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

Long COVID Is Not a Functional Neurologic Disorder

Long COVID is a common sequela of SARS-CoV-2 infection. Data from numerous scientific studies indicate that long COVID involves a complex interaction between pathophysiological processes. Long COVID may involve the development of new diagnosable health conditions and exacerbation of pre-existing health conditions. However, despite this rapidly accumulating body of evidence regarding the pathobiology of long COVID, psychogenic and functional interpretations of the illness presentation continue to be endorsed by some healthcare professionals, creating confusion and inappropriate diagnostic and therapeutic pathways for people living with long COVID. The purpose of this perspective is to present a clinical and scientific rationale for why long COVID should not be considered as a functional neurologic disorder. It will begin by discussing the parallel historical development of pathobiological and psychosomatic/sociogenic diagnostic constructs arising from a common root in neurasthenia, which has resulted in the collective understandings of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and functional neurologic disorder (FND), respectively. We will also review the case definition criteria for FND and the distinguishing clinical and neuroimaging findings in FND vs. long COVID. We conclude that considering long COVID as FND is inappropriate based on differentiating pathophysiologic mechanisms and distinguishing clinical findings.

Understanding Functional Neurological Disorder: Recent Insights and Diagnostic Challenges

Functional neurological disorder (FND), formerly called conversion disorder, is a condition characterized by neurological symptoms that lack an identifiable organic purpose. These signs, which can consist of motor, sensory, or cognitive disturbances, are not deliberately produced and often vary in severity. Its diagnosis is predicated on clinical evaluation and the exclusion of other medical or psychiatric situations. Its treatment typically involves a multidisciplinary technique addressing each of the neurological symptoms and underlying psychological factors via a mixture of medical management, psychotherapy, and supportive interventions. Recent advances in neuroimaging and a deeper exploration of its epidemiology, pathophysiology, and clinical presentation have shed new light on this disorder. This paper synthesizes the current knowledge on FND, focusing on its epidemiology and underlying mechanisms, neuroimaging insights, and the differentiation of FND from feigning or malingering. This review highlights the phenotypic heterogeneity of FND and the diagnostic challenges it presents. It also discusses the significant role of neuroimaging in unraveling the complex neural underpinnings of FND and its potential in predicting treatment response. This paper underscores the importance of a nuanced understanding of FND in informing clinical practice and guiding future research. With advancements in neuroimaging techniques and growing recognition of the disorder's multifaceted nature, the paper suggests a promising trajectory toward more effective, personalized treatment strategies and a better overall understanding of the disorder.

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.

Gait control by the frontal lobe

The frontal lobe is crucial and contributes to controlling truncal motion, postural responses, and maintaining equilibrium and locomotion. The rich repertoire of frontal gait disorders gives some indication of this complexity. For human walking, it is necessary to simultaneously achieve at least two tasks, such as maintaining a bipedal upright posture and locomotion. Particularly, postural control plays an extremely significant role in enabling the subject to maintain stable gait behaviors to adapt to the environment. To achieve these requirements, the frontal cortex (1) uses cognitive information from the parietal, temporal, and occipital cortices, (2) creates plans and programs of gait behaviors, and (3) acts on the brainstem and spinal cord, where the core posture-gait mechanisms exist. Moreover, the frontal cortex enables one to achieve a variety of gait patterns in response to environmental changes by switching gait patterns from automatic routine to intentionally controlled and learning the new paradigms of gait strategy via networks with the basal ganglia, cerebellum, and limbic structures. This chapter discusses the role of each area of the frontal cortex in behavioral control and attempts to explain how frontal lobe controls walking with special reference to postural control.

Within- and across-network alterations in the default network and in visual networkpatients with somatic symptom disorder

BACKGROUND

Somatic symptom disorders (SSDs) are common medical disorders characterized by various biological, psychological, and social pathogenic factors. Little is known about the functional profiles associated with SSDs within and between brain networks.

METHODS

In this study, resting-state functional magnetic resonance imaging (fMRI) was assessed in 60 patients with SSD and 62 matched healthy controls (HCs). Independent component analysis (ICA) of 20 components was conducted and investigated for functional connectivity changes within and acrossnetworks between patients and controls. In addition, fractional amplitudes of low-frequency fluctuation (fALFF) were used to detect intensities of spontaneous functional activity in networks successfully separated by ICA.

RESULTS

The patients with SSD exhibited significantly increased functional connectivity (FC) in the left lingual gyruswithin thevisual network, and higher fALFF values in the cingulate cortex and precuneus within the default network. Furthermore, SSD patients showed significantly decreased FC between the default and visual networks.

CONCLUSION

SSD is associated with significant changes within thevisual network, and the defaultnetwork, and decreased FC between the default network and visual network, which may indicate an imbalance within and between networks. These decouplings are likely associated with impaired perceptual and self-conscious integration in those with the disease.

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.

Shame in patients with psychogenic nonepileptic seizure: A narrative review

Psychogenic Nonepileptic Seizures (PNES) have been linked to dysregulated emotions and arousal. However, the question which emotions may be most relevant has received much less attention. In this multidisciplinary narrative review, we argue that the self-conscious emotion of shame is likely to be of particular importance for PNES. We summarize current concepts of the development of shame processing and its relationship with other emotional states. We demonstrate the potential of acute shame to cause a sudden disruption of normal cognitive function and trigger powerful behavioral, cognitive, physiological and secondary emotional responses which closely resemble key components of PNES. These responses may lead to the development of shame avoidance strategies which can become disabling in themselves. We discuss how excessive shame proneness and shame dysregulation are linked to several psychopathologies often associated with PNES (including depression and PTSD) and how they may predispose to, precipitate and perpetuate PNES disorders, not least by interacting with stigma. We consider current knowledge of the neurobiological underpinnings of shame and PNES. We explore how shame could be the link between PNES and a heterogeneous range of possible etiological factors, and how it may link historical aversive experiences with individual PNES events occurring much later and without apparent external trigger. We argue that, in view of the potential direct links between shame and PNES, the well-documented associations of shame with common comorbidities of this seizure disorder and the well-characterized relationship between chronic shame and stigma, there is a compelling case to pay greater attention to shame in relation to PNES. Its role in the treatment of patients with PNES is discussed in a separate, linked review incorporating case vignettes to highlight the complex interactions of different but interlinked shame-related issues in individual patients.

Neurostimulation for the treatment of functional neurological disorder: A systematic review

Functional Neurological Disorder (FND), also known as conversion disorder, is characterized by neurological symptoms that are incompatible with any known structural disorder and best explained by a biopsychosocial model. Evidence-based treatments for FND are limited, with cognitive behavioral therapy (CBT) and physiotherapy being the most effective interventions [1]. In recent years, functional neuroimaging studies have provided robust evidence of alterations in activity and connectivity in multiple brain networks in FND. This body of evidence suggests that neurocircuitry-based interventions, such as non-invasive brain stimulation techniques (NIBS), may also represent an effective therapeutic option for patients with FND. In this systematic review, we outline the current state of knowledge of NIBS in FND, and discuss limitations and future directions that may help establish the efficacy of NIBS as a therapeutic option for FND.

Increased Incidence of Functional (Psychogenic) Movement Disorders in Children and Adults Amid the COVID-19 Pandemic: A Cross-sectional Study

BACKGROUND AND OBJECTIVES

Functional (psychogenic) movement disorders (FMDs) are conditions in which affected patients develop abnormal movements that are incongruous with known, organic, movement disorders, often associated with psychological stressors.

METHODS

In this case series, electronic medical records of all patients who presented to our adult and pediatric tertiary care movement disorders clinics between March 1 and October 30, 2020, and during the same period in 2019 were reviewed. All patients diagnosed with functional (psychogenic) movement disorder were included if they satisfied diagnostic criteria.

RESULTS

Among 550 new patients referred for evaluation at our tertiary care movement disorders centers, 45 (8.2%) received a diagnosis of FMD; 75.6% were female, in comparison to the prior year during which time 665 new patients were evaluated and 5.1% were diagnosed with FMD. This represents a 60.1% increase (90.1% in pediatric cohort, 50.9% in adult cohort) in new patients diagnosed with FMD during the COVID-19 pandemic.

CONCLUSIONS

Within our patient population, there has been increased incidence of FMDs in the setting of the COVID-19 pandemic, possibly reflecting increased psychological and other stressors during this period.

Aberrant functional and effective connectivity of the frontostriatal network in unilateral acute tinnitus patients with hearing loss

PURPOSE

The present study combined resting-state functional connectivity (FC) and Granger causality analysis (GCA) to explore frontostriatal network dysfunction in unilateral acute tinnitus (AT) patients with hearing loss.

METHODS

The participants included 42 AT patients and 43 healthy control (HC) subjects who underwent resting-state functional magnetic resonance imaging (fMRI) scans. Based on the seed regions in the frontostriatal network, FC and GCA were conducted between the AT patients and HC subjects. Correlation analyses were used to examine correlations among altered FC values, GCA values, and clinical features in AT patients.

RESULTS

Compared with HCs, AT patients showed a general reduction in FC between the seed regions in the frontostriatal network and nonauditory areas, including the frontal cortices, midcingulate cortex (MCC), supramarginal gyrus, and postcentral gyrus (PoCG). Using the GCA algorithm, we detected abnormal effective connectivity (EC) in the inferior occipital gyrus, MCC, Cerebelum_Crus1, and PoCG. Furthermore, correlations between disrupted FC/EC and clinical characteristics, especially tinnitus distress-related characteristics, were found in AT patients.

CONCLUSIONS

Our work demonstrated abnormal FC and EC between the frontostriatal network and several nonauditory regions in AT patients with hearing loss, suggesting that multiple large-scale network dysfunctions and interactions are involved in the perception of tinnitus. These findings not only enhance the current understanding of the frontostriatal network in tinnitus but also serve as a reminder of the importance of focusing on tinnitus at an early stage.

Impaired effective functional connectivity of the sensorimotor network in interictal episodic migraineurs without aura

Background

Resting-state functional magnetic resonance imaging (Rs-fMRI) has confirmed sensorimotor network (SMN) dysfunction in migraine without aura (MwoA). However, the underlying mechanisms of SMN effective functional connectivity in MwoA remain unclear. We aimed to explore the association between clinical characteristics and effective functional connectivity in SMN, in interictal patients who have MwoA.

Methods

We used Rs-fMRI to acquire imaging data in 40 episodic patients with MwoA in the interictal phase and 34 healthy controls (HCs). Independent component analysis was used to profile the distribution of SMN and calculate the different SMN activity between the two groups. Subsequently, Granger causality analysis was used to analyze the effective functional connectivity between the SMN and other brain regions.

Results

Compared to the HCs, MwoA patients showed higher activity in the bilateral postcentral gyri (PoCG), but lower activity in the left midcingulate cortex (MCC). Moreover, MwoA patients showed decreased effective functional connectivity from the SMN to left middle temporal gyrus, right putamen, left insula and bilateral precuneus, but increased effective functional connectivity to the right paracentral lobule. There was also significant effective functional connectivity from the primary visual cortex, right cuneus and right putamen to the SMN. In the interictal period, there was positive correlation between the activity of the right PoCG and the frequency of headache. The disease duration was positively correlated with abnormal effective functional connectivity from the left PoCG to right precuneus. In addition, the headache impact scores were negatively correlated with abnormal effective functional connectivity from the left MCC to right paracentral lobule, as well as from the right precuneus to left PoCG.

Conclusions

These differential, resting-state functional activities of the SMN in episodic MwoA may contribute to the understanding of migraine-related intra- and internetwork imbalances associated with nociceptive regulation and chronification.