Longitudinal magnetic resonance imaging changes in Japanese encephalitis

Background: Japanese encephalitis is a flavivirus that can cause pandemic encephalitis, and is prevalent in Southeast Asia and Australia. Brain images of patients with Japanese encephalitis are characterized by thalamic lesions, distinct from those seen in viral encephalopathies caused by the herpes simplex virus and West Nile virus.

Aim: Herein, we describe for the first time a time-dependent magnetic resonance imaging pattern in Japanese encephalitis in a 10-month-old Japanese boy.

Case: The patient was a previously healthy 10-month-old Japanese boy, who exhibited acute-onset flaccid tetraplegia and loss of tendon reflexes.

Results: Brain MRI showed characteristic thalamic changes on diffusion weighted images from spotty to uniform and from the left to the right side, associated with low apparent diffusion coefficient maps. These images suggest that the Japanese encephalitis virus may first affect the unilateral thalamus, possibly expanding to the other side, with characteristic patterns changing from spotty to uniform in a manner consistent with the presentation of cytotoxic edema.

Conclusion: This report first showed longitudinal magnetic resonance changes in Japanese encephalitis, which may help in accurate diagnosis and in discrimination from other etiologies.