Imaging description

Lesions of the orbit can have diverse etiologies and imaging appearances. The old classification based on intraconal or extraconal location is not helpful for specific diagnosis in most cases.

Idiopathic inflammatory pseudotumor of orbit is a quasineoplastic lesion that accounts for 5–10% of all orbital lesions and is the third most common orbital disorder following thyroid orbitopathy and lymphoproliferative conditions [1,2]. Mixed inflammatory infiltrate of pseudotumor can be seen in any area of the orbit, but most commonly involves the retrobulbar compartment and takes the form of a mass. This is known as tumefactive pseudotumor; it accounts for about two-thirds of all cases (Fig. 72.1) and usually presents with proptosis, limitation of eye movements, and decreased vision.

Myositic type is the second most common, usually unilateral, involving single or multiple muscles, including the tendinous insertions (Fig. 72.2). Diplopia and limitation of ocular movements are common. Lacrimal gland pseudotumor is commonly associated with systemic disease and presents with enlarged and tender gland and proptosis of the orbital globe (Fig. 72.3). It can be associated with extraorbital extension [3]. Tolosa–Hunt syndrome is considered to be a form of pseudo-tumor involving the cavernous sinus.