Assessment of optic nerve compression in Graves' ophthalmopathy - The usefulness of a quick T1-weighted sequence

Purpose: Diagnosis of optic nerve compression can be difficult in patients with equivocal clinical signs. We examined the usefulness of a quick corona l MR sequence performed at a predetermined plane as a screening tool for se lecting patients at high risk of optic nerve compression. Material and Methods: Direct coronal images of the orbit were obtained in 3 7 patients with Graves' disease in a predetermined plane. The muscular indi ces (MI) of each orbit were calculated. Mann-Whitney U-Wilcoxon rank sum te st was used to assess if there was any statistically significant difference between patients with and without signs of optic nerve compression. The RO C curve was used to identify a value useful for discriminating patients wit h a higher risk of developing optic nerve compression. Results: There was a statistically significant difference (p<0.05) in the M I between patients with and without optic nerve compression. An MI of <grea ter than or equal to>0.48 had 100% sensitivity, 89% specificity and 91% acc uracy in identifying patients with optic nerve compression. Conclusion: A quick coronal MR image obtained at the mid-orbital plane is u seful in screening patients with Graves' disease for optic nerve compressio n.