IMAGING IN OPHTHALMOLOGY I1 0033-8389/99 $8.00 + .OO PSEUDOTUMOR OF THE ORBIT Clinical, Pathologic, and Radiologic Evaluation Alfred L. Weber, MD, Laura Vitale Romo, MD, and Nelson R. Sabates, MD Idiopathic orbital inflammation or pseudotumor orbital structures, but frequently there is associated represents a nongranulomatous inflammatory pro- fatty infiltration. The inflammatory process within cess in the orbit or eye with no known local or the orbital fat may be localized simulating a tumor systemic causes.8,31It is a diagnosis by exclusion or may be diffuse within the fatty tissue. The dis- based on history, clinical course, response to ste- ease may occur predominantly anteriorly or poste- roid therapy, laboratory tests, and biopsy in a lim- riorly. ited number of cases.52T here is a group of diverse The radiologic evaluation consists of CT and MR disease entities that can mimick pseudot~mor,3~ imaging. The imaging findings, correlated with the which are discussed in the section on differential clinical findings, allow a diagnosis in most cases diagnosis. and hence obviate the need for a biopsy. Among orbital disorders pseudotumor, after For elucidation and confirmation of the sus- Graves’ disease and lymphoproliferative disease, pected clinical diagnosis, in our experience CT is is a common ophthalmologic disease. In three the preferred method because of the inherent con- large series of orbital disorders, pseudotumor ac- trast by different attenuation values of the orbital counted for 6.3%,= 5.2Y0,3~a nd 4.7y0.5T~h e disease fat, muscle, bony structures, and air in the adjacent usually occurs in adults but may also affect chil- paranasal sinuses. Extraorbital extension, however, dren. Pediatric orbital pseudotumor encompasses especially to the cavernous sinuses is better deline- about 6% to 16% of orbital pseudotumors.8, 46 In ated on MR imaging. At times orbital fatty infil- children, there is a higher incidence of bilateral tration and perineuritis are better delineated on orbital involvement without evidence of underly- fat suppression T1-weighted MR images than on ing systemic disease. CT scans. The disease may present acutely, subacutely, or chronically in one orbit or may occur bilaterally. CLINICAL FEATURES There may be recurrent disease after a 10-year interval.*, The disease can be categorized ac- The symptoms in idiopathic orbital pseudotu- cording to which orbital structure is predomi- mor are a reflection of the degree of the inflamma- nantly involved. According to location, we distin- tory response (acute, subacute, or chronic) and the guish myositis (one or more extraocular muscles); location of the inflammatory 52 The acute dacryoadenitis (lacrimal gland); periscleritis in- form is characterized by abrupt onset of pain, lid cluding Tenon’s space; trochleitis60; and perineuri- swelling, and redness associated in some cases tis (outer dural sheath of the optic nerve and adja- with diplopia and decreased vision. In addition, cent fat). The disease may be localized to these there may be ptosis, proptosis, and decreased or- - From the Department of Radiology, Harvard Medical School (ALW); the Department of Radiology, Massachusetts Eye and Ear Infirmary (LVR); the Department of Radiology, Section of Neuroradiology, Brigham and Women’s Hospital, Harvard Medical School (LVR), Boston, Massachusetts; and the Department of Ophthalmology, Eye Foundation of Kansas City, University of Missouri, Kansas City School of Medicine, Truman Medical Center (NRS), Kansas City, Missouri RADIOLOGIC CLINICS OF NORTH AMERICA VOLUME 37 NUMBER 1 - JANUARY 1999 151 152 WEBER et a1 bital resilience with ballottement and pain on PATH0L OGY globe motion. On slit lamp examination, there is conjunctival chemosis and injection. There may be Pseudotumor is divided into acute, subacute, associated inflammation of the iris and choroid and chronic These subcategories are based with choroidal effusion and localized choroidal on the degree of inflammatory and fibrovascular and retinal detachment. The patient may complain response. In the acute form of the disease there of generalized malaise, but is usually afebrile. In is a polymorphous infiltrate composed of mature the chronic sclerosing form, evolving over weeks lymphocytes, plasma cells, macrophages, eosino- and months, signs of fixation of the orbital struc- phils, and polymorphonuclear leukocytes. Multi- tures (globe and muscles) and mass effect are more nucleated foreign body giant cells secondary to prominent.1265, This is associated with slowly pro- fibrosis have also been described, but are rare! The gressive visual loss, diplopia, and proptosis. cellular infiltrate or orbital pseudotumor tends to The lacrimal gland may be the primary focus be diffuse and multifocal. Occasionally, vasculitis of the inflammatory process, diagnosed as acute affecting small arteries to the orbit may be associ- dacryoadenitis and characterized by pain localized ated with idiopathic orbital pseudotum~r.3~7, 51~ , in the superotemporal region. The lacrimal gland In the subacute and chronic idiopathic orbital is enlarged and tender to palpation. In chronic pseudotumor there is formation of increasing inflammation, present over several months, the amounts of fibrovascular stroma affecting muscles, clinical finding may be a painless lacrimal fossa fat, and glandular elements. This fibrotic response mass. In such instances a tumor, such as an ade- may result eventually in dense fibrosis with fixa- noid cystic carcinoma, cannot be excluded and a tion of orbital structures. Lymphoid follicles with biopsy is indicated. germinal centers may be interspersed, especially When the extraocular muscles are primarily af- in the chronic phase.31The acute inflammatory flicted (myositis form) there is diplopia and pain proccess may lead gradually into the fibrotic stage. exacerbated by eye movement with restriction of Some cases of nonspecific idiopathic orbital in- ocular mobility. There may be localized conjuncti- flammation, however, are primarily sclerotic in na- val injection and chemosis at the tendinous inser- ture and may present and progress insidiously tion of the involved muscles. If the pseudotumor without passing through a prior acute inflamma- is predominantly located in the orbital apex, the tory phase.65 findings consist of optic neuropathy and ophthal- moplegia reflected by decreased visual acuity, vi- sual field defects, relative afferent pupillary de- RADIOLOGIC FINDINGS IN fects, and disc edema. Optic nerve dysfunction PSEUDOTUMOR results from inflammation of the perineural tissue or compression on the optic nerve from mass ef- The radiologic findings in pseudotumor are char- fect. The acute form of pseudotumor is highly re- acterized by inflammatory changes in the various sponsive to high doses of systemically administered intraorbital structures, such as the globe, lacrimal prednisone. Complete resolution of the inflamma- glands, extraocular muscles, orbital fat, and optic tion may ensue, although there may be a recurrence nerve.16,28,48Bo ne destruction is a rare finding in in the same or other orbit. Subacute cases have a this entity.19 The following is an outline of the most less sudden onset and may evolve over weeks and important CT and MR imaging findings based on months. In the chronic variety of pseudotumor, the the anatomic location of the inflammation. onset is insidious with gradual development of 1. Lacrimal gland involvement proptosis; diplopia; decreased vision; and, in the single advanced stage, fixation of the globe and muscles combined with other orbital tissue from diffuse fibrosis in the orbit. A variant of pseu- 2. Muscle involvement dotumor is the Tolosa-Hunt syndrome, which is single characterized by inflammatory infiltration in the multiple, often associated with orbital fat orbital apex, including superior orbital fissure and infiltration cavernous sinus.", 27, 39, 58 The disease manifests as 3. Orbital fat involvement painful opkthalmoplegia with minimal proptosis diffuse, ill-defined infiltrations and rare visual loss and external signs of orbital with or without involvement of optic inflammation. The ophthalmoplegia consists of nerve, lacrimal gland, and muscles third, fourth, and sixth cranial nerve palsies, along configuration of mass with hypoesthesia of the periorbital skin due to 4. Infiltration or mass in orbital apex involvement of the first division of the trigeminal 5. Tolosa-Hunt syndrome subtype nerve. It generally is unilateral, but bilateral cases 6. Globe involvement do occur. Immediate relief of symptoms following Tenon's space (Tenon fasciitis) high doses of steroid therapy differentiate pseu- scleritis dotumor of the orbital apex and cavernous sinus from other lesions, including meningioma, primary On CT, pseudotumor displays no specific density sino-orbital tumor, metastatic disease, invasive my- values. There is variable enhancement after admin- cotic infections, and aneurysm. istration of iodinated contrast material (Fig. 1).O n PSEUDOTUMOR OF THE ORBIT 153 Figure 1. Orbital myositis, lateral rectus muscle on left with involvement of the left lacrimal gland. A, Axial CT section through the mid orbits reveals diffuse enlargement of the left lateral rectus muscle with involvement of the muscle tendon and the left lacrimal gland and adjacent soft tissue structures. Note normal medial rectus muscle of left orbit. There is a false eye and phthisis bulbi of the right globe from previous trauma. B, Axial, T1-weighted MR image through the mid orbits demonstrates