Pattern Recognition Approach to Brain MRI Findings in Patients with Dengue Fever with Neurological Complications

Background and Purpose: Dengue can present with variable neurological complications including encephalitis, encephalopathy, acute disseminated encephalomyelitis (ADEM), and ischemic and hemorrhagic stroke. Our study describes a pattern-based approach to recognize different brain MRI findings in dengue-seropositive patients with neurological symptoms. Materials and Methods: Thirty-six serologically proven dengue patients with neurological symptoms and undergoing brain MRI over a 6-month period were included in this study. The diagnosis of dengue encephalopathy or encephalitis was established by presence of signs/symptoms of acute encephalitic syndrome with the presence of Immunoglobin M (IgM) antibody against dengue antibody in the serum and/or presence of dengue antigen (NS1) in serum. The MRI brain along with diffusion weighted imaging and susceptibility weighted imaging sequences were evaluated by an experienced neuroradiologist. Results: Eleven patients had normal MRI finding. In the rest 25 patients, 12 were found to have encephalitic pattern, 4 had encephalopathic (seizure related/metabolic) pattern, 3 had features of ADEM, and isolated micro- or macro-hemorrhages were found in 6 patients. In the encephalitis group, eight had concomitant involvement of brainstem, cerebellum, and ganglio-thalamic complexes with additional involvement of cortex and subcortical white matter (WM) found in three. Isolated brainstem and cerebellar involvement were seen in three in this group, whereas one had isolated cerebellar involvement. Interspersed hemorrhage was noted in the structures involved in eight patients in encephalitis group. Conclusion: Radiologists should be aware of various MRI brain findings in dengue and a pattern recognition approach often helps in reaching the correct diagnosis albeit after exclusion of other differentials based on laboratory studies.