Bornavirus Encephalitis Shows a Characteristic Magnetic Resonance Phenotype in Humans
Objective The number of diagnosed fatal encephalitis in humans caused by the classical Borna disease virus (BoDV‐1) is increasingly recognized, ever since it was proven that BoDV‐1 can cause human infections. However, awareness for this entity is low and a specific imaging pattern has not yet been identified. We therefore provide the first comprehensive description on the morphology of human BoDV‐1 encephalitis with histopathological verification of imaging abnormalities. Methods In an institutional review board (IRB)‐approved multi‐center study, we retrospectively analyzed 55 MRI exams of 19 patients with confirmed BoDV‐1 encephalitis. Fifty brain regions were systematically analyzed (T1w, T2w, T2*w, T1w + Gd, DWI) in order to discern a specific inflammation pattern. Histopathological analysis of 25 locations of one patient served as correlation for MRI abnormalities. Results Baseline imaging, acquired at a mean of 11 ± 10 days after symptom onset, as well as follow‐up scans of 16 patients revealed characteristic T2‐hyperintensities with predilection for the head of the caudate nucleus, insula and cortical spread to the limbic system, whereas occipital lobes and cerebellar hemispheres were unaffected. This gradient was confirmed by histology. Nine patients (47.4%) developed T1‐hyperintensities of the basal ganglia, corresponding to accumulated lipid phagocytes on histology and typical for late‐stage necrosis. Interpretation BoDV‐1 encephalitis shows a distinct inflammation pattern in both the early and late stages of the disease. Its appearance can mimic sporadic Creutzfeldt Jakob disease (sCJD) on MRI and should be considered a differential diagnosis in the case of atypical clinical presentation.