Clark Robert A, Demer Joseph L
Pediatric Ophthalmology and Strabismus Division, Jules Stein Eye Institute, University of California, Los Angeles, CA 90095-7002, USA.
Arch Ophthalmol. 2011 Jul;129(7):904-8. doi: 10.1001/archophthalmol.2011.152.
To seek evidence for causative secondary changes in extraocular muscle volume, cross-sectional area, and contractility in superior oblique (SO) palsy using magnetic resonance imaging, given that vertical deviations in SO palsy greatly exceed those explained by loss of SO vertical action alone.
High-resolution, quasi-coronal orbital magnetic resonance images in target-controlled central gaze, supraduction, and infraduction were obtained in 12 patients with chronic unilateral SO palsy and 36 age-matched healthy volunteers using an 8-cm field of view and 2-mm slice thickness. Digital image analysis was used to quantify rectus extraocular muscle and SO cross-sectional areas and volumes. Measurements were compared with those of controls in central gaze to detect hypertrophy or atrophy and during vertical gaze changes to detect excess contractility.
In central gaze, the paretic SO was significantly atrophic (P < .001) and the contralesional superior rectus (SR) was significantly hypertrophic (P = .02). Across the range of vertical duction from supraduction to infraduction, both the contralesional SR (P = .04) and inferior rectus (P = .001) exhibited significantly supernormal contractile changes in maximum cross-sectional area. Contractile changes in the ipsilesional SR and inferior rectus exhibited a similar but insignificant trend (.08 < P < .12).
Central gaze hypertrophy of the contralesional SR may be secondary to chronic excess innervation to compensate for relative hypotropia of this eye. Supernormal contralesional SR and inferior rectus contractility suggests that dynamic patterns of abnormal innervation to vertical rectus extraocular muscles may contribute to large hypertropias often observed in SO palsy.
鉴于上斜肌麻痹时垂直斜视度大大超过仅由上斜肌垂直作用丧失所解释的程度，利用磁共振成像寻找上斜肌麻痹时眼外肌体积、横截面积及收缩性继发改变的证据。
采用8厘米视野和2毫米层厚，为12例慢性单侧上斜肌麻痹患者及36名年龄匹配的健康志愿者获取目标控制下中央注视、上转和下转时的高分辨率准冠状位眼眶磁共振图像。使用数字图像分析定量测量直肌眼外肌及上斜肌的横截面积和体积。将测量结果与中央注视时的对照组进行比较以检测肥大或萎缩情况，并在垂直注视变化时进行比较以检测过度收缩情况。
在中央注视时，麻痹的上斜肌显著萎缩（P <.001），对侧上直肌显著肥大（P =.02）。在上转至下转的垂直运动范围内，对侧上直肌（P =.04）和下直肌（P =.001）在最大横截面积方面均表现出显著的超常收缩变化。同侧上直肌和下直肌的收缩变化呈现相似但不显著的趋势（.08 < P <.12）。
对侧上直肌的中央注视性肥大可能继发于慢性过度神经支配，以代偿该眼的相对低位眼。对侧上直肌和下直肌的超常收缩表明，垂直直肌眼外肌异常神经支配的动态模式可能导致上斜肌麻痹中常见的大度数上斜视。
