PMC2631031_01
Normal and Contralateral Lateral Rectus Palsy Orbit - Axial Imaging. For Subject 3, the normal right lateral rectus follows a nearly straight path from orbital apex through the pulley sleeve (small white arrows) toward the globe. The path of the paretic and atrophic left lateral rectus path is bowed temporally and posteriorly in the pulley sleeve region (large white arrowhead), as the elastic and smooth muscle components of the pulley sling pull the denervated muscle against the lateral orbital wall. For this subject, the paretic lateral rectus had a posterior path length of 41.8 mm compared with the nonparetic length of 35.8 mm, a difference of 6 mm. ON = Optic Nerve; LR = Lateral Rectus; MR = Medial Rectus.
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Table 2. The increased posterior LR path length was accompanied by a temporal and posterior bowing of the LR muscle belly in the region of the posterior part of the LR muscle pulley sleeve (Fig. 1), near the globe-optic nerve junction.
Pre- and Post-Op Lateral Rectus Recession - Axial Imaging. For Subject 9, the lateral rectus path after lateral rectus recession is bowed temporally and posteriorly in the anterior orbit (white arrowhead), increasing lateral rectus path length compared with pre-operatively (small white arrows). This displacement is similar in direction but smaller than observed with lateral rectus palsy. For this subject, the pre-operative LR posterior path length was 27.5 mm compared with 31.0 mm in the post-operative image. The post-operative change in lateral rectus path length reduced the effect of lateral rectus surgical recession by 3.5 mm, eliminating almost half the 8.0 mm of recession performed. LR = Lateral Rectus; MR = Medial rectus.
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Once again, the increased LR posterior path length was accompanied by temporal and posterior bowing of the LR muscle belly in the region of the posterior part of the LR muscle pulley sleeve near the globe-optic nerve junction, although the effect was not as profound as seen in LR palsy (Figure 2).