Abstracts

Rationale: Several lines of investigation have suggested a relationship between HHV6 and  mesial temporal lobe epilepsy (MTLE) with mesial temporal sclerosis (MTS).  Epidemiological data suggest an association between MTLE and  a history of complex or prolonged febrile seizures or febrile status epilepticus (FSE), which may in turn be associated with HHV6 infection.  However, serological evidence for past infection is present in the majority of adults, complicating  establishment of an association.  We investigated the presence of actively replicating HHV6 in surgical resections from patients with drug-resistant epilepsy in a larger cohort than reported previously.  Methods: 62 patients had surgery (mean onset age 11.9 +/- 12.1 years; age at surgery 28.5 +/- 13.7).  Forty had mesial temporal sclerosis (MTS), 14 cortical dysplasia, four vascular lesions, three tumors, one Rasmussen's Encephalitis.  We 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.   Results: Twenty-three of 40 patients with MTS, compared to four  of 22 others (three cortical dysplasia, one Rasmussen's encephalitis) were positive for HHV 6 (X²  40.9: p < 0.01).    There was no relation of HHV6 status to onset age or epilepsy duration, a history of febrile seizures (based on data obtained from adult patients), or surgical outcome, either for the whole group or patients with MTS.  Conclusions: Patients with pathological evidence for mesial temporal sclerosis are significantly more likely than patients with other pathology to have actively replicating  HHV6 in resected tissue from seizure foci.  Funding: NINDS NIH  Division of Intramural Research