Orbital inflammatory disease: Pictorial review and differential diagnosis

Table 1 Differential diagnosis of orbital inflammatory disease by site

Structure involved	Clinical condition	Common imaging findings	Differential diagnosis
Lacrimal gland	Dacryoadenitis	Diffuse lacrimal gland enlargement	Epithelial neoplasm, lymphoma
Extraocular muscles	Myositis	Unilateral EOM inflammation, usually involving surrounding fat and myotendinous junction	Dysthyroid orbitopathy
Optic nerve sheath	Perineuritis	Peripheral enhancement about the optic nerve, with varying infiltration of surrounding fat. Variable enhancement of the nerve substance	Optic nerve sheath meningioma, demyelinating optic neuritis
Orbital/periorbital fat	Cellulitis	Enhancing periorbital soft tissue with possible intraconal extension	Infectious orbital cellulitis, carotid cavernous fistula, cavernous sinus thrombosis
Orbital apex	Orbital apicitis, Tolosa-Hunt syndrome	Ill-defined, T2 hypointense enhancing tissue at orbital apex, variably involving middle cranial fossa and cavernous sinus	Meningioma, other dural infiltrative process
Periscleral	Periscleritis	Scleral thickening with periscleral edema and fluid in Tenon’s capsule	Endophthalmitis

EOM: Extraocular muscles.