title: Postural Ataxia in Cerebellar Downbeat Nystagmus: Its Relation to Visual, Proprioceptive and Vestibular Signals and Cerebellar Atrophy.
abstract: BACKGROUND
  The cerebellum integrates proprioceptive, vestibular and visual signals for postural control. Cerebellar patients with downbeat nystagmus (DBN) complain of unsteadiness of stance and gait as well as blurred vision and oscillopsia.
  
  
  OBJECTIVE
  The aim of this study was to elucidate the differential role of visual input, gaze eccentricity, vestibular and proprioceptive input on the postural stability in a large cohort of cerebellar patients with DBN, in comparison to healthy age-matched control subjects.
  
  
  METHODS
  Oculomotor (nystagmus, smooth pursuit eye movements) and postural (postural sway speed) parameters were recorded and related to each other and volumetric changes of the cerebellum (voxel-based morphometry, SPM).
  
  
  RESULTS
  Twenty-seven patients showed larger postural instability in all experimental conditions. Postural sway increased with nystagmus in the eyes closed condition but not with the eyes open. Romberg's ratio remained stable and was not different from healthy controls. Postural sway did not change with gaze position or graviceptive input. It increased with attenuated proprioceptive input and on tandem stance in both groups but Romberg's ratio also did not differ. Cerebellar atrophy (vermal lobule VI, VIII) correlated with the severity of impaired smooth pursuit eye movements of DBN patients.
  
  
  CONCLUSIONS
  Postural ataxia of cerebellar patients with DBN cannot be explained by impaired visual feedback. Despite oscillopsia visual feedback control on cerebellar postural control seems to be preserved as postural sway was strongest on visual deprivation. The increase in postural ataxia is neither related to modulations of single components characterizing nystagmus nor to deprivation of single sensory (visual, proprioceptive) inputs usually stabilizing stance. Re-weighting of multisensory signals and/or inappropriate cerebellar motor commands might account for this postural ataxia.
authors.affiliation: Department of Neurology, University of Lübeck, Lubeck, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Helmchen
authors.affiliation: Department of Neurology, University of Lübeck, Lubeck, Germany.
authors.forename: Jan-Birger
authors.initials: JB
authors.lastname: Kirchhoff
authors.affiliation: Department of Neurology, University of Lübeck, Lubeck, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Göttlich
authors.affiliation: Department of Neurology, University of Lübeck, Lubeck, Germany.|Institute of Psychology II, University of Lübeck, Lubeck, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Sprenger
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002524:Cerebellar Ataxia / Q000503:physiopathology*; D002526:Cerebellar Diseases / Q000503:physiopathology*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D008297:Male; D009759:Nystagmus, Pathologic / Q000503:physiopathology*; D015835:Ocular Motility Disorders / Q000503:physiopathology; D011187:Posture / Q000502:physiology*