A retrospective case series of 5 cases of idiopathic orbital inflammatory syndrome (IOIS) with clinical features and outcomes that presented over the course of 2 years from tertiary care hospital, India.

IOIS is an exceptionally rare, benign non-infective inflammatory condition of the orbit. It can involve any orbital tissue - either individually or in combination and may extend to the cavernous sinus. Presentation is heterogeneous and thus, it is a diagnosis of exclusion. 

Case series

All 5 cases presented primarily with headache and diplopia of a median duration of 3 weeks. 80% of them had unilateral eye involvement. Redness, watering of eyes, and mild blurring of vision were other associated symptoms. Clinical examination revealed predominantly medial, lateral, and superior recti muscle involvement in up to 80% of cases. A detailed vasculitis workup with an autoimmune screen was normal. CSF analysis was also normal in all patients.
MRI brain and orbits with contrast were consistent with medial and lateral recti hyper-intensities as the most common finding followed by involvement of superior rectus, the orbital apex in minority of the patients.  All patients were started with IV methylprednisone for 5 days followed by oral prednisone 1mg/kg given for two weeks followed by a slow taper over the next 12 weeks. All patients improved significantly at the 4, 8, and 12 week follow-up, and as such biopsy was deferred in all cases.

IOIS is a diagnostic challenge. MRI of brain and orbits with contrast is crucial in identifying the condition. Diplopia with a headache due to extraocular muscle involvement is an uncommon presentation of IOIS which masquerades as partial 3rd, 4th, and 6th cranial nerve palsy. Our case series highlights the importance of considering IOIS in the differential diagnosis of diplopia with headache.