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Movement disorders
Original research
Functional movement disorder gender, age and phenotype study: a systematic review and individual patient meta-analysis of 4905 cases
  1. Sarah C. Lidstone1,2,
  2. Michael Costa-Parke1,
  3. Emily J. Robinson3,4,
  4. Tommaso Ercoli5,
  5. Jon Stone6
  6. FMD GAP Study Group
    1. 1Integrated Movement Disorders Program, University Health Network, Toronto, Ontario, Canada
    2. 2Division of Neurology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
    3. 3Royal Marsden Clinical Trials Unit, The Royal Marsden NHS Foundation Trust, Sutton, UK
    4. 4King’s College London, School of Population Health and Environmental Sciences, London, UK
    5. 5Department of Medical Sciences and Public Health, Institute of Neurology, University of Cagliari, Cagliari, Italy
    6. 6Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
    1. Correspondence to Dr Sarah C. Lidstone, Neurology, University of Toronto, Toronto, ON M5S 1A1, Canada; sarah.lidstone{at}uhnresearch.ca

    Abstract

    Functional movement disorder (FMD) is a common manifestation of functional neurological disorder presenting with diverse phenotypes such as tremor, weakness and gait disorder. Our current understanding of the basic epidemiological features of this condition is unclear. We aimed to describe and examine the relationship between age at onset, phenotype and gender in FMD in a large meta-analysis of published and unpublished individual patient cases. An electronic search of PubMed was conducted for studies from 1968 to 2019 according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Individual patient data were collected through a research network. We described the distribution of age of onset and how this varied by gender and motor phenotype. A one-stage meta-analysis was performed using multilevel mixed-effects linear regression, including random intercepts for country and data source. A total of 4905 individual cases were analysed (72.6% woman). The mean age at onset was 39.6 years (SD 16.1). Women had a significantly earlier age of onset than men (39.1 years vs 41.0 years). Mixed FMD (23.1%), tremor (21.6%) and weakness (18.1%) were the most common phenotypes. Compared with tremor (40.7 years), the mean ages at onset of dystonia (34.5 years) and weakness (36.4 years) were significantly younger, while gait disorders (43.2 years) had a significantly later age at onset. The interaction between gender and phenotype was not significant. FMD peaks in midlife with varying effects of gender on age at onset and phenotype. The data gives some support to ‘lumping’ FMD as a unitary disorder but also highlights the value in ‘splitting’ into individual phenotypes where relevant.

    • functional neurological disorder
    • meta-analysis
    • systematic reviews

    Data availability statement

    Data are available upon reasonable request.

    https://doi.org/10.1136/jnnp-2021-328462

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      Data availability statement

      Data are available upon reasonable request.

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      Footnotes

      • Twitter @sarahlidstone, @ercolitommaso, @jonstoneneuro

      • Collaborators The FMD GAP Study Group includes the following authors: Omar Ahmad, Sepideh Akbaripanahi, Alberto Albanese, Selma Aybek, José Fidel Baizabal-Carvallo, Peter J. Beek, Kailash P. Bhatia, Verónica Cabreira, Alan J. Carson, Anna Castagna, Russell C. Dale, Carlo Dallocchio, Giovanni Defazio, Bertrand Degos, Benedetta Demartini, Günther Deuschl, Galina Diukova, Kevin R. Duque, Mark J. Edwards, Steven A. Epstein, Alberto J. Espay, Stewart A. Factor, Beatrice Garcin, Christian Geroin, Muriel Hagenaars, Mark Hallett, Thomas Hassa, Anhar Hassan, Lorena D. Herbert, Samantha K. Holden, Joseph Jankovic, Richard A. Kanaan, Lianne Kempe, Maja Kojovic, Katie Kompoliti, Vladimir S. Kostić, Kevin Kyle, Kathrin LaFaver, Anthony E. Lang, Lindsey MacGillivray, Davide Martino, João Massano, Carine W. Maurer, Laura McWhirter, Raja Mehanna, Francine Mesrati, John C. Morris, Glenn Nielsen, Anastasia Obukhova, Sanjay Pandey, David L. Perez, Igor Petrović, Seth L. Pullman, Angelo Quartarone, Karin Roelofs, Anette Schrag, Yury Seliverstov, Tereza Serranová, Ulf Søgaard, Petr Sojka, Maria Stamelou, Christopher D. Stephen, John F. Stins, Michele Tinazzi, Aleksandra Tomić, Anabela Valadas, Valerie Voon, Jeff L. Waugh, Allan D. Wu.

      • Contributors SL—guarantor of overall content, conceptualisation, data curation, methodology, project administration, supervision, data validation, writing (original draft, review and editing). MC-P—data curation, project administration, data validation, writing (original draft, review and editing). TE—data curation, project administration, writing (original draft, review and editing). EJR—formal analysis, writing (original draft, review and editing). JS—conceptualisation, methodology, supervision, data validation, writing (original draft, review and editing). FMD-GAP Study Group—data sharing, feedback on initial manuscript, editorial, critical appraisal.

      • Funding SL and MC-P were supported by an anonymous donation to the Toronto Western Hospital Movement Disorders Clinic. JS was supported by an NHS Scotland NRS Career Fellowship.

      • Map disclaimer The inclusion of any map (including the depiction of any boundaries therein), or of any geographical or locational reference, does not imply the expression of any opinion whatsoever on the part of BMJ concerning the legal status of any country, territory, jurisdiction or area or of its authorities. Any such expression remains solely that of the relevant source and is not endorsed by BMJ. Maps are provided without any warranty of any kind, either express or implied.

      • Competing interests JS reports royalties from UpToDate for articles on FND and runs a free self-help website for people with FND. He carries out independent expert medicolegal work including in relation to FND. He is secretary of the FND society and on the medical advisory board for FND Hope and FND Action.

      • Provenance and peer review Not commissioned; externally peer reviewed.

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