1. Orbital Pseudotumor: Idiopathic Orbital Inflammation Shiva Kambhampati MS4,George Washington University School of Medicine/ University of North Carolina at Chapel Hill

2. Outline  What is Orbital Pseudotumor?  Differential Diagnosis  Case Presentation  Radiological Findings and Analysis  Orbital Pseudotumor Subtypes  Treatment  Conclusions

3. What is Orbital Pseudotumor?  First described in the 1900s  AKA “Idiopathic Orbital Inflammation”, or “nonspecific Orbital Inflammatory Disease”  Nonmalignant space occupying lesion involves orbital tissue and simulates a neoplasm  Diagnosis of exclusion, based on patient history, clinical picture, response to steroids, and occasionally by biopsy  Etiology unknown  3 rd most common cause of orbital inflammation

4. Differential Diagnosis of Orbital Inflammation  Inflammatory  Thyroid Opthalmopathy  Sarcoidosis  Wegener’s  Orbital Cellulitis  Abscess  Vasculitis  Neoplastic  Lymphoma  Metastases

5. Typically acute – but can be insidious Painful Usually unilateral No real pattern of muscle involvement Ocular findings include: Diplopia Decreased Visual Acuity Proptosis Edema Absent systemic symptoms Clinical Presentation

6. Imaging Findings of Orbital Pseudotumor  Imaging findings are characterized by inflammatory changes in orbital structures such as globe, lacrimal glands, extraocular muscles, orbital fat, and the optic nerve.  MR findings:  Isointense on T1  Hypointense compared to normal muscle on T2  Enhancement on post-contrast T1 images

7. Case Presentation  62 y-o male dull ache in left eye and limited EOM  PMH: uveitis  Other Classical Clinical Presentations include:  Eye pain  Edema  Proptosis  Motility Restriction  Ophthalmoplegia  Lid Erythema

8. Case: Axial T1 Pre-Contrast Axial T1 image shows isointense infiltrative process in left eye involving the retro-ocular fat and external rectus muscle.

9. Case: Axial T2 Axial T2 image shows the process to be mostly hypointense. Note proptosis.

10. Case: Axial T1 Post-Contrast Post contrast T1 image shows the process to enhance and extend to ipsilateral cavernous sinus and along dura of left middle cranial fossa.

11. Orbital Pseudotumor Forms  Dacryoadenitis  Myositis  Sclerosis  Optic Nerve involvement  Tolosa-Hunt Syndrome  Intracranial extension

12. Differential Diagnosis of Orbital Inflammation  Inflammatory  Thyroid Opthalmopathy  Sarcoidosis  Wegener’s  Orbital Cellulitis  Abscess  Vasculitis  Neoplastic  Lymphoma  Metastases

13. Histology of Idiopathic Orbital Inflammation  Fibrous connective tissue and scant perivascular patchy polyclonal lymphocytic infiltrates

14. Treatment  Systemic Corticosteroids  Usually rapid clinical response and resolution of pain  Radiotherapy  2 nd line therapy  Adjuvant treatment when incomplete response  1 st line therapy if steroids contraindicated  Immunomodulators/Immunosuppresants

15. Conclusions  Fairly common cause of orbital inflammation (3 rd )  Diagnosis of Exclusion, other causes must be ruled out  Occasionally diagnosis by biopsy is performed  Systemic Corticosteroids is primary treatment  Rapid response to steroid treatment supports diagnosis of Orbital Pseudotumor  MRI better imaging modality for characterizing intracranial extension  Orbital Pseudotumor is not a lymphoid tumor

16. Etiology  Etiology of Idiopathic Orbital Pseudotumor is unknown, but there are some theories in the literature  Originally it was thought to be infectious in origin, with historical reports occurring after viral illnesses.  Autoimmune pathogenesis was theorized because of a strong association with and rheumatologic diseases.  Reports of circulating antibodies against extraocular muscle proteins  IgG4 Related Systemic Disease  Theory that links different inflammatory disorders that were previously thought to be unrelated

17. IgG4 Related Systemic Disease (IgG 4 -RSD)  Systemic disease that is characterized by extensive IgG4- positive plasma cells and T-lymphocyte infiltration of various organs  Pancreatitis, sclerosing cholangitis, cholecystitis, sialadenitis, retroperitoneal fibrosis, tubulointerstitial nephritis, interstitial pneumonia, prostatitis, inflammatory pseudotumor and lymphadenopathy, are all thought to be IgG4-related  The prototype is IgG4-related sclerosing pancreatitis (also known as autoimmune pancreatitis)  Disease usually responds well to steroid therapy

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