Idiopathic inflammation of 1 or more extraocular muscles typically produces ophthalmoplegia and pain, often with conjunctival hyperemia, chemosis, and sometimes proptosis. The pain may be quite intense and is exacerbated by eye movements. If the inflammation is confined to the posterior orbit, the eye may appear to be white and quiet. Results of CT or MRI typically show enlargement of 1 or more of the extraocular muscles with tendon involvement, and the inflammation often extends into the orbital fat (Fig 7-16). Orbital myositis–related pain usually responds to systemic corticosteroid therapy within 24 hours, whereas diplopia may take longer to resolve. Orbital myositis is usually an isolated phenomenon but may be part of a systemic disease such as granulomatosis with polyangiitis (formerly called Wegener granulomatosis), systemic lupus erythematosus, sarcoidosis, immunoglobulin G4–related ophthalmic disease, lymphoma, or, in rare cases, metastatic disease. Extraocular muscle biopsy should be considered in cases of recurrent orbital myositis with corticosteroid taper. (See also BCSC Section 7, Oculofacial Plastic and Orbital Surgery).
Figure 7-16 Orbital myositis. Coronal T1-weighted, fat-suppressed, contrast MRI showing enlargement and enhancement of the right superior oblique, right medial rectus, and right inferior rectus muscles. Axial views showed involvement of the tendons.
(Courtesy of Zoë R. Williams, MD.)
Yamamoto M, Hashimoto M, Takahashi H, Shinomura Y. IgG4 disease. J Neuroophthalmol. 2014;34(4):393–399.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.