Effects of TPH2 gene variation and childhood trauma on the clinical and circuit-level phenotype of functional movement disorders

Biomarkers and Rehabilitation for Functional Neurological Disorder

Functional neurological disorder, or FND, is widely misunderstood, particularly when considering recent research indicating that the illness has numerous biological markers in addition to its psychiatric disorder associations. Nonetheless, the long-held view that FND is a mental illness without a biological basis, or even a contrived (malingered) illness, remains pervasive both in current medical care and general society. This is because FND involves intermittent disability that rapidly and involuntarily alternates with improved neurological control. This has in turn caused shaming, perceived low self-efficacy, and social isolation for the patients. Until now, biomarker reviews for FND tended not to examine the features that are shared with canonical neurological disorders. This review, in contrast, examines current research on FND biomarkers, and in particular their overlap with canonical neurological disorders, along with the encouraging outcomes for numerous physical rehabilitation trials for FND. These findings support the perspective endorsed here that FND is unquestionably a neurological disorder that is also associated with many biological markers that lie outside of the central nervous system. These results suggest that FND entails multiple biological abnormalities that are widely distributed in the body. General healthcare providers would benefit their care for their patients through their improved understanding of the illness and recourses for support and treatment that are provided in this review.

Functional Movement Disorders: Updates and Clinical Overview

Functional movement disorder (FMD) is a type of functional neurological disorder that is common but often difficult to diagnose or manage. FMD can present as various phenotypes, including tremor, dystonia, myoclonus, gait disorders, and parkinsonism. Conducting a clinical examination appropriate for assessing a patient with suspected FMD is important, and various diagnostic testing maneuvers may also be helpful. Treatment involving a multidisciplinary team, either outpatient or inpatient, has been found to be most effective. Examples of such treatment protocols are also discussed in this review. While recognition and understanding of the disorder has improved over the past few decades, as well as the development of treatments, it is not uncommon for patients and physicians to continue to experience various difficulties when dealing with this disorder. In this review, I provide a practical overview of FMD and discuss how the clinical encounter itself can play a role in patients' acceptance of the diagnosis. Recent neuroimaging studies that aid in understanding the pathophysiology are also discussed.

Predictive Processing and the Pathophysiology of Functional Neurological Disorder

The contemporary neuroscience understanding of the brain as an active inference organ supports that our conscious experiences, including sensorimotor perceptions, depend on the integration of probabilistic predictions with incoming sensory input across hierarchically organized levels. As in other systems, these complex processes are prone to error under certain circumstances, which may lead to alterations in their outcomes (i.e., variations in sensations and movements). Such variations are an important aspect of functional neurological disorder, a complex disorder at the interface of brain-mind-body interactions. Thus, predictive processing frameworks offer fundamental mechanistic insights into the pathophysiology of functional neurological disorder. In recent years, many of the aspects relevant to the neurobiology of functional neurological disorder - e.g., aberrant motor and sensory processes, symptom expectation, self-agency, and illness beliefs, as well as interoception, allostasis, and emotion - have been investigated through the lens of predictive processing frameworks. Here, we provide an overview of the current state of research on predictive processing and the pathophysiology of functional neurological disorder.

The blink reflex and its modulation - Part 2: Pathophysiology and clinical utility

The blink reflex (BR) is integrated at the brainstem; however, it is modulated by inputs from various structures such as the striatum, globus pallidus, substantia nigra, and nucleus raphe magnus but also from afferent input from the peripheral nervous system. Therefore, it provides information about the pathophysiology of numerous peripheral and central nervous system disorders. The BR is a valuable tool for studying the integrity of the trigemino-facial system, the relevant brainstem nuclei, and circuits. At the same time, some neurophysiological techniques applying the BR may indicate abnormalities involving structures rostral to the brainstem that modulate or control the BR circuits. This is a state-of-the-art review of the clinical application of BR modulation; physiology is reviewed in part 1. In this review, we aim to present the role of the BR and techniques related to its modulation in understanding pathophysiological mechanisms of motor control and pain disorders, in which these techniques are diagnostically helpful. Furthermore, some BR techniques may have a predictive value or serve as a basis for follow-up evaluation. BR testing may benefit in the diagnosis of hemifacial spasm, dystonia, functional movement disorders, migraine, orofacial pain, and psychiatric disorders. Although the abnormalities in the integrity of the BR pathway itself may provide information about trigeminal or facial nerve disorders, alterations in BR excitability are found in several disease conditions. BR excitability studies are suitable for understanding the common pathophysiological mechanisms behind various clinical entities, elucidating alterations in top-down inhibitory systems, and allowing for follow-up and quantitation of many neurological syndromes.

Healthcare employment as a risk factor for functional neurological disorder: A case-control study

BACKGROUND AND PURPOSE

Female gender, younger age and stressful life events are known predisposing factors for functional neurological disorders (FNDs). Employment in a healthcare profession has also been suggested to be a predisposing factor. We set out to conduct a large-scale case-control study to estimate the rate employment in a healthcare profession among people with FND.

METHODS

We included 200 consecutive patients with a confirmed diagnosis of FND, referred to our clinic at University Hospital Bern Switzerland between October 1, 2016, and August 1, 2019. In addition, we included a control group of 200 patients with a confirmed neurological disorder, matched for age and gender, seen during the same period. The primary endpoint was to compare the prevalence of healthcare professionals between the groups. We also describe the clinical manifestations and concomitant psychiatric diagnoses in the FND cohort.

RESULTS

Female gender was predominant (70%), and the participants' mean age was 37 years. The proportion of healthcare professionals in the FND patients was 18% (33/186), which was significantly higher than in the control group, in which it was 10.6% (17/189; p = 0.019, 95% confidence interval odds ratio 1.168-4.074). Most healthcare professionals in both cohorts were nurses (21/33 among FND patients, 10/17 among controls). Among FND patients, 140 (70%) had motor symptoms and 65 (32.5%) had a concomitant psychiatric diagnosis.

CONCLUSION

This case-control study confirmed a higher rate of employment in healthcare professions in patients with FND, suggesting two potential mechanisms of FND: exposure to models/specific knowledge about neurological symptoms or stress-related professional factors. This warrants further studies on underlying mechanisms and prevention.

Polymorphism of glucocorticoid receptor gene (rs41423247) in functional seizures (psychogenic nonepileptic seizures/attacks)

OBJECTIVE

We investigated the association between the glucocorticoid receptor (GR) gene, also known as the nuclear receptor subfamily 3, group C, member 1 (NR3C1), rs41423247 polymorphism, and functional seizures (psychogenic nonepileptic seizures/attacks) in a case-control study. We hypothesized that the tested polymorphism has significant associations with functional seizures (psychogenic nonepileptic seizures/attacks) independent from comorbid depression.

METHODS

Seventy patients with functional seizures (psychogenic nonepileptic seizures/attacks), 70 with major depressive disorder (MDD), and 70 healthy controls (HCs) were studied. Their DNAs were analyzed for NR3C1 rs41423247 polymorphism.

RESULTS

Genotype and allele frequencies of rs41423247 were different between the three groups. G allele carriers were more frequent in patients with functional seizures (psychogenic nonepileptic seizures/attacks) and those with MDD compared to HCs (p = 0.0001). However no significant difference was observed with respect to allele distributions between functional seizures (psychogenic nonepileptic seizures/attacks) and MDD groups (p = 0.391). CC genotype was less often associated with functional seizures (psychogenic nonepileptic seizures/attacks) versus HC: Codominant model; p = 0.001, OR = 0.11, 95% CI = 0.05-0.24, and -2loglilkelihood = 231.7. In comparison between functional seizures (psychogenic nonepileptic seizures/attacks) group and other (MDD + HC) groups, we observed a significant association between CG genotype and functional seizures (psychogenic nonepileptic seizures/attacks) (Codominant model; p = 0.001, OR = 5.63, 95% CI = 2.60-12.40 and -2loglikelihood = 245.99).

SIGNIFICANCE

Patients with functional seizures (psychogenic nonepileptic seizures/attacks) and those with MDD were significantly more often G allele carriers in rs41423247 compared with HCs. We observed a significant association between CG genotype and functional seizures (psychogenic nonepileptic seizures/attacks). However, we could not exclude the possibility of confounding effects of depression. Future genetic studies of patients with functional seizures (psychogenic nonepileptic seizures/attacks) should include a comparison group with depression in addition to a comparison group of HCs.

Increased Frequency of Self-Reported Obsessive-Compulsive Symptoms in Patients with Functional Movement Disorders

Background

Functional movement disorders (FMD) are associated with a high prevalence of psychiatric comorbidities.

Objective

To assess the frequency of obsessive-compulsive symptoms (OCS) in FMD.

Methods

A total of 167 consecutive patients with clinically definite FMD (mean age = 44.4 years, standard deviation [SD] = 12.0, 119 females) and 145 healthy controls (mean age = 43.2 years, SD = 11.8, 103 females) completed the Obsessive-Compulsive Inventory-Revised (OCI-R), which is a widely used tool for assessing OCS. The cutoff score ≥21 is indicative of clinically significant obsessive-compulsive disorder (OCD). Motor symptom severity was assessed using the Simplified FMD Rating Scale (S-FMDRS). All subjects completed questionnaires for depression, anxiety, pain, fatigue, cognitive complaints, health-related quality of life, and childhood trauma. Personality traits were assessed using the Big Five questionnaire.

Results

FMD patients had higher mean OCI-R score and higher proportion of individuals with OCI-R ≥ 21 42%, 95% confidence interval (CI) = (30.2, 54.6) versus 16%, 95% CI = (8.2, 28.2) in controls, P < 0.001. Patients had higher scores in three domains: checking, ordering, and obsessing (P < 0.001). FMD patients with OCI-R score ≥21 had higher depression, anxiety, cognitive complaints, and lower quality of life compared to those with score <21 (P < 0.001). No correlation between OCI-R and S-FMDRS scores was found.

Conclusions

FMD patients reported higher rates of OCS compared to controls, along with higher rates of non-motor symptoms and lower quality of life. This finding may have clinical implications and raises the possibility of shared risk factors and common pathophysiological mechanisms in FMD and OCD.

Genetics of Functional Seizures; A Scoping Systematic Review

BACKGROUND

Evidence on the genetics of functional seizures is scarce, and the purpose of the current scoping systematic review is to examine the existing evidence and propose how to advance the field.

METHODS

Web of science and MEDLINE were searched, from their initiation until May 2023. The following key words were used: functional neurological disorder(s), psychogenic neurological disorder(s), functional movement disorder(s), psychogenic movement disorder(s), functional seizures(s), psychogenic seizure(s), nonepileptic seizure(s), dissociative seizure(s), or psychogenic nonepileptic seizure(s), AND, gene, genetic(s), polymorphism, genome, epigenetics, copy number variant, copy number variation(s), whole exome sequencing, or next-generation sequencing.

RESULTS

We identified three original studies. In one study, the authors observed that six (5.9%) patients with functional seizures carried pathogenic/likely pathogenic variants. In another study, the authors observed that, in functional seizures, there was a significant correlation with genes that are over-represented in adrenergic, serotonergic, oxytocin, opioid, and GABA receptor signaling pathways. In the third study, the authors observed that patients with functional seizures, as well as patients with depression, had significantly different genotypes in FKBP5 single nucleotide polymorphisms compared with controls.

CONCLUSION

Future genetic investigations of patients with functional seizures would increase our understanding of the pathophysiological and neurobiological problems underlying this common neuropsychological stress-associated condition.

Methylome changes associated with functional movement/conversion disorder: Influence of biological sex and childhood abuse exposure

Epigenetic changes, such as DNA methylation (DNAm), may represent an important mechanism implicated in the etiopathogenesis of functional movement/conversion disorder (FMD). Here, we aimed to identify methylomic variations in a case-control cohort of FMD and to uncover specific epigenetic signatures associated with female sex and childhood abuse, two key risk factors for FMD and other functional neurological disorders. Genome-wide DNAm analysis was performed from peripheral blood in 57 patients with FMD and 47 healthy controls with and without childhood abuse. Using principal component analysis, we examined the association of principal components with FMD status in abused and non-abused individuals, in the entire study sample and in female subjects only. Next, we used enrichment pathway analysis to investigate the biological significance of DNAm changes and explored differences in methylation levels of genes annotated to the top enriched biological pathways shared across comparisons. We found that FMD was associated with DNAm variation across the genome and identified a common epigenetic 'signature' enriched for biological pathways implicated in chronic stress and chronic pain. However, methylation levels of genes included in the top two shared pathways hardly overlapped, suggesting that transcriptional profiles may differ as a function of childhood abuse exposure and sex among subjects with FMD. This study is unique in providing genome-wide evidence of DNAm changes in FMD and in indicating a potential mechanism linking childhood abuse exposure and female sex to differences in FMD pathophysiology. Future studies are needed to replicate our findings in independent cohorts.

[Understanding functional neurological disorders: From biological markers to pathophysiological models]

OBJECTIVES

Functional neurological disorders have witnessed intense research activity in the fields of structural and functional neuroimaging for more than twenty years. Thus, we propose a synthesis of recent research findings and etiological hypotheses that have been proposed so far. This work should help clinicians to better understand the nature of the mechanisms involved, but also help patients to increase their knowledge about the biological features underlying their functional symptoms.

METHODS

We carried out a narrative review of international publications dealing with neuroimaging and biology of functional neurological disorders, from 1997 to 2023.

RESULTS

Several brain networks underlie functional neurological symptoms. These networks play a role in the management of cognitive resources, in attentional control, emotion regulation, in agency and in the processing of interoceptive signals. The mechanisms of the stress response are also associated with the symptoms. The biopsychosocial model helps to better understand predisposing, precipitating, and perpetuating factors involved. The functional neurological phenotype results from the interaction between: i) a specific pre-existing vulnerability resulting from biological background and epigenetic modifications, and ii) exposure to stress factors, according to the stress-diathesis model. This interaction causes emotional disturbances including hypervigilance, lack of integration of sensations and affects, and emotional dysregulation. These characteristics in turn impact the cognitive, motor and affective control processes related with the functional neurological symptoms.

CONCLUSIONS

A better knowledge of the biopsychosocial determinants of brain network dysfunctions is necessary. Understanding them would help developing targeted treatments, but is also critical for patients care.

Identification of biopsychological trait markers in functional neurological disorders

Stress is a well-known risk factor to develop a functional neurological disorder, a frequent neuropsychiatric medical condition in which patients experience a variety of disabling neurological symptoms. Only little is known about biological stress regulation, and how it interacts with predisposing biological and psychosocial risk factors. Dysregulation of the hypothalamic-pituitary-adrenal axis in patients with functional neurological disorders has been postulated, but its relationship to preceding psychological trauma and brain anatomical changes remains to be elucidated. We set out to study the hypothalamic-pituitary-adrenal axis analysing the cortisol awakening response and diurnal baseline cortisol in 86 patients with mixed functional neurological symptoms compared to 76 healthy controls. We then examined the association between cortisol regulation and the severity and duration of traumatic life events. Finally, we analysed volumetric brain alterations in brain regions particularly sensitive to psychosocial stress, acting on the assumption of the neurotoxic effect of prolonged cortisol exposure. Overall, patients had a significantly flatter cortisol awakening response (P < 0.001) and reported longer (P = 0.01) and more severe (P < 0.001) emotional neglect as compared to healthy controls. Moreover, volumes of the bilateral amygdala and hippocampus were found to be reduced in patients. Using a partial least squares correlation, we found that in patients, emotional neglect plays a role in the multivariate pattern between trauma history and hypothalamic-pituitary-adrenal axis dysfunction, while cortisol did not relate to reduced brain volumes. This suggests that psychological stress acts as a precipitating psychosocial risk factor, whereas a reduced brain volume rather represents a biological predisposing trait marker for the disorder. Contrarily, an inverse relationship between brain volume and cortisol was found in healthy controls, representing a potential neurotoxic effect of cortisol. These findings support the theory of reduced subcortical volumes representing a predisposing trait factor in functional neurological disorders, rather than a state effect of the illness. In summary, this study supports a stress-diathesis model for functional neurological disorders and showed an association between different attributes of trauma history and abnormalities in hypothalamus-pituitary-adrenal axis function. Moreover, we suggest that reduced hippocampal and amygdalar volumes represent a biological 'trait marker' for functional neurological disorder patients, which might contribute to a reduced resilience to stress.

Moving Beyond Movement: Diagnosing Functional Movement Disorder

Functional movement disorder (FMD) is a complex neuropsychiatric syndrome, encompassing abnormal movements and weakness, and is a common cause of potentially disabling neurological symptoms. It is vital to recognize that FMD is a syndrome, with nonmotor manifestations negatively affecting a patient's quality of life. This review highlights a diagnostic algorithm, where a history suggestive of FMD is combined with the presence of positive signs on examination and appropriate investigations to make the diagnosis. Positive signs indicate internal inconsistency such as variability and distractibility, and clinical findings that are incongruent with other known neurological disease. Importantly, the clinical assessment acts as the first opportunity to allow patients to understand FMD as the cause for their symptoms. Accurate and early diagnosis of FMD is necessary given that it is a treatable and potentially reversible cause of disability, with significant risk of iatrogenic harm associated with misdiagnosis.

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 borderland of multiple sclerosis and functional neurological disorder: A call for clinical research and vigilance

BACKGROUND AND PURPOSE

Functional neurological disorders (FNDs) have attracted much attention from the neurological medical community over the last decades as new developments in neurosciences have reduced stigma around these by showing brain network dysfunctions. An overlap with other neurological conditions such as multiple sclerosis (MS) is well known by clinicians but there is a lack of clinical and fundamental research in this field to better define diagnosis and therapeutic decisions, as well as a lack of deep understanding of the underlying pathophysiology.

AIM

We aimed to provide a critical commentary on the state of knowledge about the borderland between FNDs and MS.

METHODS

We based our commentary on a joint point of view between an FND specialist and an MS expert.

RESULTS

A brief review of the previous literature and relevant new studies covering the overlap between FNDs and MS is presented, along with suggestions for future research directions.

CONCLUSION

There are clear diagnostic criteria for both FNDs and MS and a strict application of these will help better diagnosis and prevent unnecessary treatment escalation in MS or absence of referral to multimodal therapy in FND. Better teaching of younger neurologists is needed as well as prospective research focusing on pathophysiology.

Cortisol and α-amylase awakening response in children and adolescents with functional neurological (conversion) disorder

OBJECTIVE

Stress system dysregulation is considered to have an important role in the aetiology of paediatric functional neurological (conversion) disorder. This study examined salivary cortisol and α-amylase awakening responses in children with functional neurological disorder to determine activation patterns of the hypothalamic-pituitary-adrenal axis and sympathetic system. A healthy cortisol awakening response involves a robust increase in cortisol within 30 minutes of awakening. Alpha-amylase awakening response is variable in children.

METHODS

Cortisol and α-amylase were measured in saliva from 32 patients with functional neurological disorder (26 girls and 6 boys, aged 11.3-16.1 years) and 31 healthy controls (23 girls and 8 boys, aged 8.6-17.7 years). Saliva samples were collected using a Salivette sampling device at two time points - upon awakening and 30 minutes after awakening.

RESULTS

Patients with functional neurological disorder showed a decrease in cortisol awakening response (-4 nmol.min/L) and controls showed an increase (107 nmol.min/L), t(55) = -.4.6, p < 0.001. Within the functional neurological disorder group, 57% showed an attenuated cortisol awakening response and 43% showed an obliterated/reversed cortisol awakening response: Cortisol awakening response was negatively correlated with adverse childhood experiences, r(58) = -0.6, p = 0.002, and subjective distress (total Depression Anxiety and Stress Scales score), r(58) = -0.4, p = 0.050. In controls, cortisol awakening response showed no correlation with adverse childhood experiences and a positive correlation with subjective distress, r(56) = 0.4, p = 0.023. Total cortisol remained similar between the functional neurological disorder and control group. No significant differences were observed between the functional neurological disorder and control group in any of the α-amylase analyses.

DISCUSSION

The results suggest dysregulation of the hypothalamic-pituitary-adrenal axis in children with functional neurological disorder. Hypothalamic-pituitary-adrenal dysregulation in children with functional neurological disorder may contribute to comorbid symptoms of fatigue, sleep disturbance and subjective loss of well-being because circadian rhythms and energy metabolism are disrupted. Hypothalamic-pituitary-adrenal dysregulation - and changes in glucocorticoid (cortisol) signalling at the molecular level - may also contribute to increased vulnerability for functional neurological disorder symptoms because of epigenetically mediated changes to neural networks implicated in functional neurological disorder.

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.

Linking gene expression patterns and brain morphometry to trauma and symptom severity in patients with functional seizures

Within stress-diathesis models, adverse life experiences (ALEs) increase the susceptibility to functional neurological symptoms through neuroplasticity effects. We aimed to characterize potential genetic influences on this relationship in 20 patients with functional seizures. Questionnaires, structural MRIs and Allen Human Brain Atlas gene expression information were used to probe the intersection of symptom severity (Somatoform Dissociation Questionnaire, SDQ-20), ALE burden, and gray matter volumes. SDQ-20 scores positively correlated with sexual trauma, emotional neglect, and threat to life experiences. Higher SDQ-20 scores related to lower bilateral insula, left orbitofrontal, right amygdala, and perigenual/posterior cingulate volumes. Higher sexual trauma burden correlated with lower right posterior insula and putamen volumes; higher emotional neglect related to lower bilateral insula/right amygdala volumes. Findings in left insula/ventral precentral gyrus (SDQ-20), right insula/putamen (sexual trauma), and right amygdala (emotional neglect) held when controlling for comorbid psychopathology. At the intersection of symptom severity and sexual trauma volumetric findings, genes overrepresented in adrenergic, serotonergic, and oxytocin receptor signaling as well as in cortical and amygdala development were spatially correlated. In conclusion, ALEs and symptom severity were associated with gray matter volumes in cingulo-insular and amygdala areas, spatially overlapping with expression patterns of genes involved in stress-related signaling and neurodevelopment.

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.

Functional neurological disorder: new subtypes and shared mechanisms

Functional neurological disorder is common in neurological practice. A new approach to the positive diagnosis of this disorder focuses on recognisable patterns of genuinely experienced symptoms and signs that show variability within the same task and between different tasks over time. Psychological stressors are common risk factors for functional neurological disorder, but are often absent. Four entities-functional seizures, functional movement disorders, persistent perceptual postural dizziness, and functional cognitive disorder-show similarities in aetiology and pathophysiology and are variants of a disorder at the interface between neurology and psychiatry. All four entities have distinctive features and can be diagnosed with the support of clinical neurophysiological studies and other biomarkers. The pathophysiology of functional neurological disorder includes overactivity of the limbic system, the development of an internal symptom model as part of a predictive coding framework, and dysfunction of brain networks that gives movement the sense of voluntariness. Evidence supports tailored multidisciplinary treatment that can involve physical and psychological therapy approaches.

Quantitative behavioral genetic and molecular genetic foundations of the approach and avoidance strategies

Two studies examined genetic and environmental influences on traits proposed by the revised Reinforcement Sensitivity Theory (rRST) of personality. Both quantitative and molecular behavioral genetic methods were applied considering the effects of COMT, DRD2, HTR1A and TPH2 single nucleotide polymorphisms (SNPs). Study one included 274 monozygotic and 154 dizygotic twins for the quantitative behavioral study; and in study two there were 431 twins for the molecular genetic study. The Reinforcement Sensitivity Questionnaire was used to assess basic personality traits defined by the rRST. Univariate biometric modeling suggested that genetic influences accounted for 34-44% of variance of Behavioral Approach System (BAS), Behavioral Inhibition System (BIS) and Fight-Fligh-Freeze System. Molecular genetic analyses proposed the significant main effect of COMT SNP on the BAS and TPH2 SNP on the BIS, and pointed out epistatic effects of COMT x DRD2 on BAS and HTR1A x TPH2 on Fight. Results demonstrated substantial heritability for all rRST constructs, as well as for differences in the molecular genetic basis of both approach-related and avoidance-related dimensions.

Toward a possible trauma subtype of functional neurological disorder: Impact on symptom severity and physical health

BACKGROUND

As a group, individuals with functional neurological disorder (FND) report an approximately 3-fold increase in adverse life experiences (ALEs) compared to healthy controls. In patients with FND, studies have identified a positive correlation between symptom severity and the magnitude of ALEs. While not all individuals with FND report ALEs, such findings raise the possibility of a trauma-subtype of FND.

OBJECTIVE

This study investigated if patients with FND, with or without probable post-traumatic stress disorder (PTSD) and/or significant childhood maltreatment, differed in their symptom severity and physical health.

MATERIALS AND METHODS

Seventy-eight patients with FND were recruited (functional seizures, n = 34; functional movement disorder, n = 56). Participants completed self-report measures of symptom severity [Somatoform Dissociation Questionniare-20 (SDQ-20), Screening for Somatoform Disorders: Conversion Disorder subscale (SOMS:CD), Patient Health Questionniare-15 (PHQ-15)], physical health [Short Form Health Survey-36 (SF36-physical health)], childhood maltreatment [Childhood Trauma Questionnaire (CTQ)], and PTSD [PTSD Checklist-5 (PCL-5)]; a psychometric battery of other common predisposing vulnerabilities was also completed. To adjust for multiple comparisons, a Bonferroni correction was applied to all univariate analyses.

RESULTS

Patients with FND and probable PTSD (n = 33) vs. those without probable PTSD (n = 43) had statistically significant increased scores on all symptom severity measures - as well as decreased physical health scores. In secondary post-hoc regression analyses, these findings remained significant adjusting for age, sex, race, college education, and: pathological dissociation; alexithymia; attachment styles; personality characteristics; resilience scores; functional seizures subtype; or moderate-to-severe childhood abuse and neglect scores; SOMS:CD and SDQ-20 findings also held adjusting for depression and anxiety scores. In a separate set of analyses, patients with FND and moderate-to-severe childhood abuse (n = 46) vs. those without moderate-to-severe childhood abuse (n = 32) showed statistically significant increased SDQ-20 and PHQ-15 scores; in post-hoc regressions, these findings held adjusting for demographic and other variables. Stratification by childhood neglect did not relate to symptom severity or physical health scores.

CONCLUSION

This study provides support for a possible trauma-subtype of FND. Future research should investigate the neurobiological and treatment relevance of a FND trauma-subtype, as well as continuing to delineate clinical characteristics and mechanisms in individuals with FND that lack a history of ALEs.

Correlation of Expression Changes between Genes Controlling 5-HT Synthesis and Genes Crh and Trh in the Midbrain Raphe Nuclei of Chronically Aggressive and Defeated Male Mice

Midbrain raphe nuclei (MRNs) contain a large number of serotonergic neurons associated with the regulation of numerous types of psychoemotional states and physiological processes. The aim of this work was to study alterations of the MRN transcriptome in mice with prolonged positive or negative fighting experience and to identify key gene networks associated with the regulation of serotonergic system functioning. Numerous genes underwent alterations of transcription in the MRNs of male mice that either manifested aggression or experienced social defeat in daily agonistic interactions. The expression of the Tph2 gene encoding the rate-limiting enzyme of the serotonin synthesis pathway correlated with the expression of many genes, 31 of which were common between aggressive and defeated mice and were downregulated in the MRNs of mice of both experimental groups. Among these common differentially expressed genes (DEGs), there were genes associated with behavior, learning, memory, and synaptic signaling. These results suggested that, in the MRNs of the mice, the transcriptome changes associated with serotonergic regulation of various processes are similar between the two groups (aggressive and defeated). In the MRNs, more DEGs correlating with Tph2 expression were found in defeated mice than in the winners, which is probably a consequence of deeper Tph2 downregulation in the losers. It was shown for the first time that, in both groups of experimental mice, the changes in the transcription of genes controlling the synthesis and transport of serotonin directly correlate with the expression of genes Crh and Trh, which control the synthesis of corticotrophin- and thyrotropin-releasing hormones. Our findings indicate that CRH and TRH locally produced in MRNs are related to serotonergic regulation of brain processes during a chronic social conflict.

Autonomic, Endocrine, and Inflammation Profiles in Functional Neurological Disorder: A Systematic Review and Meta-Analysis

OBJECTIVE

Functional neurological disorder (FND) is a core neuropsychiatric condition. To date, promising yet inconsistently identified neural circuit profiles have been observed in patients with FND, suggesting that gaps remain in our systems-level neurobiological understanding. As such, other important physiological variables, including autonomic, endocrine, and inflammation findings, need to be contextualized for a more complete mechanistic picture.

METHODS

The investigators conducted a systematic review and meta-analysis of available case-control and cohort studies of FND. PubMed, PsycINFO, and Embase databases were searched for studies from January 1, 1900, to September 1, 2020, that investigated autonomic, endocrine, and inflammation markers in patients with FND. Sixty-six of 2,056 screened records were included in the review, representing 1,699 patients; data from 20 articles were used in the meta-analysis.

RESULTS

Findings revealed that children and adolescents with FND, compared with healthy control subjects (HCs), have increased resting heart rate (HR); there is also a tendency toward reduced resting HR variability in patients with FND across the lifespan compared with HCs. In adults, peri-ictal HR differentiated patients with functional seizures from those with epileptic seizures. Other autonomic and endocrine profiles for patients with FND were heterogeneous, with several studies highlighting the importance of individual differences.

CONCLUSIONS

Inflammation research in FND remains in its early stages. Moving forward, there is a need for the use of larger sample sizes to consider the complex interplay between functional neurological symptoms and behavioral, psychological, autonomic, endocrine, inflammation, neuroimaging, and epigenetic/genetic data. More research is also needed to determine whether FND is mechanistically (and etiologically) similar or distinct across phenotypes.

A guide to functional disease for a trauma conscious generation

In part due to a greater understanding of trauma and its manifestation as disease, the field of functional neurology has seen rapid development over the past decade with the inauguration of the Functional Neurological Disorder Society. Recent developments in our understanding of functional neurology are translatable to other functional disorders and have laid the groundwork for future research opportunities that foundation trainees can contribute towards. At the very least, trainees have a responsibility to be aware of the involuntary nature of these conditions and direct patients towards appropriate help. This guide to functional neurology aims to clear the fog on this collection of poorly recognised conditions so that empathy and understanding can shine through.

What have we really learned from functional connectivity in clinical populations?

Functional connectivity (FC), or the statistical interdependence of blood-oxygen dependent level (BOLD) signals between brain regions using fMRI, has emerged as a widely used tool for probing functional abnormalities in clinical populations due to the promise of the approach across conceptual, technical, and practical levels. With an already vast and steadily accumulating neuroimaging literature on neurodevelopmental, psychiatric, and neurological diseases and disorders in which FC is a primary measure, we aim here to provide a high-level synthesis of major concepts that have arisen from FC findings in a manner that cuts across different clinical conditions and sheds light on overarching principles. We highlight that FC has allowed us to discover the ubiquity of intrinsic functional networks across virtually all brains and clarify typical patterns of neurodevelopment over the lifespan. This understanding of typical FC maturation with age has provided important benchmarks against which to evaluate divergent maturation in early life and degeneration in late life. This in turn has led to the important insight that many clinical conditions are associated with complex, distributed, network-level changes in the brain, as opposed to solely focal abnormalities. We further emphasize the important role that FC studies have played in supporting a dimensional approach to studying transdiagnostic clinical symptoms and in enhancing the multimodal characterization and prediction of the trajectory of symptom progression across conditions. We highlight the unprecedented opportunity offered by FC to probe functional abnormalities in clinical conditions where brain function could not be easily studied otherwise, such as in disorders of consciousness. Lastly, we suggest high priority areas for future research and acknowledge critical barriers associated with the use of FC methods, particularly those related to artifact removal, data denoising and feasibility in clinical contexts.

A dimensional approach to functional movement disorders: Heresy or opportunity

Functional movement disorders (FMD) are a common and disabling neuropsychiatric condition, part of the spectrum of functional neurological/conversion disorder. FMD represent one of the most enigmatic disorders in the history of medicine. However, in the twenty years after the first report of distinctive abnormal brain activity associated with functional motor symptoms, there have been tremendous advances in the pathophysiologic understanding of these disorders. FMD can be characterized as a disorder of aberrant neurocircuitry interacting with environmental and genetic factors. These developments suggest that research on FMD could be better served by an integrative, neuroscience-based approach focused on functional domains and their neurobiological substrates. This approach has been developed in 'Research Domain Criteria' (RDoC) project, which promotes a dimensional approach to psychiatric disorders. Here, we use the RDoC conceptualization to review recent neuroscience research on FMD, focusing on the domains most relevant to these disorders. We discuss how the adoption of a similar integrative framework may facilitate the identification of the mechanisms underlying FMD and could also have potential clinical applicability.

Are Functional (Psychogenic Nonepileptic) Seizures the Sole Expression of Psychological Processes?

Functional [psychogenic nonepileptic/dissociative] seizures (FND-seiz) and related functional neurological disorder subtypes were of immense interest to early founders of modern-day neurology and psychiatry. Unfortunately, the divide that occurred between the both specialties throughout the mid-twentieth century placed FND-seiz at the borderland between the two disciplines. In the process, a false Cartesian dualism emerged that labeled psychiatric conditions as impairments of the mind and neurological conditions as disturbances in structural neuroanatomy. Excitingly, modern-day neuropsychiatric perspectives now consider neurologic and psychiatric conditions as disorders of both brain and mind. In this article, we aim to integrate neurologic and psychiatric perspectives in the conceptual framing of FND-seiz. In doing so, we explore emerging relationships between symptoms, neuropsychological constructs, brain networks, and neuroendocrine/autonomic biomarkers of disease. Evidence suggests that the neuropsychological constructs of emotion processing, attention, interoception, and self-agency are important in the pathophysiology of FND-seiz. Furthermore, FND-seiz is a multi-network brain disorder, with evidence supporting roles for disturbances within and across the salience, limbic, attentional, multimodal integration, and sensorimotor networks. Risk factors, including the magnitude of previously experienced adverse life events, relate to individual differences in network architecture and neuroendocrine profiles. The time has come to use an integrated neuropsychiatric approach that embraces the closely intertwined relationship between physical health and mental health to conceptualize FND-seiz and related functional neurological disorder subtypes.

Decade of progress in motor functional neurological disorder: continuing the momentum

Functional neurological disorder (FND) is a prevalent, disabling and costly condition at the neurology-psychiatry intersection. After being marginalised in the late 20th century, there has been renewed interest in this field. In this article, we review advances that have occurred over the past decade (2011-2020) across diagnosis, mechanisms, aetiologies, treatments and stigma in patients with motor FND (mFND, that is, functional movement disorder and functional limb weakness). In each content area, we also discuss the implications of recent advances and suggest future directions that will help continue the momentum of the past decade. In diagnosis, a major advance has been the emphasis on rule-in physical signs that are specific for hyperkinetic and hypokinetic functional motor symptoms. Mechanistically, greater importance has been given to determining 'how' functional neurological symptoms develop, highlighting roles for misdirected attention, expectation and self-agency, as well as abnormal influences of emotion/threat processing brain areas on motor control circuits. Aetiologically, while roles for adverse life experiences remain of interest in mFND, there is recognition of other aetiologic contributors, and efforts are needed to investigate links between aetiological factors and mechanisms. This decade has seen the first randomised controlled trials for physiotherapy, multidisciplinary rehabilitation and psychotherapy performed in the field, with consensus recommendations for physiotherapy, occupational therapy and outcome measures also published. Across patients, clinicians, healthcare systems and society, stigma remains a major concern. While challenges persist, a patient-centred integrated clinical neuroscience approach is primed to carry forward the momentum of the past decade into the future.

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.

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.

A framework for understanding the pathophysiology of functional neurological disorder

The symptoms of functional neurological disorder (FND) are a product of its pathophysiology. The pathophysiology of FND is reflective of dysfunction within and across different brain circuits that, in turn, affects specific constructs. In this perspective article, we briefly review five constructs that are affected in FND: emotion processing (including salience), agency, attention, interoception, and predictive processing/inference. Examples of underlying neural circuits include salience, multimodal integration, and attention networks. The symptoms of each patient can be described as a combination of dysfunction in several of these networks and related processes. While we have gained a considerable understanding of FND, there is more work to be done, including determining how pathophysiological abnormalities arise as a consequence of etiologic biopsychosocial factors. To facilitate advances in this underserved and important area, we propose a pathophysiology-focused research agenda to engage government-sponsored funding agencies and foundations.