Absence of relationship between oblique muscle size and bielschowsky head tilt phenomenon in clinically diagnosed superior oblique palsy.
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.
Kono
Reika
R
Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan. opth@cc.okayama-u.ac.jp
Okanobu
Hirotaka
H
Ohtsuki
Hiroshi
H
Demer
Joseph L
JL
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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