Orbital myositis involving the oblique muscles. An echographic study.

Idiopathic orbital myositis is a common nonspecific orbital inflammatory syndrome that can involve one or more of the extraocular muscles. Oblique muscle involvement is infrequently reported, possibly because such involvement is difficult to identify clinically or by computed tomography (CT). The authors reviewed seven cases of orbital myositis involving the oblique muscles solely or in association with rectus muscle involvement. Standardized echography demonstrated homogeneous low-reflective enlargement, diagnostic of myositis, of the superior and inferior oblique muscles and tendons along their courses. The finding of massive inferior chemosis was associated with involvement of the inferior oblique muscle. Although the disease typically responds to therapy with systemic steroids, residual gaze restriction may occur. The oblique muscles may be frequently involved in idiopathic orbital myositis when evaluated by standardized orbital echography. In these cases, echography provides rapid, accurate, and reliable confirmation of the diagnosis of myositis, differentiates other orbital inflammatory diseases, and provides an objective measure of the therapeutic response.