Botulinum toxin in the treatment of writer's cramp

Does the guidance method affect the doses of botulinum toxin in writer's cramp?

PURPOSE

Botulinum neurotoxin (BoNT) injections are the main medical treatment of writer's cramp. When the outcome is favourable, patients usually receive injections several times per year in the long-term. However, we know little about the course of BoNT doses and nothing about the impact of the guidance method on the clinical outcome or injection strategy.

METHODS

We studied, in the long-term, the doses of BoNT and the target muscles in a group of patients with writer's cramp, according to the guidance method (electrical stimulation or ultrasound). Patients received at least three injection cycles guided by electrical stimulation, followed by at least three injection cycles guided by ultrasound.

RESULTS

Twenty-four patients were included. More target muscles were injected after switching to ultrasound guidance, especially the flexor carpi ulnaris and the flexor carpi radialis. The mean dose by muscle was lower when ultrasound guidance was used. When using electrical stimulation guidance, the dose in the flexors of the fingers decreased in the long-term, but increased in the flexors of the wrist. The course of the BoNT doses and of the number of target muscles per cycle were not the same during the first period (electrical stimulation) and the second period (ultrasound).

CONCLUSIONS

Switching to ultrasound guidance, the BoNT dose decreased, mainly in the flexors of the wrist. Based on the results of our study, we suggest a starting dose in several muscles (flexor carpi ulnaris, flexor carpi radialis, flexor digitorum profundus and flexor pollicis longus).

Efficacy and safety of botulinum toxin-A in writer’s cramp: a systematic review, meta-analysis, and meta-regression

Background

Botulinum toxin-A (BoNT) reduce over-firing of dystonic muscles, spasmodic contractions by enhancing function. We conducted a systematic review and random-effects meta-regression to investigate the efficacy and safety of BoNT in writer’s cramp (WC). Published electronic articles from inception till January 2022 were screened from four databases (Medline, Science Direct, Scopus, ProQuest). Effect sizes in the form of standardized mean differences were calculated for estimation of efficacy.

Results

Nineteen studies [six randomized control trials (RCTs) and 13 observational studies] involved 587 (514 experimental; 73 Controls) participants with mean age of 43.46 ± 8.84 years with mean duration of WC of 8.31 ± 5.35 years. Injection did not result in significant improvement in writing speed [standard mean difference (95% CI) 0.06 (− 0.35, 0.46)]. There was no significant difference in writing speed as compared to controls [standard mean difference (95% CI) − 0.51 (− 2.55, 1.52)]. The meta-analysis of observational studies showed a significant difference in the mean WC rating score [standard mean difference (95% CI) 0.54 (0.20, 0.88)]. Pooled analysis (observational studies and RCTs) demonstrated a significant difference in the mean Writer’s cramp rating score (WCRS) after BoNT [standard mean difference (95% CI) 0.75 (0.06, 1.44)]. No major safety concerns were reported in the included studies.

Conclusions

According to the meta-analysis of observational studies, BoNT injections are effective in WC for improving WCRS without major safety concerns. However, according to the meta-analysis of RCTs, there was no significant effect in efficacy with BoNT.

Classification of Dystonia

Dystonia is a hyperkinetic movement disorder characterized by abnormal movement or posture caused by excessive muscle contraction. Because of its wide clinical spectrum, dystonia is often underdiagnosed or misdiagnosed. In clinical practice, dystonia could often present in association with other movement disorders. An accurate physical examination is essential to describe the correct phenomenology. To help clinicians reaching the proper diagnosis, several classifications of dystonia have been proposed. The current classification consists of axis I, clinical characteristics, and axis II, etiology. Through the application of this classification system, movement disorder specialists could attempt to correctly characterize dystonia and guide patients to the most effective treatment. The aim of this article is to describe the phenomenological spectrum of dystonia, the last approved dystonia classification, and new emerging knowledge.

Current uses of botulinum toxin A as an adjunct to hand therapy interventions of hand conditions

STUDY DESIGN

Literature review.

DISCUSSION

Botulinum toxin A, a neurotoxin causing temporary muscle paralysis at the neuromuscular junction, has been used to treat multiple acquired conditions of the hand and upper extremity. Initially approved for use in treating blepharospasm and strabismus in the 1980s, indications have expanded to include spasticity associated with cerebrovascular accidents, vasospastic disorders, focal dystonias, and pain conditions. This article reviews the current literature discussing the efficacy of botulinum toxin A in management of disorders of the hand and upper extremity relevant to hand therapists.

LEVEL OF EVIDENCE

NA.

Evidence for the effectiveness of botulinum toxin for writer's cramp

We performed a comprehensive literature search of clinical studies published between 1989 and 2007 concerning the use of botulinum neurotoxin (BoNT) in the treatment of writer's cramp (WC). Publications were categorized as Classes I-IV using the scale developed by the Therapeutics and Technology Assessment (TTA) subcommittee of the American Academy of Neurology. Our search resulted in 17 clinical publications discussing the treatment of WC with BoNT. The literature search results were: one publication being Class I, two being Class II, 11 being Class III, and three being Class IV.

Clinical profile of various sub-types of writer's cramp

We profiled 141 consecutive patients of writer's cramp (WC). Simple WC (n=108) had a mean (SD) disease duration of 3.65 (2.7) years and a severity score of 2.8 (0.91) by Burke-Fahn-Marden (BFM) scale (handwriting score: 0-4 ), whereas complex WC (n=33) had a disease duration of 5.8 (2.81) years and severity score of 3.6 (0.52). Compared with focal WC, generalized WC cases had longer disease duration, severer disability, and were older. Mirror dystonia was seen in 65 patients (46.1%). Co-existent Meige's syndrome (n=4) and cervical dystonia (n=6) were seen. Some patients had abnormal posturing of the neck (n=5) and of the oromandibular region (n=3) only while writing. Those receiving botulinum toxin fared significantly better than those on oral therapy, at 1 month post treatment.

Botulinum toxin: Clinical use

Since its development for the use of blepharospasm and strabismus more than 2.5 decades ago, botulinum neurotoxin (BoNT) has become a versatile drug in various fields of medicine. It is the standard of care in different disorders such as cervical dystonia, hemifacial spasm, focal spasticity, hyperhidrosis, ophthalmological and otolaryngeal disorders. It has also found widespread use in cosmetic applications. Many other indications are currently under investigation, including gastroenterologic and urologic indications, analgesic management and migraine. This paper is an extensive review of the spectrum of BoNT clinical applications.

Treatment of dystonia

Dystonia may be a sign or symptom, that is comprised of complex abnormal and dynamic movements of different etiologies. A specific cause is identified in approximately 28% of patients, which only occasionally results in specific treatment. In most cases, treatment is symptomatic and designed to relieve involuntary movements, improve posture and function and reduce associated pain. Therapeutic options are dictated by clinical assessment of the topography of dystonia, severity of abnormal movements, functional impairment and progression of disease and consists of pharmacological, surgical and supportive approaches. Several advances have been made in treatment with newer medications, availability of different forms of botulinum toxin and globus pallidus deep brain stimulation (DBS). For patients with childhood-onset dystonia, the majority of whom later develop generalized dystonia, oral medication is the mainstay of therapy. Recently, DBS has emerged as an effective alternative therapy. Botulinum toxin is usually the treatment of choice for those with adult-onset primary dystonia in which dystonia usually remains focal. In patients with secondary dystonia, treatment is challenging and efficacy is typically incomplete and partially limited by side effects. Despite these treatment options, many patients with dystonia experience only partial benefit and continue to suffer significant disability. Therefore, more research is needed to better understand the underlying cause and pathophysiology of dystonia and to explore newer medications and surgical techniques for its treatment.

Botulinum toxin therapy of writer's cramp

The pathophysiology and management of writer's cramp is one of the most challenging amongst the various forms of focal dystonias. Frequently, the dystonic postures are confounded by compensatory muscle activity. Correct identification of target muscles for botulinum toxin (BT) injections determines the treatment success. The dosages of different preparations vary, with 1 unit of Botox roughly equalling 3.5 units of Dysport. Electromyographic guided injections yield better results and may also decrease the amount of toxin required. Weakness of target muscles interfering with other non-writing activities is a frequently encountered adverse effect. Studies have shown that BT is a safe long-term therapy option.

Does training improve writer's cramp? An evaluation of a behavioral treatment approach using kinematic analysis

Patients with writer's cramp (WC) show uncontrollable muscle co-contractions of agonists and antagonists and unusual postures of the upper limb during writing; their handwriting is inefficient and exhausting. Currently the treatment of choice is to inject botulinum toxin in selective hand muscles. However, this treatment has two drawbacks: it is short-lasting and may be associated with adverse side effects. An alternative behavioral treatment, namely, the handwriting training developed by Mai and coworkers, was carried out and evaluated in 50 patients with WC. A digitizing tablet was used to record the handwriting movements before and after training, and then again after a follow-up period. The results indicate the efficacy of the handwriting training. Speed and smoothness of the handwriting increased during the training with effects observed after an extended follow-up period. Handwriting training leads to significant improvements, but does not bring handwriting performance to normal levels. This training should be considered as an alternative or supplement to the traditional treatment with botulinum toxin or other programs based on neuroplasticity.

Factors predicting improvement in motor disability in writer's cramp treated with botulinum toxin

OBJECTIVE

To identify factors predicting improvement in motor disability in writer's cramp treated with botulinum toxin (BTX).

METHODS

47 patients with writer's cramp were treated with BTX and were evaluated by the same neurologists at initial referral, after each BTX injection, and when the effect of BTX was maximal at the time of the study. Patients and examiners simultaneously and independently rated the efficacy of BTX injections. Self assessment was a global clinical impression of the impact of treatment on writing quality, writing speed, writing errors, and legibility of handwriting; for objective assessment, the examiners used the Burke-Fahn-Marsden (BFM) scale.

RESULTS

On the BFM scale, there was a significant improvement (p<0.0001) in both severity and disability scores. Patients with a pronation/flexion pattern of dystonia showed the best and the most sustained improvement. Primary writing tremor was little improved. There was a correlation between the self assessment score and the Burke-Fahn-Marsden score. Benefit was maintained over time

CONCLUSIONS

These results have implications for the identification of patients most likely to benefit from BTX injections.

Deep brain stimulation for tremor [correction of trauma]: patient selection and evaluation

The selection of patients with movement disorders for deep brain stimulation is becoming a common neurological and neurosurgical task. Deep brain stimulation is suitable for different forms of tremor, which can often not be treated with medication. This suitability applies for essential tremor, monosymptomatic tremor at rest, cerebellar or multiple sclerosis tremor, Holmes' tremor, primary writing tremor or tremor in neuropathies. The appropriate selection of patients is critical for the outcome of surgical relief of tremors. Considering the risks of any stereotactic intervention, the following must apply: (1) motor symptoms lead to a relevant disability in activities of daily living, despite optimal medical treatment; (2) biological age of the patient; (3) neurosurgical contraindications; (4) the patient is neither demented nor severely depressed. If these conditions are fulfilled, the individual chances of improvement of the target symptoms need to be checked, based on the following guidelines: (1) the kind of tremor, (2) the natural course of the tremor, (3) the chances for medical treatment in a particular patient, (4) the outcome of surgery in a specific condition, (5) the individual risks for a patient to suffer from complications. The outcome of surgery for tremor depends on the clinical type and distribution. Distal limb tremors are easier to treat than proximal limb tremors. Intention tremor is more difficult to treat than rest or postural tremor. The indication for surgical treatment depends on the analysis of the individual risk-benefit ratio, which also has to take into account the patients' social, professional, and familial background. The patient needs to be well informed about his individual risk-benefit ratio and of alternative treatments, before undergoing stereotactic surgery.

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.

Prospective clinical study of writer's cramp

Sixty-five consecutive patients with writer's cramp were studied prospectively to evaluate clinical and demographic features, the number of writing hours per day at dystonia onset, and the existence of trigger events. Assessment of writing and drawing was done on a standardized test using categorical scales. The importance of subjective handicap and pain, of postural and action tremor, the abnormal features of hand grip and the occurrence of mirror dystonia (dystonia occurring in the dominant hand when writing with the other hand) were studied. Thirty-two patients had simple writer's cramp, whereas the others had complex writer's cramp with several activities other than writing involved. No significant differences were seen in age of onset, legibility, pain, and handicap in these two groups. Seven patients had a family history of focal dystonia and six of them had a complex form of writer's cramp. Mirror dystonia was seen in 29 patients and in some it appeared useful to distinguish dystonic movements from secondary compensatory strategies.

The current use of botulinum toxin

Botulinum toxin is the most potent neurotoxin known, and has been in clinical use since the late 1970s. The toxin inhibits the release of acetylcholine from nerve terminals by inhibiting transport of the synaptic vesicles, thus causing functional denervation lasting up to 6 months. Our understanding of the mechanism of action of the toxin and the spectrum of diseases treatable with this agent continues to increase. Efficacy has been demonstrated in hemifacial spasm, dystonia, spasticity, hyperhidrosis and other conditions. Alternative serotypes are used in some centres, generally after the development of immunoresistance to the standard toxin (serotype A), and are likely to be in routine use in the near future. This paper reviews the history, pharmacology and current uses of botulinum toxin.

Pharmacotherapy with botulinum toxin: harnessing nature's most potent neurotoxin

Botulinum toxin (BTX), a potent biologic neurotoxin, commonly is associated with lethal outbreaks of food poisoning; however, it also plays a role as a therapeutic agent. Since the 1970s physicians have investigated BTX therapy in patients with neurologic disorders. The number of applications greatly expanded over the years to include certain focal dystonias (blepharospasm, torticollis, laryngeal dystonias, writer's cramp), strabismus, and a wide variety of other indications (gastrointestinal disorders, cosmetic wrinkle correction, spasticity, hyperhidrosis). BTX's safety and efficacy are reviewed.