Identifying motor functional neurological disorder using resting-state functional connectivity

Reduced microstructural white matter integrity is associated with the severity of physical symptoms in functional neurological disorder

BACKGROUND

Functional neurological disorder (FND) is linked to functional changes in brain networks without an underlying brain lesion. However, the dichotomy between functional and structural changes has been challenged by research suggesting that not only functional but also anatomical alterations in the gray and white matter may underlie a subset of symptoms. This study aimed to characterize white matter microstructural integrity and its association with patient-reported and clinician-rated physical symptoms' severity in a large sample of FND patients.

METHODS

Diffusion-weighted imaging data were collected from 85 FND patients with mixed symptoms and 75 healthy controls (HCs), together with illness duration, clinician-rated (S-FMDRS & CGI), and patient-reported (SF-36) symptom severity. Microstructural integrity was computed based on probabilistic tractography using the Desikan-Killiany parcellation.

RESULTS

Compared to HCs, patients with FND presented widespread reduced microstructural integrity stemming from regions such as the right lateral orbitofrontal cortex, insula, putamen, and superior temporal regions. After adjusting for depression and anxiety, these differences were no longer significant. Within-group analysis revealed that reduced microstructural integrity, particularly in the left precuneus and left superior parietal cortex, was strongly correlated with both patient-reported and clinician-evaluated severity of physical symptoms in FND patients.

CONCLUSION

Patients with FND present widespread reduced microstructural integrity in the brain, predominantly originating from temporoparietal, paralimbic and associated regions involved in emotion regulation and body awareness. These changes seem to be partly explained by comorbid mood disorders and the severity of physical symptoms, suggesting a plasticity phenomenon rather than trait biomarkers, which warrants further investigation in longitudinal study designs.

Functional Neurological Disorder and Autism Spectrum Disorder: A Complex and Potentially Significant Relationship

INTRODUCTION

Functional neurological disorder (FND) and autism spectrum disorder (ASD) are two complex neuropsychiatric conditions that have been historically classified within psychiatric domains, resulting in a lack of extensive research, insufficient clinical recognition, and persistent societal stigma. In recent years, there has been an increasing recognition among professionals and affected individuals of their possible overlap. This review explores the potential clinical and mechanistic overlap between FND and ASD, with particular attention to shared symptoms across sensory, motor, and psychiatric domains.

METHODS

We conducted a narrative analysis utilizing the PubMed, CINAHL, MEDLINE, and ScienceDirect databases from inception to June 2024. The search employed specific MeSH terms related to ASD and FND. Given the limited data availability, we included all relevant articles that explored the potential connections between FND and ASD, focusing on established findings and theoretical hypotheses areas.

RESULTS

Scientific evidence indicates that FND and ASD may co-occur more frequently than previously acknowledged and with notable overlaps in their clinical presentations and pathophysiology. Theoretical models that have been applied to FND and ASD, such as the Bayesian brain theory and the tripartite model of autism, may provide valuable insights into the intersection of these conditions. Although much of the current evidence remains speculative, it underscores the need for hypothesis-driven research to investigate these potential connections further.

CONCLUSION

ASD and FND are heterogeneous conditions that appear to co-occur in a subset of individuals, with overlapping symptomatology and possibly shared underlying mechanisms. This hypothesis-generating review emphasizes the need for further research to better understand these links, ultimately aiming to improve clinical recognition and develop targeted interventions that enhance the quality of life for affected individuals.

Machine learning classification of functional neurological disorder using structural brain MRI features

BACKGROUND

Brain imaging studies investigating grey matter in functional neurological disorder (FND) have used univariate approaches to report group-level differences compared with healthy controls (HCs). However, these findings have limited translatability because they do not differentiate patients from controls at the individual-level.

METHODS

183 participants were prospectively recruited across three groups: 61 patients with mixed FND (FND-mixed), 61 age-matched and sex-matched HCs and 61 age, sex, depression and anxiety-matched psychiatric controls (PCs). Radial basis function support vector machine classifiers with cross-validation were used to distinguish individuals with FND from HCs and PCs using 134 FreeSurfer-derived grey matter MRI features.

RESULTS

Patients with FND-mixed were differentiated from HCs with an accuracy of 0.66 (p=0.005; area under the receiving operating characteristic (AUROC)=0.74); this sample was also distinguished from PCs with an accuracy of 0.60 (p=0.038; AUROC=0.56). When focusing on the functional motor disorder subtype (FND-motor, n=46), a classifier robustly differentiated these patients from HCs (accuracy=0.72; p=0.002; AUROC=0.80). FND-motor could not be distinguished from PCs, and the functional seizures subtype (n=23) could not be classified against either control group. Important regions contributing to statistically significant multivariate classifications included the cingulate gyrus, hippocampal subfields and amygdalar nuclei. Correctly versus incorrectly classified participants did not differ across a range of tested psychometric variables.

CONCLUSIONS

These findings underscore the interconnection of brain structure and function in the pathophysiology of FND and demonstrate the feasibility of using structural MRI to classify the disorder. Out-of-sample replication and larger-scale classifier efforts incorporating psychiatric and neurological controls are needed.

Forearm bisection task suggests an alteration in body schema in patients with functional movement disorders (motor conversion disorders)

OBJECTIVES

To explore potential alterations of the Body Schema, the implicit sensorimotor representation of one's own body, in patients with Functional Movement Disorders (FMD, Motor Conversion Disorders), characterized by neurological symptoms of altered voluntary motor function that cannot be explained by typical medical conditions. This investigation is prompted by the potential dissociation from their reportedly intact sense of ownership.

METHODS

10 FMD patients and 11 healthy controls (HC) underwent the Forearm Bisection Task, aimed at assessing perceived body metrics, which consists in asking the subject, blindfolded, to repeatedly point at the perceived middle point of their dominant forearm with the index finger of their contralateral hand, and a psychometric assessment for anxiety, depression, alexithymia, and tendency to dissociation.

RESULTS

FMD patients bisected their forearm more proximally (with an increased shift towards their elbow equal to 7.5%) with respect to HC; average bisection point was positively associated with anxiety levels in the whole sample, and with the tendency to dissociation in the FMD group.

CONCLUSIONS

FMD patients perceive their forearm as shorter than HC, suggesting an alteration of their Body Schema. The Body Schema can go through short- and long-term updates in the life course, mainly related to the use of each body segment; we speculate that, despite FMD being a disorder of functional nature, characterized by variability and fluctuations in symptomatology, the lack of sense of agency over a body part might be interpreted by the nervous system as disuse and hence influence the Body Schema, as deficits of organic etiology do.

Non-invasive neuromodulation of the right temporoparietal junction using theta-burst stimulation in functional neurological disorder

Background

Disrupted sense of agency (SoA)-the sense of being the agent of one's own actions-has been demonstrated in patients with functional neurological disorder (FND), and a key area of the corresponding neuronal network is the right temporoparietal junction (rTPJ). Several functional MRI (fMRI) studies have found hypoactivation as well as hyperactivation of the rTPJ in FND. In a proof-of-concept study, we tested whether repetitive transcranial magnetic stimulation (rTMS) over the rTPJ could restore this aberrant activity.

Methods

In a randomised, crossover, single-blinded, sham-controlled study design, theta-burst stimulation (tb-rTMS) was applied over the rTPJ in 23 patients with FND and 19 healthy controls (HC), with each participant undergoing three stimulatory visits (inhibitory continuous TBS (cTBS), excitatory intermittent TBS (iTBS) and sham). During fMRI, participants played a visuomotor task artificially reducing their SoA (manipulated agency, MA), repeated after each neurostimulation. We compared brain activity and behavioural SoA as primary outcomes before and after tb-rTMS and investigated the feasibility of tb-rTMS over the rTPJ in FND as secondary outcome.

Results

At baseline, patients showed decreased accuracy in detecting reduced agency compared with controls (p<0.001), paralleled by lower brain activation in the rTPJ during MA (p=0.037, volume of interest). A region of interest analysis on the rTPJ showed no effect of the sham condition in FND or HC (p=0.917; p=0.375) but revealed a significant effect of stimulation protocol (cTBS/iTBS, p=0.037) in patients with FND, with the excitatory protocol increasing the blood-oxygen-level-dependent (BOLD) signal, whereas this effect was not found in HC. In neither group, a behavioural effect of tb-rTMS was observed.

Conclusion

Aberrant processing of agency in FND was confirmed at baseline, reflected in behavioural outcome and reduced activity in the rTPJ. Tb-rTMS over this key region elicited neuronal changes in patients, paving ways for future studies exploring TMS as neurobiologically informed intervention to restore SoA in FND. We critically discuss methodological intricacies and outline further steps in this research line.

From Software to Hardware: A Case Series of Functional Neurological Symptoms and Cerebrovascular Disease

OBJECTIVE

Neuroimaging studies have identified alterations in both brain structure and functional connectivity in patients with functional neurological disorder (FND). For many patients, FND emerges from physical precipitating events. Nevertheless, there are a limited number of case series in the literature that describe the clinical presentation and neuroimaging correlates of FND following cerebrovascular disease.

METHODS

The authors collected data from two clinics in the United Kingdom on 14 cases of acute, improving, or delayed functional neurological symptoms following cerebrovascular events.

RESULTS

Most patients had functional neurological symptoms that were localized to cerebrovascular lesions, and the lesions mapped onto regions known to be part of functional networks disrupted in FND, including the thalamus, anterior cingulate gyrus, insula, and temporoparietal junction.

CONCLUSIONS

The findings demonstrate that structural lesions can lead to FND symptoms, possibly explained through changes in relevant mechanistic functional networks.

Multivariate classification provides a neural signature of Tourette disorder

BACKGROUND

Tourette disorder (TD), hallmarks of which are motor and vocal tics, has been related to functional abnormalities in large-scale brain networks. Using a fully data driven approach in a prospective, case-control study, we tested the hypothesis that functional connectivity of these networks carries a neural signature of TD. Our aim was to investigate (i) the brain networks that distinguish adult patients with TD from controls, and (ii) the effects of antipsychotic medication on these networks.

METHODS

Using a multivariate analysis based on support vector machine (SVM), we developed a predictive model of resting state functional connectivity in 48 patients and 51 controls, and identified brain networks that were most affected by disease and pharmacological treatments. We also performed standard univariate analyses to identify differences in specific connections across groups.

RESULTS

SVM was able to identify TD with 67% accuracy (p = 0.004), based on the connectivity in widespread networks involving the striatum, fronto-parietal cortical areas and the cerebellum. Medicated and unmedicated patients were discriminated with 69% accuracy (p = 0.019), based on the connectivity among striatum, insular and cerebellar networks. Univariate approaches revealed differences in functional connectivity within the striatum in patients v. controls, and between the caudate and insular cortex in medicated v. unmedicated TD.

CONCLUSIONS

SVM was able to identify a neuronal network that distinguishes patients with TD from control, as well as medicated and unmedicated patients with TD, holding a promise to identify imaging-based biomarkers of TD for clinical use and evaluation of the effects of treatment.

Functional Neurologic Disorders, disorders to be managed by neurologists, or are neurologists wandering in a dangerous field with inadequate resources?

In recent years, some neurologists reconsidered their approach to Medically Unexplained Symptoms and proposed Functional Neurologic Disorders (FND) as a new entity, claiming that neurology could offer alternative treatment options to the psychotherapies provided in psychiatry settings. FNDs, for this purpose, should include only the disorders listed as Conversion from the Somatic Symptom and Related Disorders (SSRD) group. The present review analyzes the rationale of this position and challenges the arguments provided for its support. The review also discusses the systematization of these disorders as provided by public health systems. It outlines risks stemming from economic support and public funding uncertainty, given their negligible epidemiological dimensions resulting from the parcellation of SSRD. The review underlines the unresolved issue of Factitious Disorders, which are in the same SSRD category of the international classification but are, nonetheless, overlooked by the theoretical proponents of the FND entity. Comorbidity with other psychiatric disorders is also analyzed. We propose a model that supports the continuum between different SSRD conditions, including Factitious Disorders. The model is based on the emergence of feigned death reflex and deception from frontal lobe dysfunction. Finally, the paper summarizes the wealth of historical psychiatric and psychodynamic approaches and critical reviews. The study also puts in context the categorization and interpretation efforts provided by the most eminent researchers of the past century.

Classification of Functional Movement Disorders with Resting-State Functional Magnetic Resonance Imaging

Introduction: Functional movement disorder (FMD) is a type of functional neurological disorder characterized by abnormal movements that patients do not perceive as self-generated. Prior imaging studies show a complex pattern of altered activity, linking regions of the brain involved in emotional responses, motor control, and agency. This study aimed to better characterize these relationships by building a classifier using a support vector machine to accurately distinguish between 61 FMD patients and 59 healthy controls using features derived from resting-state functional magnetic resonance imaging. Materials and Methods: First, we selected 66 seed regions based on prior related studies, then we calculated the full correlation matrix between them before performing recursive feature elimination to winnow the feature set to the most predictive features and building the classifier. Results: We identified 29 features of interest that were highly predictive of the FMD condition, classifying patients and controls with 80% accuracy. Several key features included regions in the right sensorimotor cortex, left dorsolateral prefrontal cortex, left cerebellum, and left posterior insula. Conclusions: The features selected by the model highlight the importance of the interconnected relationship between areas associated with emotion, reward, and sensorimotor integration, potentially mediating communication between regions associated with motor function, attention, and executive function. Exploratory machine learning was able to identify this distinctive abnormal pattern, suggesting that alterations in functional linkages between these regions may be a consistent feature of the condition in many FMD patients. Clinical-Trials.gov ID: NCT00500994 Impact statement Our research presents novel results that further elucidate the pathophysiology of functional movement disorder (FMD) with a machine learning model that classifies FMD and healthy controls correctly 80% of the time. Herein, we demonstrate how known differences in resting-state functional magnetic resonance imaging connectivity in FMD patients can be leveraged to better understand the complex pattern of neural changes in these patients. Knowing that there are measurable predictable differences in brain activity in patients with FMD may help both clinicians and patients conceptualize and better understand the illness at the point of diagnosis and during treatment. Our methods demonstrate how an effective combination of machine learning and qualitative approaches to analyzing functional brain connectivity can enhance our understanding of abnormal patterns of brain activity in FMD patients.

The clinical management of functional neurological disorder: A scoping review of the literature

OBJECTIVE

To date, there have been no reviews bringing together evidence on the clinical management of functional neurological disorder (FND) and patients', caregivers', and healthcare workers' experiences. This review provides an overview of the literature focused on the clinical management of FND.

METHODS

Four databases were searched, and a consultation exercise was conducted to retrieve relevant records dated from September 2010 to September 2020. Articles documenting diagnostic methods, treatments or interventions, or the experiences and perspectives of patients and healthcare workers in the clinical management of FND were included.

RESULTS

In total, 2756 records were retrieved, with 162 included in this review. The diagnostic methods reported predominantly included positive clinical signs, v-EEG and EEG. Psychological treatments and medication were the most reported treatments. Mixed findings of the effectiveness of CBT were found. Haloperidol, physiotherapy and scripted diagnosis were found to be effective in reducing FND symptoms. Several facilitators and barriers for patients accessing treatment for FND were reported.

CONCLUSION

The literature describing the clinical management for FND has increased considerably in recent times. A wide variety of diagnostic tools and treatments and interventions were found, with more focus being placed on tests that confirm a diagnosis than 'rule-out' tests. The main treatment type found in this review was medication. This review revealed that there is a lack of high-quality evidence and reflects the need for official clinical guidelines for FND, providing healthcare workers and patients the support needed to navigate the process to diagnose and manage FND.

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.

Dissociation and its biological and clinical associations in functional neurological disorder: systematic review and meta-analysis

BACKGROUND

Studies have reported elevated rates of dissociative symptoms and comorbid dissociative disorders in functional neurological disorder (FND); however, a comprehensive review is lacking.

AIMS

To systematically review the severity of dissociative symptoms and prevalence of comorbid dissociative disorders in FND and summarise their biological and clinical associations.

METHOD

We searched Embase, PsycInfo and MEDLINE up to June 2021, combining terms for FND and dissociation. Studies were eligible if reporting dissociative symptom scores or rates of comorbid dissociative disorder in FND samples. Risk of bias was appraised using modified Newcastle-Ottawa criteria. The findings were synthesised qualitatively and dissociative symptom scores were included in a meta-analysis (PROSPERO CRD42020173263).

RESULTS

Seventy-five studies were eligible (FND n = 3940; control n = 3073), most commonly prospective case-control studies (k = 54). Dissociative disorders were frequently comorbid in FND. Psychoform dissociation was elevated in FND compared with healthy (g = 0.90, 95% CI 0.66-1.14, I² = 70%) and neurological controls (g = 0.56, 95% CI 0.19-0.92, I² = 67%). Greater psychoform dissociation was observed in FND samples with seizure symptoms versus healthy controls (g = 0.94, 95% CI 0.65-1.22, I² = 42%) and FND samples with motor symptoms (g = 0.40, 95% CI -0.18 to 1.00, I² = 54%). Somatoform dissociation was elevated in FND versus healthy controls (g = 1.80, 95% CI 1.25-2.34, I² = 75%). Dissociation in FND was associated with more severe functional symptoms, worse quality of life and brain alterations.

CONCLUSIONS

Our findings highlight the potential clinical utility of assessing patients with FND for dissociative symptomatology. However, fewer studies investigated FND samples with motor symptoms and heterogeneity between studies and risk of bias were high. Rigorous investigation of the prevalence, features and mechanistic relevance of dissociation in FND is needed.

A new science of emotion: implications for functional neurological disorder

Functional neurological disorder reflects impairments in brain networks leading to distressing motor, sensory and/or cognitive symptoms that demonstrate positive clinical signs on examination incongruent with other conditions. A central issue in historical and contemporary formulations of functional neurological disorder has been the mechanistic and aetiological role of emotions. However, the debate has mostly omitted fundamental questions about the nature of emotions in the first place. In this perspective article, we first outline a set of relevant working principles of the brain (e.g. allostasis, predictive processing, interoception and affect), followed by a focused review of the theory of constructed emotion to introduce a new understanding of what emotions are. Building on this theoretical framework, we formulate how altered emotion category construction can be an integral component of the pathophysiology of functional neurological disorder and related functional somatic symptoms. In doing so, we address several themes for the functional neurological disorder field including: (i) how energy regulation and the process of emotion category construction relate to symptom generation, including revisiting alexithymia, 'panic attack without panic', dissociation, insecure attachment and the influential role of life experiences; (ii) re-interpret select neurobiological research findings in functional neurological disorder cohorts through the lens of the theory of constructed emotion to illustrate its potential mechanistic relevance; and (iii) discuss therapeutic implications. While we continue to support that functional neurological disorder is mechanistically and aetiologically heterogenous, consideration of how the theory of constructed emotion relates to the generation and maintenance of functional neurological and functional somatic symptoms offers an integrated viewpoint that cuts across neurology, psychiatry, psychology and cognitive-affective neuroscience.

Multi-centre classification of functional neurological disorders based on resting-state functional connectivity

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Using machine learning on multi-centre data, FND patients were successfully classified with an accuracy of 72%.

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The angular- and supramarginal gyri, cingular- and insular cortex, and the hippocampus were the most discriminant regions.

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To provide diagnostic utility, future studies must include patients with similar symptoms but different diagnoses.

Background

Patients suffering from functional neurological disorder (FND) experience disabling neurological symptoms not caused by an underlying classical neurological disease (such as stroke or multiple sclerosis). The diagnosis is made based on reliable positive clinical signs, but clinicians often require additional time- and cost consuming medical tests and examinations. Resting-state functional connectivity (RS FC) showed its potential as an imaging-based adjunctive biomarker to help distinguish patients from healthy controls and could represent a “rule-in” procedure to assist in the diagnostic process. However, the use of RS FC depends on its applicability in a multi-centre setting, which is particularly susceptible to inter-scanner variability. The aim of this study was to test the robustness of a classification approach based on RS FC in a multi-centre setting.

Methods

This study aimed to distinguish 86 FND patients from 86 healthy controls acquired in four different centres using a multivariate machine learning approach based on whole-brain resting-state functional connectivity. First, previously published results were replicated in each centre individually (intra-centre cross-validation) and its robustness across inter-scanner variability was assessed by pooling all the data (pooled cross-validation). Second, we evaluated the generalizability of the method by using data from each centre once as a test set, and the data from the remaining centres as a training set (inter-centre cross-validation).

Results

FND patients were successfully distinguished from healthy controls in the replication step (accuracy of 74%) as well as in each individual additional centre (accuracies of 73%, 71% and 70%). The pooled cross validation confirmed that the classifier was robust with an accuracy of 72%. The results survived post-hoc adjustment for anxiety, depression, psychotropic medication intake, and symptom severity. The most discriminant features involved the angular- and supramarginal gyri, sensorimotor cortex, cingular- and insular cortex, and hippocampal regions. The inter-centre validation step did not exceed chance level (accuracy below 50%).

Conclusions

The results demonstrate the applicability of RS FC to correctly distinguish FND patients from healthy controls in different centres and its robustness against inter-scanner variability. In order to generalize its use across different centres and aim for clinical application, future studies should work towards optimization of acquisition parameters and include neurological and psychiatric control groups presenting with similar symptoms.

Symptom-severity-related brain connectivity alterations in functional movement disorders

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Brain connectivity alterations were found in functional movement disorders.

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Hyperconnectivity in temporoparietal junction and precuneus in functional weakness.

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Consistent brain connectivity differences with four different centrality measures.

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Motor symptom severity correlates positively with connectivity in functional weakness.

Background

Functional movement disorders, a common cause of neurological disabilities, can occur with heterogeneous motor manifestations including functional weakness. However, the underlying mechanisms related to brain function and connectivity are unknown.

Objective

To identify brain connectivity alterations related to functional weakness we assessed network centrality changes in a group of patients with heterogeneous motor manifestations using task-free functional MRI in combination with different network centrality approaches.

Methods

Task-free functional MRI was performed in 48 patients with heterogeneous motor manifestations including 28 patients showing functional weakness and 65 age- and sex-matched healthy controls. Functional connectivity differences were assessed using different network centrality approaches, i.e. global correlation, eigenvector centrality, and intrinsic connectivity. Motor symptom severity was assessed using The Simplified Functional Movement Disorders Rating Scale and correlated with network centrality.

Results

Comparing patients with and without functional weakness showed significant network centrality differences in the left temporoparietal junction and precuneus. Patients with functional weakness showed increased centrality in the same anatomical regions when comparing functional weakness with healthy controls. Moreover, in the same regions, patients with functional weakness showed a positive correlation between motor symptom severity and network centrality. This correlation was shown to be specific to functional weakness with an interaction analysis, confirming a significant difference between patients with and without functional weakness.

Conclusions

We identified the temporoparietal junction and precuneus as key regions involved in brain connectivity alterations related to functional weakness. We propose that both regions may be promising targets for phenotype-specific non-invasive brain stimulation.

Dynamic connectivity alterations in anterior cingulate cortex associated with suicide attempts in bipolar disorders with a current major depressive episode

OBJECTIVE

Considering that the physiological mechanism of the anterior cingulate cortex (ACC) in suicide brain remains elusive for bipolar disorder (BD) patients. The study aims to investigate the intrinsic relevance between ACC and suicide attempts (SA) through transient functional connectivity (FC).

METHODS

We enrolled 50 un-medicated BD patients with at least one SA, 67 none-suicide attempt patients (NSA) and 75 healthy controls (HCs). The sliding window approach was utilized to study the dynamic FC of ACC via resting-state functional MRI data. Subsequently, we probed into the temporal properties of dynamic FC and then estimated the relationship between dynamic characteristics and clinical variables using the Pearson correlation.

RESULTS

We found six distinct FC states in all populations, with one of them being more associated with SA. Compared with NSA and HCs, the suicide-related functional state showed significantly reduced dwell time in SA patients, accompanied by a significantly increased FC strength between the right ACC and the regions within the subcortical (SubC) network. In addition, the number of transitions was significantly increased in SA patients relative to other groups. All these altered indicators were significantly correlated with the suicide risk.

CONCLUSIONS

The results suggested that the dysfunction of ACC was relevant to SA from a dynamic FC perspective in BD patients. It highlights the temporal properties in dynamic FC of ACC that could be used as a putative target of suicide risk assessment for BD patients.

Consistency of inclusion criteria for functional movement disorder clinical research studies: A systematic review

BACKGROUND: Functional movement disorders (FMDs) are a common cause of disability. With an increasing research interest in FMD, including the emergence of intervention trials, it is crucial that research methodology be examined, and standardized protocols be developed. OBJECTIVE: To characterize the current inclusion criteria used to select patients for FMD research studies and review the consistency and appropriateness of these criteria. METHODS: We identified studies of potential biomarkers for FMD that were published over the last two decades and performed a qualitative analysis on the finally included studies. RESULTS: We identified 79 articles and found inconsistent inclusion criteria. The Fahn-Williams and DSM-IV criteria were the most commonly applied, but neither accounted for the majority (Fahn-Williams 46%, DSM-IV 32% of the total). The selection of the inclusion criteria depended in part on the phenotype of FMD under investigation. We also identified inclusion methodologies that were not appropriate, such as the inclusion of low-certainty diagnoses and diagnosing by excluding specific biomarkers rather than including patients based on clinical characteristics that commonly are thought to suggest FMD. CONCLUSIONS: Significant variability exists with the inclusion criteria for FMD research studies. This variability could limit reproducibility and the appropriate aggregation of data for meta-analysis. Advancing FMD rehabilitation research will need standardized inclusion criteria. We make some suggestions.

Thalamic altered spontaneous activity and connectivity in obstructive sleep apnea syndrome

BACKGROUND AND PURPOSE

Obstructive sleep apnea (OSA) syndrome is a sleep disorder characterized by excessive snoring, repetitive apneas, and nocturnal arousals, that leads to fragmented sleep and intermittent nocturnal hypoxemia. Morphometric and functional brain alterations in cortical and subcortical structures have been documented in these patients via magnetic resonance imaging (MRI), even if correlational data between the alterations in the brain and cognitive and clinical indexes are still not reported.

METHODS

We examined the impact of OSA on brain spontaneous activity by measuring the fractional amplitude of low-frequency fluctuations (fALFF) in resting-state functional MRI data of 20 drug-naïve patients with OSA syndrome and 20 healthy controls matched for age, gender, and body mass index.

RESULTS

Patients showed a pattern of significantly abnormal subcortical functional activity as compared to controls, with increased activity selectively involving the thalami, specifically their intrinsic nuclei connected to somatosensory and motor-premotor cortical regions. Using these nuclei as seed regions, the subsequent functional connectivity analysis highlighted an increase in patients' thalamocortical connectivity at rest. Additionally, the correlation between fALFF and polysomnographic data revealed a possible link between OSA severity and fALFF of regions belonging to the central autonomic network.

CONCLUSIONS

Our results suggest a hyperactivation in thalamic diurnal activity in patients with OSA syndrome, which we interpret as a possible consequence of increased thalamocortical circuitry activation during nighttime due to repeated arousals.

Neural Processes of Psychological Stress and Relaxation Predict the Future Evolution of Quality of Life in Multiple Sclerosis

Health-related quality of life (HRQoL) is an essential complementary parameter in the assessment of disease burden and treatment outcome in multiple sclerosis (MS) and can be affected by neuropsychiatric symptoms, which in turn are sensitive to psychological stress. However, until now, the impact of neurobiological stress and relaxation on HRQoL in MS has not been investigated. We thus evaluated whether the activity of neural networks triggered by mild psychological stress (elicited in an fMRI task comprising mental arithmetic with feedback) or by stress termination (i.e., relaxation) at baseline (T0) predicts HRQoL variations occurring between T0 and a follow-up visit (T1) in 28 patients using a robust regression and permutation testing. The median delay between T0 and T1 was 902 (range: 363–1,169) days. We assessed HRQoL based on the Hamburg Quality of Life Questionnaire in MS (HAQUAMS) and accounted for the impact of established HRQoL predictors and the cognitive performance of the participants. Relaxation-triggered activity of a widespread neural network predicted future variations in overall HRQoL (t = 3.68, p_{family−wise error [FWE]}-corrected = 0.008). Complementary analyses showed that relaxation-triggered activity of the same network at baseline was associated with variations in the HAQUAMS mood subscale on an α_FWE = 0.1 level (t = 3.37, p_FWE = 0.087). Finally, stress-induced activity of a prefronto-limbic network predicted future variations in the HAQUAMS lower limb mobility subscale (t = −3.62, p_FWE = 0.020). Functional neural network measures of psychological stress and relaxation contain prognostic information for future HRQoL evolution in MS independent of clinical predictors.

Brain Knows Who Is on the Same Wavelength: Resting-State Connectivity Can Predict Compatibility of a Female-Male Relationship

Prediction of the initial compatibility of heterosexual individuals based on self-reported traits and preferences has not been successful, even with significantly developed information technology. To overcome the limitations of self-reported measures and predict compatibility, we used functional connectivity profiles from resting-state functional magnetic resonance imaging (fMRI) data that carry rich individual-specific information sufficient to predict psychological constructs and activation patterns during social cognitive tasks. Several days after collecting data from resting-state fMRIs, participants undertook a speed-dating experiment in which they had a 3-min speed date with every other opposite-sex participant. Our machine learning algorithm successfully predicted whether pairs in the experiment were compatible or not using (dis)similarity of functional connectivity profiles obtained before the experiment. The similarity and dissimilarity of functional connectivity between individuals and these multivariate relationships contributed to the prediction, hence suggesting the importance of complementarity (observed as dissimilarity) as well as the similarity between an individual and a potential partner during the initial attraction phase. The result indicates that the salience network, limbic areas, and cerebellum are especially important for the feeling of compatibility. This research emphasizes the utility of neural information to predict complex phenomena in a social environment that behavioral measures alone cannot predict.

Effective connectivity between emotional and motor brain regions in people with psychogenic nonepileptic seizures (PNES)

OBJECTIVE

To characterize the effective connectivity (EC) between the emotion and motor brain regions in patients with psychogenic nonepileptic seizures (PNES), based on resting-state spectral dynamic causal modeling (spDCM).

METHODS

Twenty-three patients with PNES and twenty-five healthy control (HC) subjects underwent resting-state fMRI scanning. The coupling parameters indicating the causal interactions between eight brain regions associated with emotion, executive control, and motion were estimated for both groups, using resting-state fMRI spDCM.

RESULTS

Compared to the HC subjects, in patients with PNES: (i) the left insula (INS) and left and right inferior frontal gyri (IFG) are more inhibited by the amygdala (AMYG), anterior cingulate cortex (ACC), and precentral gyrus (PCG); (ii) the left AMYG has greater inhibitory effects on the INS, IFG, dorsolateral prefrontal cortex (DLPFC), PCG, and supplementary motor area (SMA); (iii) the left ACC has more inhibitory effects on the INS and IFG; (iv) the right ACC is more inhibited by the INS and IFG, and has a less inhibitory effect on the SMA and PCG; and (v) the left caudate (CAU) had increased inhibitory effects on the AMYG and IFG and a more excitatory effect on the SMA.

CONCLUSION

Our results suggest that in patients with PNES, the emotion-processing regions have inhibitory effects on the executive control areas and motor regions. Our findings may provide further insight into the influence of emotional arousal on functional movements and the underlying mechanisms of involuntary movements during functional seizures. Furthermore, they may suggest that emotion regulation through cognitive behavioral psychotherapies can be a potentially effective treatment modality.

Early-life trauma endophenotypes and brain circuit-gene expression relationships in functional neurological (conversion) disorder

Functional neurological (conversion) disorder (FND) is a neuropsychiatric condition whereby individuals present with sensorimotor symptoms incompatible with other neurological disorders. Early-life maltreatment (ELM) is a risk factor for developing FND, yet few studies have investigated brain network-trauma relationships in this population. In this neuroimaging-gene expression study, we used two graph theory approaches to elucidate ELM subtype effects on resting-state functional connectivity architecture in 30 patients with motor FND. Twenty-one individuals with comparable depression, anxiety, and ELM scores were used as psychiatric controls. Thereafter, we compared trauma endophenotypes in FND with regional differences in transcriptional gene expression as measured by the Allen Human Brain Atlas (AHBA). In FND patients only, we found that early-life physical abuse severity, and to a lesser extent physical neglect, correlated with corticolimbic weighted-degree functional connectivity. Connectivity profiles influenced by physical abuse occurred in limbic (amygdalar-hippocampal), paralimbic (cingulo-insular and ventromedial prefrontal), and cognitive control (ventrolateral prefrontal) areas, as well as in sensorimotor and visual cortices. These findings held adjusting for individual differences in depression/anxiety, PTSD, and motor phenotypes. In FND, physical abuse also correlated with amygdala and insula coupling to motor cortices. In exploratory analyses, physical abuse correlated connectivity maps overlapped with the AHBA spatial expression of three gene clusters: (i) neuronal morphogenesis and synaptic transmission genes in limbic/paralimbic areas; (ii) locomotory behavior and neuronal generation genes in left-lateralized structures; and (iii) nervous system development and cell motility genes in right-lateralized structures. These circuit-specific architectural profiles related to individual differences in childhood physical abuse burden advance our understanding of the pathophysiology of FND.

Neuroimaging in Functional Neurological Disorder: State of the Field and Research Agenda

Functional neurological disorder (FND) was of great interest to early clinical neuroscience leaders. During the 20th century, neurology and psychiatry grew apart - leaving FND a borderland condition. Fortunately, a renaissance has occurred in the last two decades, fostered by increased recognition that FND is prevalent and diagnosed using "rule-in" examination signs. The parallel use of scientific tools to bridge brain structure - function relationships has helped refine an integrated biopsychosocial framework through which to conceptualize FND. In particular, a growing number of quality neuroimaging studies using a variety of methodologies have shed light on the emerging pathophysiology of FND. This renewed scientific interest has occurred in parallel with enhanced interdisciplinary collaborations, as illustrated by new care models combining psychological and physical therapies and the creation of a new multidisciplinary FND society supporting knowledge dissemination in the field. Within this context, this article summarizes the output of the first International FND Neuroimaging Workgroup meeting, held virtually, on June 17th, 2020 to appraise the state of neuroimaging research in the field and to catalyze large-scale collaborations. We first briefly summarize neural circuit models of FND, and then detail the research approaches used to date in FND within core content areas: cohort characterization; control group considerations; task-based functional neuroimaging; resting-state networks; structural neuroimaging; biomarkers of symptom severity and risk of illness; and predictors of treatment response and prognosis. Lastly, we outline a neuroimaging-focused research agenda to elucidate the pathophysiology of FND and aid the development of novel biologically and psychologically-informed treatments.

Brain functional connectivity in individuals with psychogenic nonepileptic seizures (PNES): An application of graph theory

OBJECTIVE

To determine brain functional connectivity (FC), based on the graph theory, in individuals with psychogenic nonepileptic seizures (PNES), in order to better understand the mechanisms underlying this disease.

METHODS

Twenty-three patients with PNES and twenty-five healthy control subjects were examined. Alterations in FC within the whole brain were examined using resting-state functional magnetic resonance imaging (MRI). We calculated measures of the nodal degree, a major feature of the graph theory, for all the cortical and subcortical regions in the brain. Pearson correlation was performed to determine the relationship between nodal degree in abnormal brain regions and patient characteristics.

RESULTS

The nodal degrees in the right caudate (CAU), left orbital part of the left inferior frontal gyrus (ORBinf), and right paracentral lobule (PCL) were significantly greater (i.e. hyper-connectivity) in individuals with PNES than in healthy control subjects. On the other hand, a lesser nodal degree (i.e. hypo-connectivity) was detected in several other brain regions including the left and right insula (INS), as well as the right putamen (PUT), and right middle occipital gyrus (MOG).

CONCLUSION

Our findings suggest that the FC of several major brain regions can be altered in individuals with PNES. Areas with hypo-connectivity may be involved in emotion processing (e.g., INS) and movement regulation (e.g., PUT), whereas areas with hyper-connectivity may play a role in the inhibition of unwanted movements and cognitive processes (e.g., CAU).

Individual differences in interoceptive accuracy and prediction error in motor functional neurological disorders: A DTI study

In motor functional neurological disorders (mFND), relationships between interoception (a construct of high theoretical relevance to its pathophysiology) and neuroanatomy have not been previously investigated. This study characterized white matter in mFND patients compared to healthy controls (HCs), and investigated associations between fiber bundle integrity and cardiac interoception. Voxel‐based analysis and tractography quantified fractional anisotropy (FA) in 38 mFND patients compared to 38 HCs. Secondary analyses compared functional seizures (FND‐seiz; n = 21) or functional movement disorders (n = 17) to HCs. Network lesion mapping identified gray matter origins of implicated fiber bundles. Within‐group mFND analyses investigated relationships between FA, heartbeat tracking accuracy and interoceptive trait prediction error (discrepancies between interoceptive accuracy and self‐reported bodily awareness). Results were corrected for multiple comparisons, and all findings were adjusted for depression and trait anxiety. mFND and HCs did not show any between‐group interoceptive accuracy or FA differences. However, the FND‐seiz subgroup compared to HCs showed decreased integrity in right‐lateralized tracts: extreme capsule/inferior fronto‐occipital fasciculus, arcuate fasciculus, inferior longitudinal fasciculus, and thalamic/striatum to occipital cortex projections. These alterations originated predominantly from the right temporoparietal junction and inferior temporal gyrus. In mFND patients, individual differences in interoceptive accuracy and interoceptive trait prediction error correlated with fiber bundle integrity originating from the insula, temporoparietal junction, putamen and thalamus among other regions. In this first study investigating brain‐interoception relationships in mFND, individual differences in interoceptive accuracy and trait prediction error mapped onto multimodal integration‐related fiber bundles. Right‐lateralized limbic and associative tract disruptions distinguished FND‐seiz from HCs.

Biomarkers in functional movement disorders: a systematic review

Functional movement disorders (FMD) are proposed to reflect a specific problem with voluntary control of movement, despite normal intent to move and an intact neural capacity for movement. In many cases, a positive diagnosis of FMD can be established on clinical grounds. However, the diagnosis remains challenging in certain scenarios, and there is a need for predictors of treatment response and long-term prognosis.In this context, we performed a systematic review of biomarkers in FMD. Eighty-six studies met our predefined criteria and were included.We found fairly reliable electroencephalography and electromyography-based diagnostic biomarkers for functional myoclonus and tremor. Promising biomarkers have also been described for functional paresis, gait and balance disorders. In contrast, there is still a lack of diagnostic biomarkers of functional dystonia and tics, where clinical diagnosis is often also more challenging. Importantly, many promising findings focus on pathophysiology and reflect group-level comparisons, but cannot differentiate on an individual basis. Some biomarkers also require access to time-consuming and resource-consuming techniques such as functional MRI.In conclusion, there are important gaps in diagnostic biomarkers in FMD in the areas of most clinical uncertainty. There is also is a lack of treatment response and prognostic biomarkers to aid in the selection of patients who would benefit from rehabilitation and other forms of treatment.

Biomarkers of Pathological Dissociation: A Systematic Review

Pathological dissociation is a severe, debilitating and transdiagnostic psychiatric symptom. This review identifies biomarkers of pathological dissociation in a transdiagnostic manner to recommend the most promising research and treatment pathways in support of the precision medicine framework. A total of 205 unique studies that met inclusion criteria were included. Studies were divided into four biomarker categories, namely neuroimaging, psychobiological, psychophysiological and genetic biomarkers. The dorsomedial and dorsolateral prefrontal cortex, bilateral superior frontal regions, (anterior) cingulate, posterior association areas and basal ganglia are identified as neurofunctional biomarkers of pathological dissociation and decreased hippocampal, basal ganglia and thalamic volumes as neurostructural biomarkers. Increased oxytocin and prolactin and decreased tumor necrosis factor alpha (TNF-α) are identified as psychobiological markers. Psychophysiological biomarkers, including blood pressure, heart rate and skin conductance, were inconclusive. For the genetic biomarker category studies related to dissociation were limited and no clear directionality of effect was found to warrant identification of a genetic biomarker. Recommendations for future research pathways and possible clinical applicability are provided.

The pathophysiology of functional movement disorders

Functional neurological disorder is characterized by neurological symptoms that cannot be explained by typical neurological diseases or other medical conditions. This review will critically discuss the literature on the pathophysiology of functional movement disorders (FMD), including functional neuroimaging studies, neurophysiological studies, studies on biomarkers and genetic studies. According to PRISMA guidelines for systematic reviews, we selected 39 studies. A complex scenario emerged, with the involvement of different areas of the brain in the pathophysiology of FMD. Our findings showed a hypoactivation of the contralateral primary motor cortex, a decreased activity in the parietal lobe, an aberrant activation of the amygdala, an increased temporo-parietal junction activity and a hyperactivation of insular regions in patients with FMD. Functional connectivity (FC) findings underlined aberrant connections between amygdala and motor areas, temporo-parietal junction and insula. We proposed amygdala hyperactivation as a possible biological marker for FMD and FC alterations between amygdala and other areas of the brain as consequent epiphenomena, accounting for the pathophysiological complexity of FMD. These conclusions might drive novel treatment hypotheses.

Microstructural Changes in Motor Functional Conversion Disorder: Multimodal Imaging Approach on a Case

BACKGROUND

Functional motor conversion disorders are characterized by neurological symptoms unrelated to brain structural lesions. The present study was conducted on a woman presenting motor symptoms causing motor dysfunction, using advanced multimodal neuroimaging techniques, electrophysiological and neuropsychological assessment.

METHODS

The patient underwent fluorodeoxyglucose-positron emission tomography-computed tomography (FDG-PET-CT) and functional magnetic resonance imaging (fMRI) with both task and resting-state paradigms and was compared with 11 healthy matched controls. To test differences in structural parameters, Bayesian comparison was performed. To test differences in functional parameters, a first- and second-level analysis was performed in task fMRI, while a seed-to-seed analysis to evaluate the connections between brain regions and identify intersubject variations was performed in resting-state fMRI.

RESULTS

FDG-PET showed two patterns of brain metabolism, involving the cortical and subcortical structures. Regarding the diffusion data, microstructural parameters were altered for U-shape fibers for the hand and feet regions. Resting-state analysis showed hypoconnectivity between the parahippocampal and superior temporal gyrus. Neurophysiological assessment showed no alterations. Finally, an initial cognitive impairment was observed, paralleled by an anxiety and mild depressive state.

CONCLUSIONS

While we confirmed no structural alterations sustaining this functional motor disorder, we report microstructural changes in sensory-motor integration for both the hand and feet regions that could functionally support clinical manifestations.

FMRI response to acute psychological stress differentiates patients with psychogenic non-epileptic seizures from healthy controls - A biochemical and neuroimaging biomarker study

We investigated psychological stress response in the brain regions involved in emotion-motor-executive control in psychogenic non-epileptic seizures (PNES). 12 PNES patients and 12 healthy controls (HCs) underwent stress task and resting state functional MRI (fMRI), mood and quality of life (QOL) assessments, and measurements of salivary cortisol, alpha-amylase, and heart rate. Group differences were assessed, and we correlated beta values from a priori selected brain regions showing stress task fMRI group differences with other stress response measures. We also used the regions showing stress task fMRI group differences as seeds for resting state functional connectivity (rs-FC) analysis. Mood and QOL were worse in PNES versus HCs. Physiological and assessment measures were similar except 'Planful Problem Solving' coping that was greater for HCs (p = .043). Perceived stress associated negatively with heart rate change (r_s = -0.74, p = .0063). There was stress fMRI hyporeactivity in left/right amygdala and left hippocampus in PNES versus HCs (corrected p < .05). PNES exhibited a positive association between alpha-amylase change and right amygdala activation (r_s = 0.71, p = .010). PNES versus HCs exhibited greater right amygdala rs-FC to left precentral and inferior/middle frontal gyri (corrected p < .05). Our findings of fMRI hyporeactivity to psychological stress, along with greater emotion-motor-executive control network rs-FC in PNES when compared to HCs suggest a dysregulation in stress response circuitry in PNES.

Corticolimbic fast-tracking: enhanced multimodal integration in functional neurological disorder

OBJECTIVE

Some individuals with functional neurological disorder (FND) exhibit motor and affective disturbances, along with limbic hyper-reactivity and enhanced motor-limbic connectivity. Given that the multimodal integration network (insula, dorsal cingulate, temporoparietal junction (TPJ)) is implicated in convergent sensorimotor, affective and interoceptive processing, we hypothesised that patients with FND would exhibit altered motor and amygdalar resting-state propagation to this network. Patient-reported symptom severity and clinical outcome were also hypothesised to map onto multimodal integration areas.

METHODS

Between-group differences in primary motor and amygdalar nuclei (laterobasal, centromedial) were examined using graph-theory stepwise functional connectivity (SFC) in 30 patients with motor FND compared with 30 healthy controls. Within-group analyses correlated functional propagation profiles with symptom severity and prospectively collected 6-month outcomes as measured by the Screening for Somatoform Symptoms Conversion Disorder subscale and Patient Health Questionnaire-15 composite score. Findings were clusterwise corrected for multiple comparisons.

RESULTS

Compared with controls, patients with FND exhibited increased SFC from motor regions to the bilateral posterior insula, TPJ, middle cingulate cortex and putamen. From the right laterobasal amygdala, the FND cohort showed enhanced connectivity to the left anterior insula, periaqueductal grey and hypothalamus among other areas. In within-group analyses, symptom severity correlated with enhanced SFC from the left anterior insula to the right anterior insula and TPJ; increased SFC from the left centromedial amygdala to the right anterior insula correlated with clinical improvement. Within-group associations held controlling for depression, anxiety and antidepressant use.

CONCLUSIONS

These neuroimaging findings suggest potential candidate neurocircuit pathways in the pathophysiology of FND.

Structural alterations in functional neurological disorder and related conditions: a software and hardware problem?

Functional neurological (conversion) disorder (FND) is a condition at the interface of neurology and psychiatry. A "software" vs. "hardware" analogy describes abnormal neurobiological mechanisms occurring in the context of intact macroscopic brain structure. While useful for explanatory and treatment models, this framework may require more nuanced considerations in the context of quantitative structural neuroimaging findings in FND. Moreover, high co-occurrence of FND and somatic symptom disorders (SSD) as defined in DSM-IV (somatization disorder, somatoform pain disorder, and undifferentiated somatoform disorder; referred to as SSD for brevity in this article) raises the possibility of a partially overlapping pathophysiology. In this systematic review, we use a transdiagnostic approach to review and appraise the structural neuroimaging literature in FND and SSD. While larger sample size studies are needed for definitive characterization, this article highlights that individuals with FND and SSD may exhibit sensorimotor, prefrontal, striatal-thalamic, paralimbic, and limbic structural alterations. The structural neuroimaging literature is contextualized within the neurobiology of stress-related neuroplasticity, gender differences, psychiatric comorbidities, and the greater spectrum of functional somatic disorders. Future directions that could accelerate the characterization of the pathophysiology of FND and DSM-5 SSD are outlined, including "disease staging" discussions to contextualize subgroups with or without structural changes. Emerging neuroimaging evidence suggests that some individuals with FND and SSD may have a "software" and "hardware" problem, although if structural alterations are present the neural mechanisms of functional disorders remain distinct from lesional neurological conditions. Furthermore, it remains unclear whether structural alterations relate to predisposing vulnerabilities or consequences of the disorder.

Neuroimaging in Functional Movement Disorders

Purpose of Review

Functional movement disorders are common and disabling causes of abnormal movement control. Here, we review the current state of the evidence on the use of neuroimaging in Functional movement disorders, particularly its role in helping to unravel the pathophysiology of this enigmatic condition.

Recent Findings

In recent years, there has been a shift in thinking about functional movement disorder, away from a focus on high-level psychological precipitants as in Freudian conversion theories, or even an implicit belief they are ‘put-on’ for secondary gain. New research has emphasised novel neurobiological models incorporating emotional processing, self-representation and agency.

Summary

Neuroimaging has provided new insights into functional movement disorders, supporting emerging neurobiological theories implicating dysfunctional emotional processing, self-image and sense of agency. Recent studies have also found subtle structural brain changes in patients with functional disorders, arguing against a strict functional/structural dichotomy.

The role of the anterior and midcingulate cortex in the neurobiology of functional neurologic disorder

Functional neurologic disorder (FND)/conversion disorder is a prevalent and disabling condition at the intersection of neurology and psychiatry. Clinicians often report feeling ill-equipped treating patients with FND, perpetuated by a historically limited understanding of neurobiologic disease mechanisms. In this review, we summarize the neuroimaging literature across the spectrum of sensorimotor FND, including functional imaging studies during rest, sensorimotor performance, and emotional-processing tasks as well as structural magnetic resonance imaging findings. Particular attention is given to studies implicating the anterior and middle cingulate cortex and related salience network structures (insula, amygdala, and periaqueductal gray) in the neurobiology of FND. Neuroimaging studies identify cingulo-insular functional alterations during rest, motor performance, and emotion processing in FND populations. The literature also supports that patients with FND exhibit heightened amygdalar and periaqueductal gray reactivity to emotionally valenced stimuli, enhanced coupling between amygdalar and motor control areas, and increased amygdalar volumes. The structural neuroimaging literature also implicates cingulo-insular areas in the pathophysiology of FND, though these findings require replication and clarification. While more research is needed to fully elucidate the pathophysiology of FND, salience network alterations appear present in some FND populations and can be contextualized using biopsychosocial models for FND.

Functional Movement Disorders and Placebo: A Brief Review of the Placebo Effect in Movement Disorders and Ethical Considerations for Placebo Therapy

Background

Functional movement disorders are common and disabling neurologic conditions. Patients with functional neurologic disorders represent a large proportion of neurology clinic referrals, and limited availability of subspecialty care creates a considerable burden for the healthcare system. These conditions are currently treated with a combination of physical therapy and cognitive behavioral therapy, with variable success.

Methods

We searched the Medline database for studies on the epidemiology and physiology of functional movement disorders, as well as those on the placebo effect in movement disorders. We reviewed and summarized the literature on these topics and explored ethical issues concerning the administration of placebos to patients with functional movement disorders.

Results

Studies of placebos, particularly in patients with movement disorders, have shown that these "inert" agents can provide demonstrable neurophysiologic benefits, even in open-label studies. Physician surveys have shown that many administer placebos for diagnostic and therapeutic purposes, although there are ethical concerns about this practice. We used a principle-based approach and reviewed ethical arguments for (justice and beneficence) and against (non-maleficence and autonomy) the use of placebos in functional movement disorders. In this context, we argue for the importance of the therapeutic alliance in preserving patient autonomy while exploring the potential benefits of placebo therapy.

Conclusions

An ethical argument is presented in support of nondeceptive clinical placebo use for the treatment of functional movement disorders. Patient and clinician attitudes regarding the use of placebos should be investigated before placebo-therapy trials are conducted.

Bridging the Great Divide: What Can Neurology Learn From Psychiatry?

Neurology and psychiatry share common historical origins and rely on similar tools to study brain disorders. Yet the practical integration of medical and scientific approaches across these clinical neurosciences remains elusive. Although much has been written about the need to incorporate emerging systems-level, cellular-molecular, and genetic-epigenetic advances into a science of mind for psychiatric disorders, less attention has been given to applying clinical neuroscience principles to conceptualize neurologic conditions with an integrated neurobio-psycho-social approach. In this perspective article, the authors briefly outline the historically interwoven and complicated relationship between neurology and psychiatry. Through a series of vignettes, the authors then illustrate how some traditional psychiatric conditions are being reconceptualized in part as disorders of neurodevelopment and awareness. They emphasize the intersection of neurology and psychiatry by highlighting conditions that cut across traditional diagnostic boundaries. The authors argue that the divide between neurology and psychiatry can be narrowed by moving from lesion-based toward circuit-based understandings of neuropsychiatric disorders, from unidirectional toward bidirectional models of brain-behavior relationships, from exclusive reliance on categorical diagnoses toward transdiagnostic dimensional perspectives, and from silo-based research and treatments toward interdisciplinary approaches. The time is ripe for neurologists and psychiatrists to implement an integrated clinical neuroscience approach to the assessment and management of brain disorders. The subspecialty of behavioral neurology & neuropsychiatry is poised to lead the next generation of clinicians to merge brain science with psychological and social-cultural factors. These efforts will catalyze translational research, revitalize training programs, and advance the development of impactful patient-centered treatments.

"Motoring in idle": The default mode and somatomotor networks are overactive in children and adolescents with functional neurological symptoms

Objective

Children and adolescents with functional neurological symptom disorder (FND) present with diverse neurological symptoms not explained by a disease process. Functional neurological symptoms have been conceptualized as somatoform dissociation, a disruption of the brain's intrinsic organization and reversion to a more primitive level of function. We used EEG to investigate neural function and functional brain organization in children/adolescents with FND.

Method

EEG was recorded in the resting eyes-open condition in 57 patients (aged 8.5-18 years) and 57 age- and sex-matched healthy controls. Using a topographical map, EEG power data were quantified for regions of interest that define the default mode network (DMN), salience network, and somatomotor network. Source localization was examined using low-resolution brain electromagnetic tomography (LORETA). The contributions of chronic pain and arousal as moderators of differences in EEG power were also examined.

Results

Children/adolescents with FND had excessive theta and delta power in electrode clusters corresponding to the DMN-both anteriorly (dorsomedial prefrontal cortex [dmFPC]) and posteriorly (posterior cingulate cortex [PCC], precuneus, and lateral parietal cortex)-and in the premotor/supplementary motor area (SMA) region. There was a trend toward increased theta and delta power in the salience network. LORETA showed activation across all three networks in all power bands and localized neural sources to the dorsal anterior cingulate cortex/dmPFC, mid cingulate cortex, PCC/precuneus, and SMA. Pain and arousal contributed to slow wave power increases in all three networks.

Conclusions

These findings suggest that children and adolescents with FND are characterized by overactivation of intrinsic resting brain networks involved in threat detection, energy regulation, and preparation for action.