Neurophysiologic studies of functional neurologic disorders

Diagnostic Utility of Clinical Neurophysiology in Jerky Movement Disorders: A Review from the MDS Clinical Neurophysiology Study Group

BACKGROUND

Myoclonus and other jerky movement disorders are hyperkinetic disorders, the diagnosis of which heavily relies on clinical neurophysiological testing. However, formal diagnostic criteria are lacking, and recently the utility and reliability of these tests have been questioned.

OBJECTIVE

The aim of this review was to assess the utilization of clinical neurophysiology testing to identify possible gaps and boundaries that might guide the development of new methods for a more precise diagnosis and in-depth understanding of myoclonus.

METHODS

We reviewed electrophysiological features of cortical myoclonus, subcortical myoclonus (ie, myoclonus associated with dystonia, brainstem myoclonus), excessive startle reflex, spinal myoclonus (ie, spinal segmental and propriospinal myoclonus), peripheral myoclonus and mimics of myoclonus of peripheral origin (hemifacial spasm, minipolymyoclonus, myokymia), functional jerky movements, chorea, and tics.

RESULTS

Electrophysiological features that support the recognition of myoclonus subtypes, such as muscle burst duration, muscle pattern of activation, measures of cortical excitability, or movement-related cortical potentials, have been identified. These significantly contribute to the diagnosis of jerky movement disorders, but their reliability is uncertain. Despite the significant advancements, several unresolved questions persist. Factors contributing to this include the absence of systematic neurophysiological assessment and standardized methods, alongside the limited number of patients investigated using these techniques.

CONCLUSION

Although clinical neurophysiology remains the "gold standard" for defining and diagnosing myoclonus, our review highlighted the need to enhance the quality and reliability of neurophysiological testing in jerky movement disorders. Further studies including larger cohorts of patients recruited from different centers, employing standardized and optimized electrophysiological techniques, are warranted.

Surface Electromyography for the Diagnosis of Tremor Syndrome: A Study of 97 Patients

BACKGROUND AND OBJECTIVES

Tremor is one of the most frequent movement disorders encountered in clinical practice with heterogeneous phenomenology and etiology. Surface electromyography (SEMG) is a noninvasive and reproducible test that can diagnose tremor syndromes.

METHODS

In this retrospective study, the clinical and electrophysiologic records of 97 consecutive patients with tremor syndromes who visited our movement disorder clinic between January 2023 and March 2024 were examined.

RESULTS

In our study, 28.8% (n = 28) of patients were of essential tremor (ET) syndrome. SEMG of ET syndrome patients showed synchronous bursts in 71.4% (n = 20), alternating bursts in 10.7% (n = 3), synchronous bursts with co-contraction of agonist and antagonist muscles in 10.7% (n = 3), and both synchronous and alternating bursts in 3.6% (n = 1) of patients. Tremor-ataxia syndrome formed 21.6% (n = 21) of our study population, with 71.4% (n = 15) of patients showing synchronous bursts and co-contraction and 28.6% (n = 6) patients having alternating bursts. Moreover, 12.3% (n = 12) patients were of parkinsonian tremor, of whom alternating bursts were present in 75% (n = 9) and synchronous bursts with co-contraction were present in 25% (n = 3) of patients. In addition, 11.3% (n = 11) of patients had dystonic tremor (DT), of whom 81.8% (n = 9) had synchronous bursts and co-contraction and 18.2% (n = 2) had alternating bursts.

CONCLUSIONS

Synchronous bursts with co-contraction suggestive of DT were observed in most patients with tremor-ataxia syndrome and a small number of patients with ET syndrome. Our data suggests that SEMG helps differentiate these two clinical syndromes, which is difficult in a clinical setting.

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.

Clinical neurophysiology of functional motor disorders: IFCN Handbook Chapter

Functional Motor Disorders are common and disabling. Clinical diagnosis has moved from one of exclusion of other causes for symptoms to one where positive clinical features on history and examination are used to make a "rule in" diagnosis wherever possible. Clinical neurophysiological assessments have developed increasing importance in assisting with this positive diagnosis, not being used simply to demonstrate normal sensory-motor pathways, but instead to demonstrate specific abnormalities that help to positively diagnose these disorders. Here we provide a practical review of these techniques, their application, interpretation and pitfalls. We also highlight particular areas where such tests are currently lacking in sensitivity and specificity, for example in people with functional dystonia and functional tic-like movements.

An investigation into mothers' experiences of their children's functional tic-like behaviour and tic attacks

OBJECTIVE

This is the first study to systematically explore the lived experiences of sudden and new onset of severe functional tics from the perspective of the mother's experiences and describes their attempts to access support services in the United Kingdom.

METHOD

Twenty-One mothers of young people aged between 12 to 17 years with functional tic-like behaviour (FTLB) took part in semi-structured interviews. Thematic analysis of the transcribed interviews revealed gaps and inconsistencies within the process of gaining access to professional services and a lack of support for the management of tics and functional tic-like movements, in addition to highlighting the impact it had on daily family life.

RESULTS

The themes generated included the occurrence and development of tics, the severity and intensity of symptoms, the psychological impact on the family and the need to make recommendations for a clear care pathway. Managing the impact of the FTLB and co-occurring conditions such as suicidal ideation and self-harm, as well as the physical and emotional trauma, commonly contributed to feelings of isolation and helplessness, which impacted negatively on the family's ability to function and participate in society.

CONCLUSIONS

The findings emphasize the urgent need to create a clear management pathway for those experiencing FTLB, including the need for more professionals with relevant knowledge, to improve the dialogue with families during the referral process, whilst prioritising the treatment of anxiety and other identified mental health concerns.

Functional neurological disorder is common in patients attending chronic pain clinics

BACKGROUND AND PURPOSE

Chronic pain is a common comorbidity in those with functional neurological disorder (FND); however, the prevalence and characteristics of FND in those with chronic pain is unknown.

METHODS

A retrospective electronic records review was made of consecutive new patients attending a chronic pain clinic of a regional service. Clinical features, medication for and outcome of chronic pain, any lifetime diagnoses of functional disorders, FND, and psychiatric disorders, and undiagnosed neurological symptoms were recorded.

RESULTS

Of 190 patients attending the chronic pain clinic, 32 (17%) had a lifetime diagnosis of FND and an additional 11 (6%) had undiagnosed neurological symptoms. Pain patients with comorbid FND were more likely to have chronic primary pain (88% with FND, 44% without FND, p < 0.0001), widespread chronic primary pain (53%, 15%, p < 0.00001), and depression (84%, 52%, p < 0.005) and less likely to have a pain-precipitating event (19% vs. 56%, p < 0.001). However, there was no significant difference between these patients in opiate prescription, benzodiazepine prescription, or pain outcome.

CONCLUSIONS

This first study of FND in a chronic pain patient population found a remarkably high prevalence of FND (17%) and is possibly an underestimation. The size of the overlap indicates that FND and chronic pain research fields are likely to have a lot to learn from each other.

Diagnostic Uncertainties in Tremor

The approach and diagnosis of patients with tremor may be challenging for clinicians. According to the most recent consensus statement by the Task Force on Tremor of the International Parkinson Movement Disorder Society, the differentiation between action (i.e., kinetic, postural, intention), resting, and other task- and position-specific tremors is crucial to this goal. In addition, patients with tremor must be carefully examined for other relevant features, including the topography of the tremor, since it can involve different body areas and possibly associate with neurological signs of uncertain significance. Following the characterization of major clinical features, it may be useful to define, whenever possible, a particular tremor syndrome and to narrow down the spectrum of possible etiologies. First, it is important to distinguish between physiological and pathological tremor, and, in the latter case, to differentiate between the underlying pathological conditions. A correct approach to tremor is particularly relevant for appropriate referral, counseling, prognosis definition, and therapeutic management of patients. The purpose of this review is to outline the possible diagnostic uncertainties that may be encountered in clinical practice in the approach to patients with tremor. In addition to an emphasis on a clinical approach, this review discusses the important ancillary role of neurophysiology and innovative technologies, neuroimaging, and genetics in the diagnostic process.

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.

Pathophysiology and Treatment of Functional Paralysis: Insight from Transcranial Magnetic Stimulation

Functional paralysis (FP) or limb weakness is a common presentation of functional movement disorders (FMD), accounting for 18.1% of the clinical manifestations of FMD. The pathophysiology of FP is not known, but imaging studies have identified changes in structural and functional connectivity in multiple brain networks. It has been proposed that noninvasive brain stimulation techniques may be used to understand the pathophysiology of FP and may represent a possible therapeutic option. In this paper, we reviewed transcranial magnetic stimulation studies on functional paralysis, focusing on their pathophysiological and therapeutical implications. Overall, there is general agreement on the integrity of corticospinal pathways in FP, while conflicting results have been found about the net excitability of the primary motor cortex and its excitatory/inhibitory circuitry in resting conditions. The possible involvement of spinal cord circuits remains an under-investigated area. Repetitive transcranial magnetic stimulation appears to have a potential role as a safe and viable option for the treatment of functional paralysis, but more studies are needed to investigate optimal stimulation parameters and clarify its role in the context of other therapeutical options.

A standardized accelerometry method for characterizing tremor: Application and validation in an ageing population with postural and action tremor

Background

Ordinal scales based on qualitative observation are the mainstay in the clinical assessment of tremor, but are limited by inter-rater reliability, measurement precision, range, and ceiling effects. Quantitative tremor evaluation is well-developed in research, but clinical application has lagged, in part due to cumbersome mathematical application and lack of established standards.

Objectives

To develop a novel method for evaluating tremor that integrates a standardized clinical exam, wrist-watch accelerometers, and a software framework for data analysis that does not require advanced mathematical or computing skills. The utility of the method was tested in a sequential cohort of patients with predominant postural and action tremor presenting to a specialized surgical clinic with the presumptive diagnosis of Essential Tremor (ET).

Methods

Wristwatch accelerometry was integrated with a standardized clinical exam. A MATLAB application was developed for automated data analysis and graphical representation of tremor. Measures from the power spectrum of acceleration of tremor in different upper limb postures were derived in 25 consecutive patients. The linear results from accelerometry were correlated with the commonly used non-linear Clinical Rating Scale for Tremor (CRST).

Results

The acceleration power spectrum was reliably produced in all consecutive patients. Tremor frequency was stable in different postures and across patients. Both total and peak power of acceleration during postural conditions correlated well with the CRST. The standardized clinical examination with integrated accelerometry measures was therefore effective at characterizing tremor in a population with predominant postural and action tremor. The protocol is also illustrated on repeated measures in an ET patient who underwent Magnetic Resonance-Guided Focused Ultrasound thalamotomy.

Conclusion

Quantitative assessment of tremor as a continuous variable using wristwatch accelerometry is readily applicable as a clinical tool when integrated with a standardized clinical exam and a user-friendly software framework for analysis. The method is validated for patients with predominant postural and action tremor, and can be adopted for characterizing tremor of different etiologies with dissemination in a wide variety of clinical and research contexts in ageing populations.

Triggers in functional motor disorder: a clinical feature distinct from precipitating factors

Background and objective

People with functional motor disorder (FMD) report triggers—sensory or motor-induced stimuli that exacerbate or initiate paroxysmal occurrences of their movement disorder. These are a distinct phenomenon from precipitating factors occurring at the initial onset of the disorder. We aimed to assess triggers in FMD and understand their relevance to paroxysmal variability often seen in FMD.

Methods

We enrolled consecutive outpatients with a definite diagnosis of FMD. Each patient underwent a detailed clinical evaluation also including the presence of trigger factors and video-recordings both during neurological examination and physiotherapy treatment. Patients were classified as having “triggers” (T-FMD) or “not having triggers” (NoT-FMD) as well as “paroxysmal” compared to “persistent with paroxysmal variability”.

Results

The study sample was 100 patients (82% female) with FMD; the mean age at onset was 41 years. Triggers were observed in 88% of patients and in 65 of these the FMD was pure paroxysmal. The most common triggers were movement or physical exercise, followed by emotional, visual, touch, and auditory stimuli; 39 (44%) were isolated and 49 (56%) were combined triggers. Among the T-FMD patients, FMD were paroxysmal in 74% (n = 65) and persistent with paroxysmal variability in 26% (n = 23). The T-FMD patients were younger (p = 0.016) and had a gait disorder (p = 0.035) more frequently than the NoT-FMD patients.

Discussion

Triggers are frequent in FMD and may have diverse overlapping clinical presentations. In this sample, FMD was most often paroxysmal, suggesting the value of noting triggers as clinical clues in the diagnosis and rehabilitation of FMD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11102-1.

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.

A practical review of functional neurological disorder (FND) for the general physician

We present a practical overview of functional neurological disorder (FND), its epidemiology, assessment and diagnosis, diagnostic pitfalls, treatment, aetiology and mechanism. We present an update on functional limb weakness, tremor, dystonia and other abnormal movements, dissociative seizures, functional cognitive symptoms and urinary retention, and 'scan-negative' cauda equina syndrome. The diagnosis of FND should rest on clear positive evidence, typically from a combination of physical signs on examination or the nature of seizures. In treatment of FND, clear communication of the diagnosis and the involvement of the multidisciplinary team is beneficial. We recommend that patients with FND are referred to specialists with expertise in neurological diagnosis. FND is a common presentation in emergency and acute medical settings and there are many practical elements to making a positive diagnosis and communication which are useful for all physicians to be familiar with.

Social Cognition and White Matter: Connectivity and Cooperation

Humans are highly social animals whose survival and well-being depend on their capacity to cooperate in complex social settings. Advances in anthropology and psychology have demonstrated the importance of cooperation for enhancing social cohesion and minimizing conflict. The understanding of social behavior is informed by the notion of social cognition, a set of mental operations including emotion perception, mentalizing, and empathy. The social brain hypothesis posits that the mammalian brain has enlarged over evolution to meet the challenges of social life, culminating in a large human brain well adapted for social cognition. The structures subserving social cognition are mainly located in the frontal and temporal lobes, and although gray matter is critical, social cognition also requires white matter. Whereas the social brain hypothesis assumes that brain enlargement has been driven by neocortical expansion, cerebral white matter has expanded even more robustly than the neocortex, coinciding with the emergence of social cognition. White matter expansion is most evident in the frontal and temporal lobes, where it enhances connectivity between regions critical for social cognition. Myelination has, in turn, conferred adaptive social advantages by enabling prompt empathic concern for offspring and by strengthening networks that support cooperation and the related capacities of altruism and morality. Social cognition deficits related to myelinated tract involvement occur in many disorders, including stroke, Binswanger disease, traumatic brain injury, multiple sclerosis, glioma, and behavioral variant frontotemporal dementia. The contribution of white matter to social cognition can be conceptualized as the enhancement of cooperation through brain connectivity.

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.

How can neurophysiological studies help with movement disorders characterization in clinical practice? A review

BACKGROUND

Neurophysiological studies are ancillary tools to better understand the features and nature of movement disorders. Electromyography (EMG), together with electroencephalography (EEG) and accelerometer, can be used to evaluate a hypo and hyperkinetic spectrum of movements. Specific techniques can be applied to better characterize the phenomenology, help distinguish functional from organic origin and assess the most probable site of the movement generator in the nervous system.

OBJECTIVE

We intend to provide an update for clinicians on helpful neurophysiological tools to assess movement disorders in clinical practice.

METHODS

Non-systematic review of the literature published up to June 2019.

RESULTS

A diversity of protocols was found and described. These include EMG analyses to define dystonia, myoclonus, myokymia, myorhythmia, and painful legs moving toes pattern; EMG in combination with accelerometer to study tremor; and EEG-EMG to study myoclonus. Also, indirect measures of cortical and brainstem excitability help to describe and diagnose abnormal physiology in Parkinson's disease, atypical parkinsonism, dystonia, and myoclonus.

CONCLUSION

These studies can be helpful for the diagnosis and are usually underutilized in neurological practice.

Pathogenesis and pathophysiology of functional (psychogenic) movement disorders

Functional movement disorders (FMDs), known over time as "hysteria", "dissociative", "conversion", "somatoform", "non-organic" and "psychogenic" disorders, are characterized by having a voluntary quality, being modifiable by attention and distraction but perceived by the patient as involuntary. Although a high prevalence of depression and anxiety is observed in these patients, a definitive role of psychiatric disorders in FMDs has not been proven, and many patients do not endorse such manifestations. Stressful events, social influences and minor trauma may precede the onset of FMDs, but their pathogenic mechanisms are unclear. Patients with FMDs have several abnormalities in their neurobiology including strengthened connectivity between the limbic and motor networks. Additionally, there is altered top-down regulation of motor activities and increased activation of areas implicated in self-awareness, self-monitoring, and active motor inhibition such as the cingulate and insular cortex. Decreased activation of the supplementary motor area (SMA) and pre-SMA, implicated in motor control and preparation, is another finding. The sense of agency defined as the feeling of controlling external events through one's own action also seems to be impaired in individuals with FMDs. Correlating with this is a loss of intentional binding, a subjective time compression between intentional action and its sensory consequences. Organic and functional dystonia may be difficult to differentiate since they share diverse neurophysiological features including decreased cortical inhibition, and similar local field potentials in the globus pallidus and thalamus; although increased cortical plasticity is observed only in patients with organic dystonia. Advances in the pathogenesis and pathophysiology of FMDs may be helpful to understand the nature of these disorders and plan further treatment strategies.

Occupational therapy for functional neurological disorders: a scoping review and agenda for research

Functional neurological disorders (FND)-also called psychogenic, nonorganic, conversion, and dissociative disorders-constitute one of the commonest problems in neurological practice. An occupational therapist (OT) is commonly involved in management, but there is no specific literature or guidance for these professionals. Classification now emphasizes the importance of positive diagnosis of FND based on physical signs, more than psychological features. Studies of mechanism have produced new clinical and neurobiological ways of thinking about these disorders. Evidence has emerged to support the use of physiotherapy and occupational therapy as part of a multidisciplinary team for functional movement disorders (FMD) and psychotherapy for dissociative (nonepileptic) attacks. The diagnosis and management of FND has entered a new evidence-based era and deserves a standard place in the OT neurological curriculum. We discuss specific management areas relevant to occupational therapy and propose a research agenda.

Impact of Transcranial Magnetic Stimulation on Functional Movement Disorders: Cortical Modulation or a Behavioral Effect?

Introduction

Recent studies suggest that repeated transcranial magnetic stimulation (TMS) improves functional movement disorders (FMDs), but the underlying mechanisms are unclear. The objective was to determine whether the beneficial action of TMS in patients with FMDs is due to cortical neuromodulation or rather to a cognitive-behavioral effect.

Method

Consecutive patients with FMDs underwent repeated low-frequency (0.25 Hz) magnetic stimulation over the cortex contralateral to the symptoms or over the spinal roots [root magnetic stimulation (RMS)] homolateral to the symptoms. The patients were randomized into two groups: group 1 received RMS on day 1 and TMS on day 2, while group 2 received the same treatments in reverse order. We blindly assessed the severity of movement disorders before and after each stimulation session.

Results

We studied 33 patients with FMDs (dystonia, tremor, myoclonus, Parkinsonism, or stereotypies). The median symptom duration was 2.9 years. The magnetic stimulation sessions led to a significant improvement (>50%) in 22 patients (66%). We found no difference between TMS and RMS.

Conclusion

We suggest that the therapeutic benefit of TMS in patients with FMDs is due more to a cognitive-behavioral effect than to cortical neuromodulation.

Conversion disorder: A systematic review of current terminology

OBJECTIVE

It has been argued that the label given to unexplained neurological symptoms is an important contributor to their often poor acceptance, and there has been recent debate on proposals to change the name from conversion disorder. There have been multiple studies of layperson and clinician preference and this article aimed to review these.

DESIGN

Multiple databases were searched using terms including "conversion disorder" and "terminology", and relative preferences for the terms extracted.

RESULTS

Seven articles were found which looked at clinician or layperson preferences for terminology for unexplained neurological symptoms. Most neurologists favoured terms such as "functional" and "psychogenic", while laypeople were comfortable with "functional" but viewed "psychogenic" as more offensive; "non-epileptic/organic" was relatively popular with both groups.

CONCLUSIONS

"Functional" is a term that is relatively popular with both clinicians and the public. It also meets more of the other criteria proposed for an acceptable label than other popular terms - however the views of neither psychiatrists nor actual patients with the disorder were considered.