Graves ophthalmopathy: MR imaging of the orbits

Thirty-nine patients with Graves ophthalmopathy were examined with magnetic resonance (MR) imaging at 0.5 T with use of a surface coil. T1- and T2-weighted spin-echo images were obtained, and T2 relaxation times of eye muscles and retrobulbar fat were calculated from a multiecho sequence. Normal values for T2 relaxation times of eye muscle were obtained by examining nine control subjects. MR imaging demonstrated eye muscle enlargement in 23 patients. Visual examination of T2-weighted and calculated T2 images showed areas of high signal intensity in enlarged eye muscles of 12 of 23 patients. Calculated T2 relaxation times of eye muscles differed significantly between control subjects and patients with stage III and IV disease. Signal intensity characteristics of these changes, as well as their correlation with well-known histologic findings, suggested their interpretation as edema caused by acute inflammation. Since computed tomography is not able to depict eye muscle edema, the MR findings of structural changes within enlarged eye muscles might have an impact on therapeutic decisions concerning the application of anti-inflammatory drugs.