A case of post-Japanese encephalitis with partial hypothalamic dysfunction showing repetitive hyperthermia in summertime.

Summary Japanese encephalitis (JE) virus is a mosquito-borne virus belonging to the flavivirus family, including the West Nile and St Louis encephalitis viruses endemic to North America. JE virus is prevalent in East Asian countries and can cause acute lethal encephalitis. Although vaccination programs have decreased the incidence of JE in Japan, the cases that do occur are often fatal or associated with considerable clinical sequelae. We report, for the first time to our knowledge, a patient who had repetitive bouts of hyperthermia in the summertime after recovery from acute JE. An insulin challenge test revealed only marginal increases in the levels of β-endorphin and growth hormone, indicating partial medial hypothalamic dysfunction. Magnetic resonance imaging showed T2 hyperintensity in both thalamic paraventricular subcortical regions, known to project to the hypothalamic paraventricular nucleus. We thus attributed the episodes of hyperthermia to secondary hypothalamic impairment with thalamic lesions.