Orbital Pseudotumor

What is Orbital pseudotumor?

Orbital pseudotumor can be defined as a benign inflammatory process that occurs at the level of the extraocular muscle, being of idiopathic cause. Some patients might present an additional involvement, such as at the level of the uvea, sclera or the lacrimal gland. The retrobulbar soft tissue can also be affected by the orbital pseudotumor. The condition was described for the first time in 1905, by Birch-Hirschfeld.

The orbital pseudotumors can be classified into the following categories:

  • Lacrimal pseudotumor – involvement of the lacrimal gland
  • Anterior pseudotumor – the localization is immediately behind the ocular globe
  • Posterior pseudotumor – no involvement of the cavernous sinus (differential diagnosis with the Tolosa-Hunt syndrome)
  • Diffuse pseudotumor – the exact involvement is difficult to identify
  • Myositic pseudotumor – involvement of extraocular muscle (tendon included); in this situation, the differential diagnosis can be made with the thyroid associated orbitopathy (no tendon involvement).

Studies have demonstrated that there are numerous conditions, both inflammatory and autoimmune, associated with the orbital pseudotumor. Among the most common associations, there are: retroperitoneal fibrosis, mediastinal fibrosis, Riedel’s thyroiditis, sclerosing cholangitis, rheumatoid arthritis, dermatomyositis, polyarteritis nodosa, systemic lupus erythematosus, Wegener’s granulomatosis and sarcoidosis.

Young women present the highest risk for developing orbital pseudotumors, even though these can appear at any age (less common in the pediatric population). No race predilection has been identified for this condition.

The orbital pseudotumor is often presented in the medical field as the idiopathic orbital inflammatory syndrome (abbreviated as IOIS). It is considered among the most common diseases of the orbit, after the thyroid orbitopathy and the lymphoproliferative disorder. The orbital pseudotumor accounts for 5-10% of all the orbital processes.

Symptoms of Orbital Pseudotumor

These are the most common symptoms caused by the orbital pseudotumor:

  • Rapid onset
  • Unilateral involvement (90% of all the cases)
  • Painful proptosis (forward protrusion of the ocular globe)
  • Diplopia (double vision)
  • Restricted movement of the eye (also because of the intense pain)
  • Reduced visual acuity
  • Conjunctival chemosis
  • Periorbital edema.

The following symptoms demonstrate that the orbital pseudotumor should be treated as a medical emergency: rapid progression of the proptosis, reduced motility in the affected eye and intense pain (alarm signals).

If the condition does appear in a child, it can lead to a series of systemic symptoms, among which these are the most common: fever, lethargy, anorexia, emesis and headaches (50% of the cases). In children, orbital pseudotumors are frequently characterized by bilateral involvement, with the inflammation of the iris and peripheral accumulation of eosinophils among the manifestations. Among the most common symptoms that children present, there are: restriction of the ocular motility, inflammation of the eyelids, protrusion of the ocular globe and high pressure at the level of the orbit.

Pathology

The histopathological analysis of the acute lesions reveals the presence of lymphocytes, which can lead to a confusion of the diagnosis (often perceived as orbital lymphoma). Apart from the lymphocytes, there are plasma cells and giant cell infiltration.

Associated optic neuropathy might be presented in some patients. The orbital pseudotumor has also been found in association with infectious diseases, such as: pharyngitis of streptococcal origin, upper tract respiratory infection (viral cause) and infection caused by organisms such as Borrelia burgdorferi.

How is Orbital Pseudotumor Diagnosed?

These are the most common methods used for the diagnosis of the orbital pseudotumor:

  • Imaging studies (MRI in particular but also X-ray, CT scan and ultrasound)
    • Enlargement of the muscle belly (ocular muscle together with tendinous insertion)
    • Additional inflammation in the tissues that surround the muscles
    • Involvement of the lacrimal gland
    • Presence of infiltrative mass – extension outside the orbit (through orbital fissures, superior or inferior)
    • Extension is possible – most common: dura mater, meninges or cavernous sinus
  • Other investigations
    • Orbital biopsy – used for the confirmation of the diagnosis; may be performed in the situation that an orbital malignancy is suspected or the response to the treatment with corticosteroids is poor.

Based on the information provided through the imaging studies, the differential diagnosis for the orbital pseudotumor can be made with the following conditions: orbital cellulitis, orbital metastases, orbital rhabdomyosarcoma, orbital lymphoma, orbital sarcoidosis, thyroid associated orbitopathy (no tendon involvement, no pain) and the Tolosa-Hunt syndrome.

In children, the differential diagnosis can be made with the following conditions: thyroid related orbitopathy, metastatic retinoblastoma, neuroblastoma, lymphangioma, ruptured dermoid cyst, orbital trauma (foreign body still present), leukemia, rhabdomyosarcoma and orbital cellulitis.

Orbital Pseudotumor Treatment

The standard treatment for the orbital pseudotumor is represented by corticosteroids. Depending on the severity of the condition, the doctor might decide to administer the corticosteroids in oral or intravenous form. The treatment with corticosteroids has the prevention of ocular functional complications as main objective. Children benefit as well as adults from the treatment with corticosteroids. Upon being treated with such medication, the clinical response is positive and the visual recovery is significant. In general, patients who are treated with corticosteroids presented a dramatic improvement within one or two days since the beginning of the treatment.

In the situation that the patient experiences a chronic progression of the condition, the treatment choices will have to include chemotherapy and radiotherapy. The surgical intervention is sometimes required to relieve the tremendous pressure experienced by the patient (removal of a portion of the orbit bone).

Other treatment solutions for the orbital pseudotumor include:

  • Administration of cytotoxic agents
  • Immunosuppressants
  • IV immunoglobulin
  • Biological therapy
  • TNF-alpha inhibitor monoclonal antibody
  • Administration of mycophenolate mofetil.

The treatments that have been suggested above are especially recommended for the management of refractory orbital pseudotumors.

Prognosis

In the majority of the cases, with mild symptoms, the prognosis is positive. The prognosis is also negative in the situation that the person does not respond well to the treatment, resulting in the loss of vision. All refractory cases present a degree of residual fibrosis.

Are there any Complications?

It is possible that the orbital pseudotumor can lead to an excessive forward protrusion of the globe. Because of such changes, the eyelids cannot close anymore and the cornea is not protected. A possible complication in such cases is the dry eye syndrome but the cornea can also become cloudy or suffer from soreness.

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