Idiopathic inflammation of the orbit

Idiopathic inflammation of the orbit may be diffuse with affection of all orbital spaces or locally confined with affection of one space or one particular structure within the orbit. ChnicaUy, idiopathic inflammation of the orbit presents with proptosis, which is oftentimes unilateral. 

Diffuse idiopathic inflammation of the orbit shows with findings at CT and MRI that are non-specific, with high contrast uptake of inflamed structures, infiltration of orbital fat tissue, and inflammation with edema of intraorbital muscles and tendons. As a differential diagnosis, autoimmune hyperthyroidism (Morbus Basedow, Graves disease, associated with endocrine orbitopathy or EO, see below. Sect. 12.6) does not affect intra-orbital tendons. 

Posterior scleritis is a special, locally confined type of idiopathic inflammation of the orbit, which presents clinically with slowly progressive, painful proptosis. Cross-sectional imaging shows diffuse thickening of the sclera and inflammation of adjacent tissue, with marked contrast uptake. As differential diagnoses, nodular scleritis does not show with contrast uptake, while uveal melanoma does take up contrast media, but usually delineates well (Mueller-Forell and Pitz 2004). 

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