Orbital Pseudotumor (Non-Specific Orbital Inflammatory Disease)
Orbital Pseudotumor which is also referred to as Idiopathic Orbital Inflammatory Disease or Orbital Inflammation or Orbital Swelling is one of the most common causes of a painful orbital mass in adults (eye diseases). There may be a marginated enhancing soft tissue mass that involves any area of the orbit (socket surrounding the eye). This being amongst the most painful orbital conditions, is linked with cranial nerve palsy, uveitis, proptosis (forward displacement of the eye) and retinal detachment. The orbital inflammation can be localized or diffuse.
When the inflammation (orbital swelling) is localized, inflammation may also affect the extraocular muscles (orbital myositis), sclera – white portion of eye (scleritis), uvea – black portion of eye (uveitis), lacrimal gland (dacryoadenitis), cavernous sinus and the superior orbital fissure (Tolosa-Hunt Syndrome). In cases when the tumor is diffuse, it may involve the orbital fatty tissues diffusely. Orbital Pseudotumor or Non Specific Orbital Inflammatory Disease (NSOID) is the third most commonly occurring orbital disease after Thyroid Eye Disease and Orbital Lymphoma. NSOI may clinically and radiologically resemble a malignant process. Hence, all other causes of inflammation should be first ruled out in orbital diseases, before making the diagnosis.
- No particular predilection for age, sex or race.
- Most likely seen in middle-aged individuals.
- NSOID is the second most common cause of exopthalmos (Proptosis – Bulging eyes out of the orbit) following Grave’s orbitopathy (thyroid eye disease) and third most commonly occurring orbital disease after Thyroid Eye Disease and Orbital Lymphoma and accounts for 5-17.6% of orbital conditions.
- Pediatric cases constitute approximately 17% of all cases of NSOID.
The exact etiology or cause of NSOI is unknown, but infectious and immune-mediated mechanisms have been predicated. Several studies have described cases where onset of orbital pseudotumor was seen simultaneously or several weeks after upper respiratory infections.
Orbital pseudotumor has also been observed in amalgamation with Crohn’s disease, rheumatoid arthritis, systemic lupus erythematosus, myasthenia gravis, diabetes mellitus and ankylosing spondylitis all of which strengthen the basis of NSOID being an immune-mediated disease. Response to corticosteroid treatment and immunosuppressive agents also support this idea.
Trauma has also been seen to precede some cases of orbital pseudotumor.
Classically, a patient presents with following symptoms:
- Redness, swelling or oedema of the eyes & peri-ocular area
- Sudden proptosis – which is painful and varies depending upon the degree of fibrosis, inflammation and mass effect.
- Rarely, ptosis, chemosis (swelling of conjunctiva), motility dysfunction (opthalmoplegia) and optic neuropathy may be seen.
- When there is extensive sclerosis, it may involve restriction, compression and destruction of the orbital tissue.
- Symptoms usually take hours to days to develop, however they have also been developed over a period of few weeks or even several months.
- There may be certain associated symptoms such as malaise, headache and nausea.
- Some uncommon presentations may be seen with cystoid macular edema, cluster headaches and temporal arteritis.
- In case of children, presentation slightly differs, in that uveitis, disc edema and tissue eosinophilia are seen commonly along with bilateral involvement.
The most accurate imaging criteria for NSOID is contrast-enhanced thin section magnetic resonance imaging (MRI) with fat suppression. The best diagnostic clue being a poorly marginated, enhancing soft tissue mass, which involves any area of the orbit.
- Inflammation of extra ocular muscles (myositis) with tendinous involvement
- Lacrimal gland inflammation and enlargement (dacroadenitis)
- Orbital fat streaking
- Involvement of the optic sheath complex, uvea and sclera
- Presence of a focal intraorbital mass or diffuse orbital involvement.
- Rarely, bone extension and intracranial extension.
Based upon the area involved, NSOID may be categorized as:
- Anterior – Involvement of the globe, retrobulbar orbit
- Diffuse – Multifocal intraconal involvement with or without an extraconal component
- Apical – Involving the orbital apex and with intracranial involvement
Tolosa-Hunt syndrome is a different type of orbital pseudotumor, in which there is extension into the cavernous sinus through the superior orbital fissure. Another disease variant is Sclerosing pseudotumor, which more often presents bilaterally and may extend into the sinuses.
In the non-enhanced CT scan, one may find a lacrimal, extra-ocular muscle, or other orbital mass. It may be focal or infiltrative and will have poorly circumscribed soft tissue. In contrast-enhanced CT scan, there is moderate diffuse irregularity and enhancement of the involved structures.
- MRI of the head
- Ultrasound of the head
- Skull X-ray
- First, the diagnosis needs to be established. A localized or incisional biopsy is performed, with histo-pathological evaluation, to diagnose the condition.
- Mild cases may resolve without treatment. Whereas, more severe cases respond well when treated with corticosteroids. Very lethal cases may lead to damaging pressure on the eye, and need surgical correction to relieve the pressure on the eyeball.
- Though the response to corticosteroids is usually quick, but they should be continued on a tapering basis to avoid breakthrough inflammation. Although many respond to corticosteroid treatment alone, there are a few cases in which alternative therapy is needed. While many alternatives are available, there is no particular well-established protocol to guide adjuvant therapy. Among the available options there is: surgery, alternative corticosteroid delivery, radiation therapy, non-steroidal anti-inflammatory drugs, cytotoxic agents (chlorambucil, cyclophosphamide), corticosteroid sparing immunosuppressants (methotrexate, cyclosporine, azathioprine), IV immune-globin, plasmapheresis, and biologic treatments (such as TNF-α inhibitors).
Severe cases of orbital pseudotumor may push the eye forward to such an extent that the lids can no longer protect the cornea, leading to drying of the affected eye. This can lead to damage to the clarity of the cornea, or to corneal ulcer (wound). The eye muscles may not be able to properly orient and move the eye, and double vision (diplopia) may result.