The non-motor syndrome of primary dystonia: clinical and pathophysiological implications

Alterations of Interhemispheric Functional Connectivity and Degree Centrality in Cervical Dystonia: A Resting-State fMRI Study

Background

Cervical dystonia (CD) is a neurological movement disorder characterized by involuntary head and neck movements and postures. Reports on microstructural and functional abnormalities in multiple brain regions not limited to the basal ganglia have been increasing in patients with CD. However, the neural bases of CD are unclear. This study is aimed at identifying cerebral functional abnormalities in CD by using resting-state functional magnetic resonance imaging (rs-fMRI).

Methods

Using rs-fMRI data, voxel-mirrored homotopic connectivity (VMHC) and degree centrality were used to compare the alterations of the rs-functional connectivity (FC) between 19 patients with CD and 21 healthy controls. Regions showing abnormal FCs from two measurements were the regions of interest for correlation analyses.

Results

Compared with healthy controls, patients with CD exhibited significantly decreased VMHC in the supplementary motor area (SMA), precuneus (PCu)/postcentral gyrus, and superior medial prefrontal cortex (MPFC). Significantly increased degree centrality in the right PCu and decreased degree centrality in the right lentiform nucleus and left ventral MPFC were observed in the patient group compared with the control group. Further correlation analyses showed that the VMHC values in the SMA were negatively correlated with dystonia severity.

Conclusion

Local abnormalities and interhemispheric interaction deficits in the sensorimotor network (SMA, postcentral gyrus, and PCu), default mode network (MPFC and PCu), and basal ganglia may be the key characteristics in the pathogenesis mechanism of CD.

[Non-motor disorders in patients with muscular dystonia]

Non-motor disturbances represented by sensory, affective, obsessive-compulsive disorders, cognitive dysfunction, sleep disturbances are often found in patients with dystonia and have a negative impact on their quality of life. The prevalence of sensory and affective disorders and sleep disturbances is above 50% in patients with cervical dystonia and is 25% in patients with blepharospasm, writing spasm; cognitive dysfunction is found in more than 25% of patients with focal dystonia. The relationship of non-motor, in particular psychiatric disorders, with the impairment of social and everyday life and worsening of quality of life in whole was shown. Common pathophysiological mechanisms of non-motor disorders as well as approaches to treatment of these disorders are discussed. The authors present the results on the positive effect of botulinum toxin therapy that reduces cognitive dysfunction, sensory disorders and depressive syndrome. Non-medication treatment of non-motor disorders in patients with dystonia is considered.

The Prevalence and Correlation of Non-motor Symptoms in Adult Patients with Idiopathic Focal or Segmental Dystonia

Background

Idiopathic focal dystonia is a motor syndrome associated with dysfunction of basal ganglia circuits. Observations have suggested that many other non-motor symptoms may also be part of the clinical picture. The aim was to assess the prevalence and correlation of non-motor symptoms in patients with common idiopathic focal or segmental dystonia.

Methods

In a single-center cross-sectional case–control study, we evaluated the presence of pain, neuropsychiatric symptoms, and sleep alterations in 28 patients with blepharospasm, 28 patients with cervical dystonia, 24 patients with writer’s cramp, and 80 control subjects matched for sex, age, and schooling. We obtained clinical and demographic data, and evaluated patients using the Fahn–Marsden Dystonia Rating Scale and other specific scales for dystonia. All subjects completed the following questionnaires: Beck Depression Inventory, Beck Anxiety Inventory, Social Phobia Inventory, Apathy Scale, Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, Brief Pain Scale, and the World Health Organization Quality of Life brief scale.

Results

The patients presented more symptoms of depression, anxiety, and apathy than the control subjects. They also reported worse quality of sleep and more pain complaints. Patients with blepharospasm were the most symptomatic subgroup. The patients had worse quality of life, and the presence of pain and symptoms of apathy and depression were the main influences for these findings, but not the severity of motor symptoms.

Discussion

Patients with dystonia, especially those with blepharospasm, showed higher prevalence of symptoms of depression, anxiety, apathy, worse quality of sleep, and pain. These symptoms had a negative impact on their quality of life.

[Emotional and personality characteristics of patients with dystonia]

AIM

To examine emotional characteristics, especially personality profile, of patients with dystonia.

MATERIAL AND METHODS

Three hundred patients with dystonia were enrolled in the study. Control groups consisted of 50 healthy individuals and 62 patients with hemifacial spasm (GFS). HADS, Beck depression inventory and Spielberger-Khanin anxiety scale were used. The 16 Personality Factors Questionnaire (16PF) was used to study personality profile.

RESULTS AND CONCLUSION

Higher levels of anxiety and depression in patients with dystonia compared to the control groups were identified. The level of anxiety and depression was not correlated with disease severity. Personality profile study confirmed the high level of anxiety in patients with dystonia and additionally showed increased emotional instability and poor emotional control. Intellectual personality characteristics of patients with dystonia had no differences compared to the control groups. An analysis of socio-psychological characteristics of personality in patients with dystonia and GFS showed restricted interpersonal and social communications since the motor defect noticeable to others leads to severe social exclusion and the desire for self-isolation.

The Use of Botulinum Toxin for Treatment of the Dystonias

Dystonias are characterized by involuntary muscle contractions, twisting movements, abnormal postures, and often tremor in various body regions. However, in the last decade several studies have demonstrated that dystonias are also characterized by sensory abnormalities. While botulinum toxin is the gold standard therapy for focal dystonia, exactly how it improves this disorder is not entirely understood. Neurophysiological studies in animals and humans have clearly demonstrated that botulinum toxin improves dystonic motor manifestations by inducing chemodenervation, therefore weakening the injected muscles. In addition, neurophysiological and neuroimaging evidence also suggests that botulinum toxin modulates the activity of various neural structures in the CNS distant from the injected site, particularly cortical motor and sensory areas. Concordantly, recent studies have shown that in patients with focal dystonias botulinum toxin ameliorates sensory disturbances, including reduced spatial discrimination acuity and pain. Overall, these observations suggest that in these patients botulinum toxin-induced effects encompass complex mechanisms beyond chemodenervation of the injected muscles.

Motor and non-motor determinants of health-related quality of life in young dystonia patients

OBJECTIVES

To systematically investigate the relationship between motor and non-motor symptoms, and health-related quality of life (HR-QoL) in children and young adults with dystonia.

METHODS

In this prospective observational cross-sectional study, 60 patients (6-25 years) with childhood-onset dystonia underwent a multidisciplinary assessment of dystonia severity (Burke-Fahn-Marsden Dystonia Rating Scale, Global Clinical Impression), motor function (Gross Motor Function Measure, Melbourne Assessment of Unilateral Upper Limb Function), pain (visual analogue scale), intelligence (Wechsler Intelligence Scale), executive functioning (Behavior Rating Inventory of Executive Function) and anxiety/depression (Child/Adult Behavior Checklist). Measures were analyzed using a principal component analysis and subsequent multiple regression to evaluate which components were associated with HR-QoL (Pediatric Quality of life Inventory) for total group, and non-lesional (primary) and lesional (secondary) subgroups.

RESULTS

Patients (29 non-lesional, 31 lesional dystonia) had a mean age of 13.6 ± 5.9 years. The principal component analysis revealed three components: 1) motor symptoms; 2) psychiatric and behavioral symptoms; and 3) pain. HR-QoL was associated with motor symptoms and psychiatric and behavioral symptoms (R2 = 0.66) for the total sample and lesional dystonia, but in the non-lesional dystonia subgroup only with psychiatric and behavioral symptoms (R2 = 0.51).

CONCLUSIONS

Non-motor symptoms are important for HR-QoL in childhood-onset dystonia. We suggest a multidisciplinary assessment of motor and non-motor symptoms to optimize individual patient management.

Protocol for N-of-1 trials proof of concept for rehabilitation of childhood-onset dystonia: Study 1: Protocole des essais de validation à effectif unique pour la réadaptation de la dystonie débutant dans l'enfance : Étude 1

BACKGROUND

Hyperkinetic movement disorders (HMD) are a heterogeneous group of neurological conditions among which dystonia is the predominant disorder and dyskinetic cerebral palsy the largest secondary dystonia group. Currently, there are no evidence-based, non-medical management options for childhood HMD. The Cognitive Orientation to daily Occupational Performance (CO-OP) Approach is a task-oriented, performance-based intervention that focuses on participation.

PURPOSE

This paper reports the protocol for a proof-of-concept study to assess feasibility and preliminary evidence regarding efficacy of CO-OP for HMD following deep brain stimulation (DBS).

METHOD

A series of N-of-1 trials with replications will be conducted with children, ages 6 and 21 years with HMD and DBS as indicated by the Manual Ability Classification System. Ten individualized CO-OP sessions, with multiple baselines before, during, and after, will be completed. The primary outcome measures are the Performance Quality Rating Scale and the Assessment of Motor and Process Skills. Outcome data will be plotted over time for each participant and supplemented with graph statistical analysis and effect size estimates.

IMPLICATIONS

A written protocol will be developed based on evidence and feedback incorporating any changes to the CO-OP intervention for children and young people with HMD, as per the Medical Research Council's Framework for Complex Interventions.

Oscillatory Cortical Activity in an Animal Model of Dystonia Caused by Cerebellar Dysfunction

The synchronization of neuronal activity in the sensorimotor cortices is crucial for motor control and learning. This synchrony can be modulated by upstream activity in the cerebello-cortical network. However, many questions remain over the details of how the cerebral cortex and the cerebellum communicate. Therefore, our aim is to study the contribution of the cerebellum to oscillatory brain activity, in particular in the case of dystonia, a severely disabling motor disease associated with altered sensorimotor coupling. We used a kainic-induced dystonia model to evaluate cerebral cortical oscillatory activity and connectivity during dystonic episodes. We performed microinjections of low doses of kainic acid into the cerebellar vermis in mice and examined activities in somatosensory, motor and parietal cortices. We showed that repeated applications of kainic acid into the cerebellar vermis, for five consecutive days, generate reproducible dystonic motor behavior. No epileptiform activity was recorded on electrocorticogram (ECoG) during the dystonic postures or movements. We investigated the ECoG power spectral density and coherence between motor cortex, somatosensory and parietal cortices before and during dystonic attacks. During the baseline condition, we found a phenomenon of permanent adaptation with a change of baseline locomotor activity coupled to an ECoG gamma band increase in all cortices. In addition, after kainate administration, we observed an increase in muscular activity, but less signs of dystonia together with modulations of the ECoG power spectra with an increase in gamma band in motor, parietal and somatosensory cortices. Moreover, we found reduced coherence in all measured frequency bands between the motor cortex and somatosensory or parietal cortices compared to baseline. In conclusion, examination of cortical oscillatory activities in this animal model of chronic dystonia caused by cerebellar dysfunction reveals a disruption in the coordination of neuronal activity across the cortical sensorimotor/parietal network, which may underlie motor skill deficits.

High frequency somatosensory stimulation in dystonia: Evidence fordefective inhibitory plasticity

BACKGROUND

Apart from motor symptoms, multiple deficits of sensory processing have been demonstrated in dystonia. The most consistent behavioural measure of this is abnormal somatosensory temporal discrimination threshold, which has recently been associated with physiological measures of reduced inhibition within the primary somatosensory area. High-frequency repetitive sensory stimulation is a patterned electric stimulation applied to the skin through surface electrodes that has been recently reported to shorten somatosensory temporal discrimination in healthy subjects and to increase the resting level of excitability in several different types of inhibitory interaction in the somatosensory and even motor areas.

OBJECTIVES

We tested whether high-frequency repetitive sensory stimulation could augment cortical inhibition and, in turn, ameliorate somatosensory temporal discrimination in cervical dystonia.

METHODS

Somatosensory temporal discrimination and a number of electrophysiological measures of sensorimotor inhibition and facilitation were measured before and after 45 minutes of high-frequency repetitive sensory stimulation.

RESULTS

As compared with a group of healthy volunteers of similar age, in whom high-frequency repetitive sensory stimulation increased inhibition and shortened somatosensory temporal discrimination, patients with cervical dystonia showed a consistent, paradoxical response: they had reduced suppression of paired-pulse somatosensory evoked potentials, as well as reduced high-frequency oscillations, lateral inhibition, and short interval intracortical inhibition. Somatosensory temporal discrimination deteriorated after the stimulation protocol, and correlated with reduced measures of inhibition within the primary somatosensory cortex.

CONCLUSIONS

We suggest that patients with dystonia have abnormal homeostatic inhibitory plasticity within the sensorimotor cortex and that this is responsible for their paradoxical response to high-frequency repetitive sensory stimulation. © 2018 International Parkinson and Movement Disorder Society.

Dystonia

Dystonia is a neurological condition characterized by abnormal involuntary movements or postures owing to sustained or intermittent muscle contractions. Dystonia can be the manifesting neurological sign of many disorders, either in isolation (isolated dystonia) or with additional signs (combined dystonia). The main focus of this Primer is forms of isolated dystonia of idiopathic or genetic aetiology. These disorders differ in manifestations and severity but can affect all age groups and lead to substantial disability and impaired quality of life. The discovery of genes underlying the mendelian forms of isolated or combined dystonia has led to a better understanding of its pathophysiology. In some of the most common genetic dystonias, such as those caused by TOR1A, THAP1, GCH1 and KMT2B mutations, and idiopathic dystonia, these mechanisms include abnormalities in transcriptional regulation, striatal dopaminergic signalling and synaptic plasticity and a loss of inhibition at neuronal circuits. The diagnosis of dystonia is largely based on clinical signs, and the diagnosis and aetiological definition of this disorder remain a challenge. Effective symptomatic treatments with pharmacological therapy (anticholinergics), intramuscular botulinum toxin injection and deep brain stimulation are available; however, future research will hopefully lead to reliable biomarkers, better treatments and cure of this disorder.

Voxel-Mirrored Homotopic Connectivity of Resting-State Functional Magnetic Resonance Imaging in Blepharospasm

Objective: Several networks in human brain are involved in the development of blepharospasm. However, the underlying mechanisms for this disease are poorly understood. A voxel-mirrored homotopic connectivity (VMHC) method was used to quantify the changes in functional connectivity between two hemispheres of the brain in patients with blepharospasm.

Methods: Twenty-four patients with blepharospasm and 24 healthy controls matched by age, sex, and education were recruited. The VMHC method was employed to analyze the fMRI data. The support vector machine (SVM) method was utilized to examine whether these abnormalities could be applied to distinguish the patients from the controls.

Results: Compared with healthy controls, patients with blepharospasm showed significantly high VMHC in the inferior temporal gyrus, interior frontal gyrus, posterior cingulate cortex, and postcentral gyrus. No significant correlation was found between abnormal VMHC values and clinical variables. SVM analysis showed a combination of increased VMHC values in two brain areas with high sensitivities and specificities (83.33 and 91.67% in the combined inferior frontal gyrus and posterior cingulate cortex; and 83.33 and 87.50% in the combined inferior temporal gyrus and postcentral gyrus).

Conclusion: Enhanced homotopic coordination in the brain regions associated with sensory integration networks and default-mode network may be underlying the pathophysiology of blepharospasm. This phenomenon may serve as potential image markers to distinguish patients with blepharospasm from healthy controls.

Cervical dystonia: Normal auditory mismatch negativity and abnormal somatosensory mismatch negativity

OBJECTIVE

Previous electrophysiological and psychophysical tests have suggested that somatosensory integration is abnormal in dystonia. Here, we hypothesised that this abnormality could relate to a more general deficit in pre-attentive error/deviant detection in patients with dystonia. We therefore tested patients with dystonia and healthy subjects using a mismatch negativity paradigm (MMN), where evoked potentials generated in response to a standard repeated stimulus are subtracted from the responses to a rare "odd ball" stimulus.

METHODS

We assessed MMN for somatosensory and auditory stimuli in patients with cervical dystonia and healthy age matched controls.

RESULTS

We found a significant group ∗ oddball type interaction effect (F (1, 34) = 4.5, p = 0.04, ρ_I = 0.63). A follow up independent t-test for sMMN data, showed a smaller sMMN amplitude in dystonic patients compared to controls (mean difference control-dystonia: -1.0 µV ± 0.3, p < 0.00, t = -3.1). However the amplitude of aMMN did not differ between groups (mean difference control-dystonia: -0.2 µV ± 0.2, p = 0.24, t = -1.2). We found a positive correlation between somatosensory MMN and somatosensory temporal discrimination threshold.

CONCLUSION

These results suggest that pre-attentive error/deviant detection, specifically in the somatosensory domain, is abnormal in dystonia. This could underlie some previously reported electrophysiological and psychophysical abnormalities of somatosensory integration in dystonia.

SIGNIFICANCE

One could hypothesize a deficit in pre-conscious orientation towards potentially salient signals might lead to a more conservative threshold for decision-making in dystonia.

Informed Consent Decision-Making in Deep Brain Stimulation

Deep brain stimulation (DBS) has proved useful for several movement disorders (Parkinson’s disease, essential tremor, dystonia), in which first and/or second line pharmacological treatments were inefficacious. Initial evidence of DBS efficacy exists for refractory obsessive-compulsive disorder, treatment-resistant major depressive disorder, and impulse control disorders. Ethical concerns have been raised about the use of an invasive surgical approach involving the central nervous system in patients with possible impairment in cognitive functioning and decision-making capacity. Most of the disorders in which DBS has been used might present with alterations in memory, attention, and executive functioning, which may have an impact on the mental capacity to give informed consent to neurosurgery. Depression, anxiety, and compulsivity are also common in DBS candidate disorders, and could also be associated with an impaired capacity to consent to treatment or clinical research. Despite these issues, there is limited empirical knowledge on the decision-making levels of these patients. The possible informed consent issues of DBS will be discussed by focusing on the specific treatable diseases.

Pain processing in functional and idiopathic dystonia: An exploratory study

BACKGROUND

Pain is often experienced by patients with functional dystonia and idiopathic cervical dystonia and is likely to be determined by different neural mechanisms.

OBJECTIVE

In this exploratory study, we tested the sensory-discriminative and cognitive-emotional component of pain in patients with functional and idiopathic dystonia.

METHODS

Ten patients with idiopathic cervical dystonia, 12 patients with functional dystonia, and 16 age- and sex-matched healthy controls underwent psychophysical testing of tactile and pain thresholds and pain tolerance. We delivered electrical pulses of increasing intensity to the index finger of each hand and the halluces of each foot. Pain threshold and pain tolerance were respectively defined as the (1) intensity at which sensation changed from unpainful to faintly painful and (2) intensity at which painful sensation was intolerable.

RESULTS

No differences were found between the three groups for tactile and pain thresholds assessed in hands and feet. Pain tolerance was significantly increased in all body regions only in functional dystonia. Patients with continuous functional dystonia had higher pain tolerance compared to subjects with paroxysmal functional dystonia and idiopathic cervical dystonia. There was no correlation between pain tolerance and pain scores, depression, anxiety, disease duration, and motor disability in both groups.

CONCLUSIONS

Patients with functional dystonia have a dissociation between the sensory-discriminative and cognitive-emotional components of pain, as revealed by normal pain thresholds and increased pain tolerance. Abnormal connectivity between the motor and limbic systems might account for abnormal pain processing in functional dystonia. © 2018 International Parkinson and Movement Disorder Society.

The cerebellum and dystonia

Dystonia is a heterogeneous disorder characterized by involuntary muscle contractions, twisting movements, and abnormal postures in various body regions. It is widely accepted that the basal ganglia are involved in the pathogenesis of dystonia. A growing body of evidence, however, is challenging the traditional view and suggest that the cerebellum may also play a role in dystonia. Studies on animals indicate that experimental manipulations of the cerebellum lead to dystonic-like movements. Several clinical observations, including those from secondary dystonia cases as well as neurophysiologic and neuroimaging studies in human patients, provide further evidence in humans of a possible relationship between cerebellar abnormalities and dystonia. Claryfing the role of the cerebellum in dystonia is an important step towards providing alternative treatments based on noninvasive brain stimulation techniques.

Disruption of network for visual perception of natural motion in primary dystonia

In healthy subjects, brain activation in motor regions is greater during the visual perception of "natural" target motion, which complies with the two-thirds power law, than of "unnatural" motion, which does not. It is unknown whether motion perception is normally mediated by a specific network that can be altered in the setting of disease. We used block-design functional magnetic resonance imaging and covariance analysis to identify normal network topographies activated in response to "natural" versus "unnatural" motion. A visual motion perception-related pattern (VPRP) was identified in 12 healthy subjects, characterized by covarying activation responses in the inferior parietal lobule, frontal operculum, lateral occipitotemporal cortex, amygdala, and cerebellum (Crus I). Selective VPRP activation during "natural" motion was confirmed in 12 testing scans from healthy subjects. Consistent network activation was not seen, however, in 29 patients with dystonia, a neurodevelopmental disorder in which motion perception pathways may be involved. Using diffusion tractography, we evaluated the integrity of anatomical connections between the major VPRP nodes. Indeed, fiber counts in these pathways were substantially reduced in the dystonia subjects. In aggregate, the findings associate normal motion perception with a discrete brain network which can be disrupted under pathological conditions.

Temporal Discrimination: Mechanisms and Relevance to Adult-Onset Dystonia

Temporal discrimination is the ability to determine that two sequential sensory stimuli are separated in time. For any individual, the temporal discrimination threshold (TDT) is the minimum interval at which paired sequential stimuli are perceived as being asynchronous; this can be assessed, with high test–retest and inter-rater reliability, using a simple psychophysical test. Temporal discrimination is disordered in a number of basal ganglia diseases including adult-onset dystonia, of which the two most common phenotypes are cervical dystonia and blepharospasm. The causes of adult-onset focal dystonia are unknown; genetic, epigenetic, and environmental factors are relevant. Abnormal TDTs in adult-onset dystonia are associated with structural and neurophysiological changes considered to reflect defective inhibitory interneuronal processing within a network which includes the superior colliculus, basal ganglia, and primary somatosensory cortex. It is hypothesized that abnormal temporal discrimination is a mediational endophenotype and, when present in unaffected relatives of patients with adult-onset dystonia, indicates non-manifesting gene carriage. Using the mediational endophenotype concept, etiological factors in adult-onset dystonia may be examined including (i) the role of environmental exposures in disease penetrance and expression; (ii) sexual dimorphism in sex ratios at age of onset; (iii) the pathogenesis of non-motor symptoms of adult-onset dystonia; and (iv) subcortical mechanisms in disease pathogenesis.

Does the Somatosensory Temporal Discrimination Threshold Change over Time in Focal Dystonia?

Background

The somatosensory temporal discrimination threshold (STDT) is defined as the shortest interval at which an individual recognizes two stimuli as asynchronous. Some evidence suggests that STDT depends on cortical inhibitory interneurons in the basal ganglia and in primary somatosensory cortex. Several studies have reported that the STDT in patients with dystonia is abnormal. No longitudinal studies have yet investigated whether STDT values in different forms of focal dystonia change during the course of the disease.

Methods

We designed a follow-up study on 25 patients with dystonia (15 with blepharospasm and 10 with cervical dystonia) who were tested twice: upon enrolment and 8 years later. STDT values from dystonic patients at the baseline were also compared with those from a group of 30 age-matched healthy subjects.

Results

Our findings show that the abnormally high STDT values observed in patients with focal dystonia remained unchanged at the 8-year follow-up assessment whereas disease severity worsened.

Conclusions

Our observation that STDT abnormalities in dystonia remain unmodified during the course of the disease suggests that the altered activity of inhibitory interneurons—either at cortical or at subcortical level—responsible for the increased STDT does not deteriorate as the disease progresses.

Network-specific resting-state connectivity changes in the premotor-parietal axis in writer's cramp

Background

Writer's cramp is a task-specific dystonia impairing writing and sometimes other fine motor tasks. Neuroimaging studies using manifold designs have shown varying results regarding the nature of changes in the disease.

Objective

To clarify and extend the knowledge of underlying changes by investigating functional connectivity (FC) in intrinsic connectivity networks with putative sensorimotor function at rest in an increased number of study subjects.

Methods

Resting-state functional magnetic resonance imaging with independent component analysis was performed in 26/27 writer's cramp patients/healthy controls, and FC within and between resting state networks with putative sensorimotor function was compared. Additionally, voxel-based morphometry was carried out on the subjects' structural images.

Results

Patients displayed increased left- and reduced right-hemispheric primary sensorimotor FC in the premotor-parietal network. Mostly bilaterally altered dorsal/ventral premotor FC, as well as altered parietal FC were observed within multiple sensorimotor networks and showed differing network-dependent directionality. Beyond within-network FC changes and reduced right cerebellar grey matter volume in the structural analysis, the positive between-network FC of the cerebellar network and the basal ganglia network was reduced.

Conclusions

Abnormal resting-state FC in multiple networks with putative sensorimotor function may act as basis of preexisting observations made during task-related neuroimaging. Further, altered connectivity between the cerebellar and basal ganglia network underlines the important role of these structures in the disease.

•

Investigation of FC changes in various sensorimotor ICNs at rest in writer's cramp.

•

We saw multiple, network-specific FC changes in primary/higher sensorimotor cortices.

•

This may act as basis of the varying nature of sensorimotor changes during task-fMRI.

•

Further, findings supporting disrupted cerebellar-basal ganglia interaction were made.

•

An additional morphometric analysis demonstrated structural cerebellar abnormality.

The Frequency and Self-perceived Impact on Daily Life of Motor and Non-motor Symptoms in Cervical Dystonia

BACKGROUND

Evidence suggests that non-motor symptoms (NMS) are the most important predictors of decreased health-related quality of life (HR-QoL) in patients with cervical dystonia (CD). In this study, we evaluate an NMS screening list and examine the influence of motor symptoms and NMS on HR-QoL.

METHODS

In 40 patients with CD, the frequency of NMS was evaluated using an extended NMS questionnaire. Furthermore, patients composed a list of their 5 most burdensome motor symptoms and NMS and scored the severity of predefined symptoms. HR-QoL was examined with the RAND 36-item Health Survey.

RESULTS

Of 40 patients, 38 experienced NMS (median number of NMS, 6.5; range, 0-13; maximum, 15). The self-perceived most burdensome symptoms were tremor/jerks, pain, sleep disturbances, daily-life limitations, and fatigue. Also, of the predefined symptom list, tremor and fatigue were identified as the most disturbing. Several domains of HR-QoL were significantly influenced by NMS, whereas motor symptoms had only a small influence on the physical functioning domain of HR-QoL.

CONCLUSION

Our findings highlight the impact of NMS on HR-QoL and emphasize the importance of a standardized, validated NMS questionnaire for patients with dystonia. This would enable us to monitor the effect of treatment for motor symptoms and NMS on an individual basis and improve treatment options.

Dystonia

INTRODUCTION

Dystonia is a clinically heterogeneous group of hyperkinetic movement disorders. Recent advances have provided a better understanding of these conditions with significant clinical impact.

SOURCES OF DATA

Peer reviewed journals and reviews. PubMed.gov.

AREAS OF AGREEMENT

A recent consensus classification, including the assessment of phenomenology and identification of the dystonia syndromes, has provided a helpful tool for the clinical assessment. New forms of monogenic dystonia have been recently identified.

AREAS OF CONTROVERSY

Despite recent advances in the understanding of dystonia, treatment remains symptomatic in most patients.

GROWING POINTS

Recent advances in genetics have provided a better understanding of the potential pathogenic mechanisms involved in dystonia. Deep brain stimulation has shown to improve focal and combined forms of dystonia and its indications are constantly expanding.

AREAS TIMELY FOR DEVELOPING RESEARCH

Growing understanding of the disease mechanisms involved will allow the development of targeted and disease-modifying therapies in the future.

Exploratory structural assessment in craniocervical dystonia: Global and differential analyses

Introduction

Our goal was to investigate the cortical thickness and subcortical volume in subjects with craniocervical dystonia and its subgroups.

Methods

We studied 49 subjects, 17 with cervical dystonia, 18 with blepharospasm or oromandibular dystonia, and 79 healthy controls. We performed a whole group analysis, followed by a subgroup analysis. We used Freesurfer software to measure cortical thickness, subcortical volume and to perform a primary exploratory analysis in the craniocervical dystonia group, complemented by a region of interest analysis. We also performed a secondary analysis, with data generated from Freesurfer for subgroups, corrected by false discovery rate. We then performed an exploratory generalized linear model with significant areas for the previous steps using clinical features as independent variables.

Results

The primary exploratory analysis demonstrated atrophy in visual processing regions in craniocervical dystonia. The secondary analysis demonstrated atrophy in motor, sensory, and visual regions in blepharospasm or oromandibular dystonia, as well as in limbic regions in cervical dystonia. Cervical dystonia patients also had greater cortical thickness than blepharospasm or oromandibular dystonia patients in frontal pole and medial orbitofrontal regions. Finally, we observed an association between precuneus, age of onset of dystonia and age at the MRI exam, in craniocervical dystonia; between motor and limbic regions and age at the exam, clinical score and time on botulinum toxin in cervical dystonia and sensory regions and age of onset and time on botulinum toxin in blepharospasm or oromandibular dystonia.

Conclusions

We detected involvement of visual processing regions in craniocervical dystonia, and a pattern of involvement in cervical dystonia and blepharospasm or oromandibular dystonia, including motor, sensory and limbic areas. We also showed an association of cortical thickness atrophy and younger onset age, older age at the MRI exam, higher clinical score and an uncertain association with longer time on botulinum toxin.

When movement disorders hurt: Addressing pain in hyperkinetic disorders

Pain is an important nonmotor symptom in movement disorders. Dystonia is a hyperkinetic movement disorder characterized by involuntary, sustained or intermittent muscle contractions causing abnormal movements, postures or both. Contrary to common views the nonmotor symptoms are present in dystonia patients. Pain is a prevailing feature of cervical dystonia (CD), the most common form of focal dystonia. The mechanism of pain in CD remains mostly unknown, but there are growing evidence that it could not be only the consequence of muscle hyperactivity. We have shown that botulinum toxin (BoNT) produced pain relief before muscle relaxation and that effect on pain relief lasted longer than the effect on motor improvement. More and more data suggest that pain relief could be attributed to the direct effect of BoNT type A on central nervous system. Pain, depression, and anxiety have been shown to be significant determinants of QoL in focal dystonia patients. Routine clinical examination in patients with dystonia should include evaluation of motor as well as non-motor symptoms. Selective rating assessment should be used in clinical practice to quantify pain. Specific assessment of pain is important to determine the effect of BoNT as the most effective treatment in focal dystonia.

Psychiatric associations of adult-onset focal dystonia phenotypes

BACKGROUND

Depression and anxiety frequently accompany the motor manifestations of isolated adult-onset focal dystonias. Whether the body region affected when this type of dystonia first presents is associated with the severity of these neuropsychiatric symptoms is unknown.

OBJECTIVES

The aim of this study was to determine whether depression, anxiety and social anxiety vary by dystonia onset site and evaluate whether pain and dystonia severity account for any differences.

METHODS

Patients with isolated focal dystonia evaluated within 5 years from symptom onset, enrolled in the Natural History Project of the Dystonia Coalition, were included in the analysis. Individual onset sites were grouped into five body regions: cervical, laryngeal, limb, lower cranial and upper cranial. Neuropsychiatric symptoms were rated using the Beck Depression Inventory, Hospital Anxiety and Depression Scale and Liebowitz Social Anxiety Scale. Pain was estimated using the 36-Item Short Form Survey.

RESULTS

Four hundred and seventy-eight subjects met our inclusion criteria. High levels of depression, anxiety and social anxiety occurred in all groups; however, the severity of anxiety and social anxiety symptoms varied by onset site group. The most pronounced differences were higher anxiety in cervical and laryngeal, lower anxiety in upper cranial and higher social anxiety in laryngeal. Increases in pain were associated with worse neuropsychiatric symptom scores within all groups. Higher anxiety and social anxiety in laryngeal and lower anxiety in upper cranial persisted after correcting for pain and dystonia severity.

CONCLUSION

Anxiety and social anxiety severity vary by onset site of focal dystonia, and this variation is not explained by differences in pain and dystonia severity.

Is there a specific psychiatric background or personality profile in functional dystonia?

OBJECTIVE

The aim of this cross-sectional study was to identify if there was a specific difference between patients with functional dystonia (DysF) and those with adult-onset, isolated idiopathic ("primary") dystonia (DysP) in terms of psychiatric disorders, psychological stressor, dissociation correlates, and personality traits.

METHODS

Thirty-nine clinically definite DysF and 30 DysP patients matched by age, gender and dystonia distribution underwent psychiatric interview based on DSM-5 criteria and additional testings for global cognitive and psychiatric functions (Mini-Mental State Examination, Hamilton Depression and Hamilton Anxiety Rating Scale, Apathy Scale, Somatoform Dissociation Questionnaire-20, Dissociative Experiences Scale II, and the five-dimensional Revised Neuroticism-Extroversion-Openness Personality Inventory).

RESULTS

Almost half of our DysF patients had prior psychiatric treatment, which was significantly more frequent when compared to DysP. Patients with DysF in comparison to DysP also had considerably more frequent preceding stress, higher apathy, dissociative and somatoform scores, as well as significantly higher rate of la belle indifférence sign. This sign, stress before dystonia and prior psychiatric disorder independently predicted having DysF. Some of psychiatric disorders (i.e. substance-related disorders, schizophrenia, adjustment disorder, borderline personality disorder, post-traumatic stress disorder, psychotic depression, delusional disorder) were exclusively present among DysF patients. DysF compared to DysP patients had lower scores for both extroversion and openness to experiences.

CONCLUSION

Our data found different pattern of psychiatric comorbidity and personality traits between DysF and DysP patients, including a higher prevalence of psychological stressor and dissociative correlates, indicating at least a partial role of psychological mechanisms in the pathogenesis of DysF.

Mind the gap: temporal discrimination and dystonia

BACKGROUND AND PURPOSE

One of the most widely studied perceptual measures of sensory dysfunction in dystonia is the temporal discrimination threshold (TDT) (the shortest interval at which subjects can perceive that there are two stimuli rather than one). However the elevated thresholds described may be due to a number of potential mechanisms as current paradigms test not only temporal discrimination but also extraneous sensory and decision-making parameters. In this study two paradigms designed to better quantify temporal processing are presented and a decision-making model is used to assess the influence of decision strategy.

METHODS

22 patients with cervical dystonia and 22 age-matched controls completed two tasks (i) temporal resolution (a randomized, automated version of existing TDT paradigms) and (ii) interval discrimination (rating the length of two consecutive intervals).

RESULTS

In the temporal resolution task patients had delayed (P = 0.021) and more variable (P = 0.013) response times but equivalent discrimination thresholds. Modelling these effects suggested this was due to an increased perceptual decision boundary in dystonia with patients requiring greater evidence before committing to decisions (P = 0.020). Patient performance on the interval discrimination task was normal.

CONCLUSIONS

Our work suggests that previously observed abnormalities in TDT may not be due to a selective sensory deficit of temporal processing as decision-making itself is abnormal in cervical dystonia.

Cerebellum: An explanation for dystonia?

Dystonia is a movement disorder that is characterized by involuntary muscle contractions, abnormal movements and postures, as well as by non-motor symptoms, and is due to abnormalities in different brain areas. In this article, we focus on the growing number of experimental studies aimed at explaining the pathophysiological role of the cerebellum in dystonia. Lastly, we highlight gaps in current knowledge and issues that future research studies should focus on as well as some of the potential applications of this research avenue. Clarifying the pathophysiological role of cerebellum in dystonia is an important concern given the increasing availability of invasive and non-invasive stimulation techniques and their potential therapeutic role in this condition.

Anodal Direct Current Stimulation of the Cerebellum Reduces Cerebellar Brain Inhibition but Does Not Influence Afferent Input from the Hand or Face in Healthy Adults

BACKGROUND

The cerebellum controls descending motor commands by outputs to primary motor cortex (M1) and the brainstem in response to sensory feedback. The cerebellum may also modulate afferent input en route to M1 and the brainstem.

OBJECTIVE

The objective of this study is to determine if anodal transcranial direct current stimulation (tDCS) to the cerebellum influences cerebellar brain inhibition (CBI), short afferent inhibition (SAI) and trigeminal reflexes (TRs) in healthy adults.

METHODS

Data from two studies evaluating effects of cerebellar anodal and sham tDCS are presented. The first study used a twin coil transcranial magnetic stimulation (TMS) protocol to investigate CBI and combined TMS and cutaneous stimulation of the digit to assess SAI. The second study evaluated effects on trigemino-cervical and trigemino-masseter reflexes using peripheral nerve stimulation of the face.

RESULTS

Fourteen right-handed healthy adults participated in experiment 1. CBI was observed at baseline and was reduced by anodal cerebellar DCS only (P < 0.01). There was SAI at interstimulus intervals of 25 and 30 ms at baseline (both P < 0.0001), but cerebellar tDCS had no effect. Thirteen right-handed healthy adults participated in experiment 2. Inhibitory reflexes were evoked in the ipsilateral masseter and sternocleidomastoid muscles. There was no effect of cerebellar DCS on either reflex.

CONCLUSIONS

Anodal DCS reduced CBI but did not change SAI or TRs in healthy adults. These results require confirmation in individuals with neurological impairment.

The Italian Dystonia Registry: rationale, design and preliminary findings

The Italian Dystonia Registry is a multicenter data collection system that will prospectively assess the phenomenology and natural history of adult-onset dystonia and will serve as a basis for future etiological, pathophysiological and therapeutic studies. In the first 6 months of activity, 20 movement disorders Italian centres have adhered to the registry and 664 patients have been recruited. Baseline historical information from this cohort provides the first general overview of adult-onset dystonia in Italy. The cohort was characterized by a lower education level than the Italian population, and most patients were employed as artisans, builders, farmers, or unskilled workers. The clinical features of our sample confirmed the peculiar characteristics of adult-onset dystonia, i.e. gender preference, peak age at onset in the sixth decade, predominance of cervical dystonia and blepharospasm over the other focal dystonias, and a tendency to spread to adjacent body parts, The sample also confirmed the association between eye symptoms and blepharospasm, whereas no clear association emerged between extracranial injury and dystonia in a body site. Adult-onset dystonia patients and the Italian population shared similar burden of arterial hypertension, type 2 diabetes, coronary heart disease, dyslipidemia, and hypothyroidism, while hyperthyroidism was more frequent in the dystonia population. Geographic stratification of the study population yielded no major difference in the most clinical and phenomenological features of dystonia. Analysis of baseline information from recruited patients indicates that the Italian Dystonia Registry may be a useful tool to capture the real world clinical practice of physicians that visit dystonia patients.

Nonmotor symptoms in primary adult-onset cervical dystonia and blepharospasm

BACKGROUND

The nature and frequency of nonmotor symptoms in primary adult-onset cervical dystonia (CD) and blepharospasm (BSP) patients in Chinese populations remain unknown.

METHODS

Hamilton's Depression Scale (HAMD), Hamilton's Anxiety Scale (HAMA), Addenbrooke's Cognitive Examination Revised (ACE-R), Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale were used to evaluate NMS in 120 patients with primary focal adult-onset dystonia (60 with BSP and 60 with CD) and 60 age-, sex-, and education level- matched healthy controls (HCs). Motor symptoms of BSP and CD patients were evaluated by Jankovic rating scale and Toronto Western Spasmodic Torticollis Rating Scale-severity scale separately.

RESULTS

Twenty patients had depression, and 29 patients had anxiety. The mean HAMD and HAMA scores were significantly higher in patient groups. Thirty-six patients had cognitive decline based on the cut-off score of 75. The total score and scores of each domain of ACE-R were significantly lower in patient groups than that in HCs. Quality of sleep was impaired in patient groups, and patients with CD had worse quality of sleep than patients with BSP. Thirty-three BSP patients and 43 CD patients suffered from sleep disorder separately. The frequency of excessive daytime sleepiness did not differ between patients and HCs. No significant correlation was found between NMS and motor severity in the two forms of dystonia.

CONCLUSIONS

Current study suggests that NMS are prevalent in Chinese CD and BSP patients, and the motor severity of dystonia did not contribute to the severity of nonmotor symptoms. Assessment of nonmotor symptoms should be considered in clinical management of focal dystonia.

A comparison of stimulus presentation methods in temporal discrimination testing

The temporal discrimination threshold (TDT) is the shortest time interval at which an individual detects two stimuli to be asynchronous (normal  =  30-50 ms). It has been shown to be abnormal in patients with disorders affecting the basal ganglia including adult onset idiopathic focal dystonia (AOIFD). Up to 97% of patients have an abnormal TDT with age- and sex-related penetrance in unaffected relatives, demonstrating an autosomal dominant inheritance pattern. These findings support the use of the TDT as a pre-clinical biomarker for AOIFD. The usual stimulus presentation method involves the presentation of progressively asynchronous stimuli; when three sequential stimuli are reported asynchronous is taken as a participant's TDT. To investigate the robustness of the 'staircase' method of presentation, we introduced a method of randomised presentation order to explore any potential 'learning effect' that may be associated with this existing method. The aim of this study was to investigate differences in temporal discrimination using two methods of stimulus presentation. Thirty healthy volunteers were recruited to the study (mean age 33.73  ±  3.4 years). Visual and tactile TDT testing using a staircase and randomised method of presentation order was carried out in a single session. There was a strong relationship between the staircase and random method for TDT values. This observed consistency between testing methods suggests that the existing experimental approach is a robust method of recording an individual's TDT. In addition, our newly devised randomised paradigm is a reproducible and more efficient method for data acquisition in the clinic setting. However, the two presentation methods yield different absolute TDT results and either of the two methods should be used uniformly in all participants in any one particular study.

Childhood Laryngeal Dystonia Following Bilateral Globus Pallidus Abnormality: A Case Study and Review of Literature

INTRODUCTION

Dystonia is a disorder of movement caused by various etiologies. Laryngeal dystonia is caused by the spasm of laryngeal muscles. It is a disorder caused by vocal fold movement in which excessive adduction or abduction of the vocal folds occurs during speech. The pathophysiology of this type of dystonia is not fully known. Some researchers have suggested that basal ganglia structures and their connections with cortical areas have been involved in the pathogenesis of dystonia.

CASE REPORT

In this paper a 7.5-year-old boy suffering from laryngeal dystonia with bilateral lesions in Globus Pallidus is presented. The patient also suffered from swallowing problems, monotone voice, vocal tremor, hypersensitivity of gag reflex, and stuttering. Drug treatment failed to cure him; therefore, he was referred to rehabilitation therapy.

CONCLUSION

In conclusion, special attention should be brought upon laryngeal dystonia, especially in patients showing Extra-pyramidal symptoms and/or abnormalities of the basal ganglia. In children, laryngeal dystonia may be potentially fatal. Lack of consideration for this condition during rehabilitation therapy can lead to serious consequences for a child.

The International Classification of Functioning (ICF) to evaluate deep brain stimulation neuromodulation in childhood dystonia-hyperkinesia informs future clinical & research priorities in a multidisciplinary model of care

The multidisciplinary team (MDT) approach illustrates how motor classification systems, assessments and outcome measures currently available have been applied to a national cohort of children and young people with dystonia and other hyperkinetic movement disorders (HMD) particularly with a focus on dyskinetic cerebral palsy (CP). The paper is divided in 3 sections. Firstly, we describe the service model adopted by the Complex Motor Disorders Service (CMDS) at Evelina London Children's Hospital and King's College Hospital (ELCH-KCH) for deep brain stimulation. We describe lessons learnt from available dystonia studies and discuss/propose ways to measure DBS and other dystonia-related intervention outcomes. We aim to report on current available functional outcome measures as well as some impairment-based assessments that can encourage and generate discussion among movement disorders specialists of different backgrounds regarding choice of the most important areas to be measured after DBS and other interventions for dystonia management. Finally, some recommendations for multi-centre collaboration in regards to functional clinical outcomes and research methodologies for dystonia-related interventions are proposed.

Recognizing the Common Origins of Dystonia and the Development of Human Movement: A Manifesto of Unmet Needs in Isolated Childhood Dystonias

Dystonia in childhood may be severely disabling and often unremitting and unrecognized. Considered a rare disorder, dystonic symptoms in childhood are pervasive in many conditions including disorders of developmental delay, cerebral palsy (CP), autism, neurometabolic, neuroinflammatory, and neurogenetic disorders. Collectively, there is a need to recognize the role of early postures and movements which characterize phases of normal fetal, infant, and child development as a backdrop to the many facets of dystonia in early childhood neurological disorders and to be aware of the developmental context of dystonic symptoms. The role of cocontraction is explored throughout infancy, childhood, young adulthood, and in the elderly. Under-recognition of pervasive dystonic disorders of childhood, including within CP is reviewed. Original descriptions of CP by Gowers are reviewed and contemporary physiological demonstrations are used to illustrate support for an interpretation of the tonic labyrinthine response as a manifestation of dystonia. Early recognition and molecular diagnosis of childhood dystonia where possible are desirable for appropriate clinical stratification and future precision medicine and functional neurosurgery where appropriate. A developmental neurobiological perspective could also be useful in exploring new clinical strategies for adult-onset dystonia disorders focusing on environmental and molecular interactions and systems behaviors.

Fatigue, Sleep Disturbances, and Their Influence on Quality of Life in Cervical Dystonia Patients

Background

Nonmotor symptoms (NMS) are highly prevalent in cervical dystonia (CD). In general, fatigue and sleep are important NMS that determine a decreased health-related quality of life (HR-QoL), but their influence in CD is unknown. The authors systematically investigated fatigue, excessive daytime sleepiness (EDS), and sleep quality in patients with CD and controls and assessed the influence of psychiatric comorbidity, pain, and dystonia motor severity. They also examined the predictors of HR-QoL.

Methods

The study included 44 patients with CD and 43 matched controls. Fatigue, EDS, and sleep quality were assessed with quantitative questionnaires and corrected for depression and anxiety using analysis of covariance. The Toronto Western Spasmodic Torticollis Rating Scale and the Clinical Global Impression Scale-jerks/tremor subscale were used to score motor severity and to assess whether motor characteristics could explain an additional part of the variation in fatigue and sleep-related measures. HR-QoL was determined with the RAND-36 item Health Survey, and predictors of HR-QoL were assessed using multiple regression.

Results

Fatigue scores were increased independently from psychiatric comorbidity (4.0 vs. 2.7; P < 0.01), whereas EDS (7.3 vs. 7.4; P = 0.95) and sleep quality (6.5 vs. 6.1; P = 0.73) were highly associated with depression and anxiety. In patients with CD, motor severity did not explain the variations in fatigue (change in the correlation coefficient [ΔR²] = 0.06; P = 0.15), EDS (ΔR² = 0.00; P = 0.96), or sleep quality (ΔR² = 0.04; P = 0.38) scores. Fatigue, EDS, psychiatric comorbidity, and pain predicted a decreased QoL.

Conclusion

Independent from psychiatric comorbidity and motor severity, fatigue appeared to be a primary NMS. Sleep-related measures were highly associated with psychiatric comorbidity, but not with motor severity. Only NMS predicted HR-QoL, which emphasizes the importance of attention to NMS in patients with CD.