MRI findings of recurrent herpes simplex encephalitis in an infant.

We report the MRI findings of a 2-year-old boy with recurrent herpes simplex encephalitis (HSE). At the age of 14 months, the patient developed a high fever that lasted over 1 week and he did not receive appropriate treatment. At 6 months after the fever, MRI showed marked atrophic changes in both deep temporal lobes with hyperintensity in the hippocampi and parahippocampal gyri. Thirteen months after the first episode of the fever, the patient was diagnosed with recurrent HSE by polymerase chain reaction assay of the CSF; MRI at this time revealed diffuse cortical swelling. Hyperintensity on T2-weighted images was noted in the occipito-parietal cortex bilaterally, the left thalamus, the subcortical white matter and the splenium of the corpus callosum. Recurrence of HSE may be more common in infants than previously thought. It is important to consider the possibility of recurrent HSE and to understand that MRI findings in HSV1 encephalitis in infants and young children appear to differ from those observed in neonates, older children and adults.