title: Modified Anderson procedure for correcting abnormal mixed head position in nystagmus.
abstract: OBJECTIVE
  Treatment of nystagmus is controversial mainly in cases where it is combined with abnormal head position. This study was carried out to demonstrate that patients with abnormal head position in all three axes associated with nystagmus show improvement in the torsional and vertical components if only horizontal factors are addressed by surgical weakening of the horizontal muscles.
  
  
  METHODS
  21 patients with horizontal nystagmus and abnormal head position were studied. All had an abnormal head position in all three axes with a predominant head turn. In all cases a modified Anderson procedure was performed---that is, 2 mm retroequatorial recessions of the horizontal yoke rectus muscles responsible for the blockage position, plus corrective surgery for strabismus when needed.
  
  
  RESULTS
  The three components of the abnormal head position were improved with surgery of horizontal yoke rectus muscles only (p=0.001).
  
  
  CONCLUSIONS
  Large recessions of the horizontal yoke rectus muscles in nystagmus with blockage position, when the head turn predominates over the vertical and torsional components, are effective in diminishing the abnormal head position on all three axes.
authors.affiliation: Pediatric Ophthalmology and Strabismus Clinic, Deparment of Ophthalmology, Hospital General de Mexico, Mexico, DF. mearroyo@mexis.com
authors.forename: M E
authors.initials: ME
authors.lastname: Arroyo-Yllanes
authors.forename: A
authors.initials: A
authors.lastname: Fonte-Vázquez
authors.forename: J F
authors.initials: JF
authors.lastname: Pérez-Pérez
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D009759:Nystagmus, Pathologic / Q000503:physiopathology / Q000601:surgery*; D009801:Oculomotor Muscles / Q000601:surgery*; D011187:Posture; D016896:Treatment Outcome