Advanced Magnetic Resonance Imaging (MRI) Characterization in Bickerstaff's Brainstem Encephalitis

Abstract Purpose Bickerstaff's brainstem encephalitis(BBE) is considered a scarce variant of Miller-Fisher syndrome(MFS) and Guillain–Barré syndrome (GBS) but accounts for a significant proportion of brainstem encephalitis.Detailed knowledge of their neuroimaging manifestations is of paramount importance for a correct early diagnosis and proper management of the affected patients.In this study,We sought to characterize neuroimaging findings,including the morphology and manifestation of advanced MR imaging and differential diagnosis. Methods Seven BBE patients (5 males,2 females; mean age 42.5 ± 5.7 years,range 17 to 63 years) were retrospectively studied using conventional MRI (T1- and T2- weighted,FLAIR sequences,postcontrast T1-weighted images) and advanced MRI such as diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (MRS).The apparent diffusion coefficient (ADC) values and the MRS ratio were calculated in lesion regions. Results 1. The distribution of these lesions typically include bilateral and symmetrical involvement of the mesencephalon,thalamus,tegmentum,infratentorial periaqueductal region,and the periventricular region surrounding the third and fourth ventricles involving white and gray matter; additional supratentorial white matter is not involved.2. MRI axial T2-weighted images and FLAIR sequences showed nearly symmetrical hyperintense signal changes with slightly spotty,patchy,or confluent homogeneous enhancement on postcontrast T1-weighted images without necrosis or hemorrhage.3. DWI signal was enhanced,and the apparent diffusion coefficient (ADC) map signal was slightly increased.ADC values of BBE lesions were in the range of 1.21 to 1.67 × 10 −3 mm/s 2 (mean 1.38 ± 0.66 × 10 −3 mm/s 2 ).4. Proton MR spectrum showed a slight increase in choline and a relative decrease in NAA peak,while Lipid and Lac doublet were not detected. Conclusion Advanced MRI imaging can provide important physiological and metabolic information of BBE and complement the morphological findings of the clinical conventional MRI.