Prevalence and clinical features of cervical dystonia in Parkinson's disease.

OBJECTIVE: To study the prevalence and clinical features of cervical dystonia in Parkinson's disease (CD-PD). BACKGROUND: PD features various forms of dystonia, including CD. Yet, the prevalence and clinical features of CD in PD patients are not well-characterized. METHODS: We conducted a single site, prospective study where consecutively evaluated PD patients were examined for the presence of CD to ascertain its prevalence. For each case of CD-PD, a standardized questionnaire assessing demographic and clinical features was completed. Statistical analysis was performed to compare CD-PD characteristics to those of a previously published large idiopathic CD cohort. RESULTS: Of 301 consecutive PD patients evaluated, 28 (9.3 %) had CD, far surpassing estimates of CD prevalence in the general population. This CD-PD cohort was predominantly male (71 %) with a mean age of 70.9 ± 8.1 years. The mean duration of PD was 10.4 ± 6.7 years. In most cases (n = 19, 68 %), CD developed after the onset of PD. Five patients reported dystonia improvements in response to levodopa, while none reported medication-induced worsening. In contrast to CD-PD, those with ICD (n = 209) were on average younger (59.7 ± 10.1) and mostly female (74 %, p < 0.001). In addition, CD-PD was overall less severe as measured by the Global Dystonia Rating Scale (GDRS) (p = 0.002) and featured less head tremor and pain. CONCLUSION: Our findings indicate CD is overrepresented in PD compared to the general population and has clinical features distinct from those of ICD. These results justify larger, more comprehensive studies of CD-PD to better understand its frequency, pathophysiology, clinical characteristics, and associated risk factors.

Duration of botulinum toxin efficacy in cervical dystonia clinical trials: A scoping review.

INTRODUCTION: Botulinum toxin (BoNT) is first-line treatment for cervical dystonia (CD). Treatment of CD with BoNT usually requires injections every 3-4 months for as long as symptoms persist, which can be for the lifetime of the individual. Duration of BoNT effect can impact quality of life since it is important that efficacy is maintained throughout an injection cycle to avoid fluctuations of effect after each injection. There is currently no consensus on how to assess duration of BoNT effect in patients with CD. METHODS: A scoping review was conducted to summarize the available evidence from phase 3 clinical trials of BoNT in CD and on the interpretation of the reported duration of effect. The available evidence was analyzed in the context of clinical experience and real-world treatment practices of CD. RESULTS: Methods for estimating duration of effect varied across publications; most were based on artificial constructs developed for clinical trials (time until a pre-specified efficacy endpoint was reached) and are not appropriate to apply in clinical practice. Clinical trial outcomes in CD were not objectively evaluated, and did not prioritize patients' needs or focus on factors that impact patients' daily living activities and quality of life. CONCLUSION: Better evidence and consistency of reporting for duration of effect for BoNT in CD is needed to help guide clinicians on when reinjection is likely to be required. The goal should be to keep patients as symptom-free as possible with flexible reinjection intervals tailored to individual needs.

Demographics and Clinical Characteristics Associated with the Spread of New-Onset Laryngeal Dystonia.

OBJECTIVES: Adult-onset idiopathic laryngeal dystonia (LD) can be associated with the risk of spread to muscles in the body. Subjects with extralaryngeal onset of dystonia have exhibited spread to the larynx. Previous studies analyze the spread of other dystonias but emphasis has not been placed on LD. The objective was to identify demographic and clinical factors contributing to the spread of dystonia to and from the larynx. METHODS: Data were obtained from the Dystonia Coalition (DC)-patients from 49 international clinical centers. Clinical and demographic data was taken from 143 out of 409 patients with diagnosed LD. Patient criteria included adult-onset LD diagnosed on exam with no co-morbid neurologic conditions and no dystonia in other locations. RESULTS: Among the 143 patients, 94 (65.7%) patients were diagnosed with focal laryngeal onset, with the remainder having extralaryngeal onset. Family history and age at study were statistically significant indicators of a patient developing laryngeal versus extralaryngeal onset of dystonia. Among the laryngeal onset group, 21 cases (22.3%) had an average time of 5.81 ± 5.79 years to spread from diagnosis, most commonly to neck (61.9%). Among extralaryngeal onset patients, mean time of larynx spread was 7.92 ± 7.737 years, most commonly to neck (22.7%). CONCLUSIONS: Our data indicates approximately a quarter of patients with laryngeal-onset dystonia will exhibit spread. There were no demographic or clinical factors that were statistically predictive of the likelihood of spread from larynx. Patients with dystonia elsewhere in the body should be counseled on the possibility of spread to larynx, and vice versa. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:2295-2299, 2024.

Inosine monophosphate dehydrogenase intranuclear inclusions are markers of aging and neuronal stress in the human substantia nigra.

We explored mechanisms involved in the age-dependent degeneration of human substantia nigra (SN) dopamine (DA) neurons. Owing to its important metabolic functions in post-mitotic neurons, we investigated the developmental and age-associated changes in the purine biosynthetic enzyme inosine monophosphate dehydrogenase (IMPDH). Tissue microarrays prepared from post-mortem samples of SN from 85 neurologically intact participants humans spanning the age spectrum were immunostained for IMPDH combined with other proteins. SN DA neurons contained two types of IMPDH structures: cytoplasmic IMPDH filaments and intranuclear IMPDH inclusions. The former were not age-restricted and may represent functional units involved in sustaining purine nucleotide supply in these highly metabolically active cells. The latter showed age-associated changes, including crystallization, features reminiscent of pathological inclusion bodies, and spatial associations with Marinesco bodies; structures previously associated with SN neuron dysfunction and death. We postulate dichotomous roles for these two subcellularly distinct IMPDH structures and propose a nucleus-based model for a novel mechanism of SN senescence that is independent of previously known neurodegeneration-associated proteins.

Ultrastructural analysis of nigrostriatal dopaminergic terminals in a knockin mouse model of DYT1 dystonia.

DYT1 dystonia is associated with decreased striatal dopamine release. In this study, we examined the possibility that ultrastructural changes of nigrostriatal dopamine terminals could contribute to this neurochemical imbalance using a serial block face/scanning electron microscope (SBF/SEM) and three-dimensional reconstruction to analyse striatal tyrosine hydroxylase-immunoreactive (TH-IR) terminals and their synapses in a DYT1(ΔE) knockin (DYT1-KI) mouse model of DYT1 dystonia. Furthermore, to study possible changes in vesicle packaging capacity of dopamine, we used transmission electron microscopy to assess the synaptic vesicle size in striatal dopamine terminals. Quantitative comparative analysis of 80 fully reconstructed TH-IR terminals in the WT and DYT1-KI mice indicate (1) no significant difference in the volume of TH-IR terminals; (2) no major change in the proportion of axo-spinous versus axo-dendritic synapses; (3) no significant change in the post-synaptic density (PSD) area of axo-dendritic synapses, while the PSDs of axo-spinous synapses were significantly smaller in DYT1-KI mice; (4) no significant change in the contact area between TH-IR terminals and dendritic shafts or spines, while the ratio of PSD area/contact area decreased significantly for both axo-dendritic and axo-spinous synapses in DYT1-KI mice; (5) no significant difference in the mitochondria volume; and (6) no significant difference in the synaptic vesicle area between the two groups. Altogether, these findings suggest that abnormal morphometric changes of nigrostriatal dopamine terminals and their post-synaptic targets are unlikely to be a major source of reduced striatal dopamine release in DYT1 dystonia.

Proprioceptive Modulation of Pallidal Physiology in Cervical Dystonia.

BACKGROUND: There is a growing body of evidence suggesting that botulinum toxin can alter proprioceptive feedback and modulate the muscle-spindle output for the treatment of dystonia. However, the mechanism for this modulation remains unclear. METHODS: We conducted a study involving 17 patients with cervical dystonia (CD), seven of whom had prominent CD and 10 with generalized dystonia (GD) along with CD. We investigated the effects of neck vibration, a form of proprioceptive modulation, on spontaneous single-neuron responses and local field potentials (LFPs) recorded from the globus pallidum externus (GPe) and internus (GPi). RESULTS: Our findings demonstrated that neck vibration notably increased the regularity of neck-sensitive GPi neurons in focal CD patients. Additionally, in patients with GD and CD, the vibration enhanced the firing regularity of non-neck-sensitive neurons. These effects on single-unit activity were also mirrored in ensemble responses measured through LFPs. Notably, the LFP modulation was particularly pronounced in areas populated with burst neurons compared to pause or tonic cells. CONCLUSION: The results from our study emphasize the significance of burst neurons in the pathogenesis of dystonia and in the efficacy of proprioceptive modulation for its treatment. Moreover, we observed that the effects of vibration on focal CD were prominent in the α band LFP, indicating modulation of pallido-cerebellar connectivity. Moreover, the pallidal effects of vibration in GD with CD involved modulation of cerebro-pallidal θ band connectivity. Our analysis provides insight into how vibration-induced changes in pallidal activity are integrated into the downstream motor circuit. © 2023 International Parkinson and Movement Disorder Society.

Cerebrospinal fluid levels of 5-HIAA and dopamine in people with HIV and depression.

Depression is a common illness in people with HIV (PWH) and is associated with substantial morbidity and mortality. The mechanisms that underpin depression in PWH remain incompletely elucidated, and more research is therefore needed to develop effective treatments. One hypothesis is that neurotransmitter levels may be altered. These levels could be influenced by the chronic inflammation and viral persistence that occurs in PWH. We examined a panel of cerebrospinal fluid (CSF) neurotransmitters in PWH on suppressive antiretroviral therapy (ART), many of whom had a current depression diagnosis. CSF monoamine neurotransmitters and their metabolites were measured from participants in studies at the Emory Center for AIDS Research (CFAR). Only participants on stable ART with suppressed HIV RNA from both plasma and CSF were analyzed. Neurotransmitter levels were measured with high-performance liquid chromatography (HPLC). Neurotransmitters and their metabolites included dopamine (DA), homovanillic acid (HVA, a major metabolite of dopamine), serotonin (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA, a major metabolite of serotonin), and 4-hydroxy-3-methoxyphenylglycol (MHPG, a major metabolite of norepinephrine). Multivariable logistic regression was used to evaluate factors associated with depression. There were 79 PWH with plasma and CSF HIV RNA levels < 200 copies/mL at the time of the visit, and 25 (31.6%) carried a current diagnosis of depression. Participants with depression were significantly older (median age 53 years versus 47 years, P = 0.014) and were significantly less likely to be African American (48.0% versus 77.8%, P = 0.008). Participants with depression had significantly lower dopamine levels (median 0.49 ng/mL versus 0.62 ng/mL, P = 0.03) and significantly lower 5-HIAA levels (median 12.57 ng/mL versus 15.41 ng/mL, P = 0.015). Dopamine and 5-HIAA were highly correlated. In the multivariable logistic regression models, lower 5-HIAA was significantly associated with the depression diagnosis when accounting for other significant demographic factors. The associations between lower 5-HIAA, lower dopamine, and depression in PWH suggest that altered neurotransmission may contribute to these comorbid conditions. However, the effects of antidepressants on neurotransmitters cannot be ruled out as a factor in the 5-HIAA results.

Does Pallidal Physiology Determine the Success of Unilateral Deep Brain Stimulation in Cervical Dystonia?

Pallidal deep brain stimulation is a well-known surgical treatment for cervical dystonia. The resolution of dystonia typically requires bilateral pallidal stimulation, but in some instances, unilateral stimulation has been successful. In such instances, generally, the stimulated hemisphere was contralateral to the dystonic sternocleidomastoid, but rarely it was ipsilateral. We sought for the physiological features that determine the basis for success and laterality of deep brain stimulation for cervical dystonia with prominent torticollis. We found that pallidal physiology such as high burst to tonic ratio and significant interhemispheric differences in the neuronal firing rate and regularity are critical determinants of successful treatment with unilateral deep brain stimulation. We also found that higher lateralized differences in pallidal physiological parameters predict more robust improvement. In three out of four patients, the stimulation of the hemisphere ipsilateral to the dystonic sternocleidomastoid muscle was effective. These patients did not have any structural brain abnormalities on clinically available imaging studies. One patient responded to the unilateral deep brain stimulation in the hemisphere contralateral to the dystonic sternocleidomastoid. This patient had a structural putamen lesion on brain MRI. These results provide objective parameters determining the success of pallidal deep brain stimulation for treatment of cervical dystonia. The results also depict differences in the pallidal physiology in patients where ipsilateral versus contralateral deep brain stimulation was effective.

Pain Reduction in Cervical Dystonia Following Treatment with IncobotulinumtoxinA: A Pooled Analysis.

This analysis pooled pain severity data from four phase 3 and 4 studies of incobotulinumtoxinA (incoBoNT-A) for the treatment of cervical dystonia (CD) in adults. CD-related pain severity was assessed at baseline, each injection visit, and 4 weeks after each injection of incoBoNT-A using the Toronto Western Spasmodic Torticollis Rating Scale pain severity subscale or a pain visual analog scale. Both were analyzed using a score range of 0-10 and pain was categorized as mild, moderate, or severe. Data for 678 patients with pain at baseline were assessed and sensitivity analyses evaluated pain responses in the subgroup not taking concomitant pain medication (n = 384 at baseline). At Week 4 after the first injection, there was a mean change of -1.25 (standard deviation 2.04) points from baseline pain severity (p < 0.0001), with 48.1% showing ≥ 30% pain reduction from baseline, 34.4% showing ≥50% pain reduction from baseline, and 10.3% becoming pain free. Pain responses were sustained over five injection cycles with a trend to incremental improvements with each successive cycle. Pain responses in the subgroup not taking concomitant pain medication demonstrated the lack of confounding effects of pain medications. These results confirmed the pain relief benefits of long-term treatment with incoBoNT-A.

The Pain in Dystonia Scale (PIDS)-Development and Validation in Cervical Dystonia.

BACKGROUND: A better understanding of pain in adult-onset idiopathic dystonia (AOID) is needed to implement effective therapeutic strategies. OBJECTIVE: To develop a new rating instrument for pain in AOID and validate it in cervical dystonia (CD). METHODS: Development and validation of the Pain in Dystonia Scale (PIDS) comprised three phases. In phase 1, international experts and participants with AOID generated and evaluated the preliminary items for content validity. In phase 2, the PIDS was drafted and revised by the experts, followed by cognitive interviews to ensure self-administration suitability. In phase 3, the PIDS psychometric properties were assessed in 85 participants with CD and retested in 40 participants. RESULTS: The final version of PIDS evaluates pain severity (by body-part), functional impact, and external modulating factors. Test-retest reliability showed a high-correlation coefficient for the total score (0.9, P < 0.001), and intraclass correlation coefficients were 0.7 or higher for all items in all body-parts subscores. The overall PIDS severity score showed high internal consistency (Cronbach's α, 0.9). Convergent validity analysis revealed a strong correlation between the PIDS severity score and the Toronto Western Spasmodic Torticollis Rating Scale pain subscale (0.8, P < 0.001) and the Brief Pain Inventory-short form items related to pain at time of the assessment (0.7, P < 0.001) and impact of pain on daily functioning (0.7, P < 0.001). CONCLUSION: The PIDS is the first specific questionnaire developed to evaluate pain in all patients with AOID, here, demonstrating high-level psychometric properties in people with CD. Future work will validate PIDS in other forms of AOID. © 2023 International Parkinson and Movement Disorder Society.

Isolated Cervical Dystonia: Diagnosis and Classification.

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

What Is Hemidystonia?

Background: Hemidystonia is defined as dystonia restricted to one side of the body. It is traditionally believed to result from a lesion in the contralateral hemisphere. Objectives: To describe a series of hemidystonia patients without lesions on brain imaging. Methods: We searched for individuals with potential hemidystonia who were included in the Dystonia Coalition or Movement Disorder Society Genetic mutation database (MDSgene), and conducted a systematic review. Results: We found 10 individuals classified as hemidystonia or with homolateral limb dystonia among 3696 cases enrolled by the Dystonia Coalition, 9 cases in MDSgene, and one idiopathic case in the literature. None had evidence of a brain lesion. Body distributions used to define hemidystonia varied considerably and were not always restricted to one side of the body. Conclusions: Hemidystonia may be idiopathic or genetic, without any obvious brain lesion. The varied use of the term suggests the need for more specific clinical criteria to define "half the body."

Validation of a guideline to reduce variability in diagnosing cervical dystonia.

BACKGROUND: Cervical dystonia is characterized by a variable pattern of neck muscle involvement. Due to the lack of a diagnostic test, cervical dystonia diagnosis is based on clinical examination and is therefore subjective. The present work was designed to provide practical guidance for clinicians in confirming or refuting suspected cervical dystonia. METHODS: Participants were video recorded according to a standardized protocol to assess 6 main clinical features possibly contributing to cervical dystonia diagnosis: presence of repetitive, patterned head/neck movements/postures inducing head/neck deviation from neutral position (item 1); sensory trick (item 2); and red flags related to conditions mimicking dystonia that should be absent in dystonia (items 3-6). Inter-/intra-rater agreement among three independent raters was assessed by k statistics. To estimate sensitivity and specificity, the gold standard was cervical dystonia diagnosis reviewed at each site by independent senior neurologists. RESULTS: The validation sample included 43 idiopathic cervical dystonia patients and 41 control subjects (12 normal subjects, 6 patients with isolated head tremor, 4 with chorea, 6 with tics, 4 with head ptosis due to myasthenia or amyotrophic lateral sclerosis, 7 with orthopedic/rheumatologic neck diseases, and 2 with ocular torticollis). The best combination of sensitivity and specificity was observed considering all the items except for an item related to capability to voluntarily suppress spasms (sensitivity: 96.1%; specificity: 81%). CONCLUSIONS: An accurate diagnosis of cervical dystonia can be achieved if, in addition to the core motor features, we also consider some clinical features related to dystonia mimics that should be absent in dystonia.

Motor and psychiatric features in idiopathic blepharospasm: A data-driven cluster analysis.

INTRODUCTION: Idiopathic blepharospasm is a clinically heterogeneous dystonia also characterized by non motor symptoms. METHODS: We used a k-means cluster analysis to assess 188 patients with idiopathic blepharospasm in order to identify relatively homogeneous subpopulations of patients, using a set of motor and psychiatric variables to generate the cluster solution. RESULTS: Blepharospasm patients reached higher scores on scales assessing depressive- and anxiety-related disorders than healthy/disease controls. Cluster analysis suggested the existence of three groups of patients that differed by type of spasms, overall motor severity, and presence/severity of psychiatric problems. The greater severity of motor symptoms was observed in Group 1, the least severity in Group 3, while the severity of blepharospasm in Group 2 was between that observed in Groups 1 and 3. The three motor subtypes also differed by psychiatric features: the lowest severity of psychiatric symptoms was observed in the group with least severe motor symptoms (group 3), while the highest psychiatric severity scores were observed in group 2 that carried intermediate motor severity rather than in the group with more severe motor symptoms (group 1). The three groups did not differ by disease duration, age of onset, sex or other clinical features. CONCLUSIONS: The present study suggests that blepharospasm patients may be classified in different subtypes according to the type of spasms, overall motor severity and presence/severity of depressive symptoms and anxiety.

Measurement Properties of Clinical Scales Rating the Severity of Blepharospasm: A Multicenter Observational Study.

Background: Several scales have been proposed to clinically evaluate the Motor Severity of Blepharospasm (BSP) but information about their measurement properties as a multicenter instrument is limited. Objective: To compare the measurement properties of four clinical scales in rating the severity of BSP in a large sample of patients from multiple sites. Methods: The Burke-Fahn-Marsden Scale (BFMS), the Global Dystonia Severity Rating Scale (GDRS), the Jankovic Rating Scale (JRS), and the Blepharospasm Severity Rating Scale (BSRS) were administered to 211 patients across 10 sites who were also requested to self-complete the Blepharospasm Disability Index (BDI). Measurement properties to be assessed included inter-/intra-observer agreement, item-to-total correlation, internal consistency, floor and ceiling effect, convergent/discriminant validity, and adherence to the distribution of BDI. Results: The BFMS had unsatisfactory measurement properties, the GDRS had acceptable reliability but other properties could not be completely testable; the JRS had satisfactory measurement properties but the scale did not accurately reflect the distribution of disability parameter (BDI) in the sample, and the BSRS had satisfactory measurement properties and also showed the best adherence to the distribution of BDI in the assessed sample. Conclusion: The comparison of the measurement properties of four rating scales to assess the motor state of the BSP in a large sample of patients from multiple sites showed that the GDRS should be used to simultaneously assess BSP and dystonia in other body parts, while the JRS (easier to use) and BSRS (better to discriminate severity) should be used to assess BSP alone.

Clinical and Structural Findings in Patients With Lesion-Induced Dystonia: Descriptive and Quantitative Analysis of Published Cases.

BACKGROUND AND OBJECTIVES: Brain lesions are a well-recognized etiology of dystonia. These cases are especially valuable because they offer causal insight into the neuroanatomical substrates of dystonia. To date, knowledge of lesion-induced dystonia comes mainly from isolated case reports or small case series, restricting broader description and analysis. METHODS: Cases of lesion-induced dystonia were first identified from a systematic review of published literature. Latent class analysis then investigated whether patients could be classified into subgroups based on lesion location and body regions affected by dystonia. Regression analyses subsequently investigated whether subgroup membership predicted clinical characteristics of dystonia. RESULTS: Three hundred fifty-nine published cases were included. Lesions causing dystonia occurred in heterogeneous locations, most commonly in the basal ganglia (46.2%), followed by the thalamus (28.1%), brainstem (22.6%), and white matter (21.2%). The most common form of lesion-induced dystonia was focal dystonia (53.2%), with the hand (49.9%) and arm (44.3%) most commonly affected. Of all cases, 86.6% reported co-occurring neurologic manifestations and 26.1% reported other movement disorders. Latent class analysis identified 3 distinct subgroups of patients: those with predominantly limb dystonias, which were associated with basal ganglia lesions; those with hand dystonia, associated with thalamic lesions; and those with predominantly cervical dystonia, associated with brainstem and cerebellar lesions. Regression demonstrated significant differences between these subgroups on a range of dystonia symptoms, including dystonic tremor, symptom latency, other movement disorders, and dystonia variability. DISCUSSION: Although dystonia can be induced by lesions to numerous brain regions, there are distinct relationships between lesion locations and dystonic body parts. This suggests that the affected brain networks are different between types of dystonia.

The apparent paradox of phenotypic diversity and shared mechanisms across dystonia syndromes.

PURPOSE OF REVIEW: We describe here how such mechanisms shared by different genetic forms can give rise to motor performance dysfunctions with a clinical aspect of dystonia. RECENT FINDINGS: The continuing discoveries of genetic causes for dystonia syndromes are transforming our view of these disorders. They share unexpectedly common underlying mechanisms, including dysregulation in neurotransmitter signaling, gene transcription, and quality control machinery. The field has further expanded to include forms recently associated with endolysosomal dysfunction. SUMMARY: The discovery of biological pathways shared between different monogenic dystonias is an important conceptual advance in the understanding of the underlying mechanisms, with a significant impact on the pathophysiological understanding of clinical phenomenology. The functional relationship between dystonia genes could revolutionize current dystonia classification systems, classifying patients with different monogenic forms based on common pathways. The most promising effect of these advances is on future mechanism-based therapeutic approaches.