Demer Joseph L, Clark Robert A
Department of Ophthalmology, University of California, Los Angeles, Los Angeles, California, United States.
Stein Eye Institute, University of California, Los Angeles, Los Angeles, California, United States.
Invest Ophthalmol Vis Sci. 2025 Sep 2;66(12):6. doi: 10.1167/iovs.66.12.6.
Simulations suggest that displacement of rectus extraocular muscle pulleys in superior oblique (SO) palsy accounts for incomitant strabismus patterns even without postulating SO contractile weakness. We asked how rectus extraocular muscle pulleys reorient during head tilt in SO palsy.
In 13 subjects with unilateral SO palsy, supine magnetic resonance imaging (MRI) in 2-mm-thick quasi-coronal planes in target-controlled central gaze was repeated in both lateral decubitus positions equivalent to 90° head tilts. From extraocular muscle centroids, we computed oculocentric pulley coordinates and compartmental posterior partial volumes (PPVs) of the rectus and SO muscles.
Validating atrophy, PPV of the palsied SO was smaller than its fellow (P < 10-4). In fellow orbits, the array of all four rectus pulleys exhibited counter-rotation during head tilt (P < 0.03), averaging 5.9°. The palsied pulley array was in both tilts excyclorotated relative to the fellow orbit, particularly by 4° to 5° for horizontal rectus pulleys (P < 0.03), and also counter-rotated with head tilt similarly to the fellow orbit. Differential compartmental changes in PPV were significant in the lateral and superior rectus and SO muscles of the fellow orbit that were consistent with observed torsion, but were absent in the palsied orbit.
Similar counter-rotation of the rectus pulley array during head tilt occurs in both eyes in unilateral SO palsy, but superimposed on excyclorotation of the array in the palsied orbit. Differential compartmental change in PPV occurs during head tilt in the lateral and superior rectus muscles of the fellow but not palsied orbit and could augment ocular counter-rolling.
模拟研究表明，即使不假定上斜肌（SO）收缩无力，上斜肌麻痹时直肌眼外肌滑车移位也可导致非共同性斜视模式。我们研究了上斜肌麻痹患者头部倾斜时直肌眼外肌滑车如何重新定向。
对13名单侧上斜肌麻痹患者，在相当于90°头部倾斜的双侧侧卧位重复进行仰卧位磁共振成像（MRI），扫描目标为控制在中央注视的2毫米厚准冠状平面。从眼外肌质心计算眼心滑车坐标以及直肌和上斜肌的肌间隔后部部分体积（PPV）。
验证萎缩情况，麻痹侧上斜肌的PPV小于健侧（P < 10-4）。在健侧眼眶中，所有四条直肌滑车阵列在头部倾斜时均出现反向旋转（P < 0.03），平均为5.9°。麻痹侧滑车阵列在两个倾斜位置相对于健侧眼眶均出现外旋转，水平直肌滑车尤其明显，外旋转4°至5°（P < 0.03），并且也与健侧眼眶类似地随头部倾斜而反向旋转。健侧眼眶中外侧和上直肌以及上斜肌的PPV在肌间隔上的差异变化显著，与观察到的眼球扭转一致，但在麻痹侧眼眶中不存在。
单侧上斜肌麻痹患者双眼在头部倾斜时直肌滑车阵列均出现类似的反向旋转，但叠加在麻痹侧眼眶滑车阵列的外旋转上。健侧而非麻痹侧眼眶的外侧和上直肌在头部倾斜时PPV出现肌间隔差异变化，这可能增强眼球的反向转动。
