Idiopathic orbital inflammation with extensive intra- and extracranial extension presenting as 6th nerve palsy--a case report and literature review.

Introduction: To report a case of idiopathic orbital inflammation with extensive extraorbital involvement presenting as 6th nerve palsy.

Materials And Methods: The patient presented with right periorbital pain, headache, and diplopia. Orthoptic examination revealed 6th nerve palsy. Investigations, including imaging (CT, MRI, MRA, chest x-ray), lumbar puncture, and screening blood tests (autoimmune disease and TB), were normal. He was lost to follow-up but presented again with no perception of light in the right eye with almost complete ophthalmoplegia and 3 mm of proptosis four months later.

Results: Repeat imaging showed a poorly defined mass involving the extraocular muscles in the posterior right orbit extending into the cavernous sinus and infratemporal fossa. Histopathologic examination showed a fibro-inflammatory infiltration of lymphocytes, plasma cells, and histiocytes, with widespread collagen deposition. No granulomas, vasculitis, or necrosis were seen. A tuberculosis screen (Mantoux) and lumbar puncture were negative. Idiopathic orbital inflammation (IOI) was diagnosed, and 60 mg of oral prednisolone and 300 mg of isoniazid were commenced. Fourteen months later, the patient remained blind, but ocular motility had returned to normal and no proptosis was evident.

Conclusions: IOI can present in an atypical fashion and early disease may be undetectable radiologically.