Bilateral medial temporal lesions in Japanese encephalitis

A 62-year-old woman presented with headache, fever, and deteriorating consciousness. Brain MRI showed bilateral lesions of the thalamus and substantia nigra. The medial temporal region was also involved bilaterally (figure). The serum hemagglutination inhibition test for Japanese encephalitis (JE) virus was initially negative; the titer was increased to 1:640 10 days later. Therefore, a diagnosis of JE was made. The patient remained in a vegetative state for 2 months before dying of pneumonia. Medial temporal lesions are seen in herpes simplex encephalitis, paraneoplastic limbic encephalitis, and neurosyphilis.¹ JE also commonly produces medial temporal lesions.² However, medial temporal lesions associated with bilateral thalamic or midbrain involvement may be more suggestive of JE, particularly in endemic areas.

• Download figure
• Open in new tab
• Download powerpoint

Figure. Fluid-attenuated inversion recovery axial MRI without contrast enhancement shows high-signal lesions in both thalami (A) and bilateral lesions of the medial temporal region and substantia nigra (B). Noncontrast brain CT taken at 4 weeks after initial MRI reveals low attenuation in both thalami (arrowheads) (C) and in both medial temporal regions (arrows) (D). Mild increase of ventricle size is also noted.

1.

2.