title: Psychogenic axial myoclonus: clinical features and long-term outcome.
abstract: BACKGROUND
  It has been increasingly recognized that the majority of patients with a diagnosis of idiopathic propriospinal myoclonus have either a subsequent clinical course or electrophysiological features indicating that the likely etiology is psychogenic. However, the clinical features of psychogenic axial myoclonus and the long-term outcome have not yet well characterized.
  
  
  METHODS
  Here we describe clinical findings with representative videos and long term outcomes of 76 patients with an electrophysiologically established diagnosis of psychogenic axial myoclonus.
  
  
  RESULTS
  Thirty-seven patients were male. Mean age at onset of symptoms was 40.1 ± 15.1 years. Thirty-two patients (42.1%) presented with isolated axial myoclonus, while 44 patients (57.9%) presented additional features, including involvement of face or limb. In all patients but six (7.9%), the axial myoclonus was in flexion. In more than one-third of patients (42.1%), jerks were multifocal, meaning that there was no clear stereotyped pattern of jerks. Comparison between groups stratified according to the clinical outcome, revealed "delay of diagnosis" as the only predictor of worse outcome.
  
  
  CONCLUSIONS
  We describe here the clinical features and long-term outcome on the largest series of patients with psychogenic axial myoclonus reported in the literature. The description of our series highlights a number of clinical features, which may help neurologists to reach a correct diagnosis on clinical grounds alone. Delay in diagnosis of a psychogenic disorder has a negative effect on long-term outcome.
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, University College London (UCL) Institute of Neurology, London WC1N 3BG, United Kingdom. Electronic address: erro.roberto@gmail.com.
authors.forename: Roberto
authors.initials: R
authors.lastname: Erro
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, University College London (UCL) Institute of Neurology, London WC1N 3BG, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Edwards
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, University College London (UCL) Institute of Neurology, London WC1N 3BG, United Kingdom.
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
authors.affiliation: Department of Neurological Science, University Federico II, Naples, Italy.
authors.forename: Marcello
authors.initials: M
authors.lastname: Esposito
authors.affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, University College London (UCL) Institute of Neurology, London WC1N 3BG, United Kingdom; Department of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: Simon F
authors.initials: SF
authors.lastname: Farmer
authors.affiliation: Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, London, United Kingdom.
authors.forename: Carla
authors.initials: C
authors.lastname: Cordivari
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003291:Conversion Disorder / Q000150:complications*; D004576:Electromyography; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009207:Myoclonus / Q000175:diagnosis / Q000209:etiology / Q000523:psychology; D017063:Outcome Assessment, Health Care; D012189:Retrospective Studies; D055815:Young Adult
keywords: Axial jerks; Bereitschafts potential; Functional movement disorders; PSM; Propriospinal myoclonus; Psychogenic movement disorders