title: Magnetic resonance imaging of the functional anatomy of the superior oblique muscle in patients with primary superior oblique overaction.
abstract: PurposeTo quantitatively determine the size and contractility of the superior oblique (SO) muscle in primary SO overaction (PSOOA).Patients and methodsA prospective, observational study was conducted on 12 patients with PSOOA, and 10 healthy, orthotropic subjects. Sets of contiguous, 2 mm slice thickness, quasi-coronal magnetic resonance imaging were obtained during different gazes, giving pixel resolution of 0.391 mm. Cross-sectional areas of the SO muscles were determined in primary position, supraduction, and infraduction to evaluate size and contractility. The cross-sectional areas of SO muscle were compared with those of controls in the primary position to detect hypertrophy or atrophy and changes in contractility could be detected during the vertical gaze. All statistical calculations were performed using PROC MIXED (SAS 9.4).ResultsThere was no difference between the ipsilesional (affected eye), contralesional (unaffected eye), and normal SO muscle cross-sections: 0.176±0.018 cm2, 0.175±0.005 cm2, and 0.173±0.015 cm2, respectively (P=0.82). The maximum contractility of SO muscle on the ipsilesional (affected) side was 0.097±0.024 cm2, and was different than on the contralesional (unaffected) side: 0.067±0.015 cm2and in control subjects: 0.063±0.018 cm2(P=0.0002).ConclusionsIn PSOOA, the ipsilesional SO is more contractile than the contralesional SO muscle and different than in controls, with no difference in SO muscle size in primary position, which suggests that excessive innervation rather than muscle hypertrophy underlies PSOOA.
authors.affiliation: Department of Optometry and Visual Science, West China Hospital/ West China School of Medicine, Sichuan University, Chengdu, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Gong
authors.affiliation: Division of MR Research, Department of Radiology and Radiological Science, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|Department of NeuroRepair, Mossakowski Medical Research Centre PAS, Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Janowski
authors.affiliation: Department of Radiology, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: H
authors.initials: H
authors.lastname: Tang
authors.affiliation: Department of Radiology, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Department of Optometry and Visual Science, West China Hospital/ West China School of Medicine, Sichuan University, Chengdu, China.
authors.forename: H
authors.initials: H
authors.lastname: Wei
authors.affiliation: Evidence-based Medicine Center, School of Basic Medical Sciences, Jiangxi University of Traditional Chinese Medicine, Nanchang, China.
authors.forename: X
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Optometry and Visual Science, West China Hospital/ West China School of Medicine, Sichuan University, Chengdu, China.|Department of Opthalmology, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: L
authors.initials: L
authors.lastname: Liu
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002681:China; D005133:Eye Movements; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009801:Oculomotor Muscles / Q000473:pathology* / Q000503:physiopathology; D015840:Oculomotor Nerve Diseases / Q000473:pathology* / Q000503:physiopathology; D011446:Prospective Studies; D013285:Strabismus / Q000473:pathology* / Q000503:physiopathology; D055815:Young Adult