title: Asymmetry of the optokinetic nystagmus in lesion of the central nervous system.
abstract: BACKGROUND
  Unilateral lesions of the central nervous system (CNS) may be associated with a reduction of the optokinetic nystagmus (OKN) slow component in the direction of the lesion. The aim of our study was to assess the role played in these cases by the direct injury of the OKN pathways and/or by a possible associated visual field defect.
  
  
  METHODS
  Monocular OKN was elicited with black and white stripes moving temporally-to-nasally (TN) or nasally-to-temporally (NT) at velocities of 15, 30, 45 and 60 degrees /s. Patients with cortical or chiasmal lesions associated with visual field defects were investigated. OKN was considered asymmetrical if the gain difference between TN and NT stimulation was not within 2 standard deviations of an age-matched control group (n = 86).
  
  
  RESULTS
  We examined 12 patients with cortical lesions and 4 patients with chiasmal lesions. Asymmetric OKN gain was measured in 7 patients with cortical lesions associated with a visual field defect, and in 2 patients with chiasmal compression and bitemporal hemianopia. In 2 patients with isolated occipital lesions, OKN asymmetry was explained by the associated visual field defect.
  
  
  CONCLUSIONS
  The interpretation of OKN asymmetry in patients with CNS lesions should not only consider a direct lesion of the OKN pathways but also a sensory deficit due to a visual field defect.
authors.affiliation: Klinik für Augenkrankheiten, Kantonsspital St. Gallen, St. Gallen, Switzerland. christophe.valmaggia@kssg.ch
authors.forename: C
authors.initials: C
authors.lastname: Valmaggia
authors.forename: F
authors.initials: F
authors.lastname: Proudlock
authors.forename: I
authors.initials: I
authors.lastname: Gottlob
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001927:Brain Diseases / Q000175:diagnosis / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology; D003937:Diagnosis, Differential; D004292:Dominance, Cerebral / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017120:Nystagmus, Optokinetic / Q000502:physiology*; D009897:Optic Chiasm / Q000503:physiopathology; D009900:Optic Nerve / Q000503:physiopathology; D009901:Optic Nerve Diseases / Q000175:diagnosis / Q000503:physiopathology*; D011237:Predictive Value of Tests