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Dystonia is conceptualized as a network disorder involving basal ganglia, thalamus, sensorimotor cortex and the cerebellum. The cerebellum has been implicated in dystonia pathophysiology, but studies testing cerebellar function in dystonia patients have provided equivocal results. This study aimed to further elucidate motor network deficits in cervical dystonia with special interest in the role of the cerebellum. To this end we investigated motor learning tasks, that differ in their dependence on cerebellar and basal ganglia functioning. In 18 cervical dystonia patients and 18 age matched healthy controls we measured implicit motor sequence learning using a 12-item serial reaction time task mostly targeting basal ganglia circuitry and motor adaptation and eyeblink conditioning as markers of cerebellar functioning. ANOVA showed that motor sequence learning was overall impaired in cervical dystonia (p = 0.01). Moreover, unlike healthy controls, patients did not show a learning effect in the first part of the experiment. Visuomotor adaptation and eyeblink conditioning were normal. In conclusion, these data lend support to the notion that motor learning deficits in cervical dystonia relate to basal ganglia-thalamo-cortical loops rather than being a result of defective cerebellar circuitry.

BACKGROUND Knowledge of characteristics in upper limb dystonia remains limited, derived primarily from small, single-site studies. OBJECTIVE The objective of this study was to characterize demographic and clinical characteristics of upper limb dystonia from the Dystonia Coalition data set, a large, international, multicenter resource. METHODS We evaluated clinical and demographic characteristics of 367 participants with upper limb dystonia from onset, comparing across subcategories of focal (with and without dystonia spread) versus nonfocal onset. RESULTS Focal onset occurred in 80%; 67% remained focal without spread. Task specificity was most frequent in this subgroup, most often writer's cramp and affecting the dominant limb (83%). Focal onset with spread was more frequent in young onset (

BACKGROUND: Sialorrhea is a troublesome symptom in a variety of neurological diseases. Recently, local injection of botulinum toxin into the salivary glands was approved for treatment of sialorrhea, and injection guidance by anatomical landmarks was suggested. OBJECTIVE: To compare the accuracy of ultrasound versus previously proposed anatomical landmarks for localizing the salivary glands. METHODS: In a cross‐sectional study in 21 adults, landmark positions (LM) of the parotid gland (PG) and the submandibular gland (SG) were identified following published recommendations. The ultrasound position (US) was defined as the position representing the maximum gland thickness. The distance between positions, gland thickness, and optimal injection depth were recorded by US. RESULTS: Gland thickness differed significantly between LM and US positions (PG, 4 vs. 17.8 mm; P

ObjectiveIsolated focal dystonia can spread to muscles beyond the initially affected body region, but risk of spread has not been evaluated in a prospective manner. Furthermore, body regions at risk for spread and the clinical factors associated with spread risk are not well characterised. We sought here to prospectively characterise risk of spread in recently diagnosed adult-onset isolated focal dystonia patients.MethodsPatients enrolled in the Dystonia Coalition with isolated dystonia affecting only the neck, upper face, hand or larynx at onset of symptoms were included. Timing of follow-up visits was based on a sliding scale depending on symptom onset and ranged from 1 to 4 years. Descriptive statistics, Kaplan-Meier survival curves and Cox proportional hazard regression models were used to assess clinical characteristics associated with dystonia spread.Results487 enrolled participants (68.3% women; mean age: 55.6±12.2 years) met our inclusion/exclusion criteria. Spread was observed in 50% of blepharospasm, 8% of cervical dystonia, 17% of hand dystonia and 16% of laryngeal dystonia cases. Most common regions for first spread were the oromandibular region (42.2%) and neck (22.4%) for blepharospasm, hand (3.5%) for cervical dystonia and neck for hand (12.8%) and laryngeal (15.8%) dystonia. Increased spread risk was associated with a positive family history (HR=2.18, p=0.012) and self-reported alcohol responsiveness (HR=2.59, p=0.009).ConclusionsInitial body region affected in isolated focal dystonia has differential risk and patterns of spread. Genetic factors likely influence the risk of spread. These findings can aid clinical prognostication and inform future investigations into potential disease-modifying treatments.

IntroductionElevated temporal discrimination thresholds (TDT) have been found in cervical dystonia (CD) and unaffected first-degree relatives, indicating autosomal dominant inheritance with reduced penetrance, serving as an endophenotype and being indicative of abnormal inhibitory processing within the brainstem-basal ganglia circuits. The blink reflex R2 recovery cycle (BRRC) is also a measure of excitability of brainstem-basal ganglia circuits, and inconsistent findings are reported in CD. The aim was to investigate TDT and BRRC in CD and evaluate its reliability as an endophenotype.Methods29 patients with isolated cervical dystonia (mean age: 56.1 ± 14.3, female n = 18) and 29 age- and gender-matched healthy controls (mean age: 56.0 ± 14.2, female n = 18) were evaluated using a TDT-paradigm, performed as previously described by testing visual, tactile and visual-tactile temporal discrimination thresholds, and the BRRC, investigated with electrical and air puff stimulation.ResultsMean visual-tactile (p = 0.001) and visual TDTs (p = 0.015) differed between CD and controls; tactile TDTs revealed no group differences (p = 0.232). No between group differences were found for BRRC using either electrical or air puff stimulation (p = 0.117). There was no correlation between the elevation of TDTs and the degree of BRRC-inhibition in CD.ConclusionOur findings support the hypothesis that the TDT is an endophenotype in CD. BRRC testing did not demonstrate disinhibition of brainstem-basal ganglia circuits in CD. In contrast to TDT, the BRRC seems not to represent an endophenotype in cervical dystonia.

BACKGROUND Several monogenic causes for isolated dystonia have been identified, but they collectively account for only a small proportion of cases. Two genome-wide association studies have reported a few potential dystonia risk loci; but conclusions have been limited by small sample sizes, partial coverage of genetic variants, or poor reproducibility. OBJECTIVE To identify robust genetic variants and loci in a large multicenter cervical dystonia cohort using a genome-wide approach. METHODS We performed a genome-wide association study using cervical dystonia samples from the Dystonia Coalition. Logistic and linear regressions, including age, sex, and population structure as covariates, were employed to assess variant- and gene-based genetic associations with disease status and age at onset. We also performed a replication study for an identified genome-wide significant signal. RESULTS After quality control, 919 cervical dystonia patients compared with 1491 controls of European ancestry were included in the analyses. We identified one genome-wide significant variant (rs2219975, chromosome 3, upstream of COL8A1, P-value 3.04 × 10-8 ). The association was not replicated in a newly genotyped sample of 473 cervical dystonia cases and 481 controls. Gene-based analysis identified DENND1A to be significantly associated with cervical dystonia (P-value 1.23 × 10-6 ). One low-frequency variant was associated with lower age-at-onset (16.4 ± 2.9 years, P-value = 3.07 × 10-8 , minor allele frequency = 0.01), located within the GABBR2 gene on chromosome 9 (rs147331823). CONCLUSION The genetic underpinnings of cervical dystonia are complex and likely consist of multiple distinct variants of small effect sizes. Larger sample sizes may be needed to provide sufficient statistical power to address the presumably multi-genic etiology of cervical dystonia. © 2021 International Parkinson and Movement Disorder Society.

The incredible capability of the brain to quickly alter performance in response to ever-changing environment is rooted in the process of adaptation. The core aspect of adaptation is to fit an existing motor program to altered conditions. Adaptation to a visuomotor rotation or an external force has been well established as tools to study the mechanisms underlying sensorimotor adaptation. In this mini-review, we summarize recent findings from the field of visuomotor adaptation. We focus on the idea that the cerebellum plays a central role in the process of visuomotor adaptation and that interactions with cortical structures, in particular, the premotor cortex and the parietal cortex, may be crucial for this process. To this end, we cover a range of methodologies used in the literature that link cerebellar functions and visuomotor adaptation; behavioral studies in cerebellar lesion patients, neuroimaging and non-invasive stimulation approaches. The mini-review is organized as follows: first, we provide evidence that sensory prediction errors (SPE) in visuomotor adaptation rely on the cerebellum based on behavioral studies in cerebellar patients. Second, we summarize structural and functional imaging studies that provide insight into spatial localization as well as visuomotor adaptation dynamics in the cerebellum. Third, we discuss premotor — cerebellar interactions and how these may underlie visuomotor adaptation. And finally, we provide evidence from transcranial direct current and magnetic stimulation studies that link cerebellar activity, beyond correlational relationships, to visuomotor adaptation .

ObjectiveTo assess the clinical manifestations and predictors of different types of tremors in individuals with different types of isolated dystonia.MethodsClinical manifestations of tremor were assessed in a multicenter, international cross-sectional, cohort study of 2,362 individuals with all types of isolated dystonia (focal, segmental, multifocal, and generalized) recruited through the Dystonia Coalition.ResultsMethodical and standardized assessments of all participants in this cohort revealed the overall prevalence of any type of tremor was 53.3%. The prevalence of dystonic tremor varied from 36.9% to 48.4%, depending on criteria used to define it. To identify the factors associated with tremors in dystonia, the data were analyzed by generalized linear modeling and cluster analyses. Generalized linear modeling indicated 2 of the strongest factors associated with tremor included body region affected by dystonia and recruitment center. Tremor was also associated with severity of dystonia and duration of dystonia, but not with sex or race. The cluster analysis distinguished 8 subgroups within the whole cohort; defined largely by body region with dystonia, and secondarily by other clinical characteristics.ConclusionThe large number of cases evaluated by an international team of movement disorder experts facilitated the dissection of several important factors that influence the apparent prevalence and phenomenology of tremor in dystonia. These results are valuable for understanding the many differences reported in prior studies, and for guiding future studies of the nosology of tremor and dystonia.

Objectives To determine the possible interactions between levodopa therapy and plasma levels of B vitamins in patients with advanced idiopathic Parkinson's disease (IPD) in the context of either oral levodopa therapy or levodopa/carbidopa intestinal gel (LCIG). Secondly, to determine the prevalence of neuropathy and its relation to plasma levels of B vitamins and homocysteine. Methods Medication doses, neurographies, and serum levels of pyridoxine, cobalamin, folate, and homocysteine of eight LCIG and 13 orally treated advanced IPD patients matched for age, Hoehn & Yahr stage, and UPRDS III were collected. This data was analyzed for correlation with daily levodopa dose (LDD). Results LICG patients had a longer disease duration and higher LDD. All LCIG patients and most orally treated patients had sensorimotor axonal polyneuropathy. Of all plasma vitamin levels, pyridoxine was decreased most and significantly lower in the LCIG group. Cobalamin and folate, however, were within the lower reference range, and homocysteine highly elevated, all without any significant difference between both groups. LDD correlated significantly with pyridoxine deficiency (p = .02) irrespective of the route of application and with hyperhomocysteinemia in the LCIG group (p = .03). At LDDs above 2,000 mg, pyridoxine deficiency was almost always detectable. Conclusions Pyridoxine deficiency and hyperhomocysteinemia are dependent on the daily levodopa/carbidopa dose, while levels of cobalamin and folate are not. The mode of application of levodopa/carbidopa has no impact on B‐vitamin levels. Neuropathy is very frequent in advanced IPD; however, it remains to be investigated further whether neuropathy is more frequent in LCIG than in orally levodopa/carbidopa‐treated advanced IPD patients.

Familial paroxysmal exercise-induced dyskinesia (PED) is a rare movement disorder that is mostly caused by mutations in the solute carrier family 2, member 1 (SLC2A1) gene and inherited in an autosomal dominant manner. Clinical, laboratory, and genetic studies were performed in three family members. The proband's symptoms were recorded in a private video. He was placed on clonazepam. The 42-year-old proband presented with a 34-year-history of "dancing fits" suggesting a psychogenic aetiology. They occurred spontaneously or were triggered by physical exercise with a frequency up to six episodes per month, duration up to 30 min and no impairment of consciousness. Cerebrospinal fluid-(CSF)-to-blood glucose ratio was slightly reduced (0.59) and electroencephalograms were unremarkable. His 63-year-old father had less severe symptoms with spontaneous recovery before age of 45. The proband and his 38-year-old only brother also reported daily absence episodes early in the morning with an onset at age three and spontaneous recovery before age 15. Genetic testing revealed a novel c.972G>A, p.S324S heterozygous variant in the SLC2A1 gene in three patients. No splicing defects at the RNA level could be demonstrated. Five milligrams per day of clonazepam allowed for excellent control of PED. PED may produce a broad range of bizarre movements mimicking psychogenic movement disorders. A positive family history suggests an organic aetiology. PED can effectively be treated with clonazepam. Clinical manifestations, autosomal dominant inheritance and CSF findings suggest a causative role of the SLC2A1 gene, although no splicing defect at the RNA level could be demonstrated for the novel variant. Additional studies such as exome sequencing are indicated.

Monitoring one’s actions is essential for goal-directed performance. In the event-related potential (ERP), errors are followed by fronto-centrally distributed negativities. These error(-related) negativity (Ne/ERN) amplitudes are often found to be attenuated in patients with Parkinson’s disease (PD) compared to healthy controls (HC). Although Ne/ERN has been proposed to be related to dopaminergic neuronal activity, previous research did not find evidence for effects of dopaminergic medication on Ne/ERN amplitudes in PD. We examined 13 PD patients “on” and “off” dopaminergic medication. Their response-locked ERP amplitudes (obtained on correct [Nc/CRN] and error [Ne/ERN] trials of a flanker task) were compared to those of 13 HC who were tested twice as well, without receiving dopaminergic medication. While PD patients committed more errors than HC, error rates were not significantly modulated by dopaminergic medication. PD patients showed reduced Ne/ERN amplitudes relative to HC; however, this attenuation of response-locked ERP amplitudes was not specific to errors in this study. PD-related attenuation of response-locked ERP amplitudes was most pronounced when PD patients were on medication. These results suggest overdosing of dopaminergic pathways that are relatively spared in PD, but that are related to the generation of the Ne/ERN, notably pathways targeted on the medial prefrontal cortex.

Cognitive inflexibility is a hallmark of executive dysfunction in Parkinson's disease (PD). This deficit consistently manifests itself in a PD-related increase in the number of perseverative errors committed on the Wisconsin Card Sorting Test (WCST). However, the neural processes underlying perseverative WCST performance in PD are still largely unknown. The present study is the first to investigate the event-related potential (ERP) correlates of cognitive inflexibility on the WCST in PD patients. Thirty-two PD patients and 35 matched control participants completed a computerized version of the WCST while the electroencephalogram (EEG) was recorded. Behavioral results revealed the expected increase in perseverative errors in patients with PD. ERP analysis focused on two established indicators of executive processes: the fronto-central P3a as an index of attentional orienting and the sustained parietal positivity (SPP) as an index of set-shifting processes. In comparison to controls, P3a amplitudes were significantly attenuated in PD patients. Regression analysis further revealed that P3a and SPP amplitudes interactively contributed to the prediction of perseverative errors in PD patients: The number of perseverative errors was only increased when both ERP amplitudes were attenuated. Notably, the two ERP markers of executive processes accounted for more than 40% of the variance in perseverative errors in PD patients. We conclude that cognitive inflexibility in PD occurs when the neural bases of multiple executive processes are affected by the pathophysiology of PD. The combined measurement of P3a and SPP might yield an electrophysiological marker of cognitive inflexibility in PD.

Objective To report a case of reversible posterior leukoencephalopathy syndrome (RPLS) after withdrawal of antipsychotic medication in a patient with acute lithium intoxication. Methods Case report. Results A patient with schizoaffective disorder was admitted with lithium intoxication, rhabdomyolysis and acute renal failure. After withdrawal of psychotropic medication, she developed a significant increase in blood pressure — though to moderately hypertensive levels — and prolonged disturbance of consciousness with profound agitation. MRI revealed RPLS. Resumption of antipsychotic treatment resulted in significant drop of blood pressure and improvement. Conclusion Acute withdrawal of antipsychotic medication may lead to rebound hypertension and development of RPLS, especially in the presence of lithium intoxication and renal dysfunction.