[Differential diagnosis of Graves' disease and orbital pseudotumor: CT findings (author's transl)].

CT scans of 25 clinically typical cases of Graves' disease and 15 cases of orbital pseudotumor (idiopathic orbital inflammation) are analyzed and differential diagnostic criteria evaluated. The CT-findings overlap and are best viewed as a continuous spectrum at both ends of which characteristic patterns can be identified. Massive swelling of ocular muscles, involving of several muscles, usually without density changes of the orbital fat, are diagnostic for Graves' disease. More or less circumscribed masses of soft tissue density surrounding the globe, eye muscles or the optic nerve, severe diffuse increase of density in the retrobulbar space masking orbital structures and calcifications indicate orbital pseudotumor. Localization of the swelling within a muscle, "scleral thickening", enhanced contrast, moderate density changes of the orbital fat, and involvement of the lacrimal gland are of minor differential diagnostic value. CT pictures of clinically typical and histologically proven cases of Graves' disease indicate heterogeneity of this group, probably reflecting different immunologic features. CT shows the extent and degree of the pathologic changes and indicates the optimal approach for tissue biopsy. Evaluation of both diseases by CT requires inclusion of coronal sections.