Cervical dystonia incidence and diagnostic delay in a multiethnic population

Comparison of different surgical strategies for cervical dystonia: Evidence from Bayesian network analysis

BACKGROUND AND PURPOSE

Several surgical techniques have been used to treat cervical dystonia (CD), however, to date, the optimal surgical technique for CD remains controversial. We therefore conducted the first network meta-analysis to compare different surgical strategies for CD to inform clinical practice.

METHODS

Electronic databases were searched for surgical strategies for treating CD. The primary outcome was improvement in total Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score. Subgroup analysis was performed to compare short-term (< 1 year) and long-term (≥ 1 year) outcomes. Safety outcomes included surgery-related adverse events (AEs).

RESULTS

A total of 55 trials with 2032 patients employing five surgical strategies were identified, including globus pallidus internus (GPi)/subthalamic nucleus (STN)-deep brain stimulation (DBS), selective peripheral denervation (SPD), microvascular decompression (MVD) and pallidotomy. All strategies led to significant improvement in total TWSTRS score (mean improvement range 18.65-28.22). GPi-DBS showed significantly greater enhancement than SPD for the whole dataset (mean difference [MD] 7.03, 95% credible interval [Crl] 1.53-12.56), while both GPi-DBS (MD 8.05, 95% Crl 2.35-13.80) and STN-DBS (MD 10.71, 95% Crl 2.22-19.20) exhibited more long-term improvement than SPD. Regarding safety outcomes, GPi/STN-DBS and MVD were associated with fewer surgery-related AEs than SPD (ln odds ratio range -1.68 to -1.41).

CONCLUSION

We conclude that DBS should be the preferred surgical option for CD, and the STN is a promising alternative target choice due to its comparable efficacy with the GPi. However, more direct evidence is still required.

Current use of neurotoxins for alleviating symptoms of cervical dystonia

INTRODUCTION

Cervical dystonia (CD) causes involuntary movements and postures of the head, neck, and shoulders, as well as nonmotor symptoms including pain, mood, and sleep dysfunction, and impacts quality of life. The first-line treatment for CD is botulinum neurotoxin (BoNT) injections.

AREAS COVERED

The clinical presentation and diagnosis of CD, as well as where BoNT resides in the treatment landscape, is reviewed first. Next, the mechanism of action and the pharmacological differences in the available preparations of BoNT products are explained. The evidence base for motor and nonmotor efficacy and safety of the available BoNT formulations is reviewed, with attention to duration of benefit as a driver of patient satisfaction. Practical determinants of BoNT efficacy are reviewed including muscle selection, accurate muscle injection, factors related to poor or deteriorating response, and immunogenicity.

EXPERT OPINION

BoNT represents a significant advancement in the treatment of CD. More accurate diagnosis, muscle selection and targeting, and dosing can improve outcomes with existing BoNT formulations. Further refinement of BoNT potency, duration of action, safety, and immunogenicity will help reduce unmet needs in the magnitude and duration of benefit. Additional validation of DBS and MRI-guided focused ultrasound may expand options for patients with toxin nonresponse.

Whole-exome sequencing in a cohort of Chinese patients with isolated cervical dystonia

Background

Dystonia is a kind of movement disorder but its pathophysiological mechanisms are still largely unknown. Recent evidence reveals that genetical defects may play important roles in the pathogenesis of dystonia.

Objectives and Methods

-To explore possible causative genes in Chinese dystonia patients, DNA samples from 42 sporadic patients with isolated cervical dystonia were subjected to whole-exome sequencing. Rare deleterious variants associated with dystonia phenotype were screened out and then classified according to the American College of Medical Genetics and Genomics (ACMG) criteria. Phenolyzer was used for analyzing the most probable candidates correlated with dystonia phenotype, and SWISS-MODEL server was for predicting the 3D structures of variant proteins.

Results

Among 42 patients (17 male and 25 female) recruited, a total of 36 potentially deleterious variants of dystonia-associated genes were found in 30 patients (30/42, 71.4 %). Four disease-causing variants including a pathogenic variant in PLA2G6 (c.797G > C) and three likely pathogenic variants in DCTN1 (c.73C > T), SPR (c.1A > C) and TH (c.56C > G) were found in four patients separately. Other 32 variants were classified as uncertain significance in 26 patients. Phenolyzer prioritized genes TH, PLA2G6 and DCTN1 as the most probable candidates correlated with dystonia phenotype. Although 3D prediction of DCTN1 and PLA2G6 variant proteins detected no obvious structural alterations, the mutation in DCTN1 (c.73C > T:p.Arg25Trp) was closely adjacent to its key functional domain.

Conclusion

Our whole-exome sequencing results identified a novel variant in DCTN1 in sporadic Chinese patients with isolated cervical dystonia, which however, needs our further study on its exact role in dystonia pathogenesis.

"I'm still the person I am. Not the body it has become." An active but challenging life with cervical dystonia

BACKGROUND

Improvement of activity and participation for the disabled and chronically ill is an important aim of rehabilitation. Cervical dystonia is a neurological movement disorder characterized by involuntary contractions of the neck muscles. Until now, research has identified factors contributing to disability rather than factors which may make it easier to be active and participate in the community.

OBJECTIVE

Explore and describe perceived experiences of activity and participation in daily life as experienced by persons with cervical dystonia.

METHODS

Sixteen informants participated in this semi-structured interview study. Inductive qualitative content analysis was performed to understand and interpret experiences shared by the informants.

RESULTS

Results from the analysis generated two themes "An active life" and "A challenging life" and six sub-themes: Using helpful coping strategies, Accepting a new life situation, Adhering to BT treatment, Facing the negative impact of stress, Experiencing a negative self-image and Suffering from pain and fatigue.

CONCLUSIONS

Our results support the importance of actions using a rehabilitation approach that consider both motor and non-motor symptoms. Future studies should compare the effects of physiotherapy taking into account wishes and challenges in patients' everyday life versus traditional physiotherapy addressing mostly the motor disorder.

Isolated Cervical Dystonia: Diagnosis and Classification

This document presents a consensus on the diagnosis and classification of isolated cervical dystonia (iCD) with a review of proposed terminology. The International Parkinson and Movement Disorder Society Dystonia Study Group convened a panel of experts to review the main clinical and diagnostic issues related to iCD and to arrive at a consensus on diagnostic criteria and classification. These criteria are intended for use in clinical research, but also may be used to guide clinical practice. The benchmark is expert clinical observation and evaluation. The criteria aim to systematize the use of terminology as well as the diagnostic process, to make it reproducible across centers and applicable by expert and non-expert clinicians. Although motor abnormalities remain central, increasing recognition has been given to nonmotor manifestations, which are incorporated into the current criteria. Three iCD presentations are described in some detail: idiopathic (focal or segmental) iCD, genetic iCD, and acquired iCD. The relationship between iCD and isolated head tremor is also reviewed. Recognition of idiopathic iCD has two levels of certainty, definite or probable, supported by specific diagnostic criteria. Although a probable diagnosis is appropriate for clinical practice, a higher diagnostic level may be required for specific research studies. The consensus retains elements proven valuable in previous criteria and omits aspects that are no longer justified, thereby encapsulating diagnosis according to current knowledge. As understanding of iCD expands, these criteria will need continuous revision to accommodate new advances. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

What can epidemiological studies teach on the pathophysiology of adult-onset isolated dystonia?

Several demographic and environmental factors may play an important role in determining the risk of developing adult-onset isolated dystonia (AOID) and/or modifying its course. However, epidemiologic studies have provided to date only partial insight on the disease mechanisms that are actively influenced by these factors. The age-related increase in female predominance in both patients diagnosed with AOID and subjects carrying its putative mediational phenotype suggests sexual dimorphism that has been demonstrated for mechanisms related to blepharospasm and cervical dystonia. The opposite relationship that spread and spontaneous remission of AOID have with age suggests age-related decline of compensatory mechanisms that protect from the progression of AOID. Epidemiological studies focusing on environmental risk factors yielded associations only with specific forms of AOID, even for those factors that are not likely to predispose exclusively to specific focal forms (for example, only writing dystonia was found associated with head trauma, and only blepharospasm with coffee intake). Other factors show biological plausibility of their mechanistic role for specific forms, e.g., dry eye syndrome or sunlight exposure for blepharospasm, scoliosis for cervical dystonia, repetitive writing for writing dystonia. Overall, the relationship between environment and AOID remains complex and incompletely defined. Both hypothesis-driven preclinical studies and well-designed cross-sectional or prospective clinical studies are still necessary to decipher this intricate relationship.

Validation of a guideline to reduce variability in diagnosing cervical dystonia

BACKGROUND

Cervical dystonia is characterized by a variable pattern of neck muscle involvement. Due to the lack of a diagnostic test, cervical dystonia diagnosis is based on clinical examination and is therefore subjective. The present work was designed to provide practical guidance for clinicians in confirming or refuting suspected cervical dystonia.

METHODS

Participants were video recorded according to a standardized protocol to assess 6 main clinical features possibly contributing to cervical dystonia diagnosis: presence of repetitive, patterned head/neck movements/postures inducing head/neck deviation from neutral position (item 1); sensory trick (item 2); and red flags related to conditions mimicking dystonia that should be absent in dystonia (items 3-6). Inter-/intra-rater agreement among three independent raters was assessed by k statistics. To estimate sensitivity and specificity, the gold standard was cervical dystonia diagnosis reviewed at each site by independent senior neurologists.

RESULTS

The validation sample included 43 idiopathic cervical dystonia patients and 41 control subjects (12 normal subjects, 6 patients with isolated head tremor, 4 with chorea, 6 with tics, 4 with head ptosis due to myasthenia or amyotrophic lateral sclerosis, 7 with orthopedic/rheumatologic neck diseases, and 2 with ocular torticollis). The best combination of sensitivity and specificity was observed considering all the items except for an item related to capability to voluntarily suppress spasms (sensitivity: 96.1%; specificity: 81%).

CONCLUSIONS

An accurate diagnosis of cervical dystonia can be achieved if, in addition to the core motor features, we also consider some clinical features related to dystonia mimics that should be absent in dystonia.

Evaluation of outcome of different neurosurgical modalities in management of cervical dystonia

Background

Cervical dystonia is the most common form of focal dystonia and is managed by multiple modalities including repeated botulinum toxin injections, in addition to medical treatment with anticholinergics, muscle relaxants, and physiotherapy. However, surgical interventions could be beneficial in otherwise refractory patients. This study aims to report our experience in the neurosurgical management of cervical dystonia and evaluate patient outcomes using reliable outcome scores for the assessment of patients with cervical dystonia and possible complications. This case series study was conducted on 19 patients with cervical dystonia of different etiologies who underwent surgical management [ten patients underwent selective peripheral denervation, five patients underwent pallidotomy, and four patients underwent bilateral globus pallidus internus (GPi) deep brain stimulation (DBS)] in the period between July 2018 and June 2021 at Ain Shams University Hospitals, Cairo, Egypt. With the assessment of surgical outcomes using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and the Tsui scale 6 months postoperatively.

Results

Surgical management of patients with cervical dystonia of either primary or secondary etiology was associated with significant improvement in head and neck postures after 6 months without major complications associated with the different surgical procedures. The mean improvement in total TWSTRS and Tsui scores were 51.2% and 64.8%, respectively, compared with preoperative scores, while the mean improvement in the TWSTRS subscales (severity, disability, and pain) were 40.2%, 66.9%, and 58.3%, respectively.

Conclusion

Cervical dystonia patients in whom non-surgical options have failed to alleviate their symptoms can be managed surgically leading to significant improvements with minimal adverse effects. However, surgical treatment should be tailored according to several factors including but not limited to the etiology, pattern of dystonic activity, and comorbidities. Therefore, management should be tailored to achieve long-term improvement with minimal risk of complications.

Longitudinal analysis of the relationship between motor and psychiatric symptoms in idiopathic dystonia

BACKGROUND AND PURPOSE

Although psychiatric diagnoses are recognized in idiopathic dystonia, no previous studies have examined the temporal relationship between idiopathic dystonia and psychiatric diagnoses at scale. Here, we determine rates of psychiatric diagnoses and psychiatric medication prescription in those diagnosed with idiopathic dystsuponia compared to matched controls.

METHODS

A longitudinal population-based cohort study using anonymized electronic health care data in Wales (UK) was conducted to identify individuals with idiopathic dystonia and comorbid psychiatric diagnoses/prescriptions between 1 January 1994 and 31 December 2017. Psychiatric diagnoses/prescriptions were identified from primary and secondary health care records.

RESULTS

Individuals with idiopathic dystonia (n = 52,589) had higher rates of psychiatric diagnosis and psychiatric medication prescription when compared to controls (n = 216,754, 43% vs. 31%, p < 0.001; 45% vs. 37.9%, p < 0.001, respectively), with depression and anxiety being most common (cases: 31% and 28%). Psychiatric diagnoses predominantly predated dystonia diagnosis, particularly in the 12 months prior to diagnosis (incidence rate ratio [IRR] = 1.98, 95% confidence interval [CI] = 1.9-2.1), with an IRR of 12.4 (95% CI = 11.8-13.1) for anxiety disorders. There was, however, an elevated rate of most psychiatric diagnoses throughout the study period, including the 12 months after dystonia diagnosis (IRR = 1.96, 95% CI = 1.85-2.07).

CONCLUSIONS

This study suggests a bidirectional relationship between psychiatric disorders and dystonia, particularly with mood disorders. Psychiatric and motor symptoms in dystonia may have common aetiological mechanisms, with psychiatric disorders potentially forming prodromal symptoms of idiopathic dystonia.

Therapeutic Efficacy and Prediction of 18F-FDG PET/CT-Assisted Botulinum Toxin Therapy in Patients With Idiopathic Cervical Dystonia

PURPOSE

This study aimed to investigate the therapeutic efficacy of 18F-FDG PET/CT-assisted botulinum toxin (BTX) injection therapy and predictive PET findings in relation to a good response in patients with idiopathic cervical dystonia (ICD).

MATERIALS AND METHODS

A total of 78 patients was enrolled from November 2007 to July 2018. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score was determined at baseline and 4 weeks after BTX injection guided by electromyography and PET/CT. The number of hypermetabolic muscles, the highest SUVmax among hypermetabolic muscles, and the total SUVmax of hypermetabolic muscles were evaluated as pretreatment PET parameters. A good response was defined as a reduction rate ≥30% and a point decrease ≥15 of the TWSTRS total score.

RESULTS

Half of the subjects showed a good response. Good responders had significantly higher baseline TWSTRS scores than poor responders (total score, P < 0.001; severity, P < 0.001; disability, P < 0.001; pain, P = 0.026). Good responders also had significantly higher numbers of hypermetabolic muscles and BTX-injected hypermetabolic muscles (P < 0.001, both). In multivariable analysis, the baseline TWSTRS disability subscale score and the number of BTX-injected hypermetabolic muscles were significant predictors for good response (P = 0.001 and P = 0.028). The aforementioned 3 PET parameters were positively correlated with the baseline TWSTRS scores. In addition, PET/CT well detected dystonic deep cervical muscles.

CONCLUSIONS

FDG PET/CT-assisted BTX injection therapy showed good therapeutic efficacy in ICD patients. The numbers of hypermetabolic cervical muscles and BTX-injected hypermetabolic muscles may be helpful in predicting a good response.

Cognitive and Neuropsychiatric Impairment in Dystonia

PURPOSE OF REVIEW

To review recent literature evaluating psychiatric and cognitive symptoms in dystonia, the two non-motor symptom groups most frequently evaluated in dystonia research and recognised in clinical practice.

RECENT FINDINGS

Recent work has embedded clinical recognition of psychiatric symptoms in dystonia, with depressive and anxiety-related symptoms routinely observed to be the most common. Less explored symptoms, such as self-harm, suicidal ideation, and substance abuse, represent newer areas of investigation, with initial work suggesting higher rates than the background population. Investigation of cognitive function has provided less consistent results, both within individual dystonia subtypes and across the spectrum of dystonias, partly reflecting the heterogeneity in approaches to assessment. However, recent work indicates impairments of higher cognitive function, e.g. social cognition, and disrupted visual and auditory sensory processing. Dystonia demonstrates psychiatric and cognitive symptom heterogeneity, with further work needed to recognise endophenotypes and improve diagnostic accuracy, symptom recognition, and management.

The prevalence of idiopathic or inherited isolated dystonia: a systematic review and meta‐analysis

Background

A systematic review of epidemiological studies of primary dystonia from 1985 and 2010 found an overall prevalence of 16.43 per 100,000 (95% CI = 12.09–22.32).

Methods

We performed a systematic review of studies from 2010 and 2022 to determine if there are important differences in epidemiology between these time periods.

Results

Nineteen studies were included. Incidence of cervical dystonia, blepharospasm, and oromandibular dystonia were each reported in one study; one study reported incidence for all adult onset idiopathic focal dystonias combined. Using data from 11 studies, we performed random effects meta‐analyses of the prevalence of cervical dystonia (9.95 per 100,000; 95% CI = 3.51–28.17), blepharospasm (2.82 per 100,000; 95% CI = 1.12–7.12), laryngeal dystonia (0.40 per 100,000; 95% CI = 0.09–1.83), upper limb dystonia (1.27 per 100,000; 95% CI = 0.36–4.52), oromandibular dystonia (0.57 per 100,000; 95% CI = 0.15–2.15), and idiopathic or inherited isolated dystonia all subtypes combined (30.85 per 100,000; 95% CI = 5.06–187.74). All studies reported more cases of dystonia in females. There was no significant difference in prevalence by subgroup analysis based on time of study publication (1985–2010 vs. 2010–2022). Subgroup analysis of differences in prevalence by dystonia subtype by continent using all studies published (1985–2022) revealed significant regional differences in the prevalence of cervical and laryngeal dystonia.

Conclusion

The incidence and prevalence of idiopathic or inherited isolated dystonia in the last decade was not significantly different from earlier reports. Population‐based studies across multiple geographic areas are needed to obtain a clearer understanding of the epidemiology of this condition.

Increased Knowledge of Adult-Onset Dystonia Amongst Medical Students via Brief Video Education: A Systematic Review and Cohort Study

Most doctors have limited knowledge of dystonia, a movement disorder that can affect people of all ages; this contributes to diagnostic delay and poor quality of life. We investigated whether a brief educational intervention could improve knowledge of dystonia amongst medical students. We conducted a systematic review on undergraduate knowledge of dystonia and created an eight-minute video on the condition. We invited medical students at the University of Leeds, UK, to answer 15 multiple choice questions before and immediately after watching the video, and again one month later. Only one previous study specifically assessed medical students’ knowledge of dystonia whilst five others tested their knowledge of movement disorders, or neurology generally, with some questions on dystonia. Of the University of Leeds medical students, 87 (100%), 77 (89%) and 40 (46%) completed the baseline, immediate-recall and delayed-recall questionnaires, respectively. The mean score for students who completed all three questionnaires increased from 7.7 (out of 15) to 12.5 on the immediate-recall questionnaire (p < 0.001), and to 10.1 on the delayed-recall questionnaire (p < 0.001). At baseline, 76% of students rated their confidence in recognising dystonia as low. After watching the video, 78% rated their confidence as a high, and none rated it low. A brief video improved their knowledge substantially, with sustained effects. This method could be incorporated into medical curricula to reduce diagnostic delays.

Development of a patient journey map for people living with cervical dystonia

Background

Patient journey maps are increasingly used as a tool that enables healthcare providers to refine their service provision to best meet patient needs. We developed a cervical dystonia patient journey map (CDPJM) that describes the holistic patient experience from pre-diagnosis through to long-term treatment.

Methods

The CDPJM was developed in 2 stages; a patient survey (open questions and multichoice) of 15 patients with CD was conducted to inform the design of the CDPJM, which was then refined and validated by an expert-patient focus group.

Results

Qualitative analysis of the patient survey supported five key stages of the patient journey: symptom onset, diagnosis and therapeutic relationship with healthcare professionals, initiation of care for CD, start of CD treatment, and living with treated CD. Following symptom onset, survey respondents described having multiple visits to their family doctor who prescribed strong pain killers and muscle relaxants and referred their patient to up to 10 different specialists for diagnosis. Over half (53.3%) of respondents had received ≥ 1 misdiagnosis. Respondents reported relief at having a diagnosis but a lack of understanding of the prognosis and treatment options; 46.7% said their neurologist did not spend enough time addressing their concerns. Survey respondents reported using a variety of alternative sources of information, including the internet (86.7%), self-help groups (66.7%) and information leaflets provided by health care professionals (60.0%). While botulinum toxin (BoNT) was consistently discussed as the main treatment option, some neurologists also mentioned physiotherapy, counselling, and other complementary approaches. However, patients were often left to seek complementary services themselves. Patients reported a ‘rollercoaster’ of relief with BoNT treatment with symptoms (and subsequent impact on daily life) returning towards the end of an injection cycle. “When BoNT works well I can return to an almost normal life … when the injections stop working so well, I have to rest more and avoid going to work and experience life restrictions.”

Conclusions

We present the first patient journey map for CD that can be used to guide local service mapping and to compare current provision with what patients say they want and need.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02270-4.

Adult-onset idiopathic dystonia: A national data-linkage study to determine epidemiological, social deprivation, and mortality characteristics

BACKGROUND AND PURPOSE

Accurate epidemiological information is essential for the improved understanding of dystonia syndromes, as well as better provisioning of clinical services and providing context for diagnostic decision-making. Here, we determine epidemiological, social deprivation, and mortality characteristics of adult-onset idiopathic dystonia in the Welsh population.

METHODS

A retrospective population-based cohort study using anonymized electronic health care data in Wales was conducted to identify individuals with dystonia between 1 January 1994 and 31 December 2017. We developed a case-ascertainment algorithm to determine dystonia incidence and prevalence, as well as characterization of the dystonia cohort, based on social deprivation and mortality.

RESULTS

The case-ascertainment algorithm (79% sensitivity) identified 54,966 cases; of these cases, 41,660 had adult-onset idiopathic dystonia (≥20 years). Amongst the adult-onset form, the median age at diagnosis was 41 years, with males significantly older at time of diagnosis compared to females. Prevalence rates ranged from 0.02% in 1994 to 1.2% in 2017. The average annual incidence was 87.7/100,000/year, increasing from 49.9/100,000/year (1994) to 96.21/100,000/year (2017). In 2017, people with dystonia had a similar life expectancy to the Welsh population.

CONCLUSIONS

We have developed a case-ascertainment algorithm, supported by the introduction of a neurologist-reviewed validation cohort, providing a platform for future population-based dystonia studies. We have established robust population-level prevalence and incidence values for adult-onset idiopathic forms of dystonia, with this reflecting increasing clinical recognition and identification of causal genes. Underlying causes of death mirrored those of the general population, including circulatory disorders, respiratory disorders, cancers, and dementia.

Predictive modeling of spread in adult-onset isolated dystonia: Key properties and effect of tremor inclusion

BACKGROUND AND PURPOSE

Several clinical and demographic factors relate to anatomic spread of adult-onset isolated dystonia, but a predictive model is still lacking. The aims of this study were: (i) to develop and validate a predictive model of anatomic spread of adult-onset isolated dystonia; and (ii) to evaluate whether presence of tremor associated with dystonia influences model predictions of spread.

METHODS

Adult-onset isolated dystonia participants with focal onset from the Dystonia Coalition Natural History Project database were included. We developed two prediction models, one with dystonia as sole disease manifestation ("dystonia-only") and one accepting dystonia OR tremor in any body part as disease manifestations ("dystonia OR tremor"). Demographic and clinical predictors were selected based on previous evidence, clinical plausibility of association with spread, or both. We used logistic regressions and evaluated model discrimination and calibration. Internal validation was carried out based on bootstrapping.

RESULTS

Both predictive models showed an area under the curve of 0.65 (95% confidence intervals 0.62-0.70 and 0.62-0.69, respectively) and good calibration after internal validation. In both models, onset of dystonia in body regions other than the neck, older age, depression and history of neck trauma were predictors of spread.

CONCLUSIONS

This predictive modeling of spread in adult-onset isolated dystonia based on accessible predictors (demographic and clinical) can be easily implemented to inform individuals' risk of spread. Because tremor did not influence prediction of spread, our results support the argument that tremor is a part of the dystonia syndrome, and not an independent or coincidental disorder.

Pain in cervical dystonia: mechanisms, assessment and treatment

INTRODUCTION

In patients with cervical dystonia (CD), pain is a major contributor to disability and social isolation and is often the main reason patients seek treatment. Surveys evaluating patient perceptions of their CD symptoms consistently highlight pain as a troublesome and disabling feature of their condition with significant impact on daily life and work.

AREAS COVERED

In this article, the authors review the epidemiology, assessment, possible mechanisms and treatment of pain in CD, including a meta-analysis of randomized controlled trial data with abobotulinumtoxinA.

EXPERT OPINION

Mechanisms of pain in CD may be muscle-based and non-muscle based. Accumulating evidence suggests that non-muscle-based mechanisms (such as abnormal transmission and processing of nociceptive stimuli, dysfunction of descending pain inhibitory pathways as well as structural and network changes in the basal ganglia, cortex and other areas) may also contribute to pain in CD alongside prolonged muscle contraction. Chemodenervation with botulinum toxin is considered the first-line treatment for CD. Treatment with botulinum toxin is usually effective, but optimization of the injection parameters should include consideration of pain as a core symptom in addition to the motor problems.

Botulinum Injections for Idiopathic Cervical Dystonia: a Longitudinal Study

Botulinum toxin (BT) injections into the cervical muscles are an effective and commonly practiced treatment approach for cervical dystonia. In this retrospective longitudinal study, we collected data from the Sheba electronic medical records on consecutive patients with idiopathic cervical dystonia (ICD), treated regularly with periodic BT injections between the years 2008-2020. All treatment visits were analyzed regarding type of toxin, dose injected, and clinical outcomes. The vast majority of patients were treated with abobotulinum toxin A. Sixty-four ICD patients (51 (79.7%) females, onset at age 45.8 ± 13.7 years) were treated over 17.1 ± 13.9 (range 3 to 49) visits per patient; BT treatment efficacy increased gradually from initial treatment sessions to visit 13, when it achieved a steady state. While the subjective report of percentage improvement and its duration were around 78.9 ± 17.1% for 2.8 ± 1.0 months, respectively, the dose of BT increased significantly over the years (p = 0.006). Side effects (SE) were not rare, and commonly recurred after subsequent sessions and were usually mild and short-lasting, with dysphagia being the most common (~17.5%), followed by neck/arm weakness (11.9%) and cervical pain (8.9%). Repeated injections of BT for ICD remain beneficial for patients over several years of therapy, and despite mild SE, patients tend to adhere to a 3-4 months interval schedule.

It's tricky: Rating alleviating maneuvers in cervical dystonia

OBJECTIVES

To investigate hypothesized sources of error when quantifying the effect of the sensory trick in cervical dystonia (CD) with the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS-2), test strategies to mitigate them, and provide guidance for future research on the sensory trick.

METHODS

Previous analyses suggested the sensory trick (or "alleviating maneuver", AM) item be removed from the TWSTRS-2 because of its poor clinimetric properties. We hypothesized three sources of clinimetric weakness for rating the AM: 1) whether patients were given sufficient time to demonstrate their AM; 2) whether patients' CD was sufficiently severe for detecting AM efficacy; and 3) whether raters were inadvertently rating the item in reverse of scale instructions. We tested these hypotheses with video recordings and TWSTRS-2 ratings by one "site rater" and a panel of five "video raters" for each of 185 Dystonia Coalition patients with isolated CD.

RESULTS

Of 185 patients, 23 (12%) were not permitted sufficient testing time to exhibit an AM, 23 (12%) had baseline CD too mild to allow confident rating of AM effect, and 1 site- and 1 video-rater each rated the AM item with a reverse scoring convention. When these confounds were eliminated in step-wise fashion, the item's clinimetric properties improved.

CONCLUSIONS

The AM's efficacy can contribute to measuring CD motor severity by addressing identified sources of error during its assessment and rating. Given the AM's sensitive diagnostic and potential pathophysiologic significance, we also provide guidance on modifications to how AMs can be assessed in future CD research.