Paretic Side/Normal Side Ratios of Cross-Sectional Areas of the Superior Oblique Muscle Vary Largely in Idiopathic Superior Oblique Palsy
Accepted 30 September 2009. published online 30 December 2009.
Purpose
To search for a new definition of muscle hypoplasia in congenital or idiopathic superior oblique muscle palsy.
Design
Retrospective case-control study.
Methods
Cross-sectional areas of the superior oblique and 4 rectus muscles near the eye globe–optic nerve junction were measured by an image analysis software on magnetic resonance images of 50 patients with congenital or idiopathic superior oblique muscle palsy and 45 patients with other disease conditions serving as a control. The paretic side/contralateral normal side ratios of the cross-sectional areas and the left side/right side ratios were calculated for the superior oblique muscle palsy patients and the control patients, respectively.
Results
The 95% confidence intervals in paretic side/contralateral side ratios of cross-sectional areas of the superior oblique muscle were 0.55 to 0.80 in the right-side superior oblique muscle palsy, and 0.48 to 0.75 in the left-side palsy, while the 95% confidence interval in the left side/right side ratios was 0.99 to 1.00 in the control. The 95% confidence intervals in the left side/right side ratios of the 4 rectus muscles were 1.00, both in the superior oblique muscle palsy and in the control.
Conclusions
The muscle hypoplasia could be defined as such when the paretic side/contralateral side ratios of cross-sectional areas of the superior oblique muscle on magnetic resonance images fell outside the 95% confidence interval of the ratios in normal controls.
Department of Ophthalmology, Okayama University Medical School and Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama City, Japan
Inquiries to Toshihiko Matsuo, MD, Department of Ophthalmology, Okayama University Medical School and Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Shikata-cho 2-5-1, Okayama City 700-8858, Japan
ABSTRACT