Myositis

 Myositis

This a special form of orbital pseudotumor in which the lymphatic infiltra-tion primarily involves one or more ocular muscles. Aside from significant painduring motion, symptoms include limited ocular motility with double vision (diplopia). Depending on the extent of the myositic changes, exophthalmoswith chemosis and eyelid swelling may also be present. Ultrasound studies (Fig. 15.6) will reveal thickening of the ocular muscles with tenonitis (inflam-mation of Tenon’s capsule).

In Graves’ disease, only the muscle belly is thickened. In myositis, the entire muscle is thickened.

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