knowledge of the anatomy of the platysma muscle and the properties of botulinum neurotoxin can lead to side effects such as dysphagia, dysphonia, and weakness of the neck muscles. Anatomically safe injection sites have been proposed for the platysma muscle, and the appropriate injection technique has been reviewed. We proposed optimal injection sites based on the external anatomical features of the mandible. The aim of these proposal was to standardize the procedure for the effective use of botulinum neurotoxin injections by minimizing the dose unit and injection points and thereby preventing adverse events.

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

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

Effective botulinum toxin injection guide for treatment of cervical dystonia

The aim of this study was to elucidate the distribution of the accessory nerve within the sternocleidomastoid muscle (SCM) to aid identifying the optimum sites for botulinum neurotoxin (BoNT) injections and applying chemical neurolysis. Thirty SCM specimens from 15 Korean cadavers were used in this study. Sihler's staining was applied to 10 of the SCM specimens. Transverse lines were drawn in 20 sections to divide the SCM into 10 divisions vertically, and a vertical line was drawn into the medial and lateral halves from the mastoid process to the sternoclavicular joint. The most densely innervated areas were 5/10-6/10 and 6/10-7/10 along the lateral and medial parts of the muscle, respectively. We suggest injecting BoNT in the medial region 6/10-7/10 along the SCM prior to injecting in the lateral region 5/10-6/10 along the muscle to ensure safe and effective treatment. Clin. Anat. 33:192-198, 2020. © 2019 Wiley Periodicals, Inc.

Imaging three-dimensional innervation zone distribution in muscles from M-wave recordings

OBJECTIVE

To localize neuromuscular junctions in skeletal muscles in vivo which is of great importance in understanding, diagnosing and managing of neuromuscular disorders.

APPROACH

A three-dimensional global innervation zone imaging technique was developed to characterize the global distribution of innervation zones, as an indication of the location and features of neuromuscular junctions, using electrically evoked high-density surface electromyogram recordings.

MAIN RESULTS

The performance of the technique was evaluated in the biceps brachii of six intact human subjects. The geometric centers of the distributions of the reconstructed innervation zones were determined with a mean distance of 9.4  ±  1.4 cm from the reference plane, situated at the medial epicondyle of the humerus. A mean depth was calculated as 1.5  ±  0.3 cm from the geometric centers to the closed points over the skin. The results are consistent with those reported in previous histology studies. It was also found that the volumes and distributions of the reconstructed innervation zones changed as the stimulation intensities increased until the supramaximal muscle response was achieved.

SIGNIFICANCE

Results have demonstrated the high performance of the proposed imaging technique in noninvasively imaging global distributions of the innervation zones in the three-dimensional muscle space in vivo, and the feasibility of its clinical applications, such as guiding botulinum toxin injections in spasticity management, or in early diagnosis of neurodegenerative progression of amyotrophic lateral sclerosis.

Clinical Practice: Evidence-Based Recommendations for the Treatment of Cervical Dystonia with Botulinum Toxin

Cervical dystonia (CD) is the most frequent form of focal dystonia. Symptoms often result in pain and functional disability. Local injections of botulinum neurotoxin are currently the treatment of choice for CD. Although this treatment has proven effective and is widely applied worldwide, many issues still remain open in the clinical practice. We performed a systematic review of the literature on botulinum toxin treatment for CD based on a question-oriented approach, with the aim to provide practical recommendations for the treating clinicians. Key questions from the clinical practice were explored. Results suggest that while the beneficial effect of botulinum toxin treatment on different aspects of CD is well established, robust evidence is still missing concerning some practical aspects, such as dose equivalence between different formulations, optimal treatment intervals, treatment approaches, and the use of supportive techniques including electromyography or ultrasounds. Established strategies to prevent or manage common side effects (including excessive muscle weakness, pain at injection site, dysphagia) and potential contraindications to this treatment (pregnancy and lactation, use of anticoagulants, neurological comorbidities) should also be further explored.

Three-Dimensional Innervation Zone Imaging from Multi-Channel Surface EMG Recordings

There is an unmet need to accurately identify the locations of innervation zones (IZs) of spastic muscles, so as to guide botulinum toxin (BTX) injections for the best clinical outcome. A novel 3D IZ imaging (3DIZI) approach was developed by combining the bioelectrical source imaging and surface electromyogram (EMG) decomposition methods to image the 3D distribution of IZs in the target muscles. Surface IZ locations of motor units (MUs), identified from the bipolar map of their MU action potentials (MUAPs) were employed as a prior knowledge in the 3DIZI approach to improve its imaging accuracy. The performance of the 3DIZI approach was first optimized and evaluated via a series of designed computer simulations, and then validated with the intramuscular EMG data, together with simultaneously recorded 128-channel surface EMG data from the biceps of two subjects. Both simulation and experimental validation results demonstrate the high performance of the 3DIZI approach in accurately reconstructing the distributions of IZs and the dynamic propagation of internal muscle activities in the biceps from high-density surface EMG recordings.

Impact of Injection-Guiding Techniques on the Effectiveness of Botulinum Toxin for the Treatment of Focal Spasticity and Dystonia: A Systematic Review

OBJECTIVE

To conduct a systematic review of the impact of different injection-guiding techniques on the effectiveness of botulinum toxin type A (BoNT-A) for the treatment of focal spasticity and dystonia.

DATA SOURCES

MEDLINE via PubMed, Academic Search Premier, PASCAL, The Cochrane Library, Scopus, SpringerLink, Web of Science, EM Premium, and PsycINFO.

STUDY SELECTION

Two reviewers independently selected studies based on predetermined inclusion criteria.

DATA EXTRACTION

Data relating to the aim were extracted. Methodological quality was graded independently by 2 reviewers using the Physiotherapy Evidence Database assessment scale for randomized controlled trials (RCTs) and the Downs and Black evaluation tool for non-RCTs. Level of evidence was determined using the modified Sackett scale.

DATA SYNTHESIS

Ten studies were included. Seven were randomized. There was strong evidence (level 1) that instrumented guiding (ultrasonography [US], electrical stimulation [ES], electromyogram [EMG]) was more effective than manual needle placement for the treatment of spasmodic torticollis, upper limb spasticity, and spastic equinus in patients with stroke, and spastic equinus in children with cerebral palsy. Three studies provided strong evidence (level 1) of similar effectiveness of US and ES for upper and lower limb spasticity in patients with stroke, and spastic equinus in children with cerebral palsy, but there was poor evidence or no available evidence for EMG or other instrumented techniques.

CONCLUSIONS

These results strongly recommend instrumented guidance of BoNT-A injection for the treatment of spasticity in adults and children (ES or US), and of focal dystonia such as spasmodic torticollis (EMG). No specific recommendations can be made regarding the choice of instrumented guiding technique, except that US appears to be more effective than ES for spastic equinus in adults with stroke.

The clinical utility of botulinum toxin injections targeted at the motor endplate zone in cervical dystonia

BACKGROUND AND PURPOSE

Cervical dystonia (CD) patients usually receive repeated botulinum neurotoxin (BoNT) injections. The aims of this study were to evaluate the feasibility of motor endplate zone (MEZ) detection of relevant cervical muscles in CD patients receiving chronic BoNT treatment and to compare the treatment effect of half-dosed, endplate-targeted injections to standard BoNT injections.

METHODS

In study 1, high-density surface electromyography (HD-sEMG) was recorded from the sternocleidomastoid (SCM) and splenius capitis (SC) muscles in 18 CD patients with ongoing BoNT treatment, by which the location of the MEZ was determined. In study 2, nine additional patients with rotational-type CD participated in a treatment effect study where they received either half of their regular BoNT dose through endplate-targeted injections or their normal BoNT dose through standard injections (crossover design). Dystonia severity was recorded before and 4 weeks after each treatment session (Toronto Western Spasmodic Torticollis Rating Scale severity subscore).

RESULTS

In the SCM muscle the MEZ was located at the lower border of the superior third part of the muscle, and in the SC muscle at half muscle length. Endplate-targeted, half-dosed BoNT injection resulted in a similar treatment effect to injecting the full dose in the standard technique.

CONCLUSIONS

Half-dosed, endplate-targeted BoNT injections lead to a similar treatment effect to the standard BoNT injection protocol. MEZ detection confronts the clinician with some technical challenges, such as the ability of accurate and technically optimal placement of the electrode grid and correct interpretation of the HD-sEMG signal.

Threshold of Clinical Severity of Cervical Dystonia for Positive (18)F-FDG PET/CT

Objective

To examine whether the clinical severity of cervical dystonia (CD) significantly correlates with ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) findings as well as to determine the threshold of the clinical severity of CD for positive ¹⁸F-FDG PET/CT study findings.

Methods

Forty-seven subjects with torticollis as one of the symptoms of CD were included. The clinical severity of CD was evaluated with the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) at the time of ¹⁸F-FDG PET/CT. The correlation between the clinical severity of CD and the highest SUVmax was examined. The threshold of the clinical severity of CD necessary for positive ¹⁸F-FDG PET/CT findings was determined using receiver operating characteristics curve analysis.

Results

Thirty-three of the 47 subjects (70.21%) showed positive ¹⁸F-FDG PET/CT findings. The ipsilateral splenius capitis/cervicis, oblique capitis inferior, and longus colli/capitis were the rotators most frequently involved. The highest SUVmax of ¹⁸F-FDG PET/CT was significant correlated with the TWSTRS. Subjects with a total TWSTRS exceeding 39 showed positive ¹⁸F-FDG PET/CT findings, with those having a total TWSTRS ≤22 showing negative ¹⁸F-FDG PET/CT results. The cutoff value of the total TWSTRS for positive ¹⁸F-FDG PET/CT findings was set at 27.5 with 90.9% sensitivity and 64.3% specificity.

Conclusion

A significant correlation was evident between the clinical severity of CD and ¹⁸F-FDG PET/CT findings, providing a threshold of the clinical severity of CD for acquisition of positive ¹⁸F-FDG PET/CT findings.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Immunogenicity of botulinum toxins

Botulinum neurotoxins are formulated biologic pharmaceuticals used therapeutically to treat a wide variety of chronic conditions, with varying governmental approvals by country. Some of these disorders include cervical dystonia, post-stroke spasticity, blepharospasm, migraine, and hyperhidrosis. Botulinum neurotoxins also have varying governmental approvals for cosmetic applications. As botulinum neurotoxin therapy is often continued over many years, some patients may develop detectable antibodies that may or may not affect their biological activity. Although botulinum neurotoxins are considered "lower risk" biologics since antibodies that may develop are not likely to cross react with endogenous proteins, it is possible that patients may lose their therapeutic response. Various factors impact the immunogenicity of botulinum neurotoxins, including product-related factors such as the manufacturing process, the antigenic protein load, and the presence of accessory proteins, as well as treatment-related factors such as the overall toxin dose, booster injections, and prior vaccination or exposure. Detection of antibodies by laboratory tests does not necessarily predict the clinical success or failure of treatment. Overall, botulinum neurotoxin type A products exhibit low clinically detectable levels of antibodies when compared with other approved biologic products. This review provides an overview of all current botulinum neurotoxin products available commercially, with respect to the development of neutralizing antibodies and clinical response.

Botulinum toxin has an increased effect when targeted toward the muscle's endplate zone: a high-density surface EMG guided study

OBJECTIVES

To compare the effect of endplate-targeted injections of a low Botulinum neurotoxin type A (BoNT-A) dose with that of injections at defined distances from the motor endplate zone.

METHODS

In eight healthy volunteers, the main endplate zones of the right and left extensor digitorum brevis (EDB) muscles were localized using high-density surface EMG. On the study side BoNT-A was injected at fixed distances from the endplate zone. On the control side, BoNT-A was administered into the endplate zone. Compound muscle action potential (CMAP) prior to the injection and 2, 12, and 24 weeks later were recorded.

RESULTS

On the control side, the mean CMAP reduction 2 weeks after BoNT-A injection was 79.3%. The difference in CMAP reduction between both EDB muscles was significantly related to the injection distance from the endplate zone. Increasing the injection distance by 1cm reduced the effect of BoNT-A by 46%.

CONCLUSIONS

Guided injection of a reduced BoNT-A dose into the muscle's endplate zone(s) is a promising strategy for optimizing the therapeutic effectiveness of BoNT-A and for minimizing side-effects such as unwanted weakness of adjacent muscles.

SIGNIFICANCE

Precise endplate-targeted injections increase the effect of BoNT-A and may thus prove to reduce required dosage and treatment costs.

Comparison between (18)F-FDG PET/CT and EMG Mapping for Identifying Dystonic Superficial Muscles in Primary Cervical Dystonia: Preliminary Results

PURPOSE

This study was conducted to compare (18)F-FDG PET/CT and electromyography (EMG) mapping in patients with primary cervical dystonia (PCD) to find dystonic superficial cervical muscles.

METHODS

Ten consecutive patients with PCD (M:F = 5:5, age 44 ± 13 years) whose dystonic posture was not relieved with conventional muscle relaxant therapy were included. Target cervical muscles for the comparison between (18)F-FDG PET/CT and EMG mapping were four representative superficial bilateral cervical muscles: splenius capitis muscle, sternocleidomstoid muscle, upper trapezius muscle, and leavator scapulae muscle. The diagnostic efficacy was compared between (18)F-FDG PET/CT and EMG mapping using physical exam and measurement of rotation angle as the gold standard.

RESULTS

Among 80 muscles evaluated, there were 21 (26%) dystonic superficial cervical muscles assessed with physical exam and motion analysis. The sensitivity, specificity, and accuracy for localizing dystonic muscles were 76, 92, and 88% for (18)F-FDG PET/CT, and 95, 66, and 74% for EMG mapping, respectively. The sensitivity of EMG mapping was significantly higher than that of (18)F-FDG PET/CT. In contrast, (18)F-FDG PET/CT was significantly superior to EMG mapping for specificity and accuracy.

CONCLUSIONS

(18)F-FDG PET/CT is more specific and accurate than EMG mapping for finding superficial dystonic cervical muscles. The high sensitivity of EMG mapping suggests that (18)F-FDG PET/CT and EMG mapping are complementary for finding dystonic superficial cervical muscles.

Cervical dystonia

Cervical dystonia is a common disorder with significant associated morbidity. Although limited benefit can be derived from oral pharmacologic agents, the advent of botulinum neurotoxin (BoNT) injection has provided a valuable tool in the treatment of this disorder. In order to provide effective treatment, the physician must have an intimate knowledge of the anatomy and function of the neck musculature. Novel BoNT formulations, even of the same serotype, are not equivalent and thus require careful dose titration. Formulation improvements may result in reduced immunoresistance. In patients labeled as treatment resistant to BoNT, careful electromyographic reassessment of select muscles for injection will frequently result in improved clinical benefit.

Meige syndrome: what's in a name?

Frequently, blepharospasm is associated with involuntary movements of the platysma, lower face and masticatory muscles. Similarly, masticatory dystonia may occur in isolation or in combination with dystonia of other cranial and cervical muscles. The non-possessive and possessive forms of Meige and Brueghel syndromes have been variably and imprecisely ascribed to various anatomical variations of craniocervical dystonia. Herein, the origin of eponymic terms as applied to craniocervical dystonia is reviewed as support for proposed elimination of these eponyms from clinical usage. Although the term "segmental craniocervical dystonia" more accurately captures the combination of blepharospasm and dystonia of other head and neck muscles, delineation of craniocervical subphenotypes is essential for etiological/genetic and treatment studies. To conclude, the clinical features, epidemiology, pathophysiology and therapeutic management of segmental craniocervical dystonia are examined with a particular focus on "blepharospasm-plus" subphenotypes.

Initial experience with imaging-guided intramuscular botulinum toxin injection in patients with idiopathic cervical dystonia

OBJECTIVE

The objective of our study was to present our initial experiences of imaging-guided intramuscular botulinum toxin (BTX) injection in patients with idiopathic cervical dystonia.

CONCLUSION

Imaging-guided BTX injection is a useful treatment technique in patients with idiopathic cervical dystonia when target muscles are located deeply or an injection must be delivered to a focal muscle area.

Comparison of botulinum neurotoxin preparations for the treatment of cervical dystonia

BACKGROUND

Comparative studies of botulinum neurotoxin preparations to date have generally examined 2 preparations at prespecified dose ratios in relatively homogeneous groups of patients under controlled study conditions. It is unclear whether the differences in adverse-event rates that have been noted under these controlled conditions can be generalized to the broader population of cervical dystonia patients, who are treated with a wider range of doses in a variety of settings.

OBJECTIVE

We conducted a systematic review and analysis of the published literature to compare rates of dysphagia and dry mouth in studies of botulinum neurotoxin products.

METHODS

We searched the MEDLINE, EMBASE, Biosis, SciSearch, JICST (Japan Science and Technology Center), and Pascal databases from 1985 through 2006 using the terms cervical dystonia, spasmodic torticollis, and botulinum toxin for original English-language studies of Botox, Dysport, or Myobloc in the treatment of cervical dystonia (or spasmodic torticollis) that documented adverse events by treatment or patient. Studies that involved patients with various types of dystonias or movement disorders were included as long as adverse events were reported separately for those with cervical dystonia. Rates of dysphagia with the original preparation of Botox were considered separately from those with the current preparation of Botox.

RESULTS

Seventy published articles were included in the analysis (30 Botox, 24 Dysport, 3 Botox + Dysport, 11 Myobloc, 2 Botox + Myobloc). Mean total doses per treatment ranged from 60 to 374 U for Botox, 125 to 1200 U for Dysport, and 579 to 19,853 U for Myobloc. Botox was associated with a significantly lower rate of dysphagia than Dysport, with mean dysphagia rates of 10.5% for original Botox, 8.9% for current Botox, and 26.8% for Dysport (both, P < 0.05). Myobloc was associated with dry mouth (3.2%-90.0%) in 9 of 13 studies, but this adverse event was not reported in a sufficient number of studies of botulinum toxin type A preparations (Botox, n = 2; Dysport, n = 6) to permit statistical comparison. In the weighted analysis, the duration of effect differed between botulinum neurotoxin products (current Botox > Myobloc > original Botox > Dysport; all, P < 0.001), but only 43 (61.4%) of the 70 studies reported duration, and the definitions varied.

CONCLUSION

The results of this analysis indicate differences in adverse-event rates between botulinum neurotoxin preparations, suggesting that use of these products should be based on their individual dosing, efficacy, and safety profiles.

Botulinum toxin for writer's cramp: a randomised, placebo-controlled trial and 1-year follow-up

BACKGROUND

Botulinum toxin type A (BoNT-A) has become the treatment of choice for most types of focal dystonia.

OBJECTIVE

To investigate the efficacy of BoNT-A injections in patients with writer's cramp in a double-blind, randomised, placebo-controlled trial and to evaluate the follow-up results.

METHODS

Forty participants were randomised to treatment with either BoNT-A or placebo injections in two sessions. Trial duration was 12 weeks. The primary outcome measure was the patients' choice to continue with the treatment, despite its possible disadvantages. Secondary outcome measures included several clinical rating scales on the levels of impairment and disability. Assessments were made at baseline and 2 months (secondary outcomes) and 3 months (primary outcome). Duration of follow-up was 1 year.

RESULTS

39 patients completed the trial. Fourteen of 20 patients (70%) receiving BoNT-A reported a beneficial effect and chose to continue treatment, versus 6 of 19 patients (31.6%) in the placebo group (p = 0.03). The changes on most of the clinical rating scales were significantly in favour of BoNT-A. Side effects reported were hand weakness, which was mostly mild and always transient, and pain at the injection site. After 1 year, 20 of 39 patients were still under treatment with a positive effect.

CONCLUSION

Treatment with BoNT-A injections led to a significantly greater improvement compared with placebo, according to patients' opinion and clinical assessment scales. Weakness in the hand is an important side effect of BoNT-A injections, but despite this disadvantage, most patients preferred to continue treatment. About 50% of our patients were still under treatment after 1 year.

Botulinum toxin treatment of children with cerebral palsy - a short review of different injection techniques

The intramuscular application of botulinum toxin type A (BoNT/A) has emerged to be an established treatment option to reduce muscular hyperactivity due to spasticity in children with cerebral palsy. Accurate injection is a prerequisite for efficient and safe treatment with BoNT/A. So far, treatment procedures have not been standardized. This paper is a short review of different injection techniques, i.e., manual needle placement as well as guidance by electromyography, electrical stimulation, and ultrasound. Advantages and disadvantages of the different injection techniques are discussed with a focus on needle positioning within the targeted muscle, injection close to the neuromuscular junction and diffusion of BoNT/A within the target muscles and through fascia. The additional information gained by each injection technique is weighed in terms of the clinical impact for children with cerebral palsy.

Treatment of cervical dystonia with botulinum toxins

Botulinum toxin (BoNT) treatment has been used extensively for the treatment of cervical dystonia. In most studies, there is significant improvement following treatment for head posture and pain. The common side effects following treatment include dysphagia, dry mouth, and neck weakness. There are five brands and two serotypes of BoNT available. The dosing of each serotype and brand differs. Perhaps more importantly, each brand and serotype may differ in immunogenic potential and occurrence of secondary unresponsiveness, an issue that is currently under active investigation. Although many aspects of the technique of injection have not been adequately studied, general guidelines are available.

Targeting the Neuromuscular Junction in Skeletal Muscles

Botulinum neurotoxins selectively weaken skeletal muscle by presynaptic blockade of vesicles containing the neurotransmitter acetylcholine. Because the location of the neuromuscular junction (found in motor endplates) is most highly concentrated in a band within the midbelly of the muscle, injection of botulinum neurotoxins are hypothesized to be more potent when specifically targeted toward the motor endplate zones. Few studies have attempted to describe the distribution of motor endplate zones in skeletal muscles, and scant experimental data exist that directly tests this hypothesis. In this article, a rationale is presented for motor endplate targeting within specific limb muscles with respect to botulinum neurotoxin therapy.

Dysport

Since the commercial launch of Dysport in 1991, after 10 years of clinical studies on its predecessor formulations, this BTX-A product has shown great therapeutic promise with a good safety profile and low incidence of treatment failures. As with all BTX products, Dysport should not be seen as a generic equivalent but as a specific product with individual unit dosing requirements and side effect profiles. Its role as an important BTX-A molecule looks set to expand as new indications for botulinum toxin arise, and as the cosmetic usage of Dysport is approved in countries outside of South America.

Botulinum toxins in neurological disease

Botulinum toxins are among the most potent neurotoxins known to humans. In the past 25 years, botulinum toxin has emerged as both a potential weapon of bioterrorism and as a powerful therapeutic agent, with growing applications in neurological and non-neurological disease. Botulinum toxin is unique in its ability to target peripheral cholinergic neurons, preventing the release of acetylcholine through the enzymatic cleavage of proteins involved in membrane fusion, without prominent central nervous system effects. There are seven serotypes of the toxin, each with a specific activity at the molecular level. Currently, serotypes A (in two preparations) and B are available for clinical use, and have been shown to be safe and effective for the treatment of dystonia, spasticity, and other disorders in which muscle overactivity gives rise to symptoms. This review focuses on the pharmacology, electrophysiology, immunology, and application of botulinum toxin in selected neurological disorders.

Botulinum toxin therapy for cervical dystonia

Botulinum toxin revolutionized the treatment of cervical dystonia. In contrast to systemically active medications, the effect of botulinum toxin results from selective administration to weaken muscles involved in the dystonic posturing of the head. This article reviews the pathophysiologic basis of symptoms in cervical dystonia and how botulinum toxin alleviates them. Other therapeutic options are reviewed for comparison. This article discusses strategies for maximizing the clinical benefit of botulinum toxin in this disorder and reviews muscle selection and identification with electromyography.

The importance of electromyographic guidance and electrical stimulation for injection of botulinum toxin

The importance of EMG or electrical stimulation for guiding injections of botulinum toxin in limb muscles to treat dystonia or spasticity is based more on theoretical and preclinical data than on controlled clinical trials. Questions remain about the preferred administration of botulinum toxin for these conditions. Future clinical research is necessary to show clearly functional benefit of any particular injection localization method.

[EMG support in botulinum toxin treatment]

INTRODUCTION

The aim of this work is to sum up how the use of EMG improves BT therapy.

METHOD

A systematic review of the literature in the Pub Med computer database, along with a manual biography, allowed us to choose the most synthetic and the most pertinent publications according to our own practical experience.

RESULTS

There is no consensus of opinion, but the great majority of authors emphasize the importance of EMG in the different stages of botulinum toxin treatment: before injections, at the time of the injection, and finally during the follow-up after the first injection or after the repeated injections that transient efficiency make necessary.

DISCUSSION

A symptomatic therapeutic means recently recognized in focal dystonias and spasticity, BT is injected locally into the muscles to be treated. EMG can be used: at pre-injection for physiopathological evaluation but above all to establish a diagnosis and precise pre-intervention evaluation; at the moment of injection to provide guidance in precise muscle selection and for maximum efficiency with reduced, therefore less costly, doses. It also limits the risk of product diffusion susceptible of causing iatrogenic side effects and/or auto-immunisation resulting in resistance to the toxin; during follow-up, to understand why treatment failed and to look for changes in the dystonia pattern leading to objective re-evaluations and adapted reinjections. Although neglected by some, electrological logistics seem to us, as to many other practitioners who inject, to be a considerably helpful aid, particularly at the moment of injection when targeting the muscle to be treated.

The accuracy of needle placement in lower-limb muscles: a blinded study

OBJECTIVE

To assess the accuracy of common anatomic guides for electromyographic needle placement in muscles.

DESIGN

Blinded study. The dissector identified different needle placements by a random number attached to a wire in the insertion site.

SETTING

A university anatomy laboratory.

CADAVERS

Ten cadaver lower limbs.

INTERVENTIONS

By using techniques published in texts by Gieringer and Delagi and Perotto, clinical electromyographers palpated and measured appropriate locations for needle placement. A thin wire was inserted through the needle into 36 different muscles in 10 cadavers, resulting in 263 targeted muscles. An anatomist blinded to intended location dissected and recorded muscles and other tissues that the wire pierced or passed near.

MAIN OUTCOME MEASURES

Targeted muscle penetration, final resting place of the wire tip, and proximity to vital structures.

RESULTS

Fifty-seven percent of insertions penetrated the intended muscle. The wire tip was in the intended muscle 45% of the time. Seventeen percent of insertions penetrated or passed within 5mm of an important structure, including nerve (9.1%), tendon (3.0%), named artery (2.7%), vein (2.7%), or joint (0.8%). Specific muscle accuracy was highly variable, from 0% for 12 tries in various deep hip muscles to 100% of 10 tries in the vastus medialis.

CONCLUSION

The accuracy of blind needle placement varied according to muscle. With the blind insertion technique, more accurate and safe needle placement strategies can be developed.

Treatment of dystonia

Therapeutic strategies in the treatment of dystonia consist primarily of pharmacologic, surgical, and supportive approaches. Many recent advances have been made in the treatment of dystonia with newer medications, availability of different botulinum toxins, and surgical procedures. However, these treatment modalities all have limiting factors and varying levels of efficacy. Studies range from case reports and open-label trials to double-blind placebo-controlled trials. More research and larger studies are needed to explore these newer medications and surgical techniques for both primary focal and generalized dystonia. Studies in functional outcome and quality of life further support the importance of discovering safe and effective means to treat dystonia. An algorithmic approach may be useful to guide the physician along the various treatment choices.

Cervical dystonia pathophysiology and treatment options

Dystonia is a syndrome of sustained involuntary muscle contractions, frequently causing twisting and repetitive movements or abnormal posturing. Cervical dystonia (CD) is a form of dystonia that involves neck muscles. However, CD is not the only cause of neck rotation. Torticollis may be caused by orthopaedic, musculofibrotic, infectious and other neurological conditions that affect the anatomy of the neck, and structural causes. It is estimated that there are between 60,000 and 90,000 patients with CD in the US. The majority of the patients present with a combination of neck rotation (rotatory torticollis or rotatocollis), flexion (anterocollis), extension (retrocollis), head tilt (laterocollis) or a lateral or sagittal shift. Neck posturing may be either tonic, clonic or tremulous, and may result in permanent and fixed contractures. Sensory tricks ('geste antagonistique') often temporarily ameliorate dystonic movements and postures. Commonly used sensory tricks by patients with CD include touching the chin, back of the head or top of the head. Patients with CD are classified according to aetiology into two groups: primary CD (idiopathic--may be genetic or sporadic) or secondary CD (symptomatic). Patients with primary CD have no evidence by history, physical examination or laboratory studies (except primary dystonia gene) of any secondary cause for the dystonic symptoms. CD is a part of either generalised or focal dystonic syndrome which may have a genetic basis, with an identifiable genetic association. Secondary or symptomatic CD may be caused by central or peripheral trauma, exposure to dopamine receptor antagonists (tardive), neurodegenerative disease, and other conditions associated with abnormal functioning of the basal ganglia. In the majority of patients with CD, the aetiology is not identifiable and the disorder is often classified as primary. Unless the aetiological investigation reveals a specific therapeutic intervention, therapy for CD is symptomatic. It includes supportive therapy and counselling, physical therapy, pharmacotherapy, chemodenervation [botulinum toxin (BTX), phenol, alcohol], and central and peripheral surgical therapy. The most widely used and accepted therapy for CD is local intramuscular injections of BTX-type A. Currently, both BTX type A and type B are commercially available, and type F has undergone testing. Pharmacotherapy, including anticholinergics, dopaminergic depleting and blocking agents, and other muscle relaxants can be used alone or in combination with other therapeutic interventions. Surgery is usually reserved for patients with CD in whom other forms of treatment have failed.

Botulinum toxin in motor disorders: practical considerations with emphasis on interventional neurophysiology

After a brief review of the pharmacological properties of the botulinum toxin (BT), its mechanism of action on the nerve endings of the neuromuscular junctions, and the general therapeutic principles and adverse side effects, we discuss the advantages of interventional neurophysiology for the treatment of focal motor disorders by means of botulinum toxin A (BTA) muscle infiltration. Electromyography (EMG) provides a valuable objective information in the diagnosis of many motor disturbances and enables the precise identification of the muscles that contribute to the abnormal movement or posture. The use of EMG guidance for BTA injection seems advisable in every muscle but it become indispensable in those difficult to access, deeply located or partially atrophied by previous toxin infiltrations. The EMG study also serves to localise the areas with the highest abnormal activity and the motor point of the muscle, where the injection of toxin exerts its maximal effect. Consequently, lower doses of BTA can be employed without decreasing the efficacy of treatment but reducing the potential risk of side effects, antibody production and the cost of treatment. Electrophysiological diagnosis and BTA treatment may be performed during the same exploration. Considerations on the particular aspects and lines of action are given referring to the main focal muscular hyperactivity motor disorders such as cervical, oromandibular and laryngeal dystonias, blepharospasm, writer's cramp, hemifacial and hemimasticatory spasms, infantile and adult forms of spasticity and some other focal disturbances such as strabismus, detrusor-sphincter dyssynergia and anismus.

Botulinum A toxin: Dysport improvement of biological availability

We investigated the efficacy and potency of Dysport, a botulinum neurotoxin type A complex approved for therapy, under various conditions. Conditions for maximal expression of biological activity were explored in vitro in the phrenic nerve-hemidiaphragm preparation, while conditions for optimal distribution of the toxin were tested in vivo in a double blind trial involving volunteers, using the foot Muscles extensor digitorum brevis. In contrast to the recommendations of the manufacturer, the biological availability of Dysport could be enhanced by (1) lowering its concentration, (2) supplementing with albumin, and (3) increasing the injection volume. On the basis of these experimental findings Dysport was diluted to a final concentration of 50 U/ml for therapeutic purposes. In a blind, single crossover study patients suffering from various forms of dystonia were treated with Dysport, first diluted and dosed as suggested by the manufacturer and then with doses cut by approximately 70% in accordance with the experimental findings. The low-dose treatment was as effective as the treatment with the recommended higher doses, but side effects were considerably less apparent. The benefits to be derived from these adjustments include a low risk of antibody formation, which could preclude continued or future treatment and substantial cost savings.

Utility of an EMG mapping study in treating cervical dystonia

Intramuscular injections of botulinum toxin are the cornerstone of treatment for cervical dystonia. Controversy exists regarding the necessity for EMG-guided injections. We compared the clinical examination of four movement disorder specialists to an electromyographic (EMG) mapping study. Clinical predictions of individual muscle involvement were only 59% sensitive and 75% specific. Muscle hypertrophy, shoulder elevation, and dominant head vector did not bolster clinical accuracy. An EMG mapping study facilitates identification of dystonic muscles in cervical dystonia, which may enhance botulinum toxin therapy.

Cervical Dystonia (Torticollis)

During the initial consultation, the patient is introduced to the five basic treatment options, acknowledging that in most cases, the choice is in the patient's control. The options are 1) supportive/social treatment, 2) physical therapies, 3) oral and intrathecal pharmacotherapy, 4) injection (botulinum toxin type A ) therapy, and 5) surgical therapy. Although a patient may be an obvious candidate for a specific intervention, the patient needs to be aware of the options, including those that he or she chooses not to use. Combination therapies are often appropriate. The option of supportive therapy is applicable in nearly all situations. All patients are encouraged to join a dystonia advocacy association. To accomplish this, literature is made available to them, and the telephone number of the local dystonia chapter is provided. For most patients with focal dystonia or symptoms limited to one region, such as those with cervical dystonia, local injections of botulinum toxin type A are core treatment. For those who cannot be treated effectively with BTX-A, or for those in whom BTX-A has failed, pharmacotherapy is instituted. Pharmacotherapy can often "take the edge off" symptoms that remain after BTX-A therapy. Physical therapies are recommended as complementary treatment for most patients receiving BTX-A in an attempt to extend the benefit from BTX-A. BTX-A may substantially change motor patterns, requiring physical therapies to help the patient relearn normal postures and functional control. In refractory cases when all other measures have failed, peripheral or brain surgery is considered. With our advancing understanding of the genetics of dystonia, it is hoped that specific therapy to either halt the progression of or bring additional relief to dystonic spasms will be available shortly.

Doxorubicin chemomyectomy as a treatment for cervical dystonia: histological assessment after direct injection into the sternocleidomastoid muscle

The sternocleidomastoid muscle (SCM) is one of the major muscles involved in producing abnormal head position in cervical dystonia patients. This study tested whether doxorubicin chemomyectomy, direct injection of doxorubicin into the SCM to permanently remove muscle fibers, has the potential to be a nonsurgical, permanent treatment for cervical dystonia. The right SCM of rabbits was injected with either 1 or 2 mg doxorubicin. Animals were sacrificed 1-2 months postinjection. The SCM was prepared for histological examination of muscle fiber loss and fiber type composition. In all cases, direct injection of doxorubicin resulted in significant decreases in total muscle cross-sectional areas ranging from 75% up to 98%. Individual myofiber cross-sectional areas were smaller than normal after 2 mg doxorubicin treatment, but similar to normal fiber size after 1 mg doxorubicin. There were increased numbers of myofibers that expressed slow and neonatal myosin heavy chain isoforms in these remaining muscle fibers compared to the untreated SCM on the contralateral side. Developmental myosin heavy chain (MHC) was also present in 53% of the remaining myofibers of the treated muscles. The fiber type composition of muscles contralateral to the doxorubicin injections was compared to the fiber type composition of SCM from normal, untreated controls; no difference was seen in the proportions of fast, slow, and neonatal MHC fiber types in these SCM muscles. In summary, the direct injection of doxorubicin into the SCM resulted in significant muscle loss. This supports the use of doxorubicin chemomyectomy as a potential permanent, nonsurgical treatment for cervical dystonia.

Evaluating motor end-plate-targeted injections of botulinum toxin type A in a canine model

Tarsal joint forces were measured in dogs over 70 days following botulinum toxin type A (BTX-A) injections. Three dogs were injected at motor end-plates located by electromyography (EMG), while 3 dogs were similarly injected, but without EMG guidance. Extension forces were significantly (P < 0.05) smaller in limbs injected at motor end-plates than in corresponding limbs on days 14 and 35. There were no significant differences at other times. Using these techniques, EMG end-plate targeting potentiates effects of BTX-A.

Muscle fiber type compartmentalization and expression of an immature myosin isoform in the sternocleidomastoid muscle of rabbits and primates

The sternocleidomastoid muscle is located in the neck and is both a neck rotator and flexor. Cervical dystonia, a focal dystonia disorder, is characterized by forceful involuntary contraction of a group of neck muscles, usually including the sternocleidomastoid. Little is known about the fiber type composition, fiber type compartmentalization and innervation patterns in this muscle in rabbit and primates. Sternocleidomastoid muscles from rabbit and monkey were analyzed for muscle fiber type composition and number, muscle fiber cross-sectional area and patterns of innervation. The sternocleidomastoid muscle was composed of two distinct regions, or compartments, with different fiber type compositions: an outer or superficial region composed of mostly type 2 myofibers and an inner deep region composed of both type 2 and type 1 myofibers. Neonatal myosin heavy chain isoform was detected in approximately 25% of the myofibers in both regions of the muscle. Neuromuscular junctions were located in seven endplate bands approximately 1-3 cm apart throughout the length of the muscle. There is clear evidence of anatomical subdivisions within this muscle. Not only is there variation in fiber type composition between superficial and deep regions of the muscle, but unlike most other mature skeletal muscles, it continues to express neonatal myosin heavy chain isoform in the adult. The motor program for neck movements is extremely complex, and the histological complexity plays a role in allowing for a continuum of movements of the head and neck, from maintenance of posture to rapid head movements.