title: Elevation deficit caused by accessory extraocular muscle.
abstract: OBJECTIVE
  To report an elevation deficit, which was caused by an accessory extraocular muscle, in a 6-year-old boy.
  
  
  METHODS
  Computed tomography and magnetic resonance imaging were used to confirm an accessory, fusiform, well-defined, solid structure in the retrobulbar space.
  
  
  RESULTS
  A supernumerary intraconal muscle was detected between the annulus of Zinn and the posterior part of the left globe.
  
  
  CONCLUSIONS
  This rare anomaly may represent an atavistic retractor bulbi muscle.
authors.affiliation: Department of Strabismus and Neuroophthalmology, Kantonsspital St. Gallen, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Valmaggia
authors.forename: W
authors.initials: W
authors.lastname: Zaunbauer
authors.forename: I
authors.initials: I
authors.lastname: Gottlob
mesh_terms: D002648:Child; D005124:Eye Abnormalities / Q000150:complications* / Q000175:diagnosis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009801:Oculomotor Muscles / Q000002:abnormalities*; D013285:Strabismus / Q000175:diagnosis / Q000209:etiology*; D014057:Tomography, X-Ray Computed