Objective. This study aims to investigate alterations of brain connectivity using multivariate electroencephalographic data to provide new insights of the brain connectivity dynamics of dystonia. Approach. We recorded electroencephalography (EEG) of patients with right upper limb idiopathic focal dystonia and paired controls during resting state, writing-from-memory, and finger-tapping tasks. We applied power spectrum analyses considering the mu, beta and gamma rhythms of the motor cortex and analyzed brain connectivity networks and microstates (MS). Main results. The power spectra results showed that patients had a loss of desynchronization of the beta rhythm during the writing task. We observed differences in the structure of the connective core in beta rhythm, as well as, in the intensity of the patient’s hubs observed with basis in path length measures in mu and beta rhythms. Abnormalities were also identified in MS of default mode networks of patients associated with its performances during motor tasks. Significance. The EEG connectivity analyses provided interesting insights about the cortical electrophysiological patterns in dystonia, such as loss of event-related desynchronization, changes in the effective connectivity with similar signature to other neurological diseases, indications of alterations in the default-mode-network. Our findings are consistent with previously described connectivity abnormalities in neuroimaging studies confirming that dystonia is a network disorder.
Background: Noninvasive stimulation has been widely used in the past 30 years to study and treat a large number of neurological diseases, including movement disorders. Objective: In this critical review, we illustrate the rationale for use of these techniques in movement disorders and summarize the best medical evidence based on the main clinical trials performed to date. Methods: A nationally representative group of experts performed a comprehensive review of the literature in order to analyze the key clinical decision-making factors driving transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) in movement disorders. Classes of evidence and recommendations were described for each disease. Results: Despite unavoidable heterogeneities and low effect size, TMS is likely to be effective for treating motor symptoms and depression in Parkinson’s disease (PD). The efficacy in other movement disorders is unclear. TMS is possibly effective for focal hand dystonia, essential tremor and cerebellar ataxia. Additionally, it is likely to be ineffective in reducing tics in Tourette syndrome. Lastly, tDCS is likely to be effective in improving gait in PD. Conclusions: There is encouraging evidence for the use of noninvasive stimulation on a subset of symptoms in selected movement disorders, although the means to optimize protocols for improving positive outcomes in routine clinical practice remain undetermined. Similarly, the best stimulation paradigms and responder profile need to be investigated in large clinical trials with established therapeutic and assessment paradigms that could also allow genuine long-term benefits to be determined.
Significance: Dystonia is a dynamic and complex disorder. Real-time analysis of brain activity during motor tasks may increase our knowledge on its pathophysiology. Functional near-infrared spectroscopy (fNIRS) is a noninvasive method that enables the measurement of cortical hemodynamic activity in unconstrained environments. Aim: We aimed to explore the feasibility of using fNIRS for the study of task-related brain activity in dystonia. Task-related functional magnetic resonance imaging (fMRI) and restingstate functional connectivity were also analyzed. Approach: Patients with idiopathic right-upper limb dystonia and controls were assessed through nonsimultaneous fMRI and fNIRS during a finger-tapping task. Seed-based connectivity analysis of resting-state fMRI was performed in both groups. Results: The fMRI results suggest nonspecific activation of the cerebellum and occipital lobe in dystonia patients during the finger-tapping task with the affected hand. Moreover, fNIRS data show lower activation in terms of oxyhemoglobin and total hemoglobin in the frontal, ipsilateral cortex, and somatosensory areas during this task. In dystonia, both fMRI and fNIRS data resulted in hypoactivation of the frontal cortex during finger tapping with both hands simultaneously. Resting-state functional connectivity analysis suggests that the cerebellar somatomotor network in dystonia has an increased correlation with the medial prefrontal cortex and the paracingulate gyrus. Conclusions: These data suggest that unbalanced activation of the cerebellum, somatosensory, and frontal cortical areas are associated with dystonia. To our knowledge, this is the first study using fNIRS to explore the pathophysiology of dystonia. We show that fNIRS and fMRI are complementary methods and highlight the potential of fNIRS for the study of dystonia and other movement disorders as it can overcome movement restrictions, enabling experiments in more naturalistic conditions.
Background Functional imaging studies have associated dystonia with abnormal activation in motor and sensory brain regions. Commonly used techniques such as functional magnetic resonance imaging impose physical constraints, limiting the experimental paradigms. Functional near-infrared spectroscopy (fNIRS) offers a new noninvasive possibility for investigating cortical areas and the neural correlates of complex motor behaviors in unconstrained settings. Methods We compared the cortical brain activation of patients with focal upper-limb dystonia and controls during the writing task under naturalistic conditions using fNIRS. The primary motor cortex (M1), the primary somatosensory cortex (S1), and the supplementary motor area were chosen as regions of interest (ROIs) to assess differences in changes in both oxyhemoglobin (oxy-Hb) and deoxyhemoglobin (deoxy-Hb) between groups. Results Group average activation maps revealed an expected pattern of contralateral recruitment of motor and somatosensory cortices in the control group and a more bilateral pattern of activation in the dystonia group. Between-group comparisons focused on specific ROIs revealed an increased activation of the contralateral M1 and S1 cortices and also of the ipsilateral M1 cortex in patients. Conclusions Overactivity of contralateral M1 and S1 in dystonia suggest a reduced specificity of the task-related cortical areas, whereas ipsilateral activation possibly indicates a primary disorder of the motor cortex or an endophenotypic pattern. To our knowledge, this is the first study using fNIRS to assess cortical activity in dystonia during the writing task under natural settings, outlining the potential of this technique for monitoring sensory and motor retraining in dystonia rehabilitation.
Introduction: The striatum is an essential hub in the motor system associated with dystonia and other movement disorders. The function of the striosomes and matrix in motor control is not clear. A recently developed method using diffusion tensor imaging (DTI) enables us to distinguish compartments of the striatum, namely matrixes-like and striosomes-like voxels. Objectives: To access striatal matrix and striosome compartments in patients with idiopathic upper limb dystonia using diffusion tensor imaging. Methods: We analyzed 3T magnetic resonance imaging (MRI) images from 26 patients with idiopathic upper limb dystonia aged 43.88 ± 11.32 years (standard deviation, SD; range 19–60) with a mean disease duration of 12.55 ± 10.25 years (SD; range 1–25) and healthy controls aged 39.42 ±1 1.42 years (SD; range 19–58). The striatum was parcellated by targeting cortical regions that favored striosomes and matrix-favoring areas. The bilateral striatum was assessed for changes in volume and mean fractional anisotropy value. Results: Patients show significant reductions of left Matrix-like voxels volume relative to controls (P = 0.022), with a moderate effect size (Cohen’s d = 0.640). No difference was observed in the right striatum compartments. Conclusion: By parcellating the striatum into striosome and matrix-like voxels, we showed that patients with idiopathic dystonia have a reduced volume in matrix-like voxels in agreement with anatomopathological findings of some genetic types of dystonia. Even in non-degenerative dystonias, volume differences may reflect an imbalance between matrix and striosome signaling, ultimately favoring the direct pathway.
Context: Parkinsonian syndromes are routinely identified by neurologists. However, the differential diagnosis among probable etiologies can be challenging and complex. In Fahr’s syndrome, calcifications of the basal ganglia secondary to disorders of calcium metabolism are observed. A possible clinical presentation associated with this entity is the presence of a parkinsonian syndrome. Case report: A 54-years-old female patient presented with a progressive tremor in the right upper and lower limbs associated with bradykinesia. Seizures were observed during the course of the disease. After extensive clinical workup, primary hypoparathyroidism was diagnosticated along with the recognition of a mutation in the calcium activator gene. Computed tomography and magnetic resonance imaging of the head showed bilateral coarse calcifications in thalami and basal ganglia compatible with Fahr’s syndrome. We began treatment for control of the underlying disease, as well as for symptomatic control of parkinsonism. Conclusions: Different pathologies could justify the parkinsonian syndrome observed initially in the case described. Among them: Iidiopathic Parkinson’s Disease, Multiple System Atrophy, Progressive Supranuclear Palsy. In our patient, the atypical evolution in a young woman led to the research of possible secondary treatable causes. A diagnosis of Fahr’s syndrome related to hypoparathyroidism was unveiled. The differential diagnosis of Parkinson’s Syndrome is broad and difficult. We must be aware of the possible atypical presentations due to the possibility of a secondary condition whose etiology could be effectively treated.
Background: Dystonia is known as a network disorder. There is evidence of volumetric changes in structures associated with the traditional physiopathology, such as basal nuclei. One approach to studying the neural pathways is through tractography, which can provide insights into the structural connectivity of neural networks that may be disrupted in dystonia. Objectives: To evaluate brain structural changes of motor networks and basal ganglia volume in dystonia. Methods: Twenty-six patients with right upper limb dystonia and 29 healthy controls underwent 3T magnetic resonance imaging and evaluated in terms of DTI and T1 data. The XTRACT FSL tool was utilized to examine fractional anisotropy of the bilateral anterior thalamic radiation, superior thalamic radiation, superior longitudinal fasciculus, cortical spinal tract, middle cerebellar peduncle, forceps major and forceps minor. Using T1-weithed data, volunteers were also evaluated in terms of volumetric changes in bilateral Putamen, Caudate, Pallidum and Thalamus extracted using Freesurfer 7.0 volumetric segmentation. For group comparison, we conducted an analysis of covariance controlling for sex and estimated intracranial volume. Results: For uncorrected p-values, patients with upper limb dystonia show diminished FA volume in the right corticospinal tract relative to controls (P = 0.025). Region of interest analysis of subcortical regions volume based on T1-weighted images shows that patients had diminished left caudate volume (P = 0.031) and right putamen (P = 0.041). However, using FDR multiple comparisons correction, no difference was observed between groups: right corticospinal tract (P = 0.329), left caudate volume (P = 0.16), right putamen volume (P = 0.16). Conclusion: Our study could not replicate previous findings describing structural changes in dystonia. This could be to methodological differences, as well as the fact that we selected only patients with upper limb dystonia, as opposed to studies that included other types of dystonia. The neuroimaging analyses were conducted with the utmost rigor, utilizing the optimal preprocessing and statistical analysis methods. The nature and characteristics of structural alterations remain unclear and may vary depending on the subtype of dystonia. Therefore, additional structural studies and meta-analyses are warranted to advance our knowledge of this network disorder.
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