title: Impaired resting vagal tone in patients with functional movement disorders.
abstract: The autonomic nervous system plays an integral role in the maintenance of homeostasis during times of stress. The functioning of the autonomic nervous system in patients with functional movement disorders (FMD) is of particular interest given the hypothesis that converted psychological stress plays a critical role in FMD disease pathogenesis. We sought to investigate autonomic nervous system activity in FMD patients by examining heart rate variability (HRV), a quantitative marker of autonomic function.
  
  
  
  35 clinically definite FMD patients and 38 age- and sex-matched healthy controls were hospitalized overnight for continuous electrocardiogram recording. Standard time and frequency domain measures of HRV were calculated in the awake and asleep stages. All participants underwent a thorough neuropsychological battery, including the Hamilton Anxiety and Depression scales and the Beck Depression Inventory.
  
  
  
  Compared to controls, patients with FMD exhibited decreased root mean square of successive differences between adjacent NN intervals (RMSSD) (p = 0.02), a marker of parasympathetic activity, as well as increased mean heart rate (p = 0.03). These measures did not correlate with the depression and anxiety scores included in our assessment as potential covariates.
  
  
  
  In this exploratory study, patients with FMD showed evidence of impaired resting state vagal tone, as demonstrated by reduced RMSSD. This decreased vagal tone may reflect increased stress vulnerability in patients with FMD.
authors.affiliation: Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA. Electronic address: carine.maurer@nih.gov.
authors.forename: Carine W
authors.initials: CW
authors.lastname: Maurer
authors.affiliation: Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA. Electronic address: victoriatl@gmail.com.
authors.forename: Victoria D
authors.initials: VD
authors.lastname: Liu
authors.affiliation: Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA; University of Louisville, Department of Neurology, Louisville, KY, USA. Electronic address: kathrin.lafaver@louisville.edu.
authors.forename: Kathrin
authors.initials: K
authors.lastname: LaFaver
authors.affiliation: Experimental Therapeutics and Pathophysiology Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA. Electronic address: amelir@mail.nih.gov.
authors.forename: Rezvan
authors.initials: R
authors.lastname: Ameli
authors.affiliation: Office of the Clinical Director, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA. Electronic address: wuti@mail.nih.gov.
authors.forename: Tianxia
authors.initials: T
authors.lastname: Wu
authors.affiliation: Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA. Electronic address: ryantoledo21@gmail.com.
authors.forename: Ryan
authors.initials: R
authors.lastname: Toledo
authors.affiliation: Georgetown University, Department of Psychiatry, Washington, DC, USA. Electronic address: epsteins@gunet.georgetown.edu.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Epstein
authors.affiliation: Human Motor Control Section, Medical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA. Electronic address: hallettm@ninds.nih.gov.
authors.forename: Mark
authors.initials: M
authors.lastname: Hallett
mesh_terms: D000328:Adult; D001008:Anxiety Disorders / Q000503:physiopathology; D001341:Autonomic Nervous System / Q000503:physiopathology*; D003866:Depressive Disorder / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006321:Heart / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000503:physiopathology*; D012146:Rest / Q000502:physiology*; D013315:Stress, Psychological / Q000503:physiopathology; D014630:Vagus Nerve / Q000503:physiopathology*
keywords: Autonomic nervous system; Conversion disorder; Functional movement disorders; Psychogenic movement disorders; Stress