Japanese Encephalitis With a Characteristic Neuropathological Distribution Following Early MRI-Based Diagnosis: An Autopsy Case.

Japanese encephalitis (JE) is a mosquito-borne viral infection of the central nervous system for which no specific antiviral treatment is available. We report the case of a 79-year-old man residing in Kumamoto Prefecture, southwestern Japan, with JE who presented with fever, impaired consciousness, and respiratory failure, and subsequently died of multiple organ failure despite early supportive care. Magnetic resonance imaging (MRI) revealed characteristic bilateral thalamic lesions, leading to an early clinical suspicion of JE before serological confirmation. Neuropathological findings, particularly, the involvement of the thalamus, substantia nigra, hippocampus, and anterior horn of the spinal cord, were consistent with previously reported cases of JE, while also demonstrating a broader distribution of lesions than suggested by antemortem MRI. As most cases of JE occur in unvaccinated individuals, vaccination should be considered in middle-aged and older adults, particularly, those with low antibody titers against the JE virus.