Increased interhemispheric resting-state functional connectivity in paroxysmal kinesigenic dyskinesia: a resting-state fMRI study

An Electroencephalography Profile of Paroxysmal Kinesigenic Dyskinesia

Paroxysmal kinesigenic dyskinesia (PKD) is associated with a disturbance of neural circuit and network activities, while its neurophysiological characteristics have not been fully elucidated. This study utilized the high-density electroencephalogram (hd-EEG) signals to detect abnormal brain activity of PKD and provide a neural biomarker for its clinical diagnosis and PKD progression monitoring. The resting hd-EEGs are recorded from two independent datasets and then source-localized for measuring the oscillatory activities and function connectivity (FC) patterns of cortical and subcortical regions. The abnormal elevation of theta oscillation in wildly brain regions represents the most remarkable physiological feature for PKD and these changes returned to healthy control level in remission patients. Another remarkable feature of PKD is the decreased high-gamma FCs in non-remission patients. Subtype analyses report that increased theta oscillations may be related to the emotional factors of PKD, while the decreased high-gamma FCs are related to the motor symptoms. Finally, the authors established connectome-based predictive modelling and successfully identified the remission state in PKD patients in dataset 1 and dataset 2. The findings establish a clinically relevant electroencephalography profile of PKD and indicate that hd-EEG can provide robust neural biomarkers to evaluate the prognosis of PKD.

The Pathogenesis of Paroxysmal Kinesigenic Dyskinesia: Current Concepts

Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by recurrent and transient episodes of involuntary movements, including dystonia, chorea, ballism, or a combination of these, which are typically triggered by sudden voluntary movement. Disturbance of the basal ganglia-thalamo-cortical circuit has long been considered the cause of involuntary movements. Impairment of the gating function of the basal ganglia can cause an aberrant output toward the thalamus, which in turn leads to excessive activation of the cerebral cortex. Structural and functional abnormalities in the basal ganglia, thalamus, and cortex and abnormal connections between these brain regions have been found in patients with PKD. Recent studies have highlighted the role of the cerebellum in PKD. Insufficient suppression from the cerebellar cortex to the deep cerebellar nuclei could lead to overexcitation of the thalamocortical pathway. Therefore, this literature review aims to provide a comprehensive overview of the current research progress to explore the neural circuits and pathogenesis of PKD and promote further understanding and outlook on the pathophysiological mechanism of movement disorders. © 2023 International Parkinson and Movement Disorder Society.

Altered brain connectivity in hyperkinetic movement disorders: A review of resting-state fMRI

BACKGROUND

Hyperkinetic movement disorders (HMD) manifest as abnormal and uncontrollable movements. Despite reported involvement of several neural circuits, exact connectivity profiles remain elusive.

OBJECTIVES

Providing a comprehensive literature review of resting-state brain connectivity alterations using resting-state fMRI (rs-fMRI). We additionally discuss alterations from the perspective of brain networks, as well as correlations between connectivity and clinical measures.

METHODS

A systematic review was performed according to PRISMA guidelines and searching PubMed until October 2022. Rs-fMRI studies addressing ataxia, chorea, dystonia, myoclonus, tics, tremor, and functional movement disorders (FMD) were included. The standardized mean difference was used to summarize findings per region in the Automated Anatomical Labeling atlas for each phenotype. Furthermore, the activation likelihood estimation meta-analytic method was used to analyze convergence of significant between-group differences per phenotype. Finally, we conducted hierarchical cluster analysis to provide additional insights into commonalities and differences across HMD phenotypes.

RESULTS

Most articles concerned tremor (51), followed by dystonia (46), tics (19), chorea (12), myoclonus (11), FMD (11), and ataxia (8). Altered resting-state connectivity was found in several brain regions: in ataxia mainly cerebellar areas; for chorea, the caudate nucleus; for dystonia, sensorimotor and basal ganglia regions; for myoclonus, the thalamus and cingulate cortex; in tics, the basal ganglia, cerebellum, insula, and frontal cortex; for tremor, the cerebello-thalamo-cortical circuit; finally, in FMD, frontal, parietal, and cerebellar regions. Both decreased and increased connectivity were found for all HMD. Significant spatial convergence was found for dystonia, FMD, myoclonus, and tremor. Correlations between clinical measures and resting-state connectivity were frequently described.

CONCLUSION

Key brain regions contributing to functional connectivity changes across HMD often overlap. Possible increases and decreases of functional connections of a specific region emphasize that HMD should be viewed as a network disorder. Despite the complex interplay of physiological and methodological factors, this review serves to gain insight in brain connectivity profiles across HMD phenotypes.

Paroxysmal dyskinesia and electrodermal volatility: The role of mindfulness, self-compassion and psychophysiological interventions

To date, there are no behavioral or psychophysiological treatment studies on paroxysmal dyskinesia (PD). PD is a group of debilitating movement disorders that present with severe episodes of dystonia, chorea, and/or ballistic like movements. This is a first case report of a 50-year-old male who received behavioral interventions (e.g., mindfulness, CBT, and biofeedback interventions) to manage his PD episodes in tandem with multidisciplinary treatments (e.g., neurology, psychiatry, etc.). The paper primarily discusses the serendipitous observation of galvanic skin response (GSR) elevations and spikes immediately before and after the onset of PD episodes. GSR volatility was noted in wave amplitude and wave morphology. Graphs are presented to illustrate GSR volatility associate with PD episodes and the reduction of GSR volatility in response to behavioral approaches. The discussion highlights the feasibility of using GSR biofeedback as an adjunct to mindfulness and CBT to manage PD as part of a multidisciplinary treatment approach. Peripherally, issues that related to misclassification of somatic symptoms and related disorders (e.g., psychogenic non-epileptic seizures) and aspects of neurocognitive disorders are discussed. The paper reviews neurological findings, MRI, neuropsychological data, and psychiatric assessment to highlight the dilemma clinician's face and clarify behavioral practices to further the management of PD.

TMEM151A Variants Cause Paroxysmal Kinesigenic Dyskinesia: A Large-Sample Study

BACKGROUND

Paroxysmal kinesigenic dyskinesia (PKD) is the most common type of paroxysmal dyskinesias. Only one-third of PKD patients are attributed to proline-rich transmembrane protein 2 (PRRT2) mutations.

OBJECTIVE

We aimed to explore the potential causative gene for PKD.

METHODS

A cohort of 196 PRRT2-negative PKD probands were enrolled for whole-exome sequencing (WES). Gene Ranking, Identification and Prediction Tool, a method of case-control analysis, was applied to identify the candidate genes. Another 325 PRRT2-negative PKD probands were subsequently screened with Sanger sequencing.

RESULTS

Transmembrane Protein 151 (TMEM151A) variants were mainly clustered in PKD patients compared with the control groups. 24 heterozygous variants were detected in 25 of 521 probands (frequency = 4.80%), including 18 missense and 6 nonsense mutations. In 29 patients with TMEM151A variants, the ratio of male to female was 2.63:1 and the mean age of onset was 12.93 ± 3.15 years. Compared with PRRT2 mutation carriers, TMEM151A-related PKD were more common in sporadic PKD patients with pure phenotype. There was no significant difference in types of attack and treatment outcome between TMEM151A-positive and PRRT2-positive groups.

CONCLUSIONS

We consolidated mutations in TMEM151A causing PKD with the aid of case-control analysis of a large-scale WES data, which broadens the genotypic spectrum of PKD. TMEM151A-related PKD were more common in sporadic cases and tended to present as pure phenotype with a late onset. Extensive functional studies are needed to enhance our understanding of the pathogenesis of TMEM151A-related PKD. © 2021 International Parkinson and Movement Disorder Society.

Cerebellum Dysfunction in Patients With PRRT2-Related Paroxysmal Dyskinesia

Background and Objectives:

The main culprit gene for paroxysmal kinesigenic dyskinesia, characterized by brief and recurrent attacks of involuntary movements, is PRRT2. The location of the primary dysfunction associated with paroxysmal dyskinesia remains a matter of debate and may vary depending on the etiology. While striatal dysfunction has often been implicated in these patients, evidence from preclinical models indicate that the cerebellum could also play a role. We aimed to investigate the role of the cerebellum in the pathogenesis of PRRT2-related dyskinesia in humans.

Methods:

We enrolled 22 consecutive right-handed patients with paroxysmal kinesigenic dyskinesia with a pathogenic variant of PRRT2, and their matched controls. Participants underwent a multi-modal neuroimaging protocol. We recorded anatomic and diffusion-weighted MRI, as well as resting-state functional MRI during which we tested the after-effects of sham and repetitive transcranial magnetic stimulation applied to the cerebellum on endogenous brain activity. We quantified: (i) the structural integrity of gray matter using voxel-based morphometry; (ii) the structural integrity of white matter using fixel-based analysis; (iii) the strength and direction of functional cerebellar connections using spectral dynamic causal modeling.

Results:

PRRT2 patients had: (i) decreased gray matter volume in the cerebellar lobule VI and in the medial prefrontal cortex; (ii) microstructural alterations of white matter in the cerebellum and along the tracts connecting the cerebellum to the striatum and the cortical motor areas; (iii) dysfunction of cerebellar motor pathways to the striatum and the cortical motor areas, as well as abnormal communication between the associative cerebellum (Crus I) and the medial prefrontal cortex. Cerebellar stimulation modulated communication within the motor and associative cerebellar networks, and tended to restore this communication to the level observed in healthy controls.

Discussion:

Patients with PRRT2-related dyskinesia have converging structural alterations of the motor cerebellum and related pathways with a dysfunction of cerebellar output towards the cerebello-thalamo-striato-cortical network. We hypothesize that abnormal cerebellar output is the primary dysfunction in patients with a PRRT2 pathogenic variant, resulting in striatal dysregulation and paroxysmal dyskinesia. More broadly, striatal dysfunction in paroxysmal dyskinesia might be secondary to aberrant cerebellar output transmitted by thalamic relays in certain disorders.

Clinical trial number:

NCT03481491 (https://ichgcp.net/clinical-trials-registry/NCT03481491)

Neural Mechanisms of Paroxysmal Kinesigenic Dyskinesia: Insights from Neuroimaging

Paroxysmal kinesigenic dyskinesia (PKD) is a rare movement disorder of the nervous system, and little is known about its pathogenesis. Currently, the diagnosis of PKD is primarily based on clinical manifestations, with little objective evidence. Neuroimaging has been used to explore the pathological changes in cerebral structure and function associated with PKD. The current review highlights recent advances in neuroimaging to provide a better understanding of the neural mechanisms and early diagnosis of this disorder. Several studies utilizing single-photon emission computed tomography (CT), positron emission tomography, and structural and functional magnetic resonance imaging have found significant localized abnormalities in the caudate nucleus, putamen, pallidum, thalamus, and frontoparietal cortex in PKD patients. These studies have also revealed alterations in interhemispheric functional connectivity between the brain regions of bilateral cerebral hemispheres such as the putamen, primary motor cortex, supplementary motor area, dorsal lateral prefrontal cortex, and primary somatosensory cortex in these patients. In addition, proline-rich transmembrane protein 2 gene mutations can affect the functional organization of the brain in PKD. These results suggest that the neural mechanisms of PKD are associated with the disruption of both structural and/or functional properties in basal ganglia-thalamo-cortical circuitry and interhemispheric functional connectivity. PKD can be considered a circuitry/network disorder and is not restricted to localized structural and/or functional abnormalities. Multimodal neuroimaging combined with gene analysis can provide additional valuable information for a better understanding of the pathogenesis and early diagnosis of this disorder.

Functional Integration Between the Two Brain Hemispheres: Evidence From the Homotopic Functional Connectivity Under Resting State

Functional integration among neural units is one of the fundamental principles in brain organization that could be examined using resting-state functional connectivity (rs-FC). Interhemispheric functional integration plays a critical role in human cognition. Homotopic functional connectivity (HoFC) under resting state provide an avenue to investigate functional integration between the two brain hemispheres, which can improve the present understanding of how interhemispheric interactions affect cognitive processing. In this review, we summarize the progress of HoFC studies under resting state and highlight how these findings have enhanced our understanding of interhemispheric functional organization of the human brain. Future studies are encouraged to address particular methodological issues and to further ascertain behavioral correlates, brain disease’s modulation, task influence, and genetic basis of HoFC.

Brain structural connectome in relation to PRRT2 mutations in paroxysmal kinesigenic dyskinesia

This study explored the topological characteristics of brain white matter structural networks in patients with Paroxysmal Kinesigenic Dyskinesia (PKD), and the potential influence of the brain network stability gene PRRT2 on the structural connectome in PKD. Thirty‐five PKD patients with PRRT2 mutations (PKD‐M), 43 PKD patients without PRRT2 mutations (PKD‐N), and 40 demographically‐matched healthy control (HC) subjects underwent diffusion tensor imaging. Graph theory and network‐based statistic (NBS) approaches were performed; the topological properties of the white matter structural connectome were compared across the groups, and their relationships with the clinical variables were assessed. Both disease groups PKD‐M and PKD‐N showed lower local efficiency (implying decreased segregation ability) compared to the HC group; PKD‐M had longer characteristic path length and lower global efficiency (implying decreased integration ability) compared to PKD‐N and HC, independently of the potential effects of medication. Both PKD‐M and PKD‐N had decreased nodal characteristics in the left thalamus and left inferior frontal gyrus, the alterations being more pronounced in PKD‐M patients, who also showed abnormalities in the left fusiform and bilateral middle temporal gyrus. In the connectivity characteristics assessed by NBS, the alterations were more pronounced in the PKD‐M group versus HC than in PKD‐N versus HC. As well as the white matter alterations in the basal ganglia‐thalamo‐cortical circuit related to PKD with or without PRRT2 mutations, findings in the PKD‐M group of weaker small‐worldness and more pronounced regional disturbance show the adverse effects of PRRT2 gene mutations on brain structural connectome.

The Phenotypic and Genetic Spectrum of Paroxysmal Kinesigenic Dyskinesia in China

BACKGROUND

Paroxysmal kinesigenic dyskinesia is a spectrum of involuntary dyskinetic disorders with high clinical and genetic heterogeneity. Mutations in proline-rich transmembrane protein 2 have been identified as the major pathogenic factor.

OBJECTIVES

We analyzed 600 paroxysmal kinesigenic dyskinesia patients nationwide who were identified by the China Paroxysmal Dyskinesia Collaborative Group to summarize the clinical phenotypes and genetic features of paroxysmal kinesigenic dyskinesia in China and to provide new thoughts on diagnosis and therapy.

METHODS

The China Paroxysmal Dyskinesia Collaborative Group was composed of departments of neurology from 22 hospitals. Clinical manifestations and proline-rich transmembrane protein 2 screening results were recorded using unified paroxysmal kinesigenic dyskinesia registration forms. Genotype-phenotype correlation analyses were conducted in patients with and without proline-rich transmembrane protein 2 mutations. High-knee exercises were applied in partial patients as a new diagnostic test to induce attacks.

RESULTS

Kinesigenic triggers, male predilection, dystonic attacks, aura, complicated forms of paroxysmal kinesigenic dyskinesia, clustering in patients with family history, and dramatic responses to antiepileptic treatment were the prominent features in this multicenter study. Clinical analysis showed that proline-rich transmembrane protein 2 mutation carriers were prone to present at a younger age and have longer attack duration, bilateral limb involvement, choreic attacks, a complicated form of paroxysmal kinesigenic dyskinesia, family history, and more forms of dyskinesia. The new high-knee-exercise test efficiently induced attacks and could assist in diagnosis.

CONCLUSIONS

We propose recommendations regarding diagnostic criteria for paroxysmal kinesigenic dyskinesia based on this large clinical study of paroxysmal kinesigenic dyskinesia. The findings offered some new insights into the diagnosis and treatment of paroxysmal kinesigenic dyskinesia and might help in building standardized paroxysmal kinesigenic dyskinesia clinical evaluations and therapies. © 2020 International Parkinson and Movement Disorder Society.

The effect of chronic neuroglycopenia on resting state networks in GLUT1 syndrome across the lifespan

Glucose transporter type I deficiency syndrome (GLUT1DS) is an encephalopathic disorder due to a chronic insufficient transport of glucose into the brain. PET studies in GLUT1DS documented a widespread cortico‐thalamic hypometabolism and a signal increase in the basal ganglia, regardless of age and clinical phenotype. Herein, we captured the pattern of functional connectivity of distinct striatal, cortical, and cerebellar regions in GLUT1DS (10 children, eight adults) and in healthy controls (HC, 19 children, 17 adults) during rest. Additionally, we explored for regional connectivity differences in GLUT1 children versus adults and according to the clinical presentation. Compared to HC, GLUT1DS exhibited increase connectivity within the basal ganglia circuitries and between the striatal regions with the frontal cortex and cerebellum. The excessive connectivity was predominant in patients with movement disorders and in children compared to adults, suggesting a correlation with the clinical phenotype and age at fMRI study. Our findings highlight the primary role of the striatum in the GLUT1DS pathophysiology and confirm the dependency of symptoms to the patients' chronological age. Despite the reduced chronic glucose uptake, GLUT1DS exhibit increased connectivity changes in regions highly sensible to glycopenia. Our results may portrait the effect of neuroprotective brain strategy to overcome the chronic poor energy supply during vulnerable ages.

Aberrant Sensory Gating of the Primary Somatosensory Cortex Contributes to the Motor Circuit Dysfunction in Paroxysmal Kinesigenic Dyskinesia

Paroxysmal kinesigenic dyskinesia (PKD) is conventionally regarded as a movement disorder (MD) and characterized by episodic hyperkinesia by sudden movements. However, patients of PKD often have sensory aura and respond excellently to antiepileptic agents. PRRT2 mutations, the most common genetic etiology of PKD, could cause epilepsy syndromes as well. Standing in the twilight zone between MDs and epilepsy, the pathogenesis of PKD is unclear. Gamma oscillations arise from the inhibitory interneurons which are crucial in the thalamocortical circuits. The role of synchronized gamma oscillations in sensory gating is an important mechanism of automatic cortical inhibition. The patterns of gamma oscillations have been used to characterize neurophysiological features of many neurological diseases, including epilepsy and MDs. This study was aimed to investigate the features of gamma synchronizations in PKD. In the paired-pulse electrical-stimulation task, we recorded the magnetoencephalographic data with distributed source modeling and time-frequency analysis in 19 patients of newly-diagnosed PKD without receiving pharmacotherapy and 18 healthy controls. In combination with the magnetic resonance imaging, the source of gamma oscillations was localized in the primary somatosensory cortex. Somatosensory evoked fields of PKD patients had a reduced peak frequency (p < 0.001 for the first and the second response) and a prolonged peak latency (the first response p = 0.02, the second response p = 0.002), indicating the synchronization of gamma oscillation is significantly attenuated. The power ratio between two responses was much higher in the PKD group (p = 0.013), indicating the incompetence of activity suppression. Aberrant gamma synchronizations revealed the defective sensory gating of the somatosensory area contributes the pathogenesis of PKD. Our findings documented disinhibited cortical function is a pathomechanism common to PKD and epilepsy, thus rationalized the clinical overlaps of these two diseases and the therapeutic effect of antiepileptic agents for PKD. There is a greater reduction of the peak gamma frequency in PRRT2-related PKD than the non-PRRT PKD group (p = 0.028 for the first response, p = 0.004 for the second response). Loss-of-function PRRT2 mutations could lead to synaptic dysfunction. The disinhibiton change on neurophysiology reflected the impacts of PRRT2 mutations on human neurophysiology.

Resting state functional MRI reveals abnormal network connectivity in orthostatic tremor

Very little is known about the pathogenesis of orthostatic tremor (OT). We have observed that OT patients might have deficits in specific aspects of neuropsychological function, particularly those thought to rely on the integrity of the prefrontal cortex, which suggests a possible involvement of frontocerebellar circuits. We examined whether resting-state functional magnetic resonance imaging (fMRI) might provide further insights into the pathogenesis on OT. Resting-state fMRI data in 13 OT patients (11 women and 2 men) and 13 matched healthy controls were analyzed using independent component analysis, in combination with a "dual-regression" technique, to identify group differences in several resting-state networks (RSNs). All participants also underwent neuropsychological testing during the same session. Relative to healthy controls, OT patients showed increased connectivity in RSNs involved in cognitive processes (default mode network [DMN] and frontoparietal networks), and decreased connectivity in the cerebellum and sensorimotor networks. Changes in network integrity were associated not only with duration (DMN and medial visual network), but also with cognitive function. Moreover, in at least 2 networks (DMN and medial visual network), increased connectivity was associated with worse performance on different cognitive domains (attention, executive function, visuospatial ability, visual memory, and language). In this exploratory study, we observed selective impairments of RSNs in OT patients. This and other future resting-state fMRI studies might provide a novel method to understand the pathophysiological mechanisms of motor and nonmotor features of OT.

Frequency-Specific Local Synchronization Changes in Paroxysmal Kinesigenic Dyskinesia

The neurobiological basis of paroxysmal kinesigenic dyskinesia (PKD) is poorly defined due to the lack of reliable neuroimaging differences that can distinguish PKD with dystonia (PKD-D) from PKD with chorea (PKD-C). Consequently, diagnosis of PKD remains largely based on the clinical phenotype. Understanding the pathophysiology of PKD may facilitate discrimination between PKD-D and PKD-C, potentially contributing to more accurate diagnosis. We conducted resting-state functional magnetic resonance imaging on patients with PKD-D (n = 22), PKD-C (n = 10), and healthy controls (n = 32). Local synchronization was measured in all 3 groups via regional homogeneity (ReHo) and evaluated using receiver operator characteristic analysis to distinguish between PKD-C and PKD-D. Cortical-basal ganglia circuitry differed significantly between the 2 groups at a specific frequency. Furthermore, the PKD-D and PKD-C patients were observed to show different spontaneous brain activity in the right precuneus, right putamen, and right angular gyrus at the slow-5 frequency band (0.01-0.027 Hz). The frequency-specific abnormal local synchronization between the 2 types of PKD offers new insights into the pathophysiology of this disorder to some extent.

Altered Functional Connectivity in Essential Tremor: A Resting-State fMRI Study

Essential tremor (ET) has been associated with a spectrum of clinical features, with both motor and nonmotor elements, including cognitive deficits. We employed resting-state functional magnetic resonance imaging (fMRI) to assess whether brain networks that might be involved in the pathogenesis of nonmotor manifestations associated with ET are altered, and the relationship between abnormal connectivity and ET severity and neuropsychological function.Resting-state fMRI data in 23 ET patients (12 women and 11 men) and 22 healthy controls (HC) (12 women and 10 men) were analyzed using independent component analysis, in combination with a "dual-regression" technique, to identify the group differences of resting-state networks (RSNs) (default mode network [DMN] and executive, frontoparietal, sensorimotor, cerebellar, auditory/language, and visual networks). All participants underwent a neuropsychological and neuroimaging session, where resting-state data were collected.Relative to HC, ET patients showed increased connectivity in RSNs involved in cognitive processes (DMN and frontoparietal networks) and decreased connectivity in the cerebellum and visual networks. Changes in network integrity were associated not only with ET severity (DMN) and ET duration (DMN and left frontoparietal network), but also with cognitive ability. Moreover, in at least 3 networks (DMN and frontoparietal networks), increased connectivity was associated with worse performance on different cognitive domains (attention, executive function, visuospatial ability, verbal memory, visual memory, and language) and depressive symptoms. Further, in the visual network, decreased connectivity was associated with worse performance on visuospatial ability.ET was associated with abnormal brain connectivity in major RSNs that might be involved in both motor and nonmotor symptoms. Our findings underscore the importance of examining RSNs in this population as a biomarker of disease.

Cortical Activation During Levitation and Tentacular Movements of Corticobasal Syndrome

Levitation and tentacular movements (LTM) are considered specific, yet rare (30%), features of Corticobasal Syndrome (CBS), and are erroneously classified as alien hand. Our study focuses on these typical involuntary movements and aims to highlight possible neural correlates.LTM were recognizable during functional magnetic resonance imaging (fMRI) in 4 of 19 CBS patients. FMRI activity was evaluated with an activation recognition program for movements, during LTM, consisting of levitaton and finger writhing, and compared with the absence of movement (rest) and voluntary movements (VM), similar to LTM, of affected and unaffected arm-hand. FMRI acquisition blocks were balanced in order to match LTM blocks with rest and VM conditions. In 1 of the 4 patients, fMRI was acquired only during LTM and with a different equipment.Despite variable intensity and range of involuntary movements, evidenced by videos, fMRI showed, during LTM, a significant (P<0.05-0.001) activation only of the contralateral primary motor cortex (M1). Voluntary movements of the affected and unaffected arm elicited the known network including frontal, supplementary, sensory-motor cortex, and cerebellum. Willed movements of the LTM-affected arm induced higher and wider activation of contralateral M1 compared with the unaffected arm.The isolated activation of M1 suggests that LTM is a cortical disinhibition symptom, not involving a network. Higher activation of M1 during VM confirms that M1 excitability changes occur in CBS. Our study calls, finally, attention to the necessity to separate LTM from other alien hand phenomena.