Magnetic resonance imaging and SPECT findings in 10 children with a diagnosis of human herpesvirus 6 (HHV-6) encephalopathy are reported from Jikei University School of Medicine, Tokyo; and Saitama Children's Medical Center, Japan. T1 and T2-weighted MR imaging showed no abnormalities, but diffusion-weighted imaging showed abnormal hyperintensity in the subcortical white matter of the frontal lobes in 6 patients tested during the acute phase. Cerebral blood flow single-photon emission CT revealed decreased perfusion in the frontal lobes of all 9 tested. These findings with localization to the frontal lobes may be specific for HHV-6 encephalopathy. 
COMMENT. HHV-6 infection is most commonly associated with febrile seizures; it accounts for one-third of all first-time cases in children up to 2 years of age . These authors detected HHV-6 DNA by PCR in 2 of 7 CSF samples of HHV-6 associated febrile seizure patients. In 9 patients with acute infantile encephalopathy predominantly affecting the frontal lobes, the associated infection was influenza type A in 3, HHV-6 in 2, measles in 1, and upper respiratory viral illness unspecified in 3 (Ped Neur Briefs March 2006;20:20-21). . Serial MRIs showed atrophic changes in both frontal lobes, and PET studies revealed decreased perfusion in frontal lobes, with normalization at 7th to 38th month after onset. Prolonged impairment of consciousness after convulsions, and behavioral sequelae were consistent with an encephalopathy. These cases are unique in the predilection for the frontal lobes, but they are not HHV-6 specific.