Teaching NeuroImages: Extensive vasogenic edema in Bickerstaff brainstem encephalitis.

Ten days after respiratory infection, a 32-year-old woman presented with headaches, ataxia, and diplopia without encephalopathy. Brain MRI revealed extensive white matter, brainstem, and cerebellar vasogenic edema, without gadolinium enhancement, partially regressive during follow-up (figure, A). CSF revealed transient elevated protein level (1.01 g/L) and hypercellularity (123 neutrophils/mm). Negative anti-GQ1b but positive anti-GD1a immunoglobulin G led to the diagnosis of Bickerstaff brainstem encephalitis (BBE). Symptoms resolved within 10 days without treatment. FDG-PET showed bilateral temporo-parieto-occipital and cerebellar hypometabolism (figure, B). Neurologists should be aware that diffuse brain hypometabolism or vasogenic edema can be associated with BBE. AUTHOR CONTRIBUTIONS E. Nerrant, C. Fourcade, S. Coulette, C. Lechiche, and E. Thouvenot participated in drafting/revising the manuscript.