title: Absence of relationship between oblique muscle size and bielschowsky head tilt phenomenon in clinically diagnosed superior oblique palsy.
abstract: OBJECTIVE
  To study whether the variation in maximum oblique muscle size accounts for individual variation in the Bielschowsky head tilt phenomenon (BHTP) in clinically diagnosed superior oblique (SO) palsy.
  
  
  METHODS
  Seventeen subjects with clinically diagnosed early-onset or idiopathic SO palsy and 14 normal subjects were enrolled in the study. Magnetic resonance imaging (MRI) in coronal and sagittal planes was used for quantitative morphometry of inferior oblique (IO) and SO muscles. Maximum cross-sectional area of the SO and IO cross section at the mid-inferior rectus crossing were determined in central gaze and compared with paretic eye hypertropia on ipsilesional versus contralesional head tilt.
  
  
  RESULTS
  Mean (+/-SD) maximum SO cross section was 18.1 +/- 3.2 mm(2) in normal subjects, 14.2 +/- 6.8 mm(2) ipsilesional to SO palsy, and 19.2 +/- 4.5 mm(2) contralesional to SO palsy. The ipsilesional SO cross section was significantly smaller than the contralesional (P = 0.004) and normal (P = 0.01) ones. The mean IO cross section was 18.3 +/- 3.5 mm(2) in normal subjects, 21.3 +/- 7.9 mm(2) ipsilesional to SO palsy (P = 0.43), and 22.0 +/- 6.7 mm(2) contralesional to SO palsy (P = 0.26). Hyperdeviation varied with head tilt by 20.1 +/- 5.5 degrees in subjects with SO atrophy, and 10.3 +/- 5.6 degrees in subjects without SO atrophy (P = 0.003). Although oblique muscle cross sections did not correlate with BHTP, subjects with clinically diagnosed SO palsy segregated into groups exhibiting normal versus atrophic SO size.
  
  
  CONCLUSIONS
  SO size does not account for the variation in BHTP in clinically diagnosed SO palsy, supporting the proposition that the BHTP is nonspecific for SO function.
authors.affiliation: Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. opth@cc.okayama-u.ac.jp
authors.forename: Reika
authors.initials: R
authors.lastname: Kono
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Okanobu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohtsuki
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Demer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003941:Diagnostic Techniques, Ophthalmological; D019416:Head Movements; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000473:pathology*; D011446:Prospective Studies; D013285:Strabismus / Q000175:diagnosis* / Q000503:physiopathology; D020432:Trochlear Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology
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