Neurosarcoidosis: clinical diagnosis of migratory chiasmitis and bilateral optic neuropathy

Sarcoidosis is a diagnostically challenging and complex multisystem disease characterised by the formation of non-caseating granulomas. This case describes a young man who developed bitemporal vision loss that rapidly progressed to complete bilateral vision loss. MRI demonstrated chiasmatic and optic neuritis. A history of pulmonary nodules was noted. Via multi-disciplinary team discussion, no safe biopsy targets were identified. A clinical diagnosis of neurosarcoidosis was established. The patient's symptoms responded well to high-dose steroids and plasma exchange. Chiasmitis and optic neuritis are characteristic but rare manifestations of sarcoidosis. The progression of symptoms suggests migratory inflammation from the optic chiasm to the nerves. Diagnostic challenges are posed by the need to exclude mimics and the lack of sensitivity in serological markers. Literature provides an algorithm to support clinical diagnosis. There are no formal treatment guidelines. High-dose steroids and immunosuppression demonstrate effective treatment.