Endocrine Abstracts

Background: Clinical evaluation of Graves’ orbitopathy (GO) is often insufficient. Frequently it is difficult to decide whether a case of GO is active, or to detect the degree of severity. STIR sequence MRI suppresses signal from fat and thus in the orbits can also detect active inflammation and oedema of extra-ocular muscles (EOMs). The aim of the present study is to examine whether imaging of rectus EOMs with STIR MRI could provide additional information for the activity and severity of GO.

Materials and methods: A 3 Tesla STIR sequence MRI was used to measure maximum diameter of rectus EOMs in 72 healthy individuals (Group A), in 24 patients with Graves’ disease without GO (Group B), and in 31 patients with moderate-to-severe GO (Group C). Additionally, the area of the EOMs was calculated: for superior and inferior rectus at the coronal plane, and at the axial plane for the medial and lateral rectus.

Results: Patients in group C had significantly larger all four EOMs, in both diameter and area, compared to group A. Also, in comparison with group B, patients in group C had significantly larger Medial, Superior and Inferior rectus, also in both diameter and area. Significantly larger, in both diameter and area, were found to be all the EOMs, except the Superior Rectus, in Group B compared to Group A. Multiple linear regression showed that age and sex did not influence dimensions of EOMs in the three groups.

Conclusions: In patients with GD orbital MRI can detect enlargement of the EOMs before expressing any ocular signs and symptoms. Orbital MRI can be used as an objective tool for the evaluation of activity and severity of GO.