title: Vestibulo-ocular reflex dynamics with head-impulses discriminates spinocerebellar ataxias types 1, 2 and 3 and Friedreich ataxia.
abstract: Although the diagnosis of inherited ataxias is ultimately genetic, this usually means an extensive and expensive process. This justifies the search for distinct clinical signs that may potentially help orient molecular diagnosis.
  
  
  
  We explored the vestibulo-ocular reflex (VOR) with the video Head Impulse Test in patients diagnosed with spinocerebellar ataxia (SCA) type 3 (n = 15), type 1 (n = 4) and type 2 (n = 4), Friedreich's ataxia (FA) (n = 9) and healthy controls (n = 40). We estimated the latency, regression (VORr) and instantaneous VOR gain at 40, 60 and 80 ms (VOR40, VOR60 and VOR80), and determined the latency, peak-velocity and occurrence rate of catch-up saccades triggered with head-impulses.
  
  
  
  VOR latency was higher in FA (p < 0.001) and SCA3 (p = 0.02) as compared to controls, discriminating FA from other ataxic patients with an overall diagnostic accuracy of 88%. VORr, VOR40 and VOR60 were significantly lower in FA and SCA3 (p < 0.01). VOR80 was only significantly lower than controls in SCA3 (p < 0.01), discriminating these from other ataxic patients with an overall diagnostic accuracy of 78%. Covert saccades were only triggered in SCA3 but with low occurrence rate and peak velocity (11.1 ± 28.5% and 77.50 ± 15.30°/s) whereas overt saccades were present in all groups. VORr gain showed a negative correlation with disease severity evaluated with SARA (Spearman r = -0.46, p = 0.01).
  
  
  
  vHIT provides phenotypic information that differentiates these autosomal ataxias and can serve as a strategy to orient genetic diagnosis. A correlation between VOR and SARA raises the possibility of using VOR gain as a neurophysiologic biomarker for disease severity.
authors.affiliation: Clinical Translational Physiology Unit, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.|Department of Surgical Specialties and Anesthesia, Otolaryngology Unit, Hospital de Cascais, Portugal.|Institute of Health Sciences, Portuguese Catholic University, Lisbon, Portugal.
authors.forename: L
authors.initials: L
authors.lastname: Luis
authors.affiliation: Clinical Translational Physiology Unit, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.|Department of Neurology, EMG and Motor Control Unit, Hospital Clínic, Universitat de Barcelona, IDIBAPS, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Costa
authors.affiliation: Department of Neurology, EMG and Motor Control Unit, Hospital Clínic, Universitat de Barcelona, IDIBAPS, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Muñoz
authors.affiliation: Clinical Translational Physiology Unit, Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: de Carvalho
authors.affiliation: Department of Neuro-otology and Pain and Headache, Instituto de Neurociencias de Buenos Aires INEBA, Buenos Aires, Argentina.
authors.forename: S
authors.initials: S
authors.lastname: Carmona
authors.affiliation: Institute of Medical Technology, Brandenburg University of Technology Cottbus - Senftenberg, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schneider
authors.affiliation: Department of Neurology, Meir Medical Center, Kfar Saba, Tel Aviv University, Tel Aviv, Israel.|Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
authors.forename: C R
authors.initials: CR
authors.lastname: Gordon
authors.affiliation: Department of Neurology, EMG and Motor Control Unit, Hospital Clínic, Universitat de Barcelona, IDIBAPS, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Valls-Solé
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D005621:Friedreich Ataxia / Q000175:diagnosis*; D064087:Head Impulse Test; D006801:Humans; D017827:Machado-Joseph Disease / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012027:Reflex, Vestibulo-Ocular; D015203:Reproducibility of Results; D012438:Saccades; D020754:Spinocerebellar Ataxias / Q000175:diagnosis*; D014724:Vestibular Function Tests
keywords: Friedreich ataxia; Neuro-otology; spinocerebellar ataxia; vestibular function tests; vestibulo-ocular reflex (VOR)