Set-shifting and behavioral dysfunction in primary focal dystonia

Social Cognition, Executive Functioning, Mood, and Disability in Cervical Dystonia

BACKGROUND

Individuals with idiopathic adult-onset isolated cervical dystonia (CD) may have cognitive difficulties and increased mood challenges. Social cognition and executive functioning may be particularly affected.

OBJECTIVE

To explore social cognition and executive functioning performance in individuals with CD, using the Cambridge Neuropsychological Test Automated Battery (CANTAB), as previous research has used traditional, nondigital neuropsychological assessments. We sought to investigate the relationships between social cognition, executive functioning, mood, and disability in individuals with CD.

METHODS

We recruited 37 individuals with CD, including 26 women with an age range of 33 to 69 years (M = 56.64, SD = 8.31) from a dystonia clinic in a hospital neurology department. The individuals completed selected tasks from the CANTAB measuring social cognition and executive functioning. We compared the individuals' performance with CANTAB normative data. Depression, anxiety, disease severity, and disability were measured.

RESULTS

The individuals with CD had significantly lower scores than the CANTAB normative data in both social cognition and executive functioning tasks, with the largest differences evident in problem-solving, attention, and positive emotion bias tasks. Poorer emotion recognition was associated with increased difficulties in problem-solving tasks. The individuals demonstrated a bias toward identifying happiness in facial affect, which was related to a poorer recognition of emotions. Cognitive performance was not related to CD severity or disability or to current mood symptoms.

CONCLUSION

Difficulties with both social cognition and executive functioning were identified in the individuals with CD, and are likely important targets for clinical interventions.

Are Cognitive Symptoms Part of the Phenotypic Spectrum of Idiopathic Adult-Onset Dystonia? Summary of Evidence from Controlled Studies

BACKGROUND

Cognitive dysfunction has been reported in idiopathic adult-onset dystonia (IAOD), but whether this is a primary or secondary component of the disorder remains uncertain.

OBJECTIVE

Here, we aimed to analyze the key domains of abnormal cognitive performance in IAOD and whether this is associated with motor or mood changes.

METHODS

Article selection for our critical review was guided by PRISMA guidelines (mesh terms "dystonia" and "cognitive," publication period: 2000-2022). Only peer-reviewed, English-language original case-control studies involving patients with IAOD who were not exposed to dopamine- or acetylcholine-modulating agents and validated cognitive assessments were included.

RESULTS

Abstract screening ultimately yielded 22 articles for full-text review and data extraction. A greater proportion of studies (17 of 22, 82%) reported abnormal cognitive performance in IAOD. Most of these studies focused on blepharospasm (BSP) and cervical dystonia (10 and 14, respectively). Most studies reporting cognitive impairment (11 of 17) identified multidomain impairment in cognition. Executive functions were the domain most frequently explored (14 of 22 studies), 79% of which detected worse performance in people with dystonia. Results related to other domains were inconclusive. Cognitive abnormalities were independent of motor symptoms in most studies (7 of 12) that explored this relationship and independent of mood status in all 8 that investigated this.

CONCLUSIONS

Within IAOD, cognitive dysfunction (in particular, executive dysfunction) has been documented mainly in BSP and cervical dystonia. More comprehensive testing is warranted to assess abnormalities in other domains and in other forms of IAOD, as well as to evaluate longitudinal progression of cognitive disturbances in this condition.

Neuropsychological Functioning in Primary Dystonia: Updated and Expanded Multidomain Meta-Analysis

BACKGROUND

Primary dystonia is conventionally considered as a motor disorder, though an emerging literature reports associated cognitive dysfunction.

OBJECTIVES

Here, we conducted meta-analyses on studies comparing clinical measures of cognition in persons with primary dystonia and healthy controls (HCs).

METHODS

We searched PubMed, Embase, Cochrane Library, Scopus, and PsycINFO (January 2000-October 2020). Analyses were modeled under random effects. We used Hedge's g as a bias-corrected estimate of effect size, where negative values indicate lower performance in dystonia versus controls. Between-study heterogeneity and bias were primarily assessed with Cochran's Q, I² , and Egger's regression.

RESULTS

From 866 initial results, 20 studies met criteria for analysis (dystonia n = 739, controls n = 643; 254 effect sizes extracted). Meta-analysis showed a significant combined effect size of primary dystonia across all studies (g = -0.56, P < 0.001), with low heterogeneity (Q = 25.26, P = 0.15, I²  =  24.78). Within-domain effects of primary dystonia were motor speed = -0.84, nonmotor speed = -0.83, global cognition = -0.65, language = -0.54, executive functioning = -0.53, learning/memory = -0.46, visuospatial/construction = -0.44, and simple/complex attention = -0.37 (P-values <0.01). High heterogeneity was observed in the motor/nonmotor speed and learning/memory domains. There was no evidence of publication bias. Moderator analyses were mostly negative but possibly underpowered. Blepharospasm samples showed worse performance than other focal/cervical dystonias. Those with inherited (ie, genetic) disease etiology demonstrated worse performance than acquired.

CONCLUSIONS

Dystonia patients consistently demonstrated lower performances on neuropsychological tests versus HCs. Effect sizes were generally moderate in strength, clustering around -0.50 SD units. Within the speed domain, results suggested cognitive slowing beyond effects from motor symptoms. Overall, findings indicate dystonia patients experience multidomain cognitive difficulties, as detected by neuropsychological tests. © 2022 International Parkinson and Movement Disorder Society.

Neuroplasticity in dystonia: Motor symptoms and beyond

This chapter first focuses on the role of altered neuroplasticity mechanisms and their regulation in the genesis of motor symptoms in the various forms of dystonia. In particular, a review of the available literature about focal dystonia suggests that use-dependent plasticity may become detrimental and produce dystonia when practice and repetition are excessive and predisposing conditions are present. Interestingly, recent evidence also shows that functional or psychogenic dystonia, despite the normal plasticity in the sensorimotor system, is characterized by plasticity-related dysfunction within limbic regions. Finally, this chapter reviews the non-motor symptoms that often accompany the motor features of dystonia, including depression and anxiety as well as obsessive-compulsive disorders, pain, and cognitive dysfunctions. Based on the current understanding of these symptoms, we discuss the evidence of their possible relationship to maladaptive plasticity in non-motor basal ganglia circuits involved in their genesis.

Psychological Traits and Behavioural Influences in Patients with Dystonia-An Observational Cohort Study in a Romanian Neurology Department

(1) Background: Emerging evidence indicates that non-motor symptoms significantly influence the quality of life in dystonic patients. Therefore, it is essential to evaluate their psychological characteristics and personality traits. (2) Methods: Subjects with idiopathic dystonia and a matched control group were enrolled in this prospective observational cohort study. Inclusion criteria for patient group included idiopathic dystonia diagnosis, evolution exceeding 1 year, and signed informed consent. Inclusion criteria for the control group included lack of neurological comorbidities and signed informed consent. All subjects completed the DECAS Personality Inventory along with an additional form of demographic factors. Data (including descriptive statistics and univariate and multivariate analysis) were analyzed with SPSS. (3) Results: In total, 95 participants were included, of which 57 were in the patient group. Females prevailed (80%), and the mean age was 54.64 ± 12.8 years. The most frequent clinical features of dystonia were focal distribution (71.9%) and progressive disease course (94.73%). The patients underwent regular treatment with botulinum toxin (85.95%). In addition, patients with dystonia obtained significantly higher openness scores than controls, even after adjusting for possible confounders (p = 0.006). Personality traits were also different between the two groups, with patients more often being fantasists (p = 0.007), experimenters (p = 0.022), sophists (p = 0.040), seldom acceptors (p = 0.022), and pragmatics (p = 0.022) than control subjects. (4) Conclusion: Dystonic patients tend to have different personality profiles compared to control subjects, which should be taken into consideration by the treating neurologist.

Non-motor features of cervical dystonia: Cognition, social cognition, psychological distress and quality of life

INTRODUCTION

Non-motor features of cervical dystonia (CD) have been identified, including depression, anxiety, and neuropsychological deficits. The aims were: to provide a clinical neuropsychological profile of CD patients with specific focus on social cognition; assess levels of psychological distress; and investigate the relationship between non-motor features of CD, including cognitive functioning, psychological distress, CD severity, pain, and health-related quality of life (HR-QoL).

METHODS

A multi-domain neuropsychological assessment battery was administered to 46 participants with CD, examining cognitive and social cognitive domains. Clinical data on dystonia severity, pain, psychological distress and HR-QoL were collected.

RESULTS

The majority of participants with CD performed within the average range across most tests of cognition. Scores were significantly lower than standardized norms in social cognition, processing speed, and aspects of memory. High levels of anxiety (Hospital Anxiety and Depression Scale [HADS-A] ≥ 11, 30%) and depression (HADS-D ≥ 11; 29%) were observed. Psychological distress, CD severity, pain and HR-QoL were not significantly associated with neuropsychological functioning after controlling for multiple comparisons. Low HR-QoL was associated with higher levels of pain and psychological distress, but not severity of motor symptoms.

CONCLUSION

Results indicate that psychological distress and deficits in cognitive and social cognitive functioning are likely distinct features of CD. While motor symptoms do not appear to impact HR-QoL, pain and psychological distress were associated with low HR-QoL. Findings highlight the importance of addressing non-motor symptoms in the treatment of CD.

Prevalence of non-motor symptoms and their association with quality of life in cervical dystonia

OBJECTIVES

Non-motor symptoms (NMS) are commonly present along with motor impairment in patients with cervical dystonia (CD) and have a significant impact on health-related quality of life (HRQoL). However, the prevalence of NMS and their association with dystonia are still unclear. The aim of our study was to assess the prevalence of depression, anxiety, fatigue, apathy, pain, sleep problems, and excessive daytime sleepiness (EDS) in CD using different evaluation approaches and to explore their association with HRQoL relative to that of motor symptoms.

MATERIALS AND METHODS

We enrolled 102 Slovak patients with CD. The severity of both motor and non-motor symptoms was assessed using validated scales. HRQoL was determined by the 36-item Short Form Health Survey (SF-36). Association of NMS with poor HRQoL was assessed using multiple regressions.

RESULTS

The most frequent NMS in our sample were sleep impairment (67.3%), anxiety (65.5%), general and physical fatigue (57.5% and 52.9%, respectively), depression (47.1%), mental fatigue (31.4%), apathy (30.4%), reduced activity (29.4%), EDS (20.2%), and reduced motivation (18.6%). Univariate analysis showed that NMS, but not motor symptoms, were significantly linked to poor HRQoL, with EDS being most commonly associated with poor HRQoL, followed by disrupted sleep, depression, and fatigue.

CONCLUSIONS

The prevalence of NMS among patients with CD is high, and some NMS are strongly associated with poor HRQoL, while motor impairment was not associated with the severity of NMS or poor HRQoL. Actively diagnosing and treating NMS should therefore be a routine part of the clinical management of patients with CD.

Structural Brain Changes in Blepharospasm: A Cortical Thickness and Diffusion Tensor Imaging Study

White matter abnormalities in blepharospasm (BSP) have been evaluated using conventional intra-voxel metrics, and changes in patterns of cortical thickness in BSP remain controversial. We aimed to determine whether local diffusion homogeneity, an inter-voxel diffusivity metric, could be valuable in detecting white matter abnormalities for BSP; whether these changes are related to disease features; and whether cortical thickness changes occur in BSP patients. Diffusion tensor and structural magnetic resonance imaging were collected for 29 patients with BSP and 30 healthy controls. Intergroup diffusion differences were compared using tract-based spatial statistics analysis and measures of cortical thickness were obtained. The relationship among cortical thickness, diffusion metric in significantly different regions, and behavioral measures were further assessed. There were no significant differences in cortical thickness and fractional anisotropy between the groups. Local diffusion homogeneity was higher in BSP patients than controls, primarily in the left superior longitudinal fasciculus, corpus callosum, left posterior corona radiata, and left posterior thalamic radiata (P < 0.05, family-wise error corrected). The local diffusion homogeneity values in these regions were positively correlated with the Jankovic rating scale (r_s = 0.416, P = 0.031) and BSP disability index (r_s = 0.453, P = 0.018) in BSP patients. These results suggest that intra- and inter-voxel diffusive parameters are differentially sensitive to detecting BSP-related white matter abnormalities and that local diffusion homogeneity might be useful in assessing disability in BSP patients.

Social cognition in cervical dystonia: A case-control study

BACKGROUND

Although considered a motor disorder, adult onset isolated focal dystonia has many non-motor symptoms. There is a paucity of neuropsychological research on cognitive processing in adult onset focal dystonia.

METHODS

We employed a battery of clinical and cognitive assessments, including basic and complex social cognition, and assessed 46 patients with adult-onset cervical dystonia, compared to 46 age-, sex-, education-, and premorbid IQ-matched healthy controls.

RESULTS

Significant between-group differences were observed in relation to measures of memory encoding, recall and recognition, as well as multimodal measures of basic Social Cognition (emotion recognition: face and prosody), but not complex Social Cognition (mentalising). There were no deficits observed in multimodal measures of executive function. Controlling for mood did not affect performance.

CONCLUSION

In this multi-dimensional assessment of cognition in cervical dystonia, we report deficits in memory encoding, and in social cognition. Further investigation of social cognitive processes, memory, and sustained attention are required. Longitudinal studies are also needed to further delineate the role of psychological distress on cognitive outcomes and document the cognitive profile over time.

Normal Temporal Discrimination in Musician's Dystonia Is Linked to Aberrant Sensorimotor Processing

OBJECTIVES

Alterations in sensory discrimination are a prominent nonmotor feature of dystonia. Abnormal temporal discrimination in focal dystonia is considered to represent its mediational endophenotype, albeit unclear pathophysiological correlates. We examined the associations between the visual temporal discrimination threshold (TDT) and brain activity in patients with musician's dystonia, nonmusician's dystonia, and healthy controls.

METHODS

A total of 42 patients and 41 healthy controls participated in the study. Between-group differences in TDT z scores were computed using inferential statistics. Statistical associations of TDT z scores with clinical characteristics of dystonia and resting-state functional brain activity were examined using nonparametric rank correlations.

RESULTS

The TDT z scores of healthy controls were significantly different from those of patients with nonmusician's dystonia, but not of patients with musician's dystonia. Healthy controls showed a significant relationship between normal TDT levels and activity in the inferior parietal cortex. This relationship was lost in all patients. Instead, TDT z scores in musician's dystonia established additional correlations with activity in premotor, primary somatosensory, ventral extrastriate cortices, inferior occipital gyrus, precuneus, and cerebellum, whereas nonmusician's dystonia showed a trending correlation in the lingual gyrus extending to the cerebellar vermis. There were no significant relationships between TDT z scores and dystonia onset, duration, or severity.

CONCLUSIONS

TDT assessment as an endophenotypic marker may only be relevant to nonmusician forms of dystonia because of the lack of apparent alterations in musician's dystonia. Compensatory adaptation of neural circuitry responsible for TDT processing likely adjusted the TDT performance to the behaviorally normal levels in patients with musician's dystonia, but not nonmusician's dystonia. © 2020 International Parkinson and Movement Disorder Society.

Neuropsychiatric profile of patients with craniocervical dystonia: A case-control study

OBJECTIVE

Depression, anxiety, and obsessive-compulsive disorder have been widely reported in patients with dystonia. On the other hand, cognitive impairment, frontal lobe function, impulsiveness and pseudobulbar affect are less studied. The objective of the study is to assess these neuropsychiatric symptoms along with the quality of life of subjects with craniocervical dystonia.

PATIENTS AND METHODS

A cross-sectional study was carried out in patients with craniocervical dystonia. Sex- and age-matched healthy controls were included. Neuropsychiatric assessment included the Montreal Cognitive Assessment (MoCA), Frontal Assessment Battery (FAB), Barrat Impulsiveness Scale (BIS-11), Center for Neurologic Study-Lability Scale (CNS-LS), Anxiety Rating Scale (HAM-A), Hamilton Depression Rating Scale (HAM-D), and the 12-item Short Form Health Survey (SF-12).

RESULTS

A total of 44 patients with craniocervical dystonia and 44 controls were included. The mean age was 57 ± 13.7 years. Depression (56.1 % vs 9.1 %, p < 0.001), anxiety (56.8 % vs 6.8 %, p < 0.001), and pseudobulbar affect (31.8 % vs 9.1 %, p = 0.02) were more common in the dystonia group in comparison to controls. No difference between groups was found in impulsiveness (p = 0.65), MoCA score (p = 0.14) or executive dysfunction (p = 0.42). Quality of life was worst in the dystonia group with 90.9 % (p = 0.03) and 61.4 % (p < 0.001) of the subjects scoring under average in the Physical Composite Score (PCS) and Mental Composite Score (MCS) of the SF-12.

CONCLUSION

MoCA scores ≤18, pseudobulbar affect, depression and anxiety are more prevalent in subjects with craniocervical dystonia in comparison to sex- and age-matched healthy controls. Regarding quality of life, MCS is more affected that the PCS in subjects with dystonia.

Flanker Task Performance in Isolated Dystonia (Blepharospasm): A Focus on Sequential Effects

Isolated dystonia manifests with involuntary muscle hyperactivity, but the extent of cognitive impairment remains controversial. We examined the executive functions in blepharospasm while accounting for motor symptom-related distractions as a factor often limiting the interpretability of neuropsychological studies in dystonia. Our control group comprised of patients with hemifacial spasm, which is a condition producing similar motor symptoms without any central nervous system pathology. Nineteen patients with blepharospasm and 22 patients with hemifacial spasm completed a flanker task. Stimulus congruency on the current trial, on the preceding trial, and a response sequence served as independent variables. We analyzed the response time and accuracy. Gross overall group differences were not discernible. While congruency, congruency sequence, and response sequence exerted the expected effects, no group differences emerged with regard to these variables. A difference between patients with blepharospasm and those with hemifacial spasm consisted in longer reaction times when responses had to be repeated following stimulus incongruency on the preceding trial. We conclude that patients with blepharospasm seem to have difficulties in repeating their responses when incongruency on preceding trials interferes with habit formation or other forms of fast routes to action. Our specific finding may provide an opportunity to study altered basal ganglia plasticity in focal dystonia.

Mental health outcomes in children with acquired dystonia after basal ganglia stroke and associations with cognitive and motor outcomes

Pediatric arterial ischemic stroke involving the basal ganglia and/or thalamus is one of the most common causes of dystonia in children. Dystonia is a movement disorder in which excessive, involuntary muscle contractions result in twisting or repetitive movements, and abnormal posturing. The basal ganglia have been implicated in mood functioning and difficulties in these domains have been noted in adults with dystonia, yet little is currently known about these outcomes in children with dystonia following stroke. The objective of this study was to explore mental health outcomes in children with basal ganglia stroke and to determine whether children with post-stroke dystonia experience additional mental health difficulties. We also examined associations between mental health, cognitive, and motor outcomes. Participants were 75 children with stroke involving the basal ganglia and/or thalamus (dystonia n = 24, no dystonia n = 51). Results supported the presence of greater levels of anxiety and depression symptoms in children with post-stroke dystonia after stroke relative to those with similar patterns of stroke, but no dystonia. There were no significant associations between motor, cognitive, and mental health outcomes in children with post-stroke dystonia aside from depression and behavioral regulation. Motor and cognitive outcome were significantly associated in the stroke only group. These findings suggest maladaptive reorganization after stroke may contribute to motor, cognitive, and mental health outcomes in children with post-stroke dystonia, and that these outcomes are independent from one another.

[Personality traits of Japanese patients with focal dystonia-Variable classification by affected body part and occupation]

We administered the Revised Neo Personality Inventory (NEO-PI-R) to 92 Japanese patients with focal dystonia and analyzed the relation of their personality traits, affected body parts, and occupations using a decision tree method. Results show that participants' personality traits were related to their occupation rather than the body part. Occupational dystonia patients including musicians exhibited neurotic tendencies and a high level of anxiety. Moreover, patients with occupational upper limb dystonia had realistic thinking patterns. Patients with musicians' dystonia were open about their emotional experiences: both positive and negative.

Neuropsychological and Neuropsychiatric Concerns for Deep Brain Stimulation in Dystonia: Preoperative Profiles in a Deep Brain Stimulation Cohort and Postoperative Changes in Three Case Series Reports

Cognitive deficits and psychiatric morbidities are commonly detected in dystonia. Psychiatric disturbances are of particular clinical concern as they not only contribute to poor quality of life and disease associated burden, but also exacerbate motor and cognitive symptoms. Bilateral deep brain stimulation of the globus pallidus internus improves motor symptoms in treatment-resistant dystonia, but its implications for non-motor manifestations are poorly understood. Improved prediction of cognitive and neuropsychiatric outcomes is important in deep brain stimulation (DBS) research and we aim to assess the latter through established assessment tools.

We document the cognitive and neuropsychiatric profiles in 11 primary and 10 secondary dystonia patients attending our DBS clinic. We performed routine multidisciplinary assessments including a comprehensive battery of neuropsychometric tests and detailed neuropsychiatric evaluations. Post-operative assessment outcomes are reported for three patients in case series.

The main cognitive deficit was on the Brixton test of spatial anticipation in primary dystonia. Background medical history included psychiatric illness in 38.1% of the patients with 76% of patients having mood abnormalities confirming elevated psychiatric morbidity in this population. Depressive illness was more prominent in primary, whereas clinically relevant histories in secondary dystonia were varied. Of the 21 patients three were able to perform on selected tests due to extensive limitations of their dystonia. No obvious alteration in intellectual functioning following DBS surgery relative to performance at the time of initial assessment was observed.

The frequency of individual impairments suggests that difficulties associated with dystonia are likely to be of clinical relevance to cognitive functions in the majority of patients. In particular, current findings suggest that executive difficulties related to inductive processes and spatial learning may be a common in primary dystonias. Psychiatric disturbances demand recognition as a central aspect of dystonia as they contribute to overall disease burden, poor quality of life and exacerbated motor disabilities. The available evidence provides overwhelming suggestion that vulnerability to depression is inherent to the dystonia phenotype.

Cognitive flexibility in neurological disorders: Cognitive components and event-related potentials

Performance deficits on the Wisconsin Card Sorting Test (WCST) in patients with prefrontal cortex (PFC) lesions are traditionally interpreted as evidence for a role of the PFC in cognitive flexibility. However, WCST deficits do not occur exclusively after PFC lesions, but also in various neurological and psychiatric disorders. We propose a multi-component approach that can accommodate this pattern of omnipresent WCST deficits: the WCST is not a pure test of cognitive flexibility, but relies on the effective functioning of multiple dissociable cognitive components. Our review of recent efforts to decompose WCST performance deficits supports this view by revealing that WCST deficits in different neurological disorders can be attributed to alterations in different components. Frontoparietal changes underlying impaired set shifting seem to give rise to WCST deficits in patients with amyotrophic lateral sclerosis, whereas the WCST deficits associated with primary dystonia and Parkinson's disease are rather related to frontostriatal changes underlying deficient rule inference. Clinical implications of these findings and of a multi-component view of WCST performance are discussed.

Cognitive Flexibility in Primary Dystonia

Objectives Although primary dystonia is typically characterized as a movement disorder, it is also associated with cognitive alterations in the domain of executive functioning which may arise from changes in cortico-basal ganglia circuits. Specifically, in comparison to healthy controls, patients with dystonia show deficits in neuropsychological tests of cognitive flexibility. However, it is unclear whether cognitive inflexibility is caused by the pathomechanisms underlying primary dystonia or by confounding factors such as depression or symptom-related distraction.Methods The present study aimed to eliminate these confounds by examining cognitive flexibility in dystonia patients and in patients with similar motor symptoms but without a comparable central pathophysiology. Eighteen patients with primary blepharospasm, a common form of dystonia affecting the muscles around the eyes, and 19 patients with hemifacial spasm, a facial nerve disorder causing similar eyelid spasms, completed a computerized version of the Wisconsin Card Sorting Test (cWCST). The two groups were further compared on tests of global cognitive functioning, psychiatric symptoms, health status, and impulsiveness. Results Blepharospasm patients committed significantly more errors on the cWCST than patients with hemifacial spasm. Group differences were most pronounced with regard to integration errors, a measure of rule-inference processes on the cWCST. Integration errors were also associated with impulsiveness in patients with blepharospasm. Conclusions Primary blepharospasm is related to deficits in cognitive flexibility, even when blepharospasm patients are compared with patients who suffer from motor symptoms of non-dystonic origin. Our results support the possibility that cognitive inflexibility results from the specific pathophysiological processes underlying primary dystonia. (JINS, 2016, 22, 662-670).

Meta-analytical and electrophysiological evidence for executive dysfunction in primary dystonia

Impaired motor control in primary dystonia has been linked to cortico-basal ganglia alterations that may also give rise to changes in executive functioning. However, no conclusive evidence for executive dysfunction in patients with primary dystonia has been reported yet. We conducted a meta-analysis of the relationship between primary dystonia and performance on the Wisconsin Card Sorting Test (WCST), an established test of executive functioning. Its results revealed a significant effect of medium size, indicating that primary dystonia is associated with moderate performance deficits on the WCST. Building on this finding, we conducted an event-related potential (ERP) study to elucidate the cognitive and neural mechanisms underlying executive dysfunction in primary dystonia. Eighteen patients with blepharospasm, a common form of primary focal dystonia, and 34 healthy matched controls completed a computerized version of the WCST. We specifically compared indicators of two distinct components of executive functioning: set shifting and rule inference. On a behavioral level, blepharospasm patients seemed to have particular difficulty integrating information to infer the correct task rule. In addition, P3a amplitude (as an electrophysiological marker of rule-inference processes) was selectively attenuated in blepharospasm patients. Executive dysfunction in blepharospasm can thus rather be attributed to a rule-inference deficit, whereas set-shifting abilities appear to be relatively unaffected by the disease. Moreover, P3a amplitude attenuation was related to disease duration, indicating that this ERP might serve as a neural indicator of disease progression and executive dysfunction in primary dystonia. These results demonstrate for the first time that pathophysiological alterations in primary dystonia might affect cortical activation for executive functioning.

Effect of subthalamic nucleus deep brain stimulation on dual-task cognitive and motor performance in isolated dystonia

OBJECTIVE

Subthalamic nucleus (STN) deep brain stimulation (DBS) can improve motor complications of Parkinson's disease (PD) but may worsen specific cognitive functions. The effect of STN DBS on cognitive function in dystonia patients is less clear. Previous reports indicate that bilateral STN stimulation in patients with PD amplifies the decrement in cognitive-motor dual-task performance seen when moving from a single-task to dual-task paradigm. We aimed to determine if the effect of bilateral STN DBS on dual-task performance in isolated patients with dystonia, who have less cognitive impairment and no dementia, is similar to that seen in PD.

METHODS

Eight isolated predominantly cervical patients with dystonia treated with bilateral STN DBS, with average dystonia duration of 10.5 years and Montreal Cognitive Assessment score of 26.5, completed working memory (n-back) and motor (forced-maintenance) tests under single-task and dual-task conditions while on and off DBS.

RESULTS

A multivariate, repeated-measures analysis of variance showed no effect of stimulation status (On vs Off) on working memory (F=0.75, p=0.39) or motor function (F=0.22, p=0.69) when performed under single-task conditions, though as working memory task difficulty increased, stimulation disrupted the accuracy of force-tracking. There was a very small worsening in working memory performance (F=9.14, p=0.019) when moving from single-task to dual-tasks when using the 'dual-task loss' analysis.

CONCLUSIONS

This study suggests the effect of STN DBS on working memory and attention may be much less consequential in patients with dystonia than has been reported in PD.

Pallidal stimulation for primary generalised dystonia: effect on cognition, mood and quality of life

We investigated the effect of pallidal deep brain stimulation (GPi-DBS) in dystonia on cognition, mood, and quality of life and also assessed if DYT1 gene status influenced cognitive outcome following GPi-DBS. Fourteen patients with primary generalized dystonia (PGD) were assessed, measuring their estimated premorbid and current IQ, memory for words and faces, and working memory, language, executive function, and sustained attention, one month before and one year or more after surgery. Changes in mood and behaviour and quality of life were also assessed. There was a significant improvement of dystonia with GPi-DBS (69 % improvement in Burke-Fahn-Marsden score, p < 0.0001). Performance on five cognitive tests either improved or declined at post-surgical follow-up. Calculation of a reliable change index suggested that deterioration in sustained attention on the PASAT was the only reliable change (worse after surgery) in cognition with GPi-DBS. DYT1 gene status did not influence cognitive outcome following GPi-DBS. Depression, anxiety and apathy were not significantly altered, and ratings of health status on the EQ5D remained unchanged. In our sample, GPi-DBS was only associated with an isolated deficit on a test of sustained attention, confirming that GPi-DBS in PGD is clinically effective and safe, without adverse effects on the main domains of cognitive function. The dissociation between GPi-DBS improving dystonia, but not having a significant positive impact on the patients’ QoL, warrants further investigation.

Impaired cognitive functions in adult-onset primary cranial cervical dystonia

BACKGROUND

Adult-onset primary dystonia is thought to be a purely motor disorder. Nevertheless, several studies provided evidence that sensory and psychiatric disturbances may contribute to the clinical spectrum of of dystonia, whereas evidence supporting cognitive impairment is still limited.

METHODS

A set of neuropsychological tests was administered to non depressed, non demented patients with cranial-cervical dystonia and healthy control subjects. The test battery included n-Back Task, Wechsler Memory Scale, Trail Making Test version A and B, and Wisconsin Card Sorting Test.

RESULTS

As compared with healthy control subjects of similar age, sex and socio-economic status, patients with cranial-cervical dystonia showed deficit on working memory functions revealed by n-Back task, impairment of mental control and visual reproduction subtests of Wechsler memory scale, deficit on information processing speed and set-shifting capacity revealed by Trail Making Test A and B.

CONCLUSION

Patients with cranial-cervical dystonia may have impairment in specific cognitive domains relative to working memory, processing speed, visual motor ability and short term memory. Probably, these deficits are not dependent on the clinical expression of dystonia but might rather reflect the cortical and subcortical changes highlighted by functional and VBM imaging studies in patients with different forms of dystonia.

Neuropsychological, neuropsychiatric, and quality of life issues in DBS for dystonia

We review the impact of dystonia and its surgical treatment with deep brain stimulation (DBS) on cognitive function, psychiatric morbidity, and health-related quality of life. The current evidence suggests that globus pallidus internus (GPi) DBS does not cause cognitive decline in primary dystonia. However, we recommend general preoperative screening of cognition in patients with dystonia to evaluate baseline cognitive status and monitor for possible postoperative changes. Patients with mild to moderate depression appear to do well postoperatively; however, there are scant data about those with severe depression. This is particularly problematic given reports of postoperative suicide. Patients with tardive dystonia seem to do well post-GPi DBS despite often having a history of depression or even having active severe depression. We make recommendations for screening and basic management strategies of patients identified as having a major psychiatric illness pre- or postoperatively. Quality of life in dystonia patients quantified by generic measures such as the SF36 showed improvement in both mental and physical categories following DBS surgery.

Cortical gray matter changes in primary blepharospasm: a voxel-based morphometry study

Previous voxel-based morphometry studies of patients with primary blepharospasm documented gray matter volumetric differences of the striatum, cerebellum, thalamus, and parietal lobe areas. However, these results were inconsistent across studies, which recruited relatively small samples and did not always provide detailed clinical information on patients with blepharospasm. The objective of this study was to analyze whole-brain gray matter volume in a larger sample of patients with blepharospasm and to expand on previous works by evaluating whether clinical features of blepharospasm correlate to whole-brain gray matter changes. Voxel-based morphometry was performed on 25 patients with primary adult-onset blepharospasm and 24 healthy subjects (controls) matched for age, sex, and handedness. Clinical data were collected through a standardized interview. Severity of blepharospasm was measured using the Jankovic Rating Scale. Patients with blepharospasm had greater gray matter volume than controls in the right middle frontal gyrus, whereas patients with blepharospasm had smaller gray matter volume than controls in the left postcentral gyrus and left superior temporal gyrus. Spearman correlation analysis with Bonferroni correction failed to show significant correlations between gray matter volume and the explored clinical variables, comprising age at onset, disease duration, blepharospasm severity, presence of an effective geste antagoniste, and dose and duration of botulinum toxin treatment. Patients with blepharospasm exhibited gray matter volume differences exclusively in cortical regions highly relevant to sensory processing and cognitive modulation of motor behavior. Gray matter changes in the primary sensory cortex may represent a common trait of primary dystonias, including blepharospasm.

Nonmotor manifestations of dystonia: a systematic review

Nonmotor symptoms are increasingly recognized as important determinants of quality of life and disability in a wide range of movement disorders. There is a limited body of research suggesting that many of these symptoms are also commonly associated with primary and other genetic forms of dystonia. However, the significance, etiology, pathophysiology, and treatment of these symptoms remain poorly described. The following is a review of the literature that focuses primarily on the association of these types of dystonia with psychiatric disorders, cognition, sleep, pain, and autonomic symptoms. We will also discuss potential mechanisms and approaches to treatment for nonmotor features of dystonia.

Focal dystonia in musicians: phenomenology, pathophysiology and triggering factors

BACKGROUND

Musician's dystonia is a task-specific movement disorder that manifests itself as a loss of voluntary motor control in extensively trained movements. In many cases, the disorder terminates the careers of affected musicians. Approximately, 1% of all professional musicians are affected. The pathophysiology of the disorder is still unclear. Findings include: (i) reduced inhibition in different levels of the central nervous system, (ii) maladaptive plasticity, e.g. in the somatosensory cortex and in the basal ganglia and (iii) alterations in sensorimotor processing.

METHODS

Review of the literature.

RESULTS

Epidemiological data demonstrated a higher risk for those musicians who play instruments requiring maximal fine-motor skills. For instruments where workload differs across hands, focal dystonia appears more often in the more intensely used hand. In psychological studies, musicians with dystonia had more perfectionist tendencies than healthy musicians. These findings strengthen the assumption that behavioural factors may be involved in the etiology of musician's dystonia. Hereditary factors may play a greater role than previously assumed.

CONCLUSIONS

We propose a heuristic model that may explain the relatively high incidence of focal dystonia in musicians. This model assumes the coactions between a predominantly genetically determined predisposition and intrinsic and extrinsic triggering factors.

Cognitive disturbances in primary blepharospasm

The common belief that primary dystonia is a purely motor disorder with no anatomical substrate and no other accompanying neurological dysfunction has recently been challenged. In addition, there is increasing evidence that the basal ganglia besides motor control, plays a role in cognitive functioning. However, no systematic cognitive performance evaluation has been carried out in patients with primary blepharospasm (BS), one of the most common forms of adult dystonia. We evaluated a series of 20 patients with primary BS and a group of 17 controls matched by severity of mood symptoms, age, and sex. BS patients performed significantly worse on the Luria sequencing test, Purdue pegboard test, reciprocal coordination, tactile denomination, and reverse visuospatial span and the differences persisted after correction for age, duration of disease, severity of BS, and degree of depression. The Wisconsin card sorting test showed no statistical difference, but BS patients made more errors and more perseverative answers than expected according to population means, whereas the control group performed poorly but within normal parameters. Our findings suggest broad cortical involvement in focal dystonia that is not correlated with the severity or duration of dystonia.

Focal hand dystonia in musicians: phenomenology, etiology, and psychological trigger factors

NARRATIVE REVIEW: Musician's dystonia is a task-specific movement disorder, which manifests itself as a loss of voluntary motor control in extensively trained movements. In many cases, the disorder terminates the careers of affected musicians. Approximately 1% of all professional musicians are affected. In the past, focal dystonia (FD) was classified as a psychological disorder. Over time, the problem was classified as a neurological problem. Although the specific pathophysiology of the disorder is still unclear, it appears the etiology is multifactorial. While there may be a family history, neurophysiological, physical, and environmental factors, trauma and stress contribute to the phenotypic development of FD. This manuscript analyzes the evidence supporting the potential contribution of the emotional brain systems in the etiology of focal hand dystonia in musicians. In addition, the psychological findings from a large descriptive study comparing healthy musicians, musicians with dystonia, and musicians with chronic pain. Information about psychogenic characteristics might be used to modify intervention strategies and music instruction to reduce the incidence of musician's dystonia.

The relationship between impairment of voluntary movements and cognitive impairment in Huntington's disease

The relationship between motor symptoms and cognitive impairment in Huntington's disease (HD) is still discussed. We analysed 45 HD patients in various stages using Unified Huntington's Disease Rating Scale motor subscale (voluntary and involuntary components were evaluated separately), verbal memory and executive functions tests. Partial correlations controlling for HD duration and age were used to estimate the relationships among factor scores for motor and cognitive impairment. Voluntary components of motor performance were found to be significantly correlated with verbal short-term memory disturbances (r = -0.361, P = 0.03), with tests of executive functions more dependent on motor performance (r = 0.640, P < 0.01) and also with tests of executive functions less dependent on motor performance (r = 0.461, P < 0.01). Involuntary components did not correlate significantly with any part of cognitive performance.