title: Congenital superior oblique palsy and trochlear nerve absence: a clinical and radiological study.
abstract: OBJECTIVE
  To evaluate patients with congenital superior oblique palsy (SOP) by classifying them according to their magnetic resonance imaging (MRI) findings and cross-comparing the clinical characteristics of each group.
  
  
  METHODS
  Retrospective, observational study.
  
  
  METHODS
  Ninety-seven consecutive patients diagnosed with congenital SOP.
  
  
  METHODS
  Medical records of patients who demonstrated typical signs of congenital SOP were reviewed. The presence or absence of the trochlear nerve was visualized with thin-section high-resolution MRI of the cranial nerves.
  
  
  METHODS
  Presence of the trochlear nerve and superior oblique (SO) muscle hypoplasia on MRI, age at the onset of symptoms or signs, ocular motility examination results, objective ocular torsion, and surgical outcomes.
  
  
  RESULTS
  Of the 97 patients with congenital SOP, 73% of patients were identified with an ipsilateral absent trochlear nerve and variable degree of SO muscle hypoplasia (absent group), whereas the remaining 27% had a normal trochlear nerve and normal symmetric SO muscle (present group). Patients with an absent trochlear nerve showed more frequent head tilt (P = 0.030) that was manifest at an earlier onset before 1 year of age (P<0.001). Patients with a normal trochlear nerve had a more prominent overelevation in adduction (P = 0.008) and more frequently were associated with dissociated vertical deviation (DVD; P = 0.025).
  
  
  CONCLUSIONS
  Congenital SOP patients without a trochlear nerve had a hypoplastic SO muscle and frequently manifested head tilt at an earlier age, whereas patients with a normal trochlear nerve showed prominent overelevation in adduction and frequent DVD.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Yang
authors.forename: Jae Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Hwang
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005124:Eye Abnormalities / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000002:abnormalities* / Q000294:innervation; D012189:Retrospective Studies; D014321:Trochlear Nerve / Q000002:abnormalities* / Q000473:pathology; D020432:Trochlear Nerve Diseases / Q000151:congenital* / Q000175:diagnosis