title: Absence of the trochlear nerve in patients with superior oblique hypoplasia.
abstract: OBJECTIVE
  Congenital cranial dysinnervation disorders (CCDDs) are developmental abnormalities involving the hypoplasia or aplasia of the cranial nerves with muscle dysinnervation. This study aimed to determine if congenital superior oblique palsy with superior oblique hypoplasia also can be classified as a CCDD.
  
  
  METHODS
  Observational case series.
  
  
  METHODS
  Ten patients with superior oblique hypoplasia.
  
  
  METHODS
  Ophthalmologic examination and thin-section magnetic resonance imaging (MRI) at the brainstem level as well as across the orbit were performed in 10 patients with superior oblique hypoplasia. To confirm the accuracy of the procedure, the results obtained were compared with those of a control group comprising 12 children by using the same technique.
  
  
  METHODS
  Examination of ductions and versions, 3-step test, angle of deviation, and presence of the trochlear nerve and superior oblique hypoplasia on MRI.
  
  
  RESULTS
  Trochlear nerve was absent on the affected side in 10 patients with confirmed hypoplastic superior oblique muscles. The trochlear nerves as well as normal-sized superior oblique muscles were observed in 24 (100%) of 24 eyes screened as controls.
  
  
  CONCLUSIONS
  Congenital superior oblique palsy with superior oblique hypoplasia also can be classified as a CCDD by the MRI documentation of congenital aplasia of the trochlear nerve.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Department of Radiology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Jae Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Hwang
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015785:Eye Diseases, Hereditary / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015835:Ocular Motility Disorders / Q000151:congenital* / Q000175:diagnosis; D009801:Oculomotor Muscles / Q000294:innervation* / Q000473:pathology; D014321:Trochlear Nerve / Q000002:abnormalities* / Q000473:pathology; D020432:Trochlear Nerve Diseases / Q000151:congenital* / Q000175:diagnosis; D055815:Young Adult