Orbital Myositis

Orbital myositis is an inflammation of mainly the extraocular muscles. Orbital myositis has a sudden onset, and the clinical course can be acute or chronic. The ocular signs and symptoms of eyes with orbital myositis are periocular pain, eyelid swelling and redness, restricted ocular motility, and strabismus. Computed tomographic (CT) scans show indistinct swelling around one or more extraocular muscles, and fat-suppressed T2weighted magnetic resonance (MR) images show localized inflammations. The exact etiology of the inflammation has not been determined, however some cases have been reported to be caused by infectious agents while other cases by autoimmunity. Spirochetotic (Lyme disease), viral (herpes zoster virus), and bacterial infections (Group A streptococcal pharyngitis) can cause orbital myositis. Autoimmune-related orbital myositis is associated with relatively specific diseases: giant cell myocarditis, Crohn disease, and linear scleroderma. Orbital myositis must be differentiated from other diseases that also have extraocular muscular enlargements, e.g., thyroid-associated orbitopathy, lymphoproliferative disorders, metastatic orbital diseases, parasitic infection, systemic anti-neutrophil cytoplasmic antibody-related vasculitis, and inflammatory conditions triggered by medications and foreign bodies. The first line of treatment of orbital myositis is systemic corticosteroids to which the inflammation responds well especially the acute type. However, there are corticosteroidresistant chronic types, and immunosuppressive and biological agents can be used in these types.