Orbital inflammation presents clinicians with the challenge of diagnosis by exclusion, as etiologies ranging from idiopathic to neoplastic have overlapping presentations.

We limit the definition of orbital inflammatory syndromes in this article to non-infectious disorders, including autoimmune, neoplastic and idiopathic. We further divide this definition into primary orbital inflammation and inflammation secondary to a separately definable orbital process.

Of the patients referred to an orbital specialist, orbital inflammation accounts for up to 60% of cases. The majority of cases are thyroid-related orbitopathy, followed by lymphoproliferative disorders and idiopathic orbital inflammation (IOI), with a small percentage of specific primary orbital inflammatory syndromes.^1-3 The differential diagnosis for orbital inflammation necessitates a comprehensive work up to guide the clinician toward an effective treatment strategy and/or the need for outside specialty referral.

The purposes of this discussion are to briefly offer our clinical perspective in working up primary and secondary orbital inflammatory disorders and to detail the diagnostic considerations for IOI.

ORBITAL INFLAMMATORY DISORDERS

Primary

The shared clinical presentations for the various orbital inflammatory disorders make this a diagnostic challenge. In thyroid-related orbitopathy, the most common cause of orbital inflammation, patients typically have a characteristic presentation with retraction of the eyelids, lid lag and unilateral or, more commonly, bilateral proptosis. Furthermore, this condition can typically be identified serologically.² Other common primary causes include granulomatosis with polyangiitis (formerly Wegener’s granulomatosis), sarcoidosis and IgG4-related disease, which can also be distinguished using clinical findings and serology (Table 1).²

Secondary

The second most common cause of orbital inflammation, lymphoproliferative disorder, is classified as a secondary orbital inflammation. Other secondary causes often have obvious clues for their clinical presentation, such as infection or trauma, which can rule out primary inflammation (Table 1). These are beyond this article’s scope.

IDIOPATHIC ORBITAL INFLAMMATION

Definition

If there is a negative work up of primary and secondary orbital inflammations, the diagnostic consideration should be given to IOI, a diagnosis of exclusion that accounts for about 6% of orbital disorders.² This definition of IOI (also called non-specific orbital inflammation, orbital inflammatory syndrome and orbital pseudotumor) is clinical and consists of subtypes with individual anatomical patterns within the orbit.⁴ Their locations are typically, but not exclusively, unilateral and can be myositic, lacrimal, anterior, diffuse, apical or a combination.^2,3 Clinical examination and CT or MRI imaging, obtained during the rule-out of other causes, aid in isolating the particular subtype(s) (Table 2, page 52).

Determining treatment

In most cases of IOI, biopsy is not required for determining treatment.⁵ Often, the clinical and radiologic presentation for IOI overlaps with infectious orbital cellulitis, making it a diagnostic dilemma.

Since empiric treatment with corticosteroids has the potential for exacerbating an orbital infection, an equivocal patient is often first empirically treated with broad spectrum IV antibiotics.

If the patient’s condition is refractory to antibiotics and fungal etiologies have been ruled out, the patient is then treated empirically with corticosteroids in what has been termed a “corticosteroid trial.” The “corticosteroid response is defined as a dramatic improvement of signs and symptoms within 48 hours after administration of systemic prednisolone, 1 mg/kg/d.”⁶ The myositic subtype of IOI is distinctly characterized by this response.

However, in patients with other forms of IOI, “the diagnostic corticosteroid trial has poor specificity and low positive predictive value.”⁶ The power of using such a trial is further questioned by studies that have reported variable responsiveness of the different subtypes.⁴ Thus, the response to a corticosteroid trial should be considered a “useful diagnostic indicator that is not [in itself] diagnostic.”⁷

When to consider biopsy

If corticosteroids do not provide a quick response or if there are atypical findings, biopsy should be performed. Biopsy is considered a low morbidity procedure and is a “critical diagnostic option ... that ... should be tailored to individual risks.”^4,6 The benefits of a biopsy procedure often far outweigh the risks, particularly in ruling out other causes of primary and secondary inflammation that correlate with increased systemic morbidity (Figure 1). In cases where orbital tissue is easily accessible for biopsy (e.g., anterior and lacrimal subtypes), a biopsy is sometimes considered before a steroid trial.²

The morbidity of biopsy increases with sampling for the myositic and apical subtypes that may present a risk of injury to the muscle or optic nerve.^3,7 In addition, myositic subtypes are typically not biopsied due to their dramatic response to steroids.

For biopsies of orbital tissues, a minimally invasive approach under local anesthesia is often the preferred technique.⁸ Fine-needle aspiration is indicated in patients with a history of systemic lymphoma or metastasis.⁴

CONCLUSION

With this review, we have aimed to provide a practical approach for the clinician to navigate the diagnostic challenges of primary and secondary orbital inflammation. We gave our clinical perspective on IOI, which is becoming a less frequent diagnosis as we continue to investigate and understand the underlying pathogenesis and clinical findings of the specific subtypes.³ OM

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About the Authors

Justin M. Refugia, BS, a second year medical student at Eastern Virginia Medical School, is planning a career in ophthalmology. He graduated with a Bachelor of Science in biology from Old Dominion University in Norfolk, Va.

Guneet S. Sodhi, MD, is a first year ophthalmology resident at Eastern Virginia Medical School. He graduated from George Washington University Medical School in Washington D.C., and completed a BS in biology from George Washington University.

Thomas J. Joly, MD, PhD, is assistant professor of ophthalmology at Eastern Virginia Medical School and ophthalmic plastic surgery consultant at Virginia Eye Consultants in Norfolk, Va. He pursued his orbital and oculoplastic surgery fellowship at the University of British Columbia and his combined MD/PhD with doctorate in neurophysiology at the State University of New York at Buffalo.