Pathologies of the Extraocular Muscles

This chapter presents muscle lesions other than those observed in dysthyroid orbitopathy and purely inflammatory lesions. Multiple and diffuse muscle hypertrophy can be related to systemic diseases: amyloidosis, porphyria, or orbital infiltration in neurofibromatosis type 1 or to a direct (post-traumatic) carotid-cavernous fistula or an (indirect) cavernous sinus dural arteriovenous fistula. When one deals with the presence of single or multiple muscle masses, one must first consider a tumor origin: in adults, metastases, and in children, rhabdomyosarcoma or more rarely metastases of neuroblastoma or localizations of leukemia or histiocytosis. Miscellaneous lesions may also be encountered: an invasion by contiguity of a bony lesion (spheno-orbital meningioma, metastasis), an infectious lesion, a parasitic localization (cysticercosis), a vascular localization (arteriovenous malformation), or giant cell myositis (sarcoidosis or myasthenia gravis). Finally, in case of muscle atrophy, one should think of sequelae of Graves’ disease, or certain mitochondriopathies if several muscles are involved, and to post-traumatic fibrosis, or post-therapeutic rearrangements if atrophy affects a single muscle.