Frequency, clinical, and paraclinical characteristics of patients with Bickerstaff brainstem encephalitis in a tertiary-referral neurological center

Background: Bickerstaff brainstem encephalitis (BBE) presents with consciousness impairment, ataxia, ophthalmoplegia, and areflexia. Objective: We aim to describe the clinical, paraclinical, and imaging features of patients with BBE from a tertiary-re-ferral neurological center. Methods: A case series was conducted from an ambispective cohort of patients with Guillain-Barré syndrome (GBS) from 2016 to 2021. Subjects ≥ 18 years and who met Odaka et al. BBE criteria were eligible. Data collected included: age, gender, prior infection, Guillain-Barré disability score (GDS score), time from symptom onset to diagnosis, altered mental state, time from symptom onset to altered mental state, cranial nerve involvement, deep tendon reflexes, ataxia, invasive mechanical ventilation (IMV) requirement, treatment, inpatient delirium, length of stay (days), and protein levels in CSF analysis. Nerve conduction studies (NCS) were performed, as well as neuroimaging (brain magnetic resonance imaging [MRI] and F 18-fluorodeoxyglucose PET-CT). Antiganglioside antibodies panel including anti-GQ1b was solicited. Results: Four patients (1.7%) met the inclusion criteria. Two patients manifested stupor and two showed somnolence throughout the course of the disease. Three patients required IMV due to bulbar dysfunction. None of the NCS met the criteria for any GBS electrophysiological variant. One patient was positive for IgM GM2 antibodies. One patient underwent 18F-FDG PET-CT, showing gene-ralized cortical hypometabolism. Conclusion: The frequency of BBE in our population is very low (1.7%). IgM GM2 is another anti-ganglioside antibody related to BBE. Imaging studies such as MRI frequently do not present abnormalities and [ F 18-FDG-PET scan might be a useful study to describe a metabolism pattern to aid the diagnosis of BBE.