CT axial CT coronal

Diagnosis: Grave's ophthalmopathy

Grave's ophthalmopathy is the most common cause of bilateral proptosis but may be unilateral in 1/4 of cases. It is typically seen in middle aged women as a complication of Grave's disease. The medial and inferior rectus muscles are most often involved, followed by the superior and lateral recti. Inflammatory change may be seen in the orbital fat on CT. The extra-ocular muscles are swollen, most often in the mid portion of the muscle. The tendinous insertion of the muscle on the globe tends to be spared. Vision may be decreased secondary to crowding of the orbital apex causing pressure upon the optic nerve. The main differential consideration is orbital pseudotumor which tends to present more acutely than Grave's disease with painful proptosis and chemosis. Response to treatment with steroids is dramatic. On CT, inflammatory changes in the orbit are often seen in pseudotumor with enlargement of one or more of the extra-ocular muscles including the tendinous insertions. Pseudotumor may be bilateral or unilateral. Lymphoma may also produce extra-ocular muscle involvement, however lymphoma tends to cause more of a soft tissue mass. Proptosis is not as prominent in lymphoma. In the case, the patient had a known history of Graves disease. Note that in spite of the diagnosis of Grave's, there is involvement of the tendinous insertion of the medial rectus. Related Cases

Wegener granulomatosis Grave's ophthalmopathy