Human herpesvirus 6 and epilepsy

We investigated the association between human herpesvirus 6 (HHV-6) and mesial temporal sclerosis (MTS) in 87 patients who had surgery for drug-resistant epilepsy. Fifty-four had MTS, 22 focal cortical dysplasia (FCD), four tumors, three vascular malformations, and three a history of encephalitis. We extracted DNA from fresh brain tissue immediately after surgery and performed viral detection with quantitative real-time polymerase chain reaction (PCR) or digital droplet PCR specific for HHV-6A and HHV-6B. Tissue was studied with standard clinical techniques, including hematoxylin and eosin, glial fibrillary acidic protein, and NeuN stains. Twenty-nine of 54 patients with MTS, six of 23 with focal cortical dysplasia (FCD), and one of three with a history of encephalitis were positive for HHV-6 (P < .02). Febrile seizure history was not associated with HHV-6 detection. Patients with MTS had significantly lower seizure onset age than those with other pathologies. Thirteen patients had positron emission tomography with [11C]PBR28, a marker for reactive astrocytes and activated microglia; there was a trend for HHV-6-positive patients to have higher binding in their seizure foci, suggesting inflammation. Our study supports a potential role for HHV-6 in the etiology of MTS.