Computed tomography in the diagnosis of orbital pseudotumor.

ABSTRACT

Eighteen patients with orbital pseudotumor were analysed. These patients were admitted into Siriraj Hospital during 1981 to 1985. They were 12 males and 6 females ranging in age from 5 to 75 years. Orbital pseudotumors are nonspecific influammatory lesions of unknown aetiology which may affect part or less frequent, al of the tissue within the orbit. Computed tomographic (CT) study of 18 patients demonstrated that these lesions could be unilateral or bilateral. In 5 patients (28%) with bilateral orbital pseudotumour, the lesions were multifocal and involved several orbital structures (globe, optic nerve, extraocular muscles and lacrimal gland). However, they could be differentiated from Graves’ opthalmopathy. In 13 patients (72%) with unilateral pseudotumour, the lesions could be classified into five anatomic patterns anterior, posterior, diffuse, lacrimal and myositic. The diffuse and isolated discrete mass lesions of orbital pseudotumour, sometimes can not be differentiated either from other infiltrative conditions as lymphoma or leukaemia or from other neoplasms within the orbit. Scleral uveal rim thickaening with contrast enhancement was found only in 3 patients (17%) with pseudotumour. This sign is not characteristic for orbital pseudotumour but it represents nonspecific inflammation of the globe. Orbital CT is not only an excellent technique in detection of orbital pseudotumour but it is also useful in the follow up of cases after treatment as well.