Boundaries of task-specificity: bimanual finger dexterity is reduced in musician's dystonia.

Task-specific dystonia leads to loss of sensorimotor control for a particular motor skill. Although focal in nature, it is hugely disabling and can terminate professional careers in musicians. Biomarkers for underlying mechanism and severity are much needed. In this study, we designed a keyboard device that measured the forces generated at all fingertips during individual finger presses. By reliably quantifying overflow to other fingers in the instructed (enslaving) and contralateral hand (mirroring) we explored whether this task could differentiate between musicians with and without dystonia. 20 right-handed professional musicians (11 with dystonia) generated isometric flexion forces with the instructed finger to match 25%, 50% or 75% of maximal voluntary contraction for that finger. Enslaving was estimated as a linear slope of the forces applied across all instructed/uninstructed finger combinations. Musicians with dystonia had a small but robust loss of finger dexterity. There was increased enslaving and mirroring, primarily during use of the symptomatic hand (enslaving p = 0.003; mirroring p = 0.016), and to a lesser extent with the asymptomatic hand (enslaving p = 0.052; mirroring p = 0.062). Increased enslaving and mirroring were seen across all combinations of finger pairs. In addition, enslaving was exaggerated across symptomatic fingers when more than one finger was clinically affected. Task-specific dystonia therefore appears to express along a gradient, most severe in the affected skill with subtle and general motor control dysfunction in the background. Recognition of this provides a more nuanced understanding of the sensorimotor control deficits at play and can inform therapeutic options for this highly disabling disorder.

How Do I Examine Laryngeal Dystonia?

Laryngeal dystonia is a potentially disabling task specific dystonia primarily affecting speech. The evaluation and diagnosis of laryngeal dystonia remain challenging, and often require a multi-disciplinary approach, involving collaboration among speech language pathologists, neurologists and laryngologists (1-5). It is crucial to correctly differentiate between the types of laryngeal dystonia due to the distinct therapeutic approaches and responses to botulinum toxin therapy or speech therapy. For educational purposes, we have divided laryngeal dystonia into two main types: adductor and abductor dystonia. In this article, we describe a series of examination techniques that can assist movement disorders neurologists diagnosing this condition, and appropriately differentiating the most common forms of laryngeal dystonia.

Can calcitonin gene-related peptide monoclonal antibodies ameliorate writer's cramp and migraine?

Recently, calcitonin gene-related peptide (CGRP) monoclonal antibodies (mAbs) have become available as a prophylactic treatment for migraine and have shown high efficacy and safety in clinical practice. CGRP mAbs have been reported to be effective not only for migraine but also for other comorbidities, such as psychiatric complications in patients with migraine. However, there are no reports examining the effect of CGRP mAbs on dystonia. We treated a patient with comorbid migraine and focal task-specific dystonia (writer's cramp) with a CGRP mAb (erenumab) because of an increase in monthly migraine days despite the addition of migraine prophylaxis. In this patient, erenumab treatment for 3 months led to improvements in symptoms of both focal dystonia and migraine, suggesting a role for CGRP in the pathophysiology of both conditions.

Gender Differences in Task Specific Dystonia: What Can we Learn from Musician's Dystonia?

BACKGROUND: Musician's Dystonia (MD) is a task specific, focal dystonia which usually occurs only at the instrument. The pathophysiology is not fully understood, but several risk factors like over-practice and genetic predisposition are known. Interestingly, 80% of those affected are men, which stands in contrast to the gender distribution in other focal dystonias, such as cervical dystonia. OBJECTIVES: Our aim was to evaluate the difference in women and men with regard to risk factors leading to MD. METHODS: We investigated known risk factors for MD in a large cohort of 364 MD patients by retrospectively collecting data on practice behavior and family history. RESULTS: In line with previous studies, we found a ratio of ~4:1 men to women. Age at onset of MD was significantly lower in women; however, subsequent analysis revealed that it was a positive family history (FH+) and not gender that was associated with a lower age at onset. Furthermore, we found that those with negative family history had accumulated more practice time until onset of MD. CONCLUSIONS: These results imply that the earlier age at onset in women did not depend on gender but was due to the higher proportion of a positive family history. In contrast, men were less likely to have a positive family history, suggesting that genetic factors may not be the primary reason for the higher prevalence of MD in men. Instead, differences in practice behaviors between men and women may contribute to this gender disparity.

Treatment of task-specific dystonia in sports: A systematic review.

Introduction: Task specific dystonia is a movement disorder only affecting a highly practiced skill and is found in a broad set of expert movements including in sports. Despite affecting many sports, there is no comprehensive review of treatment options, which is in contrast to better studied forms of task specific dystonia in musicians and writers. For this reason, studies involving an intervention to treat task specific dystonia in sports were systematically reviewed, with special attention for the quality of outcome measures. Methods: The PICO systematic search strategy was employed on task-specific dystonia, and all synonyms. Inclusion criteria were peer reviewed published studies pertaining to sports, studies with a measurement and/or intervention in TSD, all in English. We excluded abstracts, expert opinions, narrative review articles, unpublished studies, dissertations and studies exclusively relating to choking. We included case reports, case studies and case-control studies. Results: In April 2022 Pubmed, Embase, Web of Science, and Psychinfo were searched. Of the 7000 articles identified, 31 were included that described psychological and invasive and/or pharmacological interventions. There was a lack of formal standardized outcome measures in studies resulting in low quality evidence for the effectiveness of treatment options. A descriptive synthesis showed emotional regulation was effective, but was exclusively tried in golfers. Interventions like botulinum toxin or pharmacology had a similar effectiveness compared to studies in musicians dystonia, however there was almost no formal evidence for these treatments. Conclusion: The quality of studies was low with a lack of standardized outcome measures. Future studies with larger cohorts and quantitative outcome measures are needed to improve understanding of treatments for task specific dystonia in athletes.

New-Onset Focal Task Specific Oromandibular Dystonia in Association with Quran Recitation: A Case Series.

Background: Focal task-specific dystonia is a form of isolated focal dystonia that occurs during the performance of a specific skilled motor task. The occurrence of oromandibular dystonia (OMD) specifically in association with the recitation of Quranic verses have been rarely reported in the literature, in non-native Arabic-speaking patients. This case series describe a rare type of focal task-specific dystonia that occurs exclusively by reciting Quran in native Arabic-speaking patients, which has never been reported, to the best of our knowledge. Methods: In this case series, we identified five patients with new-onset OMD that was exclusively induced by reciting Quran. Cases were evaluated in our Movement Disorders outpatient clinic at Ibn Sina hospital; the main tertiary neurology center in Kuwait, between 2015 and 2023. Results: Five cases (3 males, 2 females) were identified in this study. Mean age of onset of the symptoms was 52.3 ± 4.1 years, while the median duration of the symptoms prior to diagnosis was 3 years. All patients were native Arab-speaking, with no previous history of other types of dystonia. No identifiable risk factors could be obtained including exposure to dopamine blocking agents or antipsychotics, or history of oral or dental surgery. Patients underwent a full clinical, laboratory, and radiological evaluation. All patients had OMD dystonia in varying forms and severity, while two patients had additional spasmodic dysphonia/ blepharospasm on progressive recitation. Most patients had minimal improvement with combination of oral medications and speech therapy. Four patients received botulinum toxin injections with better results. Discussion: The mental and physical stress in attempting to recite the Quranic verses could have contributed to the development of OMD. Moreover, the increased demand on the muscles of the jaw, lips, and tongue during recitation can trigger the dystonic symptoms. Highlights: OMD exclusively during Quran recitation is a rare phenomenon, and expands the spectrum of task-specific focal dystonia described in the literature. It was found to be distressing to the patients and a challenge to treat. Prompt recognition could minimize unnecessary testing and procedures, and facilitate earlier treatment.

Focal task-specific hand dystonia related to esports in a rhythm gamer: A case report.

Herein, we report a novel case of focal task-specific dystonia of the upper extremity that occurred in a 27-year-old man who presented with flexion of the left third, fourth, and fifth fingers exclusively during rhythm gameplay. Dystonia during electronic sports should be recognized as a new type of occupational dystonia.

Personality in speed skaters with skater's cramp: A preliminary cross-sectional study.

OBJECTIVE: Skater's cramp is a debilitating disorder in expert speedskaters and recent evidence from muscle and movement studies nominate it is a task-specific dystonia (TSD). Building on these studies we investigated clinical features and personality in skater's cramp, hypothesizing that similar to other TSDs, trait emotionality would be higher in affected skaters. METHODS: In a cross-sectional study we employed the HEXACO inventory to examine the personality of a cohort of skaters with skater's cramp (n = 26) compared to age, sex, and experience-matched controls (n = 28). Affected skaters were selected based on relevant clinical features important to the diagnosis of TSD. RESULTS: Sentimentality (a sub-factor of emotionality) was higher in affected skaters, but only in the male population. Extraversion was lower in skaters with skater's cramp. Clinical findings resembled other forms of TSD. DISCUSSION: Higher sentimentality is in line with previous studies in TSD. Lower Extraversion in affected skaters was an unexpected finding that may be a new feature of skater's cramp and TSD. Due to our small sample size and cross-sectional design, these findings are preliminary, but offer tentative evidence of personality differences in skater's cramp in line with TSD.

Neuromodulation in Dystonia - Harnessing the Network.

Adult-onset isolated focal dystonia (AOIFD) is a network disorder characterised by abnormalities of sensory processing and motor control. These network abnormalities give rise to both the phenomenology of dystonia and the epiphenomena of altered plasticity and loss of intracortical inhibition. Existing modalities of deep brain stimulation effectively modulate parts of this network but are limited both in terms of targets and invasiveness. Novel approaches using a variety of non-invasive neuromodulation techniques including transcranial stimulation and peripheral stimulation present an interesting alternative approach and may, in conjunction with rehabilitative strategies, have a role in tailored therapies targeting the underlying network abnormality behind AOIFD.

Is Behavioural Therapy a New Treatment Option for Task-Specific Dystonia in Athletes? A Case Series.

Background: Task-specific dystonia is a movement disorder of the central nervous system characterized by focal involuntary spasms and muscle contractions, which can negatively affect performance of a specific task. It can affect a wide range of fine motor skills, also in athletes. Current management of task-specific dystonia includes mainly prescribing drugs, exercise therapy or botulinum injections to the affected muscles. Psychological interventions for athletes suffering from task-specific dystonia have not been described extensively so far. Methods: We present a case-series of 4 different advanced skill-level athletes with suspected task-specific dystonia, which had a major impact on their performance. They all received treatment consisting of a combination of standardized behavioural therapy and relaxation techniques in the form of hypnosis in a total of 8 sessions in a 16-week time period. Results: After treatment, all athletes returned to their original high level of sport performance without further symptoms of their suspected task-specific dystonia. Discussion: Behavioural therapy in combination with a relaxation technique seems to be a safe and promising treatment for athletes with suspected task-specific dystonia. Further studies in a larger, preferably randomized controlled trial, are warranted to evaluate if this treatment strategy is effective in athletes with suspected task-specific dystonia.

A Case of Tardive Dystonia with Task Specificity Confined to the Lower Extremities only during Walking.

Background: Task-specific dystonia (TSD) confined to the lower extremities (LE) is relatively rare. This report describes dystonia confined to the LE only during forward walking. This case required careful neurological and diagnostic assessment because the patient was taking several neuropsychiatric drugs that cause symptomatic dystonia, such as aripiprazole (ARP). Case: A 53-year-old man visited our university hospital with a complaint of abnormalities in the LE that appeared only during walking. Neurological examinations other than walking were normal. Brain magnetic resonance imaging revealed meningioma in the right sphenoid ridge. The patient had been treated for depression with neuropsychiatric medications for a long time, and his abnormal gait appeared about 2 years after additional administration of ARP. After the meningioma was removed, his symptoms remained. Surface electromyography showed dystonia in both LE during forward walking, although his abnormal gait appeared to be accompanied by spasticity. The patient was tentatively diagnosed with tardive dystonia (TD). Although dystonia did not disappear clinically, it was alleviated after discontinuing ARP. Administration of trihexyphenidyl hydrochloride and concomitant rehabilitation improved his dystonia until return to work, but some residual gait abnormalities remained. Discussion: We report an unusual case of TD with task specificity confined to the LE. The TD was induced by the administration of ARP in combination with multiple psychotropic medications. Careful consideration was required for clinical diagnosis, rehabilitation, and assessment of its relevance to TSD.

Intact finger representation within primary sensorimotor cortex of musician's dystonia.

Musician's dystonia presents with a persistent deterioration of motor control during musical performance. A predominant hypothesis has been that this is underpinned by maladaptive neural changes to the somatotopic organization of finger representations within primary somatosensory cortex. Here, we tested this hypothesis by investigating the finger-specific activity patterns in the primary somatosensory and motor cortex using functional MRI and multivariate pattern analysis in nine musicians with dystonia and nine healthy musicians. A purpose-built keyboard device allowed characterization of activity patterns elicited during passive extension and active finger presses of individual fingers. We analysed the data using both traditional spatial analysis and state-of-the art multivariate analyses. Our analysis reveals that digit representations in musicians were poorly captured by spatial analyses. An optimized spatial metric found clear somatotopy but no difference in the spatial geometry between fingers with dystonia. Representational similarity analysis was confirmed as a more reliable technique than all spatial metrics evaluated. Significantly, the dissimilarity architecture was equivalent for musicians with and without dystonia. No expansion or spatial shift of digit representation maps were found in the symptomatic group. Our results therefore indicate that the neural representation of generic finger maps in primary sensorimotor cortex is intact in musician's dystonia. These results speak against the idea that task-specific dystonia is associated with a distorted hand somatotopy and lend weight to an alternative hypothesis that task-specific dystonia is due to a higher-order disruption of skill encoding. Such a formulation can better explain the task-specific deficit and offers alternative inroads for therapeutic interventions.

Diagnostic Neurophysiologic Biomarkers for Task-Specific Dystonia.

Background: Task-specific dystonia (TSD) is a challenging clinical diagnosis with no objective diagnostic biomarkers. Objective: The objective of this study was to test 2 neurophysiologic variables using transcranial magnetic stimulation as potential diagnostic biomarkers for TSD. Methods: We tested (1) cortical silent period (CSP) and (2) dorsal inferior parietal lobule-motor cortex (dIPL-M1) physiologic connectivity in 9 patients with the writer's cramp form of TSD and 12 healthy volunteers on 2 separate sessions. Results: CSP was significantly prolonged (P < 0.0001) in TSD and could classify TSD with high sensitivity and specificity with areas under the receiver operating characteristic curve (AUCs) = 0.94 and 0.90, respectively, for 2 separate sessions with an intraclass correlation = 0.79. dIPL-M1 interaction was notable for significant motor cortical inhibition in TSD compared with facilitation in healthy subjects (P < 0.0001) and could classify TSD with high sensitivity and specificity with AUCs = 0.96 and 0.86, respectively. Conclusion: CSP and dIPL-M1 physiologic connectivity can classify TSD with high sensitivity, specificity, reproducibility, and reliability.

Botulinum Toxin Therapy in Writer's Cramp and Musician's Dystonia.

Task-specific focal dystonia is characterized by muscle contraction(s) during a specific task, resulting in abnormal postures or movements. Specifically, writer's cramp involves the upper extremity during the act of writing. Musician's dystonia has a highly variable presentation, and thus makes therapeutic options more limited. Treatments include oral pharmacologic agents, neuromodulation, surgery and, most often, botulinum toxin (BoNT) injection. Selection of target muscles for toxin injection continues to be an area of active research for these task-specific movements. We present a review of the literature selected from a predefined search of the MEDLINE and ClinicalTrials.gov databases. We include six controlled studies of botulinum toxin for the management of writer's cramp and focal task-specific dystonia (FTSD), including musician's dystonia. Overall, 139 patients were included across all studies, with 99 individuals injected for writer's cramp and the remaining 40 individuals with FTSD. The age range of all patients was 18-80 years old. We included studies that utilized only the BoNT-A serotype. These studies utilized various severity scales to quantify response to toxin injection, with ratings of instrument or pen control included as subjective ratings. Of the included 139 patients in this review, pooled data for toxin response show that 73% of patients who received the drug demonstrated improvement. Specific techniques for muscle localization and targeting were difficult to study as variable methods were employed. This remains an area of ongoing exploration.