Validation of "laboratory-supported" criteria for functional (psychogenic) tremor

Functional Movement Disorders and Deep Brain Stimulation: A Review

Purpose of the Review

The aim of this narrative review was to explore the interplay between functional movement disorders (FMDs) and deep brain stimulation (DBS).

Recent Findings

Patients with unrecognized FMD who are referred for DBS usually present with functional dystonia. By contrast, patients who present with FMD after DBS are mostly presenting with functional tremor, in keeping with non-DBS FMD cohorts. Comorbid presentation of FMD in established DBS indications makes the decision to opt for surgery challenging. Many contributing factors can play a role in the development of FMD, including the trauma caused by awake neurosurgery and/or extensive DBS programming.

Summary

FMDs in the context of DBS are often overlooked and should be diagnosed promptly because they determine surgical outcome. The approach to DBS candidates with comorbid FMD and the risk factors of FMD after DBS should be further explored.

Simple biomarkers to distinguish Parkinson's disease from its mimics in clinical practice: a comprehensive review and future directions

In the last few years, a plethora of biomarkers have been proposed for the differentiation of Parkinson's disease (PD) from its mimics. Most of them consist of complex measures, often based on expensive technology, not easily employed outside research centers. MRI measures have been widely used to differentiate between PD and other parkinsonism. However, these measurements were often performed manually on small brain areas in small patient cohorts with intra- and inter-rater variability. The aim of the current review is to provide a comprehensive and updated overview of the literature on biomarkers commonly used to differentiate PD from its mimics (including parkinsonism and tremor syndromes), focusing on parameters derived by simple qualitative or quantitative measurements that can be used in routine practice. Several electrophysiological, sonographic and MRI biomarkers have shown promising results, including the blink-reflex recovery cycle, tremor analysis, sonographic or MRI assessment of substantia nigra, and several qualitative MRI signs or simple linear measures to be directly performed on MR images. The most significant issue is that most studies have been conducted on small patient cohorts from a single center, with limited reproducibility of the findings. Future studies should be carried out on larger international cohorts of patients to ensure generalizability. Moreover, research on simple biomarkers should seek measurements to differentiate patients with different diseases but similar clinical phenotypes, distinguish subtypes of the same disease, assess disease progression, and correlate biomarkers with pathological data. An even more important goal would be to predict the disease in the preclinical phase.

Functional Neurological Disorders Among Patients With Tremor

OBJECTIVE

Functional neurological disorders (FNDs) are increasingly recognized in the general population and neurology clinics, and there is evidence that patients with neurological disorders are more likely to have a FND. This study was designed to identify the clinical features of FNDs among patients with movement disorders when the two disorders coexist.

METHODS

The clinical histories and video recordings of 150 consecutive patients with tremors were examined: the types of tremor included essential tremor; essential tremor plus; dystonic tremor; tremor associated with dystonia; and drug-induced, myoclonic, orthostatic, task-specific, parkinsonian, Holmes, and unclassified tremor. Using criteria for "possible" and "probable" coexistent FND, clinical features that helped differentiate between functional and other neurological tremors were identified.

RESULTS

There were 27 (18%) patients with functional manifestations, and 17 (11% of full sample) of these patients had signs suggestive of comorbid functional tremor. Patients with comorbid functional manifestations were younger at presentation, and these patients had greater severity of tremor, particularly upper limb postural tremor. Functional manifestations were not more commonly observed among patients with any particular type of tremor, except for patients with Holmes tremor, who were more likely to have comorbid functional neurological manifestations.

CONCLUSIONS

About 18% of patients with diverse types of tremors also had comorbid functional neurological manifestations. Of the coexistent FNDs, functional tremor was the most common. Patients with co-occurring functional and other neurological tremors presented for evaluation at a younger age and had greater severity of arm tremor than those without comorbid functional neurological manifestations.

[Additional functional symptoms in Parkinson's disease and tremor syndromes]

Patients with Parkinson's Disease or a tremor syndrome may present with additional functional movement disorders. The differential diagnosis is particularly difficult. In some cases, functional symptoms occur either before the manifestation of the organic disease or can emerge as an additional symptom after Parkinson's disease or tremor became apparent. In patients with Parkinson's disease the prevalence for additional functional symptoms is 7 %. In the case that patients with Parkinson's diseases have one side that is more severely affected, additional functional motor symptoms such as functional rest tremor also occur on that same, predominantly affected side. Functional gait disorders occur frequently. Clinically, patients appear notably slow in automatized, daily tasks. Their speech is more whispering than hypophonic, bradykinesia during finger tapping manifest without a decrement. The Dopamintransporterszintigraphy (123) I FP-CIT SPECT; DaTSCANTM) may be helpful to differentiate between functional Parkinsonism and Parkinson's disease. Functional tremor in patients with an organic tremor syndrome is diagnosed with the same distraction techniques as in solely functional tremor. This includes cognitive, motor, and suggestive distraction maneuvers. In some cases, additional neurophysiological investigations such as accelerometry are useful for the differential diagnosis. It is most important to identify patients with additional functional symptoms in non-functional movement disorders, because the therapeutic approach differs and a multi professional team is required to initiate effective treatment strategies.

Bedside clinical assessment of patients with common upper limb tremor and algorithmic approach

The diagnostic approach for patients with tremor is challenging due to the complex and overlapping phenotypes among tremor syndromes. The first step in the evaluation of tremor is to identify the tremulous movement and exclude the tremor mimics. The second step is to classify the tremor syndrome based on the characteristics of tremor from historical clues and focused examination (Axis 1). Comprehensive tremor examinations involve the assessment of tremor in different conditions (rest, action or mixed, position or task-specific), distribution of tremor (upper limb, lower limb, head, jaw), positive signs for functional tremor (FT) if suspected (distractibility, entrainment, co-contraction), and associated neurological signs including parkinsonism, dystonic posture, cerebellar/brainstem signs, neuropathy, and cognitive impairment. A pivotal feature in this step is to determine any distinct feature of a specific isolated or combined tremor syndrome. In this review, we propose an algorithm to assess upper limb tremors. Ancillary testing should be performed if clinical evaluation is unclear. The choice of investigation depends on the types of tremors considered to narrow down the spectrum of etiology (Axis 2). Laboratory blood tests are considered for acute onset and acute worsening of tremors, while structural neuroimaging is indicated in unilateral tremors with acute onset, nonclassical presentations, and a combination of neurological symptoms. Neurophysiological study is an important tool that aids in distinguishing between tremor and myoclonus, etiology of tremor and document specific signs of FT. Treatment is mainly symptomatic based depending on the etiology of the tremor and the patient's disabilities.

Global Perceptions and Utilization of Clinical Neurophysiology in Movement Disorders

BACKGROUND

Clinical neurophysiology (CNP) involves the use of neurophysiological techniques to make an accurate clinical diagnosis, to quantify the severity, and to measure the treatment response. Despite several studies showing CNP to be a useful diagnostic tool in Movement Disorders (MD), its more widespread utilization in clinical practice has been limited.

OBJECTIVES

To better understand the current availability, global perceptions, and challenges for implementation of diagnostic CNP in the clinical practice of MD.

METHODS

The International Parkinson and Movement Disorders Society (IPMDS) formed a Task Force on CNP. The Task Force distributed an online survey via email to all the members of the IPMDS between August 5 and 30, 2021. Descriptive statistics were used for analysis of the survey results. Some results are presented by IPMDS geographical sections namely PanAmerican (PAS), European (ES), African (AFR), Asian and Oceanian (AOS).

RESULTS

Four hundred and ninety-one IPMDS members (52% males), from 196 countries, responded. The majority of responders from the AFR (65%) and PAS (63%) sections had no formal training in diagnostic CNP (40% for AOS and 37% for ES). The most commonly used techniques are electroencephalography (EEG) (72%) followed by surface EMG (71%). The majority of responders think that CNP is somewhat valuable or very valuable in the assessment of MD. All the sections identified "lack of training" as one of the biggest challenges for diagnostic CNP studies in MD.

CONCLUSIONS

CNP is perceived to be a useful diagnostic tool in MD. Several challenges were identified that prevent widespread utilization of CNP in MD.

Essential Tremor and Essential Tremor Plus Are Essentially Similar Electrophysiologically

BACKGROUND

The merits of classifying the heterogeneous group of essential tremors into essential tremor (ET) and essential tremor plus (ETP) are debated.

OBJECTIVES

We studied the electrophysiological and spiral characteristics of tremor in ET and ETP.

METHODS

We reviewed standardized videos from a tremor database and clinically classified patients into ET, ETP, or dystonic tremor (DT). The following variables were derived from combined tri-axial accelerometry-surface electromyography (EMG)-peak frequency, total power, peak power, full width half maximum, tremor stability index and EMG-coherence. We analyzed hand-drawn spirals to derive mean deviation, tremor variability, inter-, and intra-loop widths. We compared these variables among the groups.

RESULTS

We recruited 72 participants (81.9% male) with mean age 47.7 ± 16.1 years and Fahn-Tolosa-Marin Tremor Rating Scale total score 31.1 ± 14.1. Patients with ET were younger (P = 0.014) and had less severe tremor (P = 0.020) compared to ETP and DT. In ETP group, 48.6% had subtle dystonia. Peak frequency was greater in ETP (7.3 ± 0.3 Hz) compared to DT (6.1 ± 0.4 Hz; P = 0.024). Peak power was greater in ETP and DT for postural tremor. Rest tremor was recordable on accelerometry in 26.7% of ET. Other variables were similar among the groups.

CONCLUSION

Electrophysiological evaluation revealed postural tremor of frequency 6 to 7 Hz in ET, ETP, and DT with subtle differences more severe tremor in ETP and DT, and higher frequency in ETP compared to DT. Our findings suggest a similar tremor oscillator in these conditions, supporting the view that these entities are part of a spectrum of tremor disorders, rather than distinct etiological entities.

The selfie sign in the diagnosis of functional tremor

Functional tremor (FT) is the most common phenotype of functional movement disorders (FMD). Its diagnosis can often be challenging. While positive signs such as tremor variability, distractibility, and entrainment support a diagnosis of FT, these diagnostic clues may not always be present and can be challenging to assess. In this case series, we identify another examination technique which could be of value when assessing FT. In our Movement Disorders clinic, charts were retrospectively reviewed for relevant clinical information. Video examinations were conducted. Obtained videos were either synchronous, via the use of screen recording software during telehealth visits or asynchronous, from self-recorded home videos. In both settings, patients were instructed to self-record their tremor using their phone cameras. Three patients with FT or comorbid FT were identified as demonstrating a unique examination sign. Videos showed an improvement or suppression of the tremor when the phone was held by the affected hand. When compared to a patient with tremor-dominant Parkinson's disease serving as a control, this "selfie sign" was not observed. These observations are preliminary and larger studies are needed to confirm the usefulness of the selfie sign in diagnosing FT. Patient-recorded videos of their tremor can be a convenient and practical way of evaluating suspected FT, especially when paroxysmal or variable symptoms limit the usefulness of classic signs often assessed in the clinic.

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.

Electrophysiology in Functional Movement Disorders: An Update

Background

Functional movement disorders (FMD) are a diagnostic and therapeutic challenge, both to the neurologist and psychiatrists. The phenomenology is varied and can present as tremors, dystonia, jerks/myoclonus, gait disorder, other abnormal movements or a combination. There has been an increase in the use of electrophysiological studies that are an important tool in the evaluation of FMDs.

Methods

We searched the database platforms of MEDLINE, Google scholar, Web of Sciences, Scopus using the Medical Subject Heading terms (MeSH) for all the articles from 1st January 1970 till November 2022. A total of 658 articles were obtained by the search mechanism. A total of 79 relevant articles were reviewed thoroughly, of which 26 articles that had electrophysiological data were included in the present review.

Results

Variability, distractibility and entertainability can be demonstrated in functional tremors by using multichannel surface electromyography. Voluntary ballistic movements tend to decrease the tremor, while loading the tremulous limb with weight causes the tremor amplitude to increase in functional tremor. Presence of Bereitschaftspotential demonstrates the functional nature of palatal tremor and myoclonus. Co-contraction testing may be helpful in differentiating functional from organic dystonia. The R2 blink reflex recovery cycle has been found to be abnormally enhanced in organic blepharospasm, whereas it is normal in presumed functional blepharospasm. Plasticity is found to be abnormally high in organic dystonia and normal in functional dystonia, in addition to enhanced facilitation in patients with organic dystonia.

Conclusions

Electrophysiological tests supplement clinical examination and helps in differentiating FMD from organic movement disorders.

The role of laboratory investigations in the classification of tremors

INTRODUCTION

Tremor is the most common movement disorder. Although clinical examination plays a significant role in evaluating patients with tremor, laboratory tests are useful to classify tremors according to the recent two-axis approach proposed by the International Parkinson and Movement Disorders Society.

METHODS

In the present review, we will discuss the usefulness and applicability of the various diagnostic methods in classifying and diagnosing tremors. We will evaluate a number of techniques, including laboratory and genetic tests, neurophysiology, and neuroimaging. The role of newly introduced innovative tremor assessment methods will also be discussed.

RESULTS

Neurophysiology plays a crucial role in tremor definition and classification, and it can be useful for the identification of specific tremor syndromes. Laboratory and genetic tests and neuroimaging may be of paramount importance in identifying specific etiologies. Highly promising innovative technologies are being developed for both clinical and research purposes.

CONCLUSIONS

Overall, laboratory investigations may support clinicians in the diagnostic process of tremor. Also, combining data from different techniques can help improve understanding of the pathophysiological bases underlying tremors and guide therapeutic management.

Utility of Neurophysiological Evaluation in Movement Disorders Clinical Practice

Background

Quantitative and objective neurophysiological assessment can help to define the predominant phenomenology and provide diagnoses that have prognostic and therapeutic implications for movement disorders.

Objectives

Evaluate the agreement between initial indications and final diagnoses after neurophysiological evaluations in a specialized movement disorders center.

Methods

Electrophysiological studies conducted for movement disorders from 2003 to 2021 were reviewed. The indications were classified according to predominant phenomenology and the diagnoses categorized in subgroups of phenomenology.

Results

A total of 509 studies were analyzed. 51% (259) of patients were female, with a mean age of 51 years (ranges 5 to 89 years). The most common reasons for referral were evaluation of functional movement disorders (FMD), followed by jerky movements, tremor and postural instability. Regarding FMD referrals, there was a diagnostic change in 13% of the patients after electrophysiological assessment. The patients with jerky movements as indication had a diagnosis other than myoclonus in 27% of them, and tremor was not confirmed in 20% of the cases. In patients with an electrophysiological diagnosis of FMD, it was not suspected in 30% of the referrals. Similarly, tremor was not mentioned in the referral of 17% of the patients with this electrophysiological diagnosis and myoclonus was not suspected in 13% of the cases.

Conclusions

Electrophysiological assessment has utility in the evaluation of movement disorders, even in patients evaluated by movement disorders neurologists. More studies are needed to standardize the protocols between centers and to promote the availability and use of these techniques among movement disorders clinics.

[Functional neurological disorders: A clinical anthology]

Functional neurological disorders have a broad phenotypic spectrum and include different clinical syndromes, which are sometimes associated to each other or appear consecutively over the course of the disease. This clinical anthology provides details on the specific and sensitive positive signs that are to be sought in the context of a suspected functional neurological disorder. Beside these positive elements leading to the diagnosis of functional neurological disorder, we should keep in mind the possibility of an associated organic disorder as the combination of both organic and functional disorders is a relatively frequent situation in clinical practice. Here we describe the clinical characteristics of different functional neurological syndromes: motor deficits, abnormal hyperkinetic and hypokinetic movements, voice or speech disorders, sensory disorders, and functional dissociative seizures. The clinical examination and the identification of positive signs play a critical role in the diagnosis of functional neurological disorder. Knowledge of the specific signs associated with each phenotype render possible to make an early diagnosis. For that matter, it contributes to the improvement of patient care management. It allows to a better engagement in an appropriate care pathway, which influence their prognosis. Highlighting and discussing positive signs with patients can also be an interesting step in the process of explaining the disease and its management.

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.

Diagnostic accuracy of clinical signs and investigations for functional weakness, sensory and movement disorders: A systematic review

INTRODUCTION

Patients with functional neurological disorders (FND) present with weakness, sensory or movement disorder without corresponding brain pathology. The current classificatory systems suggest an inclusionary approach to diagnose FND. Hence, there is a need to systematically evaluate the diagnostic accuracy of clinical signs and electrophysiological investigations in view of the lack of gold standard tests to diagnose FND.

METHODS

PubMed and SCOPUS databases were searched for studies published from Jan 1950 to Jan 2022 which reported the diagnostic accuracy of clinical signs and electrophysiological investigations in patients with FND. The Newcastle Ottawa scale was used to assess the quality of the studies.

RESULTS

Twenty-one studies (727 cases and 932 controls), of which 16 reported clinical signs and, five reported electrophysiological investigations, were included in the review. Two studies were of good quality, 17 of moderate quality, and two of poor quality. We identified 46 clinical signs (24 in weakness, 3 in sensory, and 19 in movement disorders) and 17 investigations (all in movement disorders). Specificity values for signs and investigations were comparatively high compared to the wide variance in sensitivity values.

CONCLUSION

Electrophysiological investigations appear to have a promising role in diagnosing FND, particularly functional movement disorders. The combined use of individual clinical signs and electrophysiological investigations may support and improve diagnostic certainty of FND. Future research can focus on improving the methodology and validating the existing clinical signs and electrophysiological investigations to enhance the validity of the composite diagnostic criterias for FND diagnosis.

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.

Functional Neurological Disorders: Clinical Spectrum, Diagnosis, and Treatment

BACKGROUND

Functional neurological disorders (FNDs) are common but often misdiagnosed.

REVIEW SUMMARY

The incidence of FNDs is between 4 and 12 per 100,000, comparable to multiple sclerosis and amyotrophic lateral sclerosis, and it is the second most common diagnosis in neurology clinics. Some clues in the history are sudden onset, intermittent time course, variability of manifestation over time, childhood trauma, and history of other somatic symptoms. Anxiety and depression are common, but not necessarily more than in the general population. Although there are no tests currently capable of demonstrating whether symptoms are willfully produced, there may not be a clear categorical difference between voluntary and involuntary symptoms. The prognosis of an FND is linked to early diagnosis and symptom duration, but unfortunately, the majority of the patients are diagnosed after considerable delays.

CONCLUSIONS

A positive diagnosis of FNDs can be made on the basis of history and neurological signs without reliance on psychological stressors. Past sensitizing events and neurobiological abnormalities contribute to the pathogenesis of FNDs. Physical rehabilitation and psychological interventions alone or in combination are helpful in the treatment.

Functional tremor developing after successful MRI-guided focused ultrasound thalamotomy for essential tremor

OBJECTIVE

To describe a case of functional tremor occurring after a successful MR-guided focused ultrasound thalamotomy (MRgFUS) for essential tremor.

METHODS

A 71-year-old right-handed man with essential tremor was referred to us for consideration of deep brain stimulation surgery for worsening bilateral upper limb tremor after a successful left MRgFUS for essential tremor.

RESULTS

On clinical exam, signs compatible with a functional tremor were noted, including entertainability and suppressibility. Electrophysiological studies were consistent with essential tremor and superimposed tremor fulfilling the laboratory-supported criteria for functional tremor.

DISCUSSION

We describe the first reported case of a functional movement disorder occurring after successful MRgFUS procedure for essential tremor. Recognising this entity and its development after such therapeutic interventions is essential to avoid further unnecessary invasive therapies.

Distractibility predicts favourable response of functional tremor to transcranial magnetic stimulation: An electrophysiological study

BACKGROUND

Generation of functional tremor relies on the structures involved in the control of voluntary movements. The clinical diagnosis is based on the presence of "positive signs", which are expression of cognitive and motor distractibility and reflect functional tremor dependence on explicit motor control. In patients who manifest less distractibility, habitual (implicit) control may be of greater significance. Habitual behaviours are inflexible and difficult to eradicate.

OBJECTIVES

To investigate if motor and cognitive distractibility predicts response to treatment with repetitive transcranial magnetic stimulation.

METHODS

21 patients with functional tremor underwent 5-day repeated sessions of continuous theta burst stimulation over primary motor cortex. A battery of tests to provoke positive signs was performed during accelerometry recordings and the total functional tremor accelerometry score was calculated for each patient. Response to treatment was measured as change in tremor amplitude, expressed as total power of the spectra between 1 and 30 Hz.

RESULTS

On the group level, cTBS significantly changed postural tremor amplitude (Z = -1.9; p = 0.05), with the median decrease of 40%, IQR (-90-(+24)). There was a positive correlation between the functional tremor accelerometry score and reduction of postural tremor amplitude with treatment (r_s = -0.75, p < 10^-3). Responders had higher functional tremor accelerometry scores compared to non-responders (p = 0.001). The total functional tremor accelerometry score was a significant predictor of treatment response (OR = 2.8, p = 0.03; 95% CI 1.1; 7.2).

CONCLUSIONS

Patients who are more distractible are better candidates for treatment with transcranial magnetic stimulation. The likely explanation is the between-subjects differences on the reliance of functional tremor generation on explicit vs. implicit motor network.

Electrophysiological testing aids the diagnosis of tremor and myoclonus in clinically challenging patients

Objective

We investigated how clinical neurophysiological testing can help distinguish tremor and myoclonus and their subtypes.

Methods

We retrospectively analysed clinical and neurophysiological data from patients who had undergone polymyography (EMG + accelerometry) to diagnose suspected tremor or myoclonus. We show a systematic approach, which includes contraction pattern, rhythm regularity, burst duration and evidence of cortical drive.

Results

We detected 773 patients in our database, of which 556 patients were ultimately diagnosed with tremor (enhanced physiological tremor n = 169, functional tremor n = 140, essential tremor n = 90, parkinsonism associated tremor n = 64, cerebellar tremor n = 19, Holmes tremor n = 12, dystonic tremor n = 8, tremor not further specified n = 9), 140 with myoclonus and 23 with a combination of tremor and myoclonus. Polymyography confirmed the presumptive diagnosis in the majority of the patients and led to a change of diagnosis in 287 patients (37%). Conversions between diagnoses of tremor and myoclonus occurred most frequently between enhanced physiological tremor, essential tremor, functional tremor and cortical myoclonus.

Conclusions

Neurophysiology is a valuable additional tool in clinical practice to differentiate between tremor and myoclonus, and can guide towards a specific subtype.

Significance

We show how the stepwise neurophysiological approach used at our medical center aids the diagnosis of tremor versus myoclonus.

Diagnosis and management of functional neurological disorder

Functional neurological disorder (FND), previously regarded as a diagnosis of exclusion, is now a rule-in diagnosis with available treatments. This represents a major step toward destigmatizing the disorder, which was often doubted and deemed untreatable. FND is prevalent, generally affecting young and middle aged adults, and can cause severe disability in some individuals. An early diagnosis, with subsequent access to evidence based rehabilitative and/or psychological treatments, can promote recovery-albeit not all patients respond to currently available treatments. This review presents the latest advances in the use of validated rule-in examination signs to guide diagnosis, and the range of therapeutic approaches available to care for patients with FND. The article focuses on the two most frequently identified subtypes of FND: motor (weakness and/or movement disorders) and seizure type symptoms. Twenty two studies on motor and 27 studies on seizure type symptoms report high specificities of clinical signs (64-100%), and individual signs are reviewed. Rehabilitative interventions (physical and occupational therapy) are treatments of choice for functional motor symptoms, while psychotherapy is an emerging evidence based treatment across FND subtypes. The literature to date highlights heterogeneity in responses to treatment, underscoring that more research is needed to individualize treatments and develop novel interventions.

Utility of routine surface electrophysiology to screen for functional tremor prior to surgical treatment of essential tremor

Background

Patients with functional tremor may be clinically misdiagnosed as “medication-refractory” essential tremor (ET) and referred for surgical treatment. Electrophysiology can screen for functional tremor and avoid inappropriate surgery.

Objective

To report the utility of surface electrophysiology (SEMG) to screen for functional tremor in patients referred for ET surgery.

Methods

Retrospective review of consecutive ET patients referred to the Mayo Clinic DBS clinic over 1.5 years. Included subjects had a clinical diagnosis of medication-refractory ET and completed presurgical workup including routine SEMG tremor study.

Results

Of 87 subjects, 9 (10%) were clinically suspected of functional tremor by the DBS neurologist. Electrophysiology confirmed functional tremor features in 7/9 and ET in the other 2/9; and newly identified 5 additional cases of functional tremor. There were 12 total confirmed cases of functional tremor: isolated in 1, and mixed functional tremor and ET in 11. Of 11 mixed patients, 6 with mild functional overlay were approved for surgery. The remaining 5 patients with moderate-severe functional overlay and the single patient with isolated functional tremor were referred to the functional tremor motor retraining program. Of these, 1 patient with mixed tremor had residual disabling organic ET after program completion and was later approved for surgery. Thus, 5/87 patients (6%) avoided unnecessary surgery.

Conclusions

Functional tremor may frequently overlay “medication-refractory” ET amongst patients referred for surgery, affecting 1 of 7 patients in our quaternary referral DBS center. Electrophysiology studies are useful to routinely screen patients and prevent unnecessary surgery.

Sudden Onset, Fixed Dystonia and Acute Peripheral Trauma as Diagnostic Clues for Functional Dystonia

Background

The differentiation of functional dystonia from idiopathic dystonia may be clinically challenging.

Objective

To identify clinical features suggestive of functional dystonia to guide physicians to distinguish functional dystonia from idiopathic dystonia.

Methods

Patient data were extracted from the Italian Registry of Functional Motor Disorders and the Italian Registry of Adult Dystonia. Patients with functional and idiopathic dystonia were followed up at the same clinical sites, and they were similar in age and sex.

Results

We identified 113 patients with functional dystonia and 125 with idiopathic dystonia. Sudden onset of dystonia, evidence of fixed dystonia, and acute peripheral trauma before dystonia onset were more frequent in the functional dystonia group. No study variable alone achieved satisfactory sensitivity and specificity, whereas a combination of variables yielded 85% sensitivity and 98% specificity. A diagnostic algorithm was developed to reduce the risk of misclassifying functional dystonia.

Conclusion

Our findings extend the current diagnostic approach to functional dystonia by showing that clinical information about symptom onset, fixed dystonia, and history of peripheral trauma may provide key clues in the diagnosis of functional dystonia.

Utility of tremor electrophysiology studies

Objective

To determine the utility of tremor electrophysiology testing in differentiating clinically indeterminate tremor due to organic, functional, and mixed tremor types.

Background

Prior studies have shown that electrophysiological studies increase diagnostic sensitivity of tremor syndromes; however, few have examined mixed organic and functional tremors.

Methods

Patients referred for tremor to the Mayo Clinic, Rochester movement disorders lab were consecutively selected and retrospectively reviewed. Surface electromyography (EMG) recordings of upper limb muscles were performed at rest, posture, with action and distractibility tasks.

Results

Of 116 patients, all were clinically described as having either a resting tremor, postural tremor, action tremor, postural and action tremor, mixed resting, postural, and action tremor, or nonspecific tremulousness. Based on electrophysiological features, patients were diagnosed with organic tremor (parkinsonian, essential, mixed, rubral, cerebellar, non-specific tremulousness), functional tremor, or mixed functional and organic tremors. The median disease duration at electrophysiological confirmation of diagnosis was shorter for functional tremor at 1.5 years (IQR 1-9.3), and organic tremor at 3 years (IQR 1-15), versus mixed organic and functional tremor at 11 years (IQR 2-15) (p = 0.0422). The electrophysiology study clarified the referral/clinical diagnosis in 87 patients (75%), 26 (29.5%) of whom had functional tremor, and 61 (70.1%) had organic tremor or mixed organic/functional tremor. Variability of tremor during electrophysiology testing was associated with a change in diagnosis (p = 0.0286).

Conclusion

Our findings show that electrophysiological assessment of tremor can be helpful in the clinical diagnosis of patients with both organic and functional tremor.

Evaluation of movement and brain activity

Clinical neurophysiology studies can contribute important information about the physiology of human movement and the pathophysiology and diagnosis of different movement disorders. Some techniques can be accomplished in a routine clinical neurophysiology laboratory and others require some special equipment. This review, initiating a series of articles on this topic, focuses on the methods and techniques. The methods reviewed include EMG, EEG, MEG, evoked potentials, coherence, accelerometry, posturography (balance), gait, and sleep studies. Functional MRI (fMRI) is also reviewed as a physiological method that can be used independently or together with other methods. A few applications to patients with movement disorders are discussed as examples, but the detailed applications will be the subject of other articles.

How Positive Are Conversion Disorder Diagnoses?: Patterns of Referral to a Functional Neurology Clinic

ABSTRACT

The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) diagnostic criteria for conversion disorder have replaced the criterion of evidence of a "psychogenic" etiology with a criterion that patients must be "positively" diagnosed on the basis of their neurological assessment. We retrospectively studied referrals to a specialist functional neurology clinic to see how commonly the new criteria were met since DSM-5's introduction. Positive signs were reported in a quarter of referrals (26.5%), which was associated with diagnosticians' confidence (p = 0.001) and with the clinic confirming the diagnosis (p = 0.01). Our clinic found positive signs in 28.6% of the referrals. In 13 (13.3%) patients, the new criterion was not met. In conclusion, positive signs are diagnostically helpful but are only reported in a minority of assessments. A significant group of those currently believed to have conversion disorder would not meet the revised diagnostic criteria based on this.

A Review and Expert Opinion on the Neuropsychiatric Assessment of Motor Functional Neurological Disorders

Functional neurological (conversion) disorder (FND) is a prevalent and disabling condition at the intersection of neurology and psychiatry. Advances have been made in elucidating an emerging pathophysiology for motor FND, as well as in identifying evidenced-based physiotherapy and psychotherapy treatments. Despite these gains, important elements of the initial neuropsychiatric assessment of functional movement disorders (FND-movt) and functional limb weakness/paresis (FND-par) have yet to be established. This is an important gap from both diagnostic and treatment planning perspectives. In this article, the authors performed a narrative review to characterize clinically relevant variables across FND-movt and FND-par cohorts, including time course and symptom evolution, precipitating factors, medical and family histories, psychiatric comorbidities, psychosocial factors, physical examination signs, and adjunctive diagnostic tests. Thereafter, the authors propose a preliminary set of clinical content that should be assessed during early-phase patient encounters, in addition to identifying physical signs informing diagnosis and potential use of adjunctive tests for challenging cases. Although clinical history should not be used to make a FND diagnosis, characteristics such as acute onset, precipitating events (e.g., injury and surgery), and a waxing and waning course (including spontaneous remissions) are commonly reported. Active psychiatric symptoms (e.g., depression and anxiety) and ongoing psychosocial stressors also warrant evaluation. Positive physical examination signs (e.g., Hoover's sign and tremor entrainment) are key findings, as one of the DSM-5 diagnostic criteria. The neuropsychiatric assessment proposed emphasizes diagnosing FND by using "rule-in" physical signs while also considering psychiatric and psychosocial factors to aid in the development of a patient-centered treatment plan.

The diagnostic value of clinical neurophysiology in hyperkinetic movement disorders: A systematic review

INTRODUCTION

To guide the neurologist and neurophysiologist with interpretation and implementation of clinical neurophysiological examinations, we aim to provide a systematic review on evidence of electrophysiological features used to differentiate between hyperkinetic movement disorders.

METHODS

A PRISMA systematic search and QUADAS quality evaluation has been performed in PubMed to identify diagnostic test accuracy studies comparing electromyography and accelerometer features. We included papers focusing on tremor, dystonia, myoclonus, chorea, tics and ataxia and their functional variant. The features were grouped as 1) basic features (e.g., amplitude, frequency), 2) the influence of tasks on basic features (e.g., entrainment, distraction), 3) advanced analyses of multiple signals, 4) and diagnostic tools combining features.

RESULTS

Thirty-eight cross-sectional articles were included discussing tremor (n = 28), myoclonus (n = 5), dystonia (n = 5) and tics (n = 1). Fifteen were rated as 'high quality'. In tremor, the basic and task-related features showed great overlap between clinical tremor syndromes, apart from rubral and enhanced physiological tremor. Advanced signal analyses were best suited for essential, parkinsonian and functional tremor, and cortical, non-cortical and functional jerks. Combinations of electrodiagnostic features could identify essential, enhanced physiological and functional tremor.

CONCLUSION

Studies into the diagnostic accuracy of electrophysiological examinations to differentiate between hyperkinetic movement disorders have predominantly been focused on clinical tremor syndromes. No single feature can differentiate between them all; however, a combination of analyses might improve diagnostic accuracy.

Functional Neurologic Disorders: The Need for a Model of Care

Neurologists are commonly consulted for patients with a functional neurologic disorder. Best practices as to their diagnosis and treatment have been established, and multiple academic centers have programs in place for their treatment. However, given the number of patients suffering from this condition, a comprehensive model of care that can be broadly implemented needs to be developed and applied beyond specialized academic programs.

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.

Suggestibility as a valuable criterion for laboratory-supported definite functional movement disorders

OBJECTIVE

To evaluate the application of suggestibility in electrophysiologic studies as a tool to increase the diagnostic certainty of "laboratory-supported definite" FMD.

METHODS

We retrospectively reviewed the electrophysiologic studies performed in our center on patients with FMD. Recordings where suggestibility was included in the test battery were then selected.

RESULTS

We present three cases with equivocal clinical features, but with findings on electrophysiologic studies that were consistent with "laboratory-supported definite" FMD.

CONCLUSION

When combined with other tests, demonstration of suggestibility in electrophysiologic studies may increase the accuracy in differentiating functional from organic movement disorders.

SIGNIFICANCE

This case series is an essential first step in evaluating the applicability of suggestibility as an electrophysiologic criterion to aid in the diagnosis of FMD. Application in a larger cohort, incorporation in a test battery, and validation studies, including quantitative evaluation of suggestibility, are required to assess the reliability and the added value of this test.

Diagnosis and therapy of functional tremor a systematic review illustrated by a case report

Background

Diagnosis of functional movement disorders and specifically functional tremor (FT) (representing 50% of them) remains demanding. Additionally, due to heterogeneity of the disorders, structured concepts and guidelines for diagnosis and therapy are difficult to establish. Ascertaining the state of knowledge to derive instructions for operating procedures is the aim of this review.

Main text

Based on a standardized systematic literature research using the term “psychogenic tremor” in the MEDLINE database dating back ten years, 76 studies were evaluated. Conventional features of FT are variability of frequency and amplitude. Further, response to distraction by motor and cognitive tasks is a key diagnostic feature in differentiation between organic and functional origin. A variety of electrophysiological tests have been evaluated including surface electromyography and accelerometry to establish laboratory-supported criteria for diagnosing tremor. Also, finger tapping tests have been used to identify FT, showing positive potential as supplementary evidence.

Imaging studies in general are mostly underpowered and imaging cannot be used on an individual basis. Therapeutic studies in FT often have a diagnostic component. Cognitive behavioral therapy should be the preferred psychological treatment independent of additional psychiatric symptoms. Other psychotherapeutic methods show lack of evidence concerning FT. Relaxation techniques and physiotherapy are an important additional feature, especially in children and adolescents. In regard to drug therapy, randomized and blinded trials are not available. A significant decrease in rating scales could be detected after active, not sham repetitive transcranial magnetic stimulation with a long-lasting effect. Also root magnetic stimulation seems to be effective. The clinical feature of tremor entrainment in FT can be used in combination with biofeedback as so-called tremor retrainment, using self-modulation of frequency and severity, to bring the movements under volitional control.

Conclusion

Diagnosis and treatment of FT is challenging and should include a combination of intensive clinical examination and targeted addition of standardized testing, especially electrophysiological methods. Often therapeutic effects have a diagnostic component. A multimodal strategy, considering psychological factors as a potential origin as well as maintaining effects seems to be most effective.

Biomarkers in functional movement disorders: a systematic review

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

Functional movement disorder comorbidity in Parkinson's disease: Unraveling the web

Functional movement disorders are commonly seen in neurology services and may coexist with other neurological diseases. This combination is known as "functional overlay" and an increasing interest on this topic has emerged in the past decade as the field of functional neurological disorders has moved forward. Some neurological diseases may be more prone to develop "functional overlay" than others, and within the field of movement disorders, most studies have focused on patients with Parkinson's disease. This review comprehensively summarizes the current body of knowledge on this topic and provides an expert opinion to equip clinicians with a pragmatic approach to recognize functional movement disorders in patients with Parkinson's disease, to communicate the diagnosis and to become familiar with potential therapies in this complex clinical scenario. Potential underlying mechanisms and risk factors that may play a role in increasing the vulnerability of Parkinson's disease patients to develop functional movement disorder comorbidity are also discussed within the framework of modern neurobiological theories of brain functioning.

Functional Motor Symptoms in Parkinson's Disease and Functional Parkinsonism: A Systematic Review

OBJECTIVE

Whereas functional symptoms are common in Parkinson's disease (PD), a parkinsonian syndrome may occasionally reflect a pure functional disorder (also named functional parkinsonism [FP]). This review aimed to decipher these entities to clarify the link between functional manifestations and PD.

METHODS

Following the PRISMA guidelines, the authors performed a systematic literature search of the PubMed and Science Direct databases for the period 1988 to December 2018 to identify studies of patients with either FP or PD associated with functional neurological symptoms.

RESULTS

From the 844 articles screened, 22 were retained, including 12 studies of functional neurological symptoms in PD and 16 studies of FP. The studies of functional symptoms in PD included 121 patients-57% were women, and the mean age was 61.3 years. Psychiatric history (mostly depression) and exposure to triggering stressors were frequent: 60% and 82.5%, respectively. The most common symptom was tremor (33.8%), most often located on the side most affected by PD (50%). Studies of FP included a total of 120 patients-62% were women, and the mean age was 50.7 years. The first FP symptoms appeared on average 5 years before diagnosis, with an abrupt onset in half the cases; 67.6% had a psychiatric history, and 46.8% were exposed to triggering stressors, such as physical injury, stress at work, or loss of family or friends.

CONCLUSIONS

Findings suggest a possible relationship between PD and FP. Clinicians should keep in mind the possibility of functional symptoms in PD patients.

Functional or not functional; that's the question: Can we predict the diagnosis functional movement disorder based on associated features?

Background and purpose

Functional movement disorders (FMDs) pose a diagnostic challenge for clinicians. Over the years several associated features have been shown to be suggestive for FMDs. Which features mentioned in the literature are discriminative between FMDs and non‐FMDs were examined in a large cohort. In addition, a preliminary prediction model distinguishing these disorders was developed based on differentiating features.

Method

Medical records of all consecutive patients who visited our hyperkinetic outpatient clinic from 2012 to 2019 were retrospectively reviewed and 12 associated features in FMDs versus non‐FMDs were compared. An independent t test for age of onset and Pearson chi‐squared analyses for all categorical variables were performed. Multivariate logistic regression analysis was performed to develop a preliminary predictive model for FMDs.

Results

A total of 874 patients were eligible for inclusion, of whom 320 had an FMD and 554 a non‐FMD. Differentiating features between these groups were age of onset, sex, psychiatric history, family history, more than one motor phenotype, pain, fatigue, abrupt onset, waxing and waning over long term, and fluctuations during the day. Based on these a preliminary predictive model was computed with a discriminative value of 91%.

Discussion

Ten associated features are shown to be not only suggestive but also discriminative between hyperkinetic FMDs and non‐FMDs. Clinicians can use these features to identify patients suspected for FMDs and can subsequently alert them to test for positive symptoms at examination. Although a first preliminary model has good predictive accuracy, further validation should be performed prospectively in a multi‐center study.

Systematic clinical approach for diagnosing upper limb tremor

Tremor is the most common movement disorder worldwide, but diagnosis is challenging. In 2018, the task force on tremor of the International Parkinson and Movement Disorder Society published a consensus statement that proposes a tremor classification along two independent axes: a clinical tremor syndrome and its underlying aetiology. In line with this statement, we here propose a stepwise diagnostic approach that leads to the correct clinical and aetiological classification of upper limb tremor. We also describe the typical clinical signs of each clinical tremor syndrome. A key feature of our algorithm is the distinction between isolated and combined tremor syndromes, in which tremor is accompanied by bradykinesia, cerebellar signs, dystonia, peripheral neuropathy or brainstem signs. This distinction subsequently informs the selection of appropriate diagnostic tests, such as neurophysiology, laboratory testing, structural and dopaminergic imaging and genetic testing. We highlight treatable metabolic causes of tremor, as well as drugs and toxins that can provoke tremor. The stepwise approach facilitates appropriate diagnostic testing and avoids unnecessary investigations. We expect that the approach offered in this article will reduce diagnostic uncertainty and increase the diagnostic yield in patients with tremor.

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.

Principles of Electrophysiological Assessments for Movement Disorders

Electrophysiological studies can provide objective and quantifiable assessments of movement disorders. They are useful in the diagnosis of hyperkinetic movement disorders, particularly tremors and myoclonus. The most commonly used measures are surface electromyography (sEMG), electroencephalography (EEG) and accelerometry. Frequency and coherence analyses of sEMG signals may reveal the nature of tremors and the source of the tremors. The effects of voluntary tapping, ballistic movements and weighting of the limbs can help to distinguish between organic and functional tremors. The presence of Bereitschafts-potentials and beta-band desynchronization recorded by EEG before movement onset provide strong evidence for functional movement disorders. EMG burst durations, distributions and muscle recruitment orders may identify and classify myoclonus to cortical, subcortical or spinal origins and help in the diagnosis of functional myoclonus. Organic and functional cervical dystonia can potentially be distinguished by EMG power spectral analysis. Several reflex circuits, such as the long latency reflex, blink reflex and startle reflex, can be elicited with different types of external stimuli and are useful in the assessment of myoclonus, excessive startle and stiff person syndrome. However, limitations of the tests should be recognized, and the results should be interpreted together with clinical observations.

Psychogenic (Functional) Movement Disorders

PURPOSE OF REVIEW

This article reviews a practical approach to psychogenic movement disorders to help neurologists identify and manage this complex group of disorders.

RECENT FINDINGS

Psychogenic movement disorders, also referred to as functional movement disorders, describe a group of disorders that includes tremor, dystonia, myoclonus, parkinsonism, speech and gait disturbances, and other movement disorders that are incongruent with patterns of pathophysiologic (organic) disease. The diagnosis is based on positive clinical features that include variability, inconsistency, suggestibility, distractibility, suppressibility, and other supporting information. While psychogenic movement disorders are often associated with psychological and physical stressors, the underlying pathophysiology is not fully understood. Although insight-oriented behavioral and pharmacologic therapies are helpful, a multidisciplinary approach led by a neurologist, but also including psychiatrists and physical, occupational, and speech therapists, is needed for optimal outcomes.

SUMMARY

The diagnosis of psychogenic movement disorders is based on clinical features identified on neurologic examination, and neurophysiologic and imaging studies can provide supporting information.