A Rare Case of Adult-Onset Bilateral Nonspecific Orbital Inflammation (NSOI) With Concomitant Unilateral Third Cranial Nerve Palsy.

Nonspecific orbital inflammation (NSOI), also known as orbital pseudotumor, is a condition characterized by inflammation in the tissues around the eye socket (orbit) without a clearly identifiable cause. This inflammatory disorder can affect various structures within the orbit, including muscles, fat, and connective tissues, leading to symptoms such as pain, swelling, and changes in vision. A 74-year-old man with a history of previous orbital trauma presented with acute-onset head and orbital pain, followed by restricted left eye movements in all directions, left ptosis, and a dilated left pupil. Orbital imaging revealed bilateral inflammation of the lateral rectus muscles and orbital fat, suggestive of bilateral NSOI, while brain and laboratory studies ruled out other differential diagnoses. The presence of left ptosis, a dilated pupil, and limited upward, downward, and inward movements in the left eye suggested intraorbital involvement of both the superior and inferior divisions of the left third nerve. The complete resolution of orbital symptoms and third nerve function after systemic corticosteroid therapy supported the inflammatory nature of the nerve involvement in this case. The case is notable in terms of bilateral involvement in adult-onset NSOI, the possible role of previous orbital trauma in the development of the disease, and the inflammatory involvement of third nerve divisions following the extension of inflammation into the orbital tissues. NSOI can mimic other, more serious conditions, making accurate diagnosis crucial for effective management and treatment. Understanding its presentation, potential causes, and appropriate diagnostic approaches is essential in providing optimal care for patients affected by this complex inflammatory condition.