Table 2.

Differential diagnosis of GO.

	GO	Orbital lymphoma	IgG4 related ophthalmopathy	Idiopathic orbital inflammation	Carotid-Cavernous Fistulas
Sex distribution	Female	Male	No difference	No difference	Male
Thyroid Dysfunction	Always	Rarely	Rarely	Rarely	Rarely
Increased IgG4	Slightly	Rarely	Obviously	Rarely	Rarely
Clinical manifestations
Bilateral	Frequently	Rarely	Frequently	Sometimes	Rarely
Pain	Frequently	Sometimes	Rarely	Frequently	Sometimes
Eyelid swelling	Frequently	Rarely	Frequently	Frequently	Rarely
Multiple organs involvement	Always, such as thyroid and pretibial myxedema	Frequently, such as periorbital bone	Always, such as salivary gland and pancreas	Rarely	Rarely
Proptosis	Frequently	Frequently	Frequently	Rarely	Frequently
Conjunctiva involvement	Frequently	Sometimes	Rarely	Frequently	Frequently
MRI features
Extraocular muscle enlargement	Frequently, without tendon involved	Rarely	Sometimes, tendon can be involved	Sometimes, often in medial muscle, tendon can be involved	Frequently, multiple muscles
Lacrimal gland enlargement	Frequently	Frequently	Always	Sometimes	Rarely
Nerve involved	Sometimes, optic nerve compression	Sometimes, optic nerve compression	Rarely	Rarely	Rarely
Character of lesion on MRI	Active phase: T2WI ↑ Inactive phase: T1 T2 WI –/↓	T1WI – T2WI –/↓ with irregular margin	T1WI – T2WI –/↓ with homogenous and well-defined	Similar to GO	Enlargement and internal signal void of cavernous sinus on T1WI and T2WI

GO, Graves ophthalmopathy; IGG4, immunoglobulin G4; MRI, magnetic resonance imaging; T1WI, T1 weighted-image; T2WI, T2 weighted image. ↑, signal increased; ↓, signal decreased.