Neuropsychiatry J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2020-323953 on 15 March 2021. Downloaded from Review Decade of progress in motor functional neurological disorder: continuing the momentum David L Perez ,1 Mark J Edwards,2 Glenn Nielsen,2 Kasia Kozlowska,3 Mark Hallett ,4 W Curt LaFrance, Jr 5 ► Additional material is ABSTRACT specificity, an expanding ‘toolbox’ of treatments published online only. To view, Functional neurological disorder (FND) is a prevalent, and new pathophysiological models that embrace please visit the journal online patient- centred biopsychosocial formulations.3 A (http:// dx. doi. org/ 10. 1136/ disabling and costly condition at the neurology– jnnp- 2020- 323953). psychiatry intersection. After being marginalised in the newly formed professional society ( www. fndsociety. late 20th century, there has been renewed interest org), authoritative FND textbooks4 5 and recent 1Neurology and Psychiatry, in this field. In this article, we review advances that special journal issues on this topic have further Massachusetts General Hospital, have occurred over the past decade (2011–2020) energised clinical and research efforts in FND. Boston, Massachusetts, USA 2Neuroscience Research Centre, across diagnosis, mechanisms, aetiologies, treatments In this narrative review, we highlight important St George’s University of and stigma in patients with motor FND (mFND, that advancements and their implications for motor London, London, UK is, functional movement disorder and functional limb FND (mFND) over the past 10 years (2011–2020)— 3 Westmead Institute of Medical weakness). In each content area, we also discuss the spanning functional movement disorder and func- Research, The Children’s tional limb/face weakness. We use a transdiagnostic Hospital at Westmead, Sydney implications of recent advances and suggest future Medical School, Westmead, New directions that will help continue the momentum of the approach across the range of functional motor South Wales, Australia past decade. In diagnosis, a major advance has been symptoms given high phenotypic overlap across 4NIH, NINDS, Bethesda, the emphasis on rule- in physical signs that are specific populations (eg, functional tremor with concurrent Maryland, USA for hyperkinetic and hypokinetic functional motor functional weakness in the same limb).S3 Isolated 5Psychiatry and Neurology, Rhode Island Hospital, symptoms. Mechanistically, greater importance has functional (psychogenic non- epileptic/dissociative) Providence, Rhode Island, USA been given to determining ’how’ functional neurological seizures, functional speech/voice disorder, func- symptoms develop, highlighting roles for misdirected tional cognitive disorder, functional sensory deficits copyright. Correspondence to attention, expectation and self- agency, as well as and the spectrum of functional somatic disorders Dr W Curt LaFrance, Jr, abnormal influences of emotion/threat processing brain are beyond the scope of this article and have been Psychiatry and Neurology, areas on motor control circuits. Aetiologically, while reviewed elsewhere.S4 S5 Sections here detail recent Rhode Island Hospital, Providence, RI 2903, USA; roles for adverse life experiences remain of interest developments in diagnosis, mechanisms, aetiolog- william_ lafrance_ jr@ brown. edu in mFND, there is recognition of other aetiologic ical factors, treatments and stigma in patients with contributors, and efforts are needed to investigate links mFND. In each content area, future directions are Received 30 December 2020 between aetiological factors and mechanisms. This also suggested, aimed at continuing the momentum Revised 8 February 2021 of the past decade. Accepted 23 February 2021 decade has seen the first randomised controlled trials Published Online First 15 March for physiotherapy, multidisciplinary rehabilitation and 2021 psychotherapy performed in the field, with consensus recommendations for physiotherapy, occupational DIAGNOSIS http://jnnp.bmj.com/ therapy and outcome measures also published. Across New developments patients, clinicians, healthcare systems and society, Establishing the diagnosis of mFND has been made S6 stigma remains a major concern. While challenges more practicable, as physical examination find- persist, a patient- centred integrated clinical neuroscience ings with diagnostic specificity have been identified approach is primed to carry forward the momentum of (eg, Hoover’s sign with an estimated specificity 6 the past decade into the future. of 95.7%–99.9%). Educational efforts have also made neurologists more confident in their ability to on September 30, 2021 by guest. Protected accurately diagnose patients with mFND, discour- aging extensive laboratory testing unless a comorbid INTRODUCTION neurological disorder is suspected.7 Functional neurological disorder (FND), also The Diagnostic and Statistical Manual of Mental known as conversion disorder, is a common, Disorders- Fifth Edition (DSM-5) criteria for FND disabling and costly condition at the intersection include the diagnostic features of inconsistency of neurology and psychiatry.1 2 While of interest to and incongruity on examination, emphasising posi- founding leaders across the clinical neurosciences in tive neurological features; identifying an under- © Author(s) (or their employer(s)) 2021. No the late 19th century, FND was largely abandoned lying psychological trauma has been relegated to a 1 S3 S6 commercial re-use . See rights by academics and researchers alike during the late discussion note and removed as a criterion. and permissions. Published 20th century.S1 The rationale for these difficulties Inconsistency refers to changes in manifestation by BMJ. were based in part on a Cartesian dualism of the over time, such as variation in tremor frequency To cite: Perez DL, Edwards brain and mind, limited neuropathophysiologic and amplitude or remissions and exacerbations. S2 MJ, Nielsen G, et al. J Neurol understanding and few evidence- based treatments. Incongruity refers to discordance with other known Neurosurg Psychiatry In the 21st century, a resurgence of interest in FND neurological disorders or human anatomy and 2021;92:668–677. has occurred, catalysed by improved diagnostic physiology. Additional general diagnostic features 668 Neuropsychiatry J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp-2020-323953 on 15 March 2021. Downloaded from Table 1 Positive clinical features (phenotype specific) and useful adjunctive laboratory tests for the diagnosis of functional movement disorder Functional motor symptom Clinical features Laboratory tests Tremor Entrainment (tremor takes on the rhythm of paced movements performed with another Clinical neurophysiological measurements can quantify entrainment, body part) pause with quick movement, variability, tonic contraction at onset, Pause with quick movement of another limb increase amplitude with weighting and coherence between limbs Variability in frequency, amplitude Tonic contraction at onset Increase in amplitude with weighting Coherence of tremor between two limbs Whack- a- mole sign (restraint of tremor induces tremor in another body part) Myoclonus Variability and long duration of the movement Long electromyography bursts Complex movement Presence of a Bereitschaftspotential (readiness potential) before the Appearance of startle jerk Long and variable latency of stimulus induced jerks With stimulus- induced jerks: long and variable latency Jerks when tendon hammer stops short of contact Tic Lack of urge Normal Bereitschaftspotential Lack of voluntary control (suppressibility) Dystonia Certain patterns such as fixed dystonia or pulling lip to one side Normal blink reflex recovery Normal plasticity with paired associative conditioning Parkinsonism Marked slowness or incoordination in examination but not with normal movements Normal dopamine transporter scan Gegenhalten (variable resistance during passive movement) Lack of sequence effect (slowness without amplitude decrement during repetitive movements) Huffing and puffing sign (fatigue with minimal effort) Gait disorders Specific patterns including knee buckling, dragging a monoplegic leg, astasia- abasia, None excessive slowness and atypical limping Better balance than claimed, including improvement with distraction Either no falls, controlled falls or falling toward support Chair test (can use legs to move a chair better than walking) are distractibility and suggestibility. Most other diagnostic signs intermittent lip deviation to one side15 are commonly identified are phenotype specific and can be augmented by certain clinical functional patterns. Functional facial spasm, a common stroke copyright. neurophysiological tests.S7 Clinical neurophysiological tests (eg, mimic, is characterised by platysma hyperactivation, jaw devia- electromyography- assisted identification of tremor pause during tion and ipsilateral eyebrow depression.15 ballistic movements) can either objectify bedside observations or In support of the stability of an mFND diagnosis based on identify features that clinicians cannot readily appreciate.8 examination signs, a 14- year prospective study in 76 patients Positive signs on examination that characterise functional limb with functional limb weakness showed only a 1% misdiagnosis weakness (and functional sensory and gait disorders) have been rate.16 Notably, some patients have both functional neurolog- analysed for their statistical properties (including sensitivities ical