title: The bereitschaftspotential in jerky movement disorders.
abstract: OBJECTIVE
  To assess the diagnostic value of the bereitschaftspotential (BP) in jerky movement disorders.
  
  
  METHODS
  A cross-sectional case series of 48 patients with psychogenic jerks, Gilles de la Tourette syndrome (GTS) or myoclonus was investigated. We measured the BP prior to the spontaneous jerk and voluntary wrist extension. In addition, the various jerky movements were imitated by 25 healthy subjects.
  
  
  RESULTS
  For patients with psychogenic jerks, we observed significantly more BPs; however, the BP was not identified prior to self-paced wrist extensions in 59% of cases. In contrast, none of the patients with the clinical diagnosis of myoclonus had a BP prior to their jerks but did have a BP prior to intentional wrist extension. In GTS, we demonstrated a BP in a minority of cases preceding motor tics and with a shorter duration in comparison with patients with psychogenic jerks. In healthy control subjects, a BP was found preceding all movements in all cases. The absence of a BP prior to intended wrist extension had a sensitivity of 0.59, specificity of 0.98 and positive likelihood ratio of 25 for the diagnosis of psychogenic jerks.
  
  
  CONCLUSIONS
  We demonstrate that the BP can aid in the differentiation of jerky movements. Patients with psychogenic jerks significantly more often have a BP prior to their jerks and with a significantly earlier onset compared with GTS patients. A novel finding of our study is the absence of a BP prior to intentional movements for patients with psychogenic jerks. Validation in a prospective cohort is needed.
authors.affiliation: Department of Neurology and Clinical Neurophysiology, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Sandra M A
authors.initials: SM
authors.lastname: van der Salm
authors.forename: Marina A J
authors.initials: MA
authors.lastname: Tijssen
authors.forename: Johannes H T M
authors.initials: JH
authors.lastname: Koelman
authors.forename: Anne-Fleur
authors.initials: AF
authors.lastname: van Rootselaar
mesh_terms: D000328:Adult; D000368:Aged; D003265:Contingent Negative Variation; D004569:Electroencephalography; D004576:Electromyography; D055724:Electrophysiological Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology*; D009207:Myoclonus / Q000145:classification / Q000175:diagnosis; D009460:Neurologic Examination; D005879:Tourette Syndrome / Q000175:diagnosis / Q000503:physiopathology; D014953:Wrist; D055815:Young Adult