title: Anticompensatory quick eye movements after head impulses: A peripheral vestibular sign in spontaneous nystagmus.
abstract: BACKGROUND
  Differentiating central from peripheral origins of spontaneous nystagmus (SN) is challenging. Looking for a simple sign of peripheral disease with the video Head Impulsive Test we noticed anti-compensatory eye movements (AQEM) in patients with peripheral etiologies of spontaneous nystagmus (SN). Here we assess the diagnostic accuracy of AQEM in differentiating peripheral from central vestibular disorders.
  
  
  METHODS
  We recorded the eye movements in response to horizontal head impulses in a group of 43 consecutive patients with acute vestibular syndrome (12 with central, 31 with peripheral disorders), 5 patients after acute vestibular neurectomy (positive controls) and 39 healthy subjects (negative controls). AQEM were defined as quick eye movements (peak velocity above 50°/s) in the direction of the head movement.
  
  
  RESULTS
  All patients with peripheral disorders and positive controls had AQEM (latency 231 ± 53 ms, amplitude 3.4 ± 1.4°, velocity 166 ± 55°/s) when their head was moved to the opposite side of the lesion. Central patients did not have AQEM. AQEM occurrence rate was higher in peripheral patients with contralesional (74 ± 4%, mean ± SD) in comparison to ipsilesional (1 ± 4%) impulses (p< 0.001). Overall diagnostic accuracy for differentiating central from peripheral patients was 96% (95% CI for AUC ROC curve: 0.90 to 1.0) for VOR gain and 100% (95% CI: 1.0 to 1.0) for AQEM occurrence rate.
  
  
  CONCLUSIONS
  These results suggest that AQEM are a sign of vestibular imbalance in a peripheral deficit. In addition to VOR gain they should be added to the evaluation of the head impulse test.
authors.affiliation: Health Sciences Institute, Portuguese Catholic University, Lisbon, Portugal.|Translational Clinical Physiology Unit, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Portugal.|Otolaryngology Unit, Hospital de Cascais, Cascais, Portugal.
authors.forename: L
authors.initials: L
authors.lastname: Luis
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Germany.|Department of Neurology, Munich University Hospital, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Lehnen
authors.affiliation: EMG and Motor Control Unit, Neurology Department, Hospital Clínic, Universitat de Barcelona, IDIBAPS, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Muñoz
authors.affiliation: Translational Clinical Physiology Unit, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: de Carvalho
authors.affiliation: German Center for Vertigo and Balance Disorders, Munich University Hospital, Germany.|Institute for Clinical Neurosciences, Munich University Hospital, Germany.|Institute of Medical Technology, Brandenburg University of Technology, Cottbus-Senftenberg, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schneider
authors.affiliation: EMG and Motor Control Unit, Neurology Department, Hospital Clínic, Universitat de Barcelona, IDIBAPS, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Valls-Solé
authors.affiliation: Translational Clinical Physiology Unit, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Portugal.|EMG and Motor Control Unit, Neurology Department, Hospital Clínic, Universitat de Barcelona, IDIBAPS, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Costa
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005133:Eye Movements; D005260:Female; D007839:Functional Laterality; D006257:Head; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000175:diagnosis* / Q000503:physiopathology; D010812:Physical Stimulation; D012027:Reflex, Vestibulo-Ocular; D015837:Vestibular Diseases / Q000503:physiopathology; D014724:Vestibular Function Tests / Q000379:methods*; D014725:Vestibular Nerve / Q000601:surgery
keywords: Neuro-otology; vestibular function tests; vestibulo-ocular reflex (VOR)