Orbital Pseudotumour: Clinical and Radiological Assessment

Abstract

Orbital Pseudotumour (OP) is an antiquated term that denotes an idiopathic and nonspecific space-occuping inflammation of any of the orbital structures. The clinical presentation can be acute, subacute or chronic and depends on the structures involved. Aim of the study is to evaluate the different anatomic variants of OP, with emphasis on the differential diagnosis with other pathologies, especially malignancies. We report a retrospective comparison of the clinical, CT and MR findings of 50 patients with non-traumatic orbital pathology, diagnosed between 1993 and 1996. We stratified the radiologic examinations on the basis of the main anatomic structure involved: Lacrimal gland (8 cases); Extrinsic ocular muscle(s) (14 cases); Optic nerve-optic nerve sheaths complex (12 cases); Superior ophthalmic vein (7 cases); Orbital apex (5 cases); Retrobulbar soft tissues (3 cases). We found no specific clinical signs or pathognomonic CT or MR findings to establish a certain diagnosis, although contrast enhancement was present in 100% of the cases and could thus be considered a distinguishing feature. We also found a good correlation between the location and the extent of the disease as identified on CT and MR scans with the clinical presentation. With regard to differential diagnosis we found: Lacrimal gland: PO (4), Lymphoma (2), Septic dacryoadenitis (2); Extrinsic ocular muscle(s): PO (7), Thyroid ophthalmopathy (5), Metastasis (2); Optic nerve-optic nerve sheaths complex: PO (4), Autoimmune diseases (4), meningioma (2), Lymphoma (1), Glioma (1); Superior ophthalmic vein: PO (1), Carotid-cavernous fistula (3), orbital varyx (3); Orbital Apex: PO (2), Metastasis (2), Meningioma (1); Retrobulbar soft tissues: PO (1), Lymphoma (1), Septic cellulitis (1). OP represents a frequent cause of orbital pathology in the adult. The differential diagnosis with other entities is not always simply on the basis of morphologic pattern and the biopsy may also be inconclusive, especially in distinguishing between OP and lymphoma. All but one patients improved clinically following administration of corticosteroids and the abnormalities on the CT and MR scans disappeared or became less prominent within 45 days after starting the steroid treatment. The radiologic recognition of this particular disease is important since the response to steroid therapy is almost always dramatic and the prognosis for complete recovery is relatively good. Biopsy is reserved only to steroid non-responder patients.