Teaching NeuroImages: Chiasmal enlargement and enhancement in Leber hereditary optic neuropathy

A 19-year-old man was admitted for subacute severe painless bilateral loss of vision. The patient was known to be a healthy carrier of the mitochondrial G11778A mutation, with a family history of Leber hereditary optic neuropathy. Funduscopy revealed bilateral optic disc elevation and hyperemia (figure). Goldmann visual fields demonstrated large central scotomas in both eyes. CSF disclosed normal opening pressure and cytochemical examination. Unexpectedly, brain MRI revealed an asymmetrical chiasmal enlargement and enhancement (figure). Similar cases have rarely been reported. These findings would suggest disruption of the blood-brain barrier at the early stage of the disease, likely due to an inflammatory-like mechanism.