MON-367 MRI-Guided Assessment of Thyroid Eye Disease: Insights from Japanese Clinical Experience

Abstract Disclosure: I. Yamauchi: Amgen Inc, Research fund. T. Sugawa: None. A. Sakurai: None. S. Kimura: None. D. Kosugi: None. K. Okamoto: None. T. Hakata: None. Y. Ueda: Amgen Inc, Research fund. D. Taura: Amgen Inc, Research fund. D. Yabe: None. Background: In Japan, patients with thyroid eye disease (TED) often receive steroid pulse therapy due to severe diplopia, unless they exhibit low clinical activity score (CAS). Disease activity is generally assessed using magnetic resonance imaging (MRI). Here, we demonstrate categorization of thyroid eye disease (TED) through our clinical experience guided by MRI findings. [Methods] We conducted a retrospective analysis of 50 TED cases treated at our department between 2015 and 2022 with a combination of steroid pulse therapy and radiation. For patients who received multiple therapies, data from the first therapy session were used. Results are expressed as medians with interquartile ranges. [Results] The characteristics of all cases were as follows: age, 59 (49-68) years; sex, 14 males and 36 females; CAS, 3 (1-4) out of 7; diplopia, 44 cases (88.0%); and thyroid stimulating antibody (TSAb), 1215 (350-4369)% (reference range: <120%, measured using a bioassay kit from Yamasa). We analyzed 44 cases with diplopia by dividing them into a severe group (17 cases with diplopia in the primary position) and a non-severe group (27 cases with diplopia only in non-primary positions). The severe group was older (67 [60-72] years) and had lower TSAb titers (324 [186-1870]%) compared to the non-severe group (56 [47-66] years, TSAb 2443 [528-5007]%) (p = 0.008 and p = 0.006, respectively). CAS was similar between the groups: severe group, 2 (1-4); and non-severe group, 3 (1-4) (p = 0.279). MRI findings revealed that proptosis was more pronounced in the non-severe group: severe group, 17.5 (15.7-22.1); and non-severe group, 21.4 (18.3-22.1) (p = 0.049). However, the difference in proptosis between eyes was larger in the severe group (2.0 [1.1-2.8] mm) compared to the non-severe group (0.9 [0.3-2.0] mm) (p = 0.009). High signal intensity of orbital fat on the short-tau inversion recovery (STIR) sequence was more frequently observed in the non-severe group (15 cases, 68.2%) than in the severe group (3 cases, 20.0%) (p = 0.005). Discussion: TED patients with severe diplopia were characterized by older age, lower TSAb titers, and greater asymmetry in proptosis. In contrast, CAS and STIR signal intensity of orbital fat were not indicative of severity. MRI-guided assessments of TED can provide valuable insights for clinical decision-making and improve management strategies. Presentation: Monday, July 14, 2025