GRAVES OPHTHALMOPATHY - INTRACRANIAL FAT PROLAPSE ON CT IMAGES AS AN INDICATOR OF OPTIC-NERVE COMPRESSION

PURPOSE: To determine the usefulness of a number of imaging features i n the differentiation of patients with Graves ophthalmopathy who had o ptic neuropathy from those who did not. Intracranial herniation of orb ital fat through the superior ophthalmic fissure and its clinical impo rtance was also assessed. MATERIALS AND METHODS: The computed tomograp hic (CT) appearance of the orbital apex was examined in 50 patients wi thout and in 50 patients with Graves ophthalmopathy. The clinical diag nosis of optic neuropathy was made by an ophthalmologist who was unawa re of the imaging appearances and was based on clinical features and a bnormalities of visual evoked potentials or changes at automated perim etry. RESULTS: Intracranial fat prolapse (P < .001) and optic nerve cr owding (P < .05) were the only imaging features that were independentl y related to optic neuropathy. The presence of intracranial fat prolap se or optic nerve crowding on CT scans helped identify 16 of 17 patien ts with optic neuropathy. Sensitivity was 94%, specificity was 91%, po sitive predictive value was 69%, and negative predictive value was 98% . CONCLUSION: Intracranial fat prolapse correlates closely to the pres ence of optic neuropathy in Graves ophthalmopathy. This sign, in combi nation with optic nerve crowding, demonstrates a closer correlation to optic neuropathy than previously described imaging features.