Brain samples obtained from surgical resections in 8 patients with mesial temporal lobe epilepsy (MTLE) and 7 patients with neocortical epilepsy (NE) were quantitatively analyzed for HHV-6 in a study at the National Institute of Neurological Disorders and Stroke, Bethesda, MD. DNA obtained from 4 patients with MTLE had significantly elevated levels of HHV-6 determined by real-time PCR assay, but HHV-6 was not amplified in specimens from NE patients. Hippocampal sections from MTLE cases had the highest levels of HHV-6, subtype HHV-6B. Expression of HHV-6 was localized to astrocytes and confirmed by western blot analysis and immunohistochemistry. 
COMMENT. The detection of HHV-6 in hippocampal and temporal lobe astrocytes of patients with MTLE suggests a possible role for reactivation of the virus in infected astrocytes as a cause of MTLE. The specificity of the finding requires additional studies in patients without seizures. HHV-6 and roseola infantum are also associated with febrile convulsions, a proposed antecedent to mesial temporal sclerosis and MTLE. (see Progress in Pediatric Neurology III, PNB Publishers, 1997;pp24-28).