title: Association of superior oblique muscle volumes with the presence or absence of the trochlear nerve on high-resolution MR imaging in congenital superior oblique palsy.
abstract: OBJECTIVE
  Congenital superior oblique palsy is known to relate to trochlear nerve absence and a variable degree of superior oblique muscle hypoplasia. The purpose of this study was to determine whether superior oblique muscle volume predicts trochlear nerve absence in congenital superior oblique palsy.
  
  
  METHODS
  A retrospective study of high-resolution MR imaging to evaluate the presence of the trochlear nerve and to measure superior oblique muscle areas and volumes with the image analysis tools of a PACS was performed in 128 consecutive patients with unilateral congenital superior oblique palsy and 34 age-matched healthy controls.
  
  
  RESULTS
  Of the 128 patients with congenital superior oblique palsy, 88 had an ipsilateral trochlear nerve absence (absent group) and 40 had both trochlear nerves (present group). In patients with congenital superior oblique palsy, the paretic side superior oblique muscle volume was significantly smaller compared with the normal side only in the absent group (P < .001). The left and right side superior oblique muscle volumes were not significantly different in controls (P = .750), and the paretic and normal side superior oblique muscle volumes were not significantly different in the present group (P = .536). The cutoff value of the paretic/normal side superior oblique muscle volume ratio for diagnosing trochlear nerve absence was ≤0.75 (sensitivity 98.9%, specificity 95.0%) in patients with congenital superior oblique palsy.
  
  
  CONCLUSIONS
  The ratio of paretic/normal side superior oblique muscle area and volume has an excellent predictability in diagnosing trochlear nerve absence in congenital superior oblique palsy.
authors.affiliation: From the Departments of Ophthalmology (H.K.Y., D.S.L., J.-M.H.).
authors.forename: H K
authors.initials: HK
authors.lastname: Yang
authors.affiliation: From the Departments of Ophthalmology (H.K.Y., D.S.L., J.-M.H.).
authors.forename: D S
authors.initials: DS
authors.lastname: Lee
authors.affiliation: Radiology (J.H.K.), Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam, Korea. hjm@snu.ac.kr jaehkim@snubh.org.
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.affiliation: From the Departments of Ophthalmology (H.K.Y., D.S.L., J.-M.H.) hjm@snu.ac.kr jaehkim@snubh.org.
authors.forename: J-M
authors.initials: JM
authors.lastname: Hwang
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000473:pathology*; D012189:Retrospective Studies; D014321:Trochlear Nerve / Q000002:abnormalities*; D020432:Trochlear Nerve Diseases / Q000473:pathology*; D055815:Young Adult