Reduction in Extraocular Muscle Cross-sectional Area and Correlation With Extraocular Motility and Diplopia Following Teprotumumab for Thyroid Eye Disease

Abstract

To quantify changes in extraocular muscle (EOM) cross-sectional areas (CSA) on orbital imaging in patients with thyroid eye disease before and after teprotumumab treatment, and assess for correlation with clinical outcomes.Methods: This retrospective study included thyroid eye disease patients treated with teprotumumab who had pre-and post-treatment CT imaging. Reformatted oblique coronal images were created for each orbit in a plane perpendicular to the optic nerve. EOM CSA measurements were performed by 2 radiographic reviewers and averaged. Primary outcomes included change in ratio of total EOM to orbit CSA, and of each individual muscle group to orbit CSA, before and after treatment. Secondary outcomes included subanalysis based on age (≥40, <40 years) and Clinical Activity Score (CAS) (≥4, <4), and comparison with clinical outcomes including CAS, Hertel exophthalmometry, Gorman diplopia score, and extraocular motility.Results: Forty-eight orbits of 24 patients (16 female, mean age 57.9 years) were included. There was a significant reduction in the total EOM to orbit CSA ratio (p < 0.01) and for each individual rectus muscle to orbit CSA ratio (p < 0.01 for all groups). Total EOM to orbit CSA ratios were reduced for 21 patients (87.5%); this was statistically significant in 13 patients (54.2%). There was significant improvement in CAS, proptosis, diplopia, and EOM motility (p < 0.01 for all categories). There was a significant correlation between reduction of EOM CSA, and reduction of diplopia (p < 0.01) and EOM motility (p < 0.01).Conclusions: EOM CSA is significantly reduced following treatment with teprotumumab, and correlates with clinical findings including improvement in extraocular motility and diplopia.

Teprotumumab for Thyroid Eye Disease-related Strabismus

“…Ugradar et al 15 added that the greatest improvement is in sursumversion. Reshef et al 26 further described clinico-radiological correlations, reporting a reduction in composite motility restriction and total extraocular muscle cross-sectional area. Little information on strabismus was offered in either of the latter 2 studies.…”

“…The dissociation between improvements in motility without similarly consistent improvements in strabismus is curious, yet consistent with previous reports. 14,15,26 It is not completely clear how these results can be reconciled. It is possible that the improvements in motility may occur without altering the relative size and strength imbalance between agonists and antagonist EOMs so that strabismus persists.…”

Re: “Reduction in Extraocular Muscle Cross-sectional Area and Correlation With Extraocular Motility and Diplopia Following Teprotumumab for Thyroid Eye Disease”

“…The authors have read with interest the recent study by Reshef et al, 1 which demonstrated a radiological reduction in extraocular muscle (EOM) cross-sectional area and EOM to orbit ratio following teprotumumab treatment. In this study, the authors aimed to correlate the mechanism of teprotumumab with anatomic changes and clinical response to treatment.…”

Magnetic resonance imaging of extraocular rectus muscles abnormalities in acute acquired concomitant esotropia

“…Several research has examined the connection between EOM size and clinical signs of EOM motility, and several of them have found a specific link between radiographic EOM enlargement and motility restriction. The two-dimensional measurement of mean cross-sectional area would give a more precise indication of the true "size" of the muscles, particularly in thyroid eye illness [12][13][14] . A systematic study of human horizontal rectus EOM contractility has demonstrated that EOM morphologic changes in single-plane maximum cross-sectional areas and posterior partial volumes (PPVs) provide accurate and quantitative measures of EOM contractility [15] , which indicated the morphologic changes of EOM in response to EOM strength.…”