Usefulness of diffusion-weighted MRI in human herpesvirus-6 encephalitis

We report a patient with human herpesvirus-6 (HHV-6) encephalitis diagnosed by diffusion-weighted magnetic resonance imaging (DW-MRI). A previously healthy 10-month-old girl developed acute encephalopathy. HHV-6 DNA was detected in her cerebrospinal fluid during the acute phase of the disease by polymerase chain reaction. The patient demonstrated cortical diffusion abnormalities in affected brain parenchyma, partially as the initial or most sensitive sign of encephalitis that could be detected not by conventional MRI but by DW-MRI. Serial imaging showed that the diffusion abnormality DW-MRI returned to normal after 45 days. Conclusion: DW-MRI may be a valuable tool for early detection and diagnosis of HHV-6 encephalitis and is more sensitive than conventional MRI to detect a subtle edematous change in the brain.