Psychogenic tremor: a video guide to its distinguishing features

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.

Mechanism of stress-induced attacks in an episodic neurologic disorder

Stress is the most common trigger among episodic neurologic disorders. In episodic ataxia type 2 (EA2), physical or emotional stress causes episodes of severe motor dysfunction that manifest as ataxia and dystonia. We used the tottering (tg/tg) mouse, a faithful animal model of EA2, to dissect the mechanisms underlying stress-induced motor attacks. We find that in response to acute stress, activation of α1-adrenergic receptors (α1-Rs) on Purkinje cells by norepinephrine leads to their erratic firing and consequently motor attacks. We show that norepinephrine induces erratic firing of Purkinje cells by disrupting their spontaneous intrinsic pacemaking via a casein kinase 2 (CK2)-dependent signaling pathway, which likely reduces the activity of calcium-dependent potassium channels. Moreover, we report that disruption of this signaling cascade at a number of nodes prevents stress-induced attacks in the tottering mouse. Together, our results suggest that norepinephrine and CK2 are required for the initiation of stress-induced attacks in EA2 and provide previously unidentified targets for therapeutic intervention.

Tremor Syndromes: An Updated Review

Tremor is the most commonly encountered movement disorder in clinical practice. A wide range of pathologies may manifest with tremor either as a presenting or predominant symptom. Considering the marked etiological and phenomenological heterogeneity, it would be desirable to develop a classification of tremors that reflects their underlying pathophysiology. The tremor task force of the International Parkinson Disease and Movement Disorders Society has worked toward this goal and proposed a new classification system. This system has remained a prime topic of scientific communications on tremor in recent times. The new classification is based on two axes: 1. based on the clinical features, history, and tremor characteristics and 2. based on the etiology of tremor. In this article, we discuss the key aspects of the new classification, review various tremor syndromes, highlight some of the controversies in the field of tremor, and share the potential future perspectives.

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.

Towards an Outpatient Model of Care for Motor Functional Neurological Disorders: A Neuropsychiatric Perspective

Functional neurological disorder (FND), a condition at the intersection of neurology and psychiatry, is a common and disabling outpatient referral to neurology and neuropsychiatry clinics. In this perspective article, we focus on the motor spectrum of FND (mFND), including individuals with functional movement disorders (FND-movt), functional limb weakness/paresis (FND-par) and functional [psychogenic non-epileptic/dissociative] seizures (FND-seiz). Over the past several decades, there have been dedicated efforts within the neurologic and psychiatric communities to create "rule-in" diagnostic criteria, as well as thoughtful approaches to the clinical interview, delivery of the diagnosis and the development of a patient-centered treatment plan. These advances allow the promotion of good clinical practices in the outpatient assessment and management of mFND. Informed by the literature and our prior clinical experiences, we provide suggestions on how to evaluate individuals with suspected functional motor symptoms - including conducting sensitive psychiatric and psychosocial screenings. Additional sections discuss common "rule-in" neurological examination and semiologic signs of motor FND, as well as approaches to deliver the diagnosis and formulate a treatment plan based on individual patient needs. To aid the development of shared (partially overlapping) expertise that catalyzes an interdisciplinary approach to mFND, the use of physiotherapy for therapeutic motor retraining and cognitive behavioral therapy to examine relationships between symptoms, thoughts, behaviors and emotions are also discussed. Additional clinical research is needed to further refine and operationalize the assessment and management of mFND, across clinics, healthcare settings and countries.

The Rehapiano-Detecting, Measuring, and Analyzing Action Tremor Using Strain Gauges

We have developed a device, the Rehapiano, for the fast and quantitative assessment of action tremor. It uses strain gauges to measure force exerted by individual fingers. This article verifies the device's capability to measure and monitor the development of upper limb tremor. The Rehapiano uses a precision, 24-bit, analog-to-digital converter and an Arduino microcomputer to transfer raw data via a USB interface to a computer for processing, database storage, and evaluation. First, our experiments validated the device by measuring simulated tremors with known frequencies. Second, we created a measurement protocol, which we used to measure and compare healthy patients and patients with Parkinson's disease. Finally, we evaluated the repeatability of a quantitative assessment. We verified our hypothesis that the Rehapiano is able to detect force changes, and our experimental results confirmed that our system is capable of measuring action tremor. The Rehapiano is also sensitive enough to enable the quantification of Parkinsonian tremors.

Processing of Emotion in Functional Neurological Disorder

Emotions have traditionally been considered crucial in the development of functional neurological disorder, but the evidence underpinning this association is not clear. We aimed to summarize evidence for association between functional neurological disorder and emotions as formulated by Breuer and Freud in their conception of hysterical conversion. Based on a systematic literature search, we identified 34 controlled studies and categorized them into four groups: (i) autonomic arousal, (ii) emotion-motion interactions, (iii) social modulation of symptoms, and (iv) bodily awareness in FND. We found evidence for autonomic dysregulation in FND; convergent neuroimaging findings implicate abnormal limbic-motor interactions in response to emotional stimuli in FND. Our results do not provide enough empirical evidence for social modulation of the symptoms, but there is a clinical support for the role of suggestion and placebo in FND. Our results provide evidence for abnormal bodily awareness in FND. Based on these findings, we propose that functional neurological symptoms are forms of emotional reactions shaped into symptoms by previous experience with illness and possibly reinforced by actual social contexts. Additional research should investigate the effect of social context on the intensity of functional neurological symptoms and associated brain regions.

Hemiataxia: A Novel Presentation of Anti-NMDA Receptor Antibody Mediated Encephalitis in an Adolescent

Anti-NMDA receptor antibody associated encephalitis as a cause of new-onset neuropsychiatric manifestations in children and adults can represent a significant diagnostic challenge for clinicians. Clinical signs often include encephalopathy, new-onset psychosis, and movement phenomenon. Although orofacial dyskinesias were initially identified as a characteristic movement phenomenon in this type of encephalitis, an expanded range of abnormalities has recently been reported, including isolated ataxia. We report a case of isolated hemiataxia in a young adult with mild initial psychiatric manifestations. A personal and family history of preceding neuropsychiatric symptoms produced diagnostic confusion and resulted in a significant diagnostic and therapeutic delay. Our case confirms the unilateral movement manifestations that have been emphasized in recent reports. Additionally, it confirms the need for involvement of neurologic as well as psychiatric services in the evaluation of such cases and emphasizes the importance of the neurologic examination in presentations with an initial psychiatric predominance.

Are Patients with Psychogenic Movement Disorders More Likely to be Healthcare Workers?

Background

Reported risk factors for the development of a psychogenic movement disorder (PMD) include young age, female gender, history of abuse, current or past psychiatric disorder, lower levels of education and socioeconomic status, and employment as a healthcare worker. Although employment in healthcare is included in several diagnostic criteria for PMD, as well as in many case series, this association has never been validated.

Methods

Using the University of Maryland Movement Disorder Database (UMMDD), we identified PMD cases, as well as patients with isolated focal dystonia as controls. An experienced movement disorder specialist diagnosed all patients, and all cases met criteria for clinically established PMD. Demographic and occupational histories were obtained from medical records and were supplemented by telephone interviews. PMD cases and controls were compared using t tests/χ² tests.

Results

Controls (n = 148) were older than PMD cases (n = 132), with an average age of 61.4 and 52.1 years, respectively (P < 0.001); there were no significant differences between groups with respect to gender, education level, and ethnicity. The proportion of healthcare workers was not significantly different between PMD cases and controls (25% of PMD cases vs. 20% of controls; P = 0.28).

Conclusions

In contrast to traditional teaching, this investigation demonstrates that in our patient population, patients with a PMD were no more likely to be employed as healthcare workers than patients with isolated focal dystonia. This study calls into question the use of employment in healthcare as a reliable criterion to support the diagnosis of PMD.

The therapeutic potential of cannabinoids for movement disorders

There is growing interest in the therapeutic potential of marijuana (cannabis) and cannabinoid-based chemicals within the medical community and, particularly, for neurological conditions. This interest is driven both by changes in the legal status of cannabis in many areas and increasing research into the roles of endocannabinoids within the central nervous system and their potential as symptomatic and/or neuroprotective therapies. We review basic science as well as preclinical and clinical studies on the therapeutic potential of cannabinoids specifically as it relates to movement disorders. The pharmacology of cannabis is complex, with over 60 neuroactive chemicals identified to date. The endocannabinoid system modulates neurotransmission involved in motor function, particularly within the basal ganglia. Preclinical research in animal models of several movement disorders have shown variable evidence for symptomatic benefits, but more consistently suggest potential neuroprotective effects in several animal models of Parkinson's (PD) and Huntington's disease (HD). Clinical observations and clinical trials of cannabinoid-based therapies suggests a possible benefit of cannabinoids for tics and probably no benefit for tremor in multiple sclerosis or dyskinesias or motor symptoms in PD. Data are insufficient to draw conclusions regarding HD, dystonia, or ataxia and nonexistent for myoclonus or RLS. Despite the widespread publicity about the medical benefits of cannabinoids, further preclinical and clinical research is needed to better characterize the pharmacological, physiological, and therapeutic effects of this class of drugs in movement disorders.

Recognizing uncommon presentations of psychogenic (functional) movement disorders

BACKGROUND

Psychogenic or functional movement disorders (PMDs) pose a challenge in clinical diagnosis. There are several clues, including sudden onset, incongruous symptoms, distractibility, suggestibility, entrainment of symptoms, and lack of response to otherwise effective pharmacological therapies, that help identify the most common psychogenic movements such as tremor, dystonia, and myoclonus.

METHODS

In this manuscript, we review the frequency, distinct clinical features, functional imaging, and neurophysiological tests that can help in the diagnosis of uncommon presentations of PMDs, such as psychogenic parkinsonism, tics, and chorea; facial, palatal, and ocular movements are also reviewed. In addition, we discuss PMDs at the extremes of age and mass psychogenic illness.

RESULTS

Psychogenic parkinsonism (PP) is observed in less than 10% of the case series about PMDs, with a female-male ratio of roughly 1:1. Lack of amplitude decrement in repetitive movements and of cogwheel rigidity help to differentiate PP from true parkinsonism. Dopamine transporter imaging with photon emission tomography can also help in the diagnostic process. Psychogenic movements resembling tics are reported in about 5% of PMD patients. Lack of transient suppressibility of abnormal movements helps to differentiate them from organic tics. Psychogenic facial movements can present with hemifacial spasm, blepharospasm, and other movements. Some patients with essential palatal tremor have been shown to be psychogenic. Convergence ocular spasm has demonstrated a high specificity for psychogenic movements. PMDs can also present in the context of mass psychogenic illness or at the extremes of age.

DISCUSSION

Clinical features and ancillary studies are helpful in the diagnosis of patients with uncommon presentations of psychogenic movement disorders.