Abstract
Purpose. To evaluate whether inferior rectus muscle (IRM) thickness, the degree of adipose change in the IRM, smoking status, and the previous history of orbital radiotherapy can predict the dose-effect relationship regarding unilateral IRM recession in thyroid eye disease (TED). Methods. Twenty-five patients were retrospectively reviewed. We calculated the largest IRM cross-sectional area and evaluated the degree of adipose change in the IRM using magnetic resonance imaging. The degree of adipose change and smoking status were classified using grading scales (0–3); previous orbital radiotherapy was graded as 0 when a history was not available and 1 when it was available. The correlation between the dose-effect relationship and the hypothesized predictive factors was evaluated using stepwise multiple regression analysis. Results. The multiple regression model, with the exception of the history of the previous orbital radiotherapy, estimated a significant dose-effect relationship for the parameters evaluated (Y DOSE-EFFECT = 0.013X IRM AREA − 0.222X ADIPOSE − 0.102X SMOKING + 1.694; r = 0.668; adjusted r 2 = 0.367; P = 0.005). Conclusions. The dose-effect relationship regarding unilateral IRM recession in TED could be predicted using IRM thickness, degree of intramuscular adipose change, and smoking status but could not be predicted using the previous orbital radiotherapy history.
Highlights
Inferior rectus myopathy is a common but severe sequela in patients with thyroid eye disease (TED) [1,2,3]
Recession of inextensible inferior rectus muscle (IRM) is the first step in the correction of a restrictive hypotropia in TED
We examined whether IRM thickness, the degree of adipose changes in the IRM, smoking status, and a previous history of orbital radiotherapy are International Journal of Endocrinology predictors of the dose-effect relationship regarding unilateral IRM recession in TED patients
Summary
Inferior rectus myopathy is a common but severe sequela in patients with thyroid eye disease (TED) [1,2,3]. TEDrelated inferior rectus myositis induces fibroadipose changes, which cause inextensibility of the inferior rectus muscle (IRM), resulting in restrictive hypotropia [3,4,5,6]. Mild hypotropia can be compensated for by a chin-up, severe hypotropia cannot be adjusted using any ocular or head positions. This causes impairment of single vision, which has a strong negative impact on the activities of daily living [3, 4]. Recession of inextensible IRM is the first step in the correction of a restrictive hypotropia in TED. As interindividual variation in fibrous changes in the IRM results in very limited reproducibility, reoperation is frequently required [3, 6, 9]
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