Is there an autoimmune encephalitis-like brain metabolism pattern in patients with Bickerstaff brainstem encephalitis?

Abstract:  Background: Brain 18 FDG PET is very useful in the diagnosis of autoimmune encephalitides against post-synaptic receptors. However, little is known about the metabolic changes in other autoimmune encephalitides, such as Bickerstaff stem encephalitis (BBE). Objective: to report the case of a patient with BBE with an 18 FDG PET study and to review the literature. Results: A 20-year-old man with no relevant history presented to the emergency department due to a clinical picture of 7 days of evolution, characterized by non-painful distal paresthesias in the 4 extremities, diplopia, instability on gait and dysphagia. On the day of his hospital stay, he presented alterations in his awake state. The clinical diagnosis of Bikerstaff's stem encephalitis was made. In his paraclinical tests, the cerebrospinal fluid was normal. He received treatment with human immunoglobulin (2 grams/kg) for 5 days. An 18 FDG PET study reported hypermetabolism in the putamen and bilateral caudate nucleus and bilateral occipital hypometabolism. Conclusion: brain 18-FDG PET may be a subrogate marker for understanding CNS compromise in BBE.