title: Validation of "laboratory-supported" criteria for functional (psychogenic) tremor.
abstract: BACKGROUND
  In a small group of patients, we have previously shown that a combination of electrophysiological tests was able to distinguish functional (psychogenic) tremor and organic tremor with excellent sensitivity and specificity.
  
  
  OBJECTIVE
  This study aims to validate an electrophysiological test battery as a tool to diagnose patients with functional tremor with a "laboratory-supported" level of certainty.
  
  
  METHODS
  For this prospective data collection study, we recruited 38 new patients with functional tremor (mean age 37.9 ± 24.5 years; mean disease duration 5.9 ± 9.0 years) and 73 new patients with organic tremor (mean age 55.4 ± 25.4 years; mean disease duration 15.8 ± 17.7 years). Tremor was recorded at rest, posture (with and without loading), action, while performing tapping tasks (1, 3, and 5 Hz), and while performing ballistic movements with the less-affected hand. Electrophysiological tests were performed by raters blinded to the clinical diagnosis. We calculated a sum score for all performed tests (maximum of 10 points) and used a previously suggested cut-off score of 3 points for a diagnosis of laboratory-supported functional tremor.
  
  
  RESULTS
  We demonstrated good interrater reliability and test-retest reliability. Patients with functional tremor had a higher average score on the test battery when compared with patients with organic tremor (3.6 ± 1.4 points vs 1.0 ± 0.8 points; P < .001), and the predefined cut-off score for laboratory-supported functional tremor yielded a test sensitivity of 89.5% and a specificity of 95.9%.
  
  
  CONCLUSIONS
  We now propose this test battery as the basis of laboratory-supported criteria for the diagnosis of functional tremor, and we encourage its use in clinical and research practice.
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.|Division of Neuroradiology, Department of Radiology, Medical University of Graz, Graz, Austria.
authors.forename: Petra
authors.initials: P
authors.lastname: Schwingenschuh
authors.affiliation: Sobell Department, UCL Institute of Neurology, London, United Kingdom.
authors.forename: Tabish A
authors.initials: TA
authors.lastname: Saifee
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Petra
authors.initials: P
authors.lastname: Katschnig-Winter
authors.affiliation: Sobell Department, UCL Institute of Neurology, London, United Kingdom.
authors.forename: Antonella
authors.initials: A
authors.lastname: Macerollo
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Mariella
authors.initials: M
authors.lastname: Koegl-Wallner
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Valeriu
authors.initials: V
authors.lastname: Culea
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Christine
authors.initials: C
authors.lastname: Ghadery
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.|Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz, Austria.
authors.forename: Edith
authors.initials: E
authors.lastname: Hofer
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Tamara
authors.initials: T
authors.lastname: Pendl
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Stephan
authors.initials: S
authors.lastname: Seiler
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Werner
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Franthal
authors.affiliation: Department of Neurology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Natasha M
authors.initials: NM
authors.lastname: Maurits
authors.affiliation: Department of Neurology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Marina A
authors.initials: MA
authors.lastname: Tijssen
authors.affiliation: Department of Neurology, Medical University of Graz, Graz, Austria.
authors.forename: Reinhold
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: Sobell Department, UCL Institute of Neurology, London, United Kingdom.
authors.forename: John C
authors.initials: JC
authors.lastname: Rothwell
authors.affiliation: Sobell Department, UCL Institute of Neurology, London, United Kingdom.
authors.forename: Kailash P
authors.initials: KP
authors.lastname: Bhatia
authors.affiliation: Sobell Department, UCL Institute of Neurology, London, United Kingdom.|Department for Cardiovascular and Cell Sciences, St. George's University of London, London, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Edwards
mesh_terms: D061725:Accelerometry / Q000379:methods* / Q000592:standards; D000328:Adult; D000368:Aged; D004576:Electromyography / Q000379:methods* / Q000592:standards; D019317:Evidence-Based Medicine; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination / Q000379:methods* / Q000592:standards; D011602:Psychophysiologic Disorders / Q000175:diagnosis* / Q000503:physiopathology; D015203:Reproducibility of Results; D016037:Single-Blind Method; D014202:Tremor / Q000175:diagnosis* / Q000503:physiopathology
keywords: Psychogenic; diagnostic criteria; electrophysiological criteria; functional