Orbital Muscle Enlargement: What if It’s Not Graves’ Disease?

Purpose of Review: To provide the radiologist with tools to recognize findings atypical for Graves’ ophthalmopathy and differentiate between the most important and common alternative causes of extraocular muscle enlargement on CT and MR imaging. Recent findings: We introduce five ‘red flags’ representing features that are atypical for Graves’ ophthalmopathy: unilateral disease, atypical pattern of muscle involvement, adjacent structure involvement, restricted diffusion, and absence of pain. Summary: About 95% of the cases with extraocular enlargement are due to Graves’ ophthalmopathy, other causes are less well known and recognized. The ‘red flags’ may aid in recognizing and suggesting alternative diagnoses.