Optic perineuritis in polyarthritis nodosa.

A 52-year-old male patient with polyarthritis nodosa (PAN) was referred to our neurology outpatient clinic. His main symptom was paroxysmal alternating bilateral blindness. Subsequently, he developed retro-orbital pain. Neurological examination including funduscopy was normal and laboratory tests showed no relevant abnormalities. MRI orbits showed remarkable perineural thickening and contrast enhancement of the optic nerve sheaths with sparing of the central optic nerve. These findings are pathognomonic for the clinical-radiological diagnosis of optic perineuritis (OPN). The patient was treated with high-dose immunosuppressants and had a good clinical outcome. Rapid diagnosis of OPN is important because early treatment is associated with a better outcome.