Nonspecific Orbital Inflammation

Excerpt

Orbital pseudotumor, also known as orbital inflammatory pseudotumors (OIP), idiopathic orbital inflammation (IOI), idiopathic orbital inflammatory syndrome (IOIS), idiopathic orbital inflammatory pseudotumor (IOIP), or nonspecific orbital inflammation (NSOI) is a benign, space-occupying, and noninfectious inflammatory condition of the orbit but may extend in the periorbital area. No identifiable infectious, systemic, or neoplastic disorder is associated with it. It is the third most common orbital disease in adults, following thyroid orbitopathy and lymphoproliferative diseases.

Many orbital inflammations may be associated with systemic conditions or remote organ dysfunction. Categories of orbital pseudotumor according to location include anterior, diffuse, posterior, or apical. Other classifications include myositis, dacryoadenitis, periscleritis, perineuritis, and focal mass.

Orbital pseudotumor is rare in children. The most common ophthalmic findings include periorbital edema and blepharoptosis. A palpable mass may be present. On orbital radiography, common findings are dacryoadenitis, orbital mass, or myositis. In children, systemic signs are present in up to 50% of patients. Headache, emesis, anorexia, lethargy, and fever are the most common systemic signs. Additionally, there are likely associations with iritis, uveitis, disc edema, and peripheral eosinophilia.

The pathophysiology of orbital pseudotumor, first identified more than a century ago, is still unknown, adding to the difficulties in diagnosis and uncertainty surrounding treatment. However, advances in imaging, histology, and immunology have illuminated the underlying mechanisms of the illness, previously believed to be essentially idiopathic. These mechanisms involve a complex interaction of immunological dysregulation, viral triggers, and genetic predisposition.

Understanding the clinical spectrum and diagnostic criteria of orbital pseudotumor is essential for accurate diagnosis and effective treatment. Patients commonly present with unilateral proptosis, discomfort, diplopia, and visual abnormalities, which can be either acute or subacute. These symptoms often resemble other orbital diseases such as neoplasms, infections, or thyroid eye disease. Clinical assessment, imaging modalities (such as computed tomography [CT] and magnetic resonance imaging [MRI]), and occasionally histological examination acquired via biopsy are utilized to differentiate orbital pseudotumor from these conditions.