Isolated Optic Nerve Involvement in Idiopathic Inflammatory Pseudotumor.

Introduction/Background: Orbitary pseudotumour or idiopathic inflammation of the orbit (IIO), is a benign, non-granulomatous inflammatory process in the orbit or eye without identifiable local or systemic cause. Although classically described as pain, proptosis and ophthalmoparesis, the optic nerve may be affected and its isolated involvement is extremely rare. The purpose of this study is to report a case of isolated optic nerve inflammatory pseudotumour presenting with painful unilateral vision loss and dramatic clinical and anatomical response to steroids. Methods: Case report. Results: A 54 year-old male presented with a 10-day history of painful and gradually decreased vision in his right eye. He had a history of intravenous drug abuse 10 years ago and no other relevant past medical history. On examination, his best-corrected visual acuity (BCVA) was 0.3 in his right eye. Anterior segment examination, intraocular pressure and ocular motility were unremarkable. His right fundoscopy and OCT examinations showed a swollen optic disc with peripapillary haemorrhages and choroidal folds. The MRI revealed a 1.1x0.7 mm gadolinium-enhanced mass located at the orbital apex surrounding the right optic nerve. His neurologic and general examinations were otherwise unremarkable. After a course of oral prednisone (1 mg/Kg), a dramatic clinical improvement was observed during the first week. The funduscopy showed a complete optic disc edema resolution, and another MRI performed 1 month later confirmed the complete regression of the orbitary mass. Conclusions: The IIO constitutes the third most common ophthalmic disorder following Grave's disease and lymphoproliferative disorder. Clinical presentation mainly depends on the location and degree of inflammation. It is considered a clinical diagnosis of exclusion and its physiopathology still remains unknown. In the case reported, the lack of systemic symptoms, serologic markers and the dramatic response to steroids makes the diagnosis. A trial of corticosteroids should be considered when a case of orbitary pseudotumor is suspected. Acknowledgements: None. [ABSTRACT FROM AUTHOR]